Anemia

MILWAUKEE – A new study of children with sickle cell disease found prevalent opioid use, with one in five preschoolers having had an opioid prescribed and filled for them.

Kari Oakes/MDedge News

The Medicaid claims database analysis looked at a one-year snapshot of prescriptions filled for a variety of opioids among children and young adults in North Carolina, said Nancy Crego, PhD, in an interview at a poster session of the scientific meeting of the American Pain Society.

Dr. Crego and her colleagues at Duke University School of Nursing, Durham, N.C., studied 1,560 children and young adults aged 0-22 years with sickle cell disease who received Medicaid; in all, 586 (38%) had an opioid prescription filled during the year-long study period.

Among adolescents and young adults with sickle cell disease, outpatient opioid prescriptions were common, with increasing prescription fills seen through the middle years and young adulthood. “Opioid prescription claims were prevalent across all age groups,” wrote Dr. Crego and her associates.

Though 20% of preschoolers (87 of 428) had had a prescription filled for opioids, the rates of opioid prescribing increased with age. Of adolescents aged 15-18 years, 54% (154 of 284) had filled an opioid prescription, as had 50% (110 of 221) of those aged 19-22 years.

For the 366 school-aged children aged 6-10 years, 117 (32%) had an opioid prescription filled. The number of prescriptions filled per patient on an annual basis for this age group ranged from one to 10.


There was a wide variation in the number of prescriptions filled in all other age groups over the study period as well. For school-aged children, the range was 1 to 10, and 1 to 18 for middle schoolers aged 11-14 years. Adolescents filled from 1-30 prescriptions, and for young adults, the range was 1-24.

Though the rates of opioid prescribing increased with age, the number of doses per prescription actually fell throughout the adolescent and young adult years. In an interview at the poster presentation, Dr. Crego speculated that this decrease observed with increasing age might reflect provider concern about opioid misuse and diversion, though the study methodology didn’t allow them to examine this.

Dr. Crego said that she was surprised by the high numbers of children who were receiving opioid prescriptions in the preschool years. “I wonder what their parents are being taught about how to administer these medications” to this very young age group, she commented.

Opioids included in the claims database analysis included morphine, hydromorphone, hydrocodone, oxycodone, oxymorphone, methadone, fentanyl, codeine, and tramadol.

Children with sickle cell disease are exposed to opioids in early childhood,” Dr. Crego and her colleagues wrote in the poster, but they acknowledged that “it is unknown if this early exposure increases the risk of opioid misuse later in life in this population ... Prescribers should incorporate continuous assessments for potential misuse and abuse in all age groups.”

“Most of the data that we have on opioid prescription claims in children usually exclude chronically ill children; they’re almost all of acutely ill children, and quite a bit of it is on postoperative care,” Dr. Crego said. The current study captures early-life prescribing “for somebody who’s going to be on opioids for a lot of their life,” she noted.

The studies of opioids used for acute pain, she said, showed that parents would often “administer opioids for inappropriate indications.” She is now conducting a qualitative study investigating pharmacologic and non-pharmacologic pain interventions for children with sickle cell disease. She’s also investigating how parents decide to administer opioids: “What did they see in their child that would prompt them to give an opioid versus giving another type of analgesic?”

There are some limitations to working with a claims database, acknowledged Dr. Crego: “We don’t know about their actual use, because we don’t know how often they are taking it, but we know it’s a filled opioid prescription.”

Dr. Crego said that more work is needed to examine how parents administer opioids to their children with sickle cell disease, and to learn more about what parents are told – and what they understand – about how their child’s pain should be managed. Also, she added, more research is needed on non-pharmacologic pain management for pediatric patients with sickle cell disease.

The study was funded by the Agency for Healthcare Research and Quality. Dr. Crego and her coauthors reported no conflicts of interest.

[email protected]

SOURCE: Crego, N. et al. APS 2019.

MILWAUKEE – A new study of children with sickle cell disease found prevalent opioid use, with one in five preschoolers having had an opioid prescribed and filled for them.

Kari Oakes/MDedge News

The Medicaid claims database analysis looked at a one-year snapshot of prescriptions filled for a variety of opioids among children and young adults in North Carolina, said Nancy Crego, PhD, in an interview at a poster session of the scientific meeting of the American Pain Society.

Dr. Crego and her colleagues at Duke University School of Nursing, Durham, N.C., studied 1,560 children and young adults aged 0-22 years with sickle cell disease who received Medicaid; in all, 586 (38%) had an opioid prescription filled during the year-long study period.

Among adolescents and young adults with sickle cell disease, outpatient opioid prescriptions were common, with increasing prescription fills seen through the middle years and young adulthood. “Opioid prescription claims were prevalent across all age groups,” wrote Dr. Crego and her associates.

Though 20% of preschoolers (87 of 428) had had a prescription filled for opioids, the rates of opioid prescribing increased with age. Of adolescents aged 15-18 years, 54% (154 of 284) had filled an opioid prescription, as had 50% (110 of 221) of those aged 19-22 years.

For the 366 school-aged children aged 6-10 years, 117 (32%) had an opioid prescription filled. The number of prescriptions filled per patient on an annual basis for this age group ranged from one to 10.


There was a wide variation in the number of prescriptions filled in all other age groups over the study period as well. For school-aged children, the range was 1 to 10, and 1 to 18 for middle schoolers aged 11-14 years. Adolescents filled from 1-30 prescriptions, and for young adults, the range was 1-24.

Though the rates of opioid prescribing increased with age, the number of doses per prescription actually fell throughout the adolescent and young adult years. In an interview at the poster presentation, Dr. Crego speculated that this decrease observed with increasing age might reflect provider concern about opioid misuse and diversion, though the study methodology didn’t allow them to examine this.

Dr. Crego said that she was surprised by the high numbers of children who were receiving opioid prescriptions in the preschool years. “I wonder what their parents are being taught about how to administer these medications” to this very young age group, she commented.

Opioids included in the claims database analysis included morphine, hydromorphone, hydrocodone, oxycodone, oxymorphone, methadone, fentanyl, codeine, and tramadol.

Children with sickle cell disease are exposed to opioids in early childhood,” Dr. Crego and her colleagues wrote in the poster, but they acknowledged that “it is unknown if this early exposure increases the risk of opioid misuse later in life in this population ... Prescribers should incorporate continuous assessments for potential misuse and abuse in all age groups.”

“Most of the data that we have on opioid prescription claims in children usually exclude chronically ill children; they’re almost all of acutely ill children, and quite a bit of it is on postoperative care,” Dr. Crego said. The current study captures early-life prescribing “for somebody who’s going to be on opioids for a lot of their life,” she noted.

The studies of opioids used for acute pain, she said, showed that parents would often “administer opioids for inappropriate indications.” She is now conducting a qualitative study investigating pharmacologic and non-pharmacologic pain interventions for children with sickle cell disease. She’s also investigating how parents decide to administer opioids: “What did they see in their child that would prompt them to give an opioid versus giving another type of analgesic?”

There are some limitations to working with a claims database, acknowledged Dr. Crego: “We don’t know about their actual use, because we don’t know how often they are taking it, but we know it’s a filled opioid prescription.”

Dr. Crego said that more work is needed to examine how parents administer opioids to their children with sickle cell disease, and to learn more about what parents are told – and what they understand – about how their child’s pain should be managed. Also, she added, more research is needed on non-pharmacologic pain management for pediatric patients with sickle cell disease.

The study was funded by the Agency for Healthcare Research and Quality. Dr. Crego and her coauthors reported no conflicts of interest.

[email protected]

SOURCE: Crego, N. et al. APS 2019.

MILWAUKEE – A new study of children with sickle cell disease found prevalent opioid use, with one in five preschoolers having had an opioid prescribed and filled for them.

Kari Oakes/MDedge News

The Medicaid claims database analysis looked at a one-year snapshot of prescriptions filled for a variety of opioids among children and young adults in North Carolina, said Nancy Crego, PhD, in an interview at a poster session of the scientific meeting of the American Pain Society.

Dr. Crego and her colleagues at Duke University School of Nursing, Durham, N.C., studied 1,560 children and young adults aged 0-22 years with sickle cell disease who received Medicaid; in all, 586 (38%) had an opioid prescription filled during the year-long study period.

Among adolescents and young adults with sickle cell disease, outpatient opioid prescriptions were common, with increasing prescription fills seen through the middle years and young adulthood. “Opioid prescription claims were prevalent across all age groups,” wrote Dr. Crego and her associates.

Though 20% of preschoolers (87 of 428) had had a prescription filled for opioids, the rates of opioid prescribing increased with age. Of adolescents aged 15-18 years, 54% (154 of 284) had filled an opioid prescription, as had 50% (110 of 221) of those aged 19-22 years.

For the 366 school-aged children aged 6-10 years, 117 (32%) had an opioid prescription filled. The number of prescriptions filled per patient on an annual basis for this age group ranged from one to 10.


There was a wide variation in the number of prescriptions filled in all other age groups over the study period as well. For school-aged children, the range was 1 to 10, and 1 to 18 for middle schoolers aged 11-14 years. Adolescents filled from 1-30 prescriptions, and for young adults, the range was 1-24.

Though the rates of opioid prescribing increased with age, the number of doses per prescription actually fell throughout the adolescent and young adult years. In an interview at the poster presentation, Dr. Crego speculated that this decrease observed with increasing age might reflect provider concern about opioid misuse and diversion, though the study methodology didn’t allow them to examine this.

Dr. Crego said that she was surprised by the high numbers of children who were receiving opioid prescriptions in the preschool years. “I wonder what their parents are being taught about how to administer these medications” to this very young age group, she commented.

Opioids included in the claims database analysis included morphine, hydromorphone, hydrocodone, oxycodone, oxymorphone, methadone, fentanyl, codeine, and tramadol.

Children with sickle cell disease are exposed to opioids in early childhood,” Dr. Crego and her colleagues wrote in the poster, but they acknowledged that “it is unknown if this early exposure increases the risk of opioid misuse later in life in this population ... Prescribers should incorporate continuous assessments for potential misuse and abuse in all age groups.”

“Most of the data that we have on opioid prescription claims in children usually exclude chronically ill children; they’re almost all of acutely ill children, and quite a bit of it is on postoperative care,” Dr. Crego said. The current study captures early-life prescribing “for somebody who’s going to be on opioids for a lot of their life,” she noted.

The studies of opioids used for acute pain, she said, showed that parents would often “administer opioids for inappropriate indications.” She is now conducting a qualitative study investigating pharmacologic and non-pharmacologic pain interventions for children with sickle cell disease. She’s also investigating how parents decide to administer opioids: “What did they see in their child that would prompt them to give an opioid versus giving another type of analgesic?”

There are some limitations to working with a claims database, acknowledged Dr. Crego: “We don’t know about their actual use, because we don’t know how often they are taking it, but we know it’s a filled opioid prescription.”

Dr. Crego said that more work is needed to examine how parents administer opioids to their children with sickle cell disease, and to learn more about what parents are told – and what they understand – about how their child’s pain should be managed. Also, she added, more research is needed on non-pharmacologic pain management for pediatric patients with sickle cell disease.

The study was funded by the Agency for Healthcare Research and Quality. Dr. Crego and her coauthors reported no conflicts of interest.

[email protected]

SOURCE: Crego, N. et al. APS 2019.

Doubling total body irradiation improved rates of engraftment without altering safety in patients with severe hemoglobinopathies undergoing haploidentical hematopoietic cell transplantation, new findings suggest.

Dr_Microbe/Thinkstock

“[A]lthough our previous study showed cures in most patients and low toxicity, the graft failure rate – albeit all with full host recovery – was 50%,” Francisco Javier Bolaños-Meade, MD, of Johns Hopkins University, Baltimore, and his colleagues wrote in the Lancet Haematology. The present study set out to decrease graft failure in these patients.

The researchers conducted a single-center study of 17 consecutive patients who underwent haploidentical hematopoietic cell transplantation for a severe hemoglobinopathy. A total of 12 patients had sickle cell disease and 5 had beta-thalassemia major.

Study participants received a nonmyeloablative conditioning regimen consisting of haploidentical related donors and postprocedure cyclophosphamide.

“The primary endpoint of the study was modified to evaluate engraftment by measurement of blood chimerism,” they wrote.

After analysis, Dr. Bolaños-Meade and his colleagues found that increasing total body irradiation dose from 200 cGy to 400 cGy lowered graft failure without raising toxicity. In particular, only one participant had primary graft failure, but experienced recovery of host hematopoiesis.

Of the 17 patients, 13 patients (76%) achieved full donor chimerism and 3 patients (18%) had mixed donor-host chimerism. Three patients remained on immunosuppression, the researchers reported.

With respect to safety, five patients developed acute GVHD, which varied from grade 2 to 4; chronic GVHD was seen in three patients.

“The results of our study warrant further investigation to determine whether the curative potential of allogeneic bone marrow transplantation can extend beyond the traditionally small fraction of patients with severe hemoglobinopathies who have matched donors and are healthy enough to receive myeloablative conditioning,” they wrote.

The study was funded by the National Institutes of Health and the Maryland Stem Cell Research Fund. The researchers reported financial disclosures related to Aduro Biotech, Amgen, Alexion Pharmaceuticals, Celgene, Takeda, and others.

SOURCE: Bolaños-Meade FJ et al. Lancet Haematol. 2019 Mar 13. doi: 10.1016/S2352-3026(19)30031-6.

Doubling total body irradiation improved rates of engraftment without altering safety in patients with severe hemoglobinopathies undergoing haploidentical hematopoietic cell transplantation, new findings suggest.

Dr_Microbe/Thinkstock

“[A]lthough our previous study showed cures in most patients and low toxicity, the graft failure rate – albeit all with full host recovery – was 50%,” Francisco Javier Bolaños-Meade, MD, of Johns Hopkins University, Baltimore, and his colleagues wrote in the Lancet Haematology. The present study set out to decrease graft failure in these patients.

The researchers conducted a single-center study of 17 consecutive patients who underwent haploidentical hematopoietic cell transplantation for a severe hemoglobinopathy. A total of 12 patients had sickle cell disease and 5 had beta-thalassemia major.

Study participants received a nonmyeloablative conditioning regimen consisting of haploidentical related donors and postprocedure cyclophosphamide.

“The primary endpoint of the study was modified to evaluate engraftment by measurement of blood chimerism,” they wrote.

After analysis, Dr. Bolaños-Meade and his colleagues found that increasing total body irradiation dose from 200 cGy to 400 cGy lowered graft failure without raising toxicity. In particular, only one participant had primary graft failure, but experienced recovery of host hematopoiesis.

Of the 17 patients, 13 patients (76%) achieved full donor chimerism and 3 patients (18%) had mixed donor-host chimerism. Three patients remained on immunosuppression, the researchers reported.

With respect to safety, five patients developed acute GVHD, which varied from grade 2 to 4; chronic GVHD was seen in three patients.

“The results of our study warrant further investigation to determine whether the curative potential of allogeneic bone marrow transplantation can extend beyond the traditionally small fraction of patients with severe hemoglobinopathies who have matched donors and are healthy enough to receive myeloablative conditioning,” they wrote.

The study was funded by the National Institutes of Health and the Maryland Stem Cell Research Fund. The researchers reported financial disclosures related to Aduro Biotech, Amgen, Alexion Pharmaceuticals, Celgene, Takeda, and others.

SOURCE: Bolaños-Meade FJ et al. Lancet Haematol. 2019 Mar 13. doi: 10.1016/S2352-3026(19)30031-6.

Doubling total body irradiation improved rates of engraftment without altering safety in patients with severe hemoglobinopathies undergoing haploidentical hematopoietic cell transplantation, new findings suggest.

Dr_Microbe/Thinkstock

“[A]lthough our previous study showed cures in most patients and low toxicity, the graft failure rate – albeit all with full host recovery – was 50%,” Francisco Javier Bolaños-Meade, MD, of Johns Hopkins University, Baltimore, and his colleagues wrote in the Lancet Haematology. The present study set out to decrease graft failure in these patients.

The researchers conducted a single-center study of 17 consecutive patients who underwent haploidentical hematopoietic cell transplantation for a severe hemoglobinopathy. A total of 12 patients had sickle cell disease and 5 had beta-thalassemia major.

Study participants received a nonmyeloablative conditioning regimen consisting of haploidentical related donors and postprocedure cyclophosphamide.

“The primary endpoint of the study was modified to evaluate engraftment by measurement of blood chimerism,” they wrote.

After analysis, Dr. Bolaños-Meade and his colleagues found that increasing total body irradiation dose from 200 cGy to 400 cGy lowered graft failure without raising toxicity. In particular, only one participant had primary graft failure, but experienced recovery of host hematopoiesis.

Of the 17 patients, 13 patients (76%) achieved full donor chimerism and 3 patients (18%) had mixed donor-host chimerism. Three patients remained on immunosuppression, the researchers reported.

With respect to safety, five patients developed acute GVHD, which varied from grade 2 to 4; chronic GVHD was seen in three patients.

“The results of our study warrant further investigation to determine whether the curative potential of allogeneic bone marrow transplantation can extend beyond the traditionally small fraction of patients with severe hemoglobinopathies who have matched donors and are healthy enough to receive myeloablative conditioning,” they wrote.

The study was funded by the National Institutes of Health and the Maryland Stem Cell Research Fund. The researchers reported financial disclosures related to Aduro Biotech, Amgen, Alexion Pharmaceuticals, Celgene, Takeda, and others.

SOURCE: Bolaños-Meade FJ et al. Lancet Haematol. 2019 Mar 13. doi: 10.1016/S2352-3026(19)30031-6.

Earlier this year, the Food and Drug Administration approved Cablivi (caplacizumab-yhdp) (Sanofi Genzyme, Cambridge, Mass.) for the treatment of acquired thrombotic thrombocytopenic purpura (TTP), making it the first medication specifically indicated for the treatment of TTP.

The approval of caplacizumab and the clinical trial results that approval is based on are the most promising developments in the treatment of TTP since the introduction of plasma exchange (PE) therapy. However, many questions remain about how to best administer caplacizumab, specifically, which patients should receive it? Should all TTP patients start on caplacizumab therapy or should it be limited to patients with histories of TTP or those slow to respond to standard therapy with PE and immunosuppression?

TTP is a rare thrombotic microangiopathy characterized by thrombocytopenia and microangiopathic hemolytic anemia caused by the inhibition of ADAMTS13, a metalloproteinase, which cleaves large-molecular-weight von Willebrand factor (vWF) multimers. Caplacizumab is a humanized bivalent, variable domain-only immunoglobulin fragment. The drug targets the A1 domain of vWF and inhibits the binding between vWF and the platelet glycoprotein Ib-IX-V receptor, preventing the formation of the microvascular thrombi and platelet loss associated with TTP.

FDA approval of caplacizumab came shortly after the publication of the results of the HERCULES trial in the New England Journal of Medicine by Marie Scully, MD, and her colleagues (N Engl J Med. 2019; 380[4]: 335-46).

HERCULES was an international phase 3, double blinded, placebo-controlled, randomized study designed to evaluate the efficacy and safety of caplacizumab. In total, 145 patients participated in the trial. Caplacizumab or placebo were given in addition to standard therapy of plasma exchange (PE) and immunosuppression. Caplacizumab or placebo were administered as an intravenous loading dose prior to the first PE after randomization and subcutaneously once daily until 30 days after the last PE. All patients received daily PE until 2 days after platelet count normalization.

The primary measure of the study was the time to platelet count response of greater than 150 x 10⁹/L following the cessation of daily PE. Secondary measures included TTP-related death; TTP relapse; major thromboembolic events; proportion of subjects with refractory TTP; normalization of organ damage markers including lactate dehydrogenase, cardiac troponin I, and serum creatinine; and other adverse events.

The authors found that the median time of normalization of the platelet count was shorter in the caplacizumab group, compared with placebo, with the caplacizumab group being 1.55 times more likely to have a normalized platelet count at any given time point in the study. While statistically significant differences were identified in the rate of platelet normalization, the median number of days of PE until normalization was only 2 days less in the caplacizumab group (five treatments) than in the placebo group (seven treatments), which may not be clinically significant for the treating physician.

In fact, the secondary endpoints of the study seem much more clinically promising in the treatment of TTP. The composite rate of TTP-related death, TTP recurrence, or major thromboembolic events during the treatment period was significantly lower in the caplacizumab group (12%) versus placebo (49%). No TTP-related deaths occurred in the caplacizumab group. The caplacizumab group was also statistically less likely to have a TTP exacerbation, defined as disease recurrence within 30 days from the last PE, than the placebo group.

End organ damage serum markers also improved faster in the caplacizumab group, although there was no significant difference between groups. Overall hospitalization (median of 9 vs. 12 days) and ICU stays (median of 3 vs. 5 days) were shorter in the caplacizumab group, compared with the placebo group.

While several relapses, defined as disease recurrence after 30 days from the last PE, occurred in the caplacizumab group, the relapses were only found in patients with ADAMTS13 activity of less than 10% at the end of the treatment period. Mild side effects, such as mucocutaneous bleeding were more frequent in the caplacizumab group. No major bleeding complications were observed.

The HERCULES trial generates more questions about the role of ADAMTS13 activity testing to monitor treatment response and to make therapy decisions. Extremely low ADAMTS13 activity levels at the cessation of therapy may be a sign of treatment inadequacy and may warrant closer follow-up of at-risk patients on caplacizumab.

Sanofi Genzyme estimates that the U.S. list price will be approximately $270,000 for a standard treatment course, according to a news release from the company. Whether payers will add it to formularies remains uncertain, but the high drug cost may be countered by potential savings in the reduction of hospital and ICU days with caplacizumab therapy. Sanofi Genzyme will also have a patient support program for eligible patients.

Caplacizumab has been approved in Europe since August 2018, but is not readily available in the United States. Given the dearth of clinical experience with the drug outside of the TITAN and HERCULES trials, strong recommendations for when and how to initiate therapy remain elusive.

As caplacizumab is further introduced into clinical practice, more studies are needed to identify which patient groups will benefit most from therapy. The current data for caplacizumab shows that it will be used as an adjunct to standard PE therapy, rather than as a replacement. How the drug is used in combination with current TTP treatments – such as corticosteroids, rituximab, bortezomib, vincristine, N-acetylcysteine, and splenectomy – should be evaluated to identify which treatment combinations not only improve platelet counts, but also reduce mortality and morbidity while remaining cost effective.

Dr. Ricci is a staff physician and Apheresis Director at the Taussig Cancer Institute at the Cleveland Clinic. She reported having no conflicts of interest.

Earlier this year, the Food and Drug Administration approved Cablivi (caplacizumab-yhdp) (Sanofi Genzyme, Cambridge, Mass.) for the treatment of acquired thrombotic thrombocytopenic purpura (TTP), making it the first medication specifically indicated for the treatment of TTP.

The approval of caplacizumab and the clinical trial results that approval is based on are the most promising developments in the treatment of TTP since the introduction of plasma exchange (PE) therapy. However, many questions remain about how to best administer caplacizumab, specifically, which patients should receive it? Should all TTP patients start on caplacizumab therapy or should it be limited to patients with histories of TTP or those slow to respond to standard therapy with PE and immunosuppression?

TTP is a rare thrombotic microangiopathy characterized by thrombocytopenia and microangiopathic hemolytic anemia caused by the inhibition of ADAMTS13, a metalloproteinase, which cleaves large-molecular-weight von Willebrand factor (vWF) multimers. Caplacizumab is a humanized bivalent, variable domain-only immunoglobulin fragment. The drug targets the A1 domain of vWF and inhibits the binding between vWF and the platelet glycoprotein Ib-IX-V receptor, preventing the formation of the microvascular thrombi and platelet loss associated with TTP.

FDA approval of caplacizumab came shortly after the publication of the results of the HERCULES trial in the New England Journal of Medicine by Marie Scully, MD, and her colleagues (N Engl J Med. 2019; 380[4]: 335-46).

HERCULES was an international phase 3, double blinded, placebo-controlled, randomized study designed to evaluate the efficacy and safety of caplacizumab. In total, 145 patients participated in the trial. Caplacizumab or placebo were given in addition to standard therapy of plasma exchange (PE) and immunosuppression. Caplacizumab or placebo were administered as an intravenous loading dose prior to the first PE after randomization and subcutaneously once daily until 30 days after the last PE. All patients received daily PE until 2 days after platelet count normalization.

The primary measure of the study was the time to platelet count response of greater than 150 x 10⁹/L following the cessation of daily PE. Secondary measures included TTP-related death; TTP relapse; major thromboembolic events; proportion of subjects with refractory TTP; normalization of organ damage markers including lactate dehydrogenase, cardiac troponin I, and serum creatinine; and other adverse events.

The authors found that the median time of normalization of the platelet count was shorter in the caplacizumab group, compared with placebo, with the caplacizumab group being 1.55 times more likely to have a normalized platelet count at any given time point in the study. While statistically significant differences were identified in the rate of platelet normalization, the median number of days of PE until normalization was only 2 days less in the caplacizumab group (five treatments) than in the placebo group (seven treatments), which may not be clinically significant for the treating physician.

In fact, the secondary endpoints of the study seem much more clinically promising in the treatment of TTP. The composite rate of TTP-related death, TTP recurrence, or major thromboembolic events during the treatment period was significantly lower in the caplacizumab group (12%) versus placebo (49%). No TTP-related deaths occurred in the caplacizumab group. The caplacizumab group was also statistically less likely to have a TTP exacerbation, defined as disease recurrence within 30 days from the last PE, than the placebo group.

End organ damage serum markers also improved faster in the caplacizumab group, although there was no significant difference between groups. Overall hospitalization (median of 9 vs. 12 days) and ICU stays (median of 3 vs. 5 days) were shorter in the caplacizumab group, compared with the placebo group.

While several relapses, defined as disease recurrence after 30 days from the last PE, occurred in the caplacizumab group, the relapses were only found in patients with ADAMTS13 activity of less than 10% at the end of the treatment period. Mild side effects, such as mucocutaneous bleeding were more frequent in the caplacizumab group. No major bleeding complications were observed.

The HERCULES trial generates more questions about the role of ADAMTS13 activity testing to monitor treatment response and to make therapy decisions. Extremely low ADAMTS13 activity levels at the cessation of therapy may be a sign of treatment inadequacy and may warrant closer follow-up of at-risk patients on caplacizumab.

Sanofi Genzyme estimates that the U.S. list price will be approximately $270,000 for a standard treatment course, according to a news release from the company. Whether payers will add it to formularies remains uncertain, but the high drug cost may be countered by potential savings in the reduction of hospital and ICU days with caplacizumab therapy. Sanofi Genzyme will also have a patient support program for eligible patients.

Caplacizumab has been approved in Europe since August 2018, but is not readily available in the United States. Given the dearth of clinical experience with the drug outside of the TITAN and HERCULES trials, strong recommendations for when and how to initiate therapy remain elusive.

As caplacizumab is further introduced into clinical practice, more studies are needed to identify which patient groups will benefit most from therapy. The current data for caplacizumab shows that it will be used as an adjunct to standard PE therapy, rather than as a replacement. How the drug is used in combination with current TTP treatments – such as corticosteroids, rituximab, bortezomib, vincristine, N-acetylcysteine, and splenectomy – should be evaluated to identify which treatment combinations not only improve platelet counts, but also reduce mortality and morbidity while remaining cost effective.

Dr. Ricci is a staff physician and Apheresis Director at the Taussig Cancer Institute at the Cleveland Clinic. She reported having no conflicts of interest.

Earlier this year, the Food and Drug Administration approved Cablivi (caplacizumab-yhdp) (Sanofi Genzyme, Cambridge, Mass.) for the treatment of acquired thrombotic thrombocytopenic purpura (TTP), making it the first medication specifically indicated for the treatment of TTP.

The approval of caplacizumab and the clinical trial results that approval is based on are the most promising developments in the treatment of TTP since the introduction of plasma exchange (PE) therapy. However, many questions remain about how to best administer caplacizumab, specifically, which patients should receive it? Should all TTP patients start on caplacizumab therapy or should it be limited to patients with histories of TTP or those slow to respond to standard therapy with PE and immunosuppression?

TTP is a rare thrombotic microangiopathy characterized by thrombocytopenia and microangiopathic hemolytic anemia caused by the inhibition of ADAMTS13, a metalloproteinase, which cleaves large-molecular-weight von Willebrand factor (vWF) multimers. Caplacizumab is a humanized bivalent, variable domain-only immunoglobulin fragment. The drug targets the A1 domain of vWF and inhibits the binding between vWF and the platelet glycoprotein Ib-IX-V receptor, preventing the formation of the microvascular thrombi and platelet loss associated with TTP.

FDA approval of caplacizumab came shortly after the publication of the results of the HERCULES trial in the New England Journal of Medicine by Marie Scully, MD, and her colleagues (N Engl J Med. 2019; 380[4]: 335-46).

HERCULES was an international phase 3, double blinded, placebo-controlled, randomized study designed to evaluate the efficacy and safety of caplacizumab. In total, 145 patients participated in the trial. Caplacizumab or placebo were given in addition to standard therapy of plasma exchange (PE) and immunosuppression. Caplacizumab or placebo were administered as an intravenous loading dose prior to the first PE after randomization and subcutaneously once daily until 30 days after the last PE. All patients received daily PE until 2 days after platelet count normalization.

The primary measure of the study was the time to platelet count response of greater than 150 x 10⁹/L following the cessation of daily PE. Secondary measures included TTP-related death; TTP relapse; major thromboembolic events; proportion of subjects with refractory TTP; normalization of organ damage markers including lactate dehydrogenase, cardiac troponin I, and serum creatinine; and other adverse events.

The authors found that the median time of normalization of the platelet count was shorter in the caplacizumab group, compared with placebo, with the caplacizumab group being 1.55 times more likely to have a normalized platelet count at any given time point in the study. While statistically significant differences were identified in the rate of platelet normalization, the median number of days of PE until normalization was only 2 days less in the caplacizumab group (five treatments) than in the placebo group (seven treatments), which may not be clinically significant for the treating physician.

In fact, the secondary endpoints of the study seem much more clinically promising in the treatment of TTP. The composite rate of TTP-related death, TTP recurrence, or major thromboembolic events during the treatment period was significantly lower in the caplacizumab group (12%) versus placebo (49%). No TTP-related deaths occurred in the caplacizumab group. The caplacizumab group was also statistically less likely to have a TTP exacerbation, defined as disease recurrence within 30 days from the last PE, than the placebo group.

End organ damage serum markers also improved faster in the caplacizumab group, although there was no significant difference between groups. Overall hospitalization (median of 9 vs. 12 days) and ICU stays (median of 3 vs. 5 days) were shorter in the caplacizumab group, compared with the placebo group.

While several relapses, defined as disease recurrence after 30 days from the last PE, occurred in the caplacizumab group, the relapses were only found in patients with ADAMTS13 activity of less than 10% at the end of the treatment period. Mild side effects, such as mucocutaneous bleeding were more frequent in the caplacizumab group. No major bleeding complications were observed.

The HERCULES trial generates more questions about the role of ADAMTS13 activity testing to monitor treatment response and to make therapy decisions. Extremely low ADAMTS13 activity levels at the cessation of therapy may be a sign of treatment inadequacy and may warrant closer follow-up of at-risk patients on caplacizumab.

Sanofi Genzyme estimates that the U.S. list price will be approximately $270,000 for a standard treatment course, according to a news release from the company. Whether payers will add it to formularies remains uncertain, but the high drug cost may be countered by potential savings in the reduction of hospital and ICU days with caplacizumab therapy. Sanofi Genzyme will also have a patient support program for eligible patients.

Caplacizumab has been approved in Europe since August 2018, but is not readily available in the United States. Given the dearth of clinical experience with the drug outside of the TITAN and HERCULES trials, strong recommendations for when and how to initiate therapy remain elusive.

As caplacizumab is further introduced into clinical practice, more studies are needed to identify which patient groups will benefit most from therapy. The current data for caplacizumab shows that it will be used as an adjunct to standard PE therapy, rather than as a replacement. How the drug is used in combination with current TTP treatments – such as corticosteroids, rituximab, bortezomib, vincristine, N-acetylcysteine, and splenectomy – should be evaluated to identify which treatment combinations not only improve platelet counts, but also reduce mortality and morbidity while remaining cost effective.

Dr. Ricci is a staff physician and Apheresis Director at the Taussig Cancer Institute at the Cleveland Clinic. She reported having no conflicts of interest.

Single-dose tafenoquine therapy safely reduces the risk of Plasmodium vivax relapse in patients with normal glucose-6-phosphate dehydrogenase (G6PD) activity, according to the results of two phase 3, double-blind, randomized controlled trials.

Courtesy NIAID

Findings from both studies were published in two separate reports in the New England Journal of Medicine.

In the first study, the Dose and Efficacy Trial Evaluating Chloroquine and Tafenoquine in Vivax Elimination (DETECTIVE), the risk of P. vivax recurrence was approximately 70% lower with tafenoquine versus placebo, wrote Marcus V.G. Lacerda, MD, of Fundação de Medicina Tropical Doutor Heitor Vieira Dourado in Manaus, Brazil, and his colleagues.

The study included 522 patients with confirmed P. vivax infection from Peru, Brazil, Ethiopia, Cambodia, Thailand, and the Philippines. Patients received 3 days of chloroquine therapy (600 mg on days 1 and 2, and 300 mg on day 3) and were randomly assigned on a 2:1:1 basis to receive a single 300-mg dose of tafenoquine on day 1 or 2, primaquine once daily for 14 days, or placebo.

Since primaquine and tafenoquine can cause clinically significant hemolysis in individuals with G6PD deficiency, the study included only patients with normal G6PD activity.

In the second study, Global Assessment of Tafenoquine Hemolytic Risk (GATHER), Alejandro Llanos-Cuentas, MD, of Universidad Peruana Cayetano Heredia, Lima, Peru, and his colleagues enrolled 251 patients with confirmed P. vivax infection from Peru, Brazil, Columbia, Vietnam, and Thailand. They attempted to recruit women with moderate G6PD levels, but only one participant met this criterion – all others had normal G6PD activity.

Patients received 3-day course of chloroquine and were randomly assigned on a 2:1 basis to either tafenoquine or primaquine at the same doses as in the DETECTIVE trial.

At 6 months, 2% (95% CI, 1%-6%) of tafenoquine recipients and 1% (95% CI, 0.2%-6%) of primaquine recipients had decreased hemoglobin levels, but none consequently needed treatment. The medications also caused a similar degree and time course of hemoglobin decrease, the investigators noted.

A meta-analysis of GATHER and DETECTIVE confirmed that tafenoquine more often led to a decreased hemoglobin level (4% versus 1.5% with primaquine). Tafenoquine also did not meet prespecified criteria for noninferiority compared with primaquine, with respective 6-month recurrence rates of 67% versus 73%.

However, GATHER deployed “extensive” support to help patients adhere to the 15-day primaquine course, Dr. Llanos-Cuentas and his colleagues wrote. “Without such interventions, adherence to primaquine has been reported to be as low as 24% in Southeast Asia, with a corresponding attenuation of efficacy.”

GlaxoSmithKline and Medicines for Malaria Venture funded both studies, and GSK funded and conducted the meta-analysis. Dr. Llanos-Cuentas and several coinvestigators reported ties to GSK, Medicines for Malaria Venture, the Gambia, and LSTMH. Dr. Lacerda reported having no conflicts of interest.

SOURCES: Lacerda MVG et al. N Engl J Med 2019;380:215-28, and Llanos-Cuentas A et al. N Engl J Med 2019;380:229-41.

Single-dose tafenoquine therapy safely reduces the risk of Plasmodium vivax relapse in patients with normal glucose-6-phosphate dehydrogenase (G6PD) activity, according to the results of two phase 3, double-blind, randomized controlled trials.

Courtesy NIAID

Findings from both studies were published in two separate reports in the New England Journal of Medicine.

In the first study, the Dose and Efficacy Trial Evaluating Chloroquine and Tafenoquine in Vivax Elimination (DETECTIVE), the risk of P. vivax recurrence was approximately 70% lower with tafenoquine versus placebo, wrote Marcus V.G. Lacerda, MD, of Fundação de Medicina Tropical Doutor Heitor Vieira Dourado in Manaus, Brazil, and his colleagues.

The study included 522 patients with confirmed P. vivax infection from Peru, Brazil, Ethiopia, Cambodia, Thailand, and the Philippines. Patients received 3 days of chloroquine therapy (600 mg on days 1 and 2, and 300 mg on day 3) and were randomly assigned on a 2:1:1 basis to receive a single 300-mg dose of tafenoquine on day 1 or 2, primaquine once daily for 14 days, or placebo.

Since primaquine and tafenoquine can cause clinically significant hemolysis in individuals with G6PD deficiency, the study included only patients with normal G6PD activity.

In the second study, Global Assessment of Tafenoquine Hemolytic Risk (GATHER), Alejandro Llanos-Cuentas, MD, of Universidad Peruana Cayetano Heredia, Lima, Peru, and his colleagues enrolled 251 patients with confirmed P. vivax infection from Peru, Brazil, Columbia, Vietnam, and Thailand. They attempted to recruit women with moderate G6PD levels, but only one participant met this criterion – all others had normal G6PD activity.

Patients received 3-day course of chloroquine and were randomly assigned on a 2:1 basis to either tafenoquine or primaquine at the same doses as in the DETECTIVE trial.

At 6 months, 2% (95% CI, 1%-6%) of tafenoquine recipients and 1% (95% CI, 0.2%-6%) of primaquine recipients had decreased hemoglobin levels, but none consequently needed treatment. The medications also caused a similar degree and time course of hemoglobin decrease, the investigators noted.

A meta-analysis of GATHER and DETECTIVE confirmed that tafenoquine more often led to a decreased hemoglobin level (4% versus 1.5% with primaquine). Tafenoquine also did not meet prespecified criteria for noninferiority compared with primaquine, with respective 6-month recurrence rates of 67% versus 73%.

However, GATHER deployed “extensive” support to help patients adhere to the 15-day primaquine course, Dr. Llanos-Cuentas and his colleagues wrote. “Without such interventions, adherence to primaquine has been reported to be as low as 24% in Southeast Asia, with a corresponding attenuation of efficacy.”

GlaxoSmithKline and Medicines for Malaria Venture funded both studies, and GSK funded and conducted the meta-analysis. Dr. Llanos-Cuentas and several coinvestigators reported ties to GSK, Medicines for Malaria Venture, the Gambia, and LSTMH. Dr. Lacerda reported having no conflicts of interest.

SOURCES: Lacerda MVG et al. N Engl J Med 2019;380:215-28, and Llanos-Cuentas A et al. N Engl J Med 2019;380:229-41.

Single-dose tafenoquine therapy safely reduces the risk of Plasmodium vivax relapse in patients with normal glucose-6-phosphate dehydrogenase (G6PD) activity, according to the results of two phase 3, double-blind, randomized controlled trials.

Courtesy NIAID

Findings from both studies were published in two separate reports in the New England Journal of Medicine.

In the first study, the Dose and Efficacy Trial Evaluating Chloroquine and Tafenoquine in Vivax Elimination (DETECTIVE), the risk of P. vivax recurrence was approximately 70% lower with tafenoquine versus placebo, wrote Marcus V.G. Lacerda, MD, of Fundação de Medicina Tropical Doutor Heitor Vieira Dourado in Manaus, Brazil, and his colleagues.

The study included 522 patients with confirmed P. vivax infection from Peru, Brazil, Ethiopia, Cambodia, Thailand, and the Philippines. Patients received 3 days of chloroquine therapy (600 mg on days 1 and 2, and 300 mg on day 3) and were randomly assigned on a 2:1:1 basis to receive a single 300-mg dose of tafenoquine on day 1 or 2, primaquine once daily for 14 days, or placebo.

Since primaquine and tafenoquine can cause clinically significant hemolysis in individuals with G6PD deficiency, the study included only patients with normal G6PD activity.

In the second study, Global Assessment of Tafenoquine Hemolytic Risk (GATHER), Alejandro Llanos-Cuentas, MD, of Universidad Peruana Cayetano Heredia, Lima, Peru, and his colleagues enrolled 251 patients with confirmed P. vivax infection from Peru, Brazil, Columbia, Vietnam, and Thailand. They attempted to recruit women with moderate G6PD levels, but only one participant met this criterion – all others had normal G6PD activity.

Patients received 3-day course of chloroquine and were randomly assigned on a 2:1 basis to either tafenoquine or primaquine at the same doses as in the DETECTIVE trial.

At 6 months, 2% (95% CI, 1%-6%) of tafenoquine recipients and 1% (95% CI, 0.2%-6%) of primaquine recipients had decreased hemoglobin levels, but none consequently needed treatment. The medications also caused a similar degree and time course of hemoglobin decrease, the investigators noted.

A meta-analysis of GATHER and DETECTIVE confirmed that tafenoquine more often led to a decreased hemoglobin level (4% versus 1.5% with primaquine). Tafenoquine also did not meet prespecified criteria for noninferiority compared with primaquine, with respective 6-month recurrence rates of 67% versus 73%.

However, GATHER deployed “extensive” support to help patients adhere to the 15-day primaquine course, Dr. Llanos-Cuentas and his colleagues wrote. “Without such interventions, adherence to primaquine has been reported to be as low as 24% in Southeast Asia, with a corresponding attenuation of efficacy.”

GlaxoSmithKline and Medicines for Malaria Venture funded both studies, and GSK funded and conducted the meta-analysis. Dr. Llanos-Cuentas and several coinvestigators reported ties to GSK, Medicines for Malaria Venture, the Gambia, and LSTMH. Dr. Lacerda reported having no conflicts of interest.

SOURCES: Lacerda MVG et al. N Engl J Med 2019;380:215-28, and Llanos-Cuentas A et al. N Engl J Med 2019;380:229-41.

Aplastic anemia is a rare hematologic disorder marked by pancytopenia and a hypocellular marrow. Aplastic anemia results from either inherited or acquired causes, and the treatment approach varies significantly between the 2 causes. This article reviews the treatment of inherited and acquired forms of aplastic anemia. The approach to evaluation and diagnosis of aplastic anemia is reviewed in a separate article.

Inherited Aplastic Anemia

First-line treatment options for patients with inherited marrow failure syndromes (IMFS) are androgen therapy and hematopoietic stem cell transplant (HSCT). When evaluating patients for HSCT, it is critical to identify the presence of an IMFS, as the risk and mortality associated with the conditioning regimen, stem cell source, graft-versus-host disease (GVHD), and secondary malignancies differ between patients with IMFS and those with acquired marrow failure syndromes or hematologic malignancies.

Potential sibling donors need to be screened for donor candidacy as well as for the inherited defect.¹ Among patients with Fanconi anemia or a telomere biology disorder, the stem cell source must be considered, with bone marrow demonstrating lower rates of acute GVHD than a peripheral blood stem cell source.^2-4 In IMFS patients, the donor cell type may affect the choice of conditioning regimen.^5,6 Reduced-intensity conditioning in lieu of myeloablative conditioning without total body irradiation has proved feasible in patients with Fanconi anemia, and is associated with a reduced risk of secondary malignancies.^5,6 Incorporation of fludarabine in the conditioning regimen of patients without a matched sibling donor is associated with superior engraftment and survival^2,5,7 compared to cyclophosphamide conditioning, which was historically used in matched related donors.^6,8 The addition of fludarabine appears to be especially beneficial in older patients, in whom its use is associated with lower rates of graft failure, likely due to increased immunosuppression at the time of engraftment.^7,9 Fludarabine has also been incorporated into conditioning regimens for patients with a telomere biology disorder, but outcomes data is limited.⁵

For patients presenting with acute myeloid leukemia (AML) or a high-risk myelodysplastic syndrome (MDS) who are subsequently diagnosed with an IMFS, treatment can be more complex, as these patients are at high risk for toxicity from standard chemotherapy. Limited data suggests that induction therapy and transplantation are feasible in this group of patients, and this approach is associated with increased overall survival (OS) despite lower OS rates than those of IMFS patients who present prior to the development of MDS or AML.^10,11 Further work is needed to determine the optimal induction regimen that balances the risks of treatment-related mortality and complications associated with conditioning regimens, risk of relapse, and risk of secondary malignancies, especially in the cohort of patients diagnosed at an older age.

Acquired Aplastic Anemia

Supportive Care

While the workup and treatment plan is being established, attention should be directed at supportive care for prevention of complications. The most common complications leading to death in patients with significant pancytopenia and neutropenia are opportunistic infections and hemorrhagic complications.¹²

Transfusion support is critical to avoid symptomatic anemia and hemorrhagic complications related to thrombocytopenia, which typically occur with platelet counts lower than 10,000 cells/µL. However, transfusion carries the risk of alloimmunization (which may persist for years following transfusion) and transfusion-related graft versus host disease (trGVHD), and thus use of transfusion should be minimized when possible.^13,14 Transfusion support is often required to prevent complications associated with thrombocytopenia and anemia; all blood products given to patients with aplastic anemia should be irradiated and leukoreduced to reduce the risk of both alloimmunization and trGVHD. Guidelines from the British Society for Haematology recommend routine screening for Rh and Kell antibodies to reduce the risk of alloimmunization.¹⁵ Infectious complications remain a common cause of morbidity and mortality in patients with aplastic anemia who have prolonged neutropenia (defined as an absolute neutrophil count [ANC] < 500 cells/µL).^16-19 Therefore, patients should receive broad-spectrum antibiotics with antipseudomonal coverage. In a study by Tichelli and colleagues evaluating the role of granulocyte-colony stimulating factor (G-CSF) in patients with SAA receiving immunosuppressive therapy, 55% of all patient deaths were secondary to infection.²⁰ There was no OS benefit seen in patients who received G-CSF, though a significantly lower rate of infection was observed in the G-CSF arm compared to those not receiving G-CSF (56% versus 81%, P = 0.006).This difference was largely driven by a decrease in infectious episodes in patients with very severe aplastic anemia (VSAA) treated with G-CSF as compared to those who did not receive this therapy (22% versus 48%, P = 0.014).²⁰

Angio-invasive pulmonary aspergillosis and Zygomycetes (eg, Rhizopus, Mucor species) remain major causes of mortality related to opportunistic mycotic infections in patients with aplastic anemia.¹⁸ The infectious risk is directly related to the duration and severity of neutropenia, with one study demonstrating a significant increase in risk in AML patients with neutropenia lasting longer than 3 weeks.²¹ Invasive fungal infections carry a high mortality in patients with severe neutropenia, though due to earlier recognition and empiric antifungal therapy with extended-spectrum azoles, overall mortality secondary to invasive fungal infections is declining.^19,22

While neutropenia related to cytotoxic chemotherapy is commonly associated with gram-negative bacteria due to disruption of mucosal barriers, patients with aplastic anemia have an increased incidence of gram-positive bacteremia with staphylococcal species compared to other neutropenic populations.^18,19 This appears to be changing with time. Valdez and colleagues demonstrated a decrease in prevalence of coagulase-negative staphylococcal infections, increased prevalence of gram-positive bacilli bacteremia, and no change in prevalence of gram-negative bacteremia in patients with aplastic anemia treated between 1989 and 2008.²² Gram-negative bacteremia caused by Stenotrophomonas maltophila, Escherichia coli, Klebsiella pneumoniae, Citrobacter, and Proteus has also been reported.¹⁹ Despite a lack of clinical trials investigating the role of antifungal and antibacterial prophylaxis for patients with aplastic anemia, most centers initiate antifungal prophylaxis in patients with severe aplastic anema (SAA) or VSAA with an anti-mold agent such as voriconazole or posaconazole (which has the additional benefit compared to voriconazole of covering Mucor species).^17,23 This is especially true for patients who have received ATG or undergone HSCT. For antimicrobial prophylaxis, a fluoroquinolone antibiotic with a spectrum of activity against Pseudomonas should be considered for patients with an ANC < 500 cells/µL.¹⁷ Acyclovir or valacyclovir prophylaxis is recommended for varicella-zoster virus and herpes simplex virus. Cytomegalovirus reactivation is minimal in patients with aplastic anemia, unless multiple courses of ATG are used.

Iron overload is another complication the provider must be aware of in the setting of increased transfusions in aplastic anemia patients. Lee and colleagues demonstrated that iron chelation therapy using deferasirox is effective at reducing serum ferritin levels in patients with aplastic anemia (median ferritin level: 3254 ng/mL prior to therapy, 1854 ng/mL following), and is associated with no serious adverse events (most common adverse events included nausea, diarrhea, vomiting, and rash).²⁴ Approximately 25% of patients in this trial demonstrated an increase in creatinine, with patients taking concomitant cyclosporine more affected than those on chelation therapy alone.²⁴ For patients following HSCT or with improved hematopoiesis following immunosuppressive therapy, phlebotomy can be used to treat iron overload in lieu of chelation therapy.¹⁵

Approach to Therapy

The main treatment options for SAA and VSAA include allogeneic bone marrow transplant and immunosuppression. The deciding factors as to which treatment is best initially depends on the availability of HLA-matched related donors and age (Figure 1 and Figure 2). Survival is decreased in patients with SAA or VSAA who delay initiation of therapy, and therefore prompt referral for HLA typing and evaluation for bone marrow transplant is a very important first step in managing aplastic anemia.

Matched Sibling Donor Transplant

Current standards of care recommend HLA-matched sibling donor transplant for patients with SAA or VSAA who are younger than 50 years of age, with the caveat that integration of fludarabine and reduced cyclophosphamide dosing along with ATG shows the best overall outcomes. Locasciulli and colleagues examined outcomes in patients given either immunosuppressive therapy or sibling HSCT between 1991-1996 and 1997-2002, respectively, and found that sibling HSCT was associated with a superior 10-year OS compared to immunosuppressive therapy (73% versus 68%).²⁵ Interestingly in this study, there was no OS improvement seen with immunosuppressive therapy alone (69% versus 73%) between the 2 time periods, despite increased OS in both sibling HSCT (74% and 80%) and matched unrelated donor HSCT (38% and 65%).²⁵ Though total body irradiation has been used in the past, it is typically not included in current conditioning regimens for matched related donor transplants.²⁶

Current conditioning regimens typically use a combination of cyclophosphamide and ATG^27,28 with or without fludarabine. Fludarabine-based conditioning regimens have shown promise in patients undergoing sibling HSCT. Maury and colleagues evaluated the role of fludarabine in addition to low-dose cyclophosphamide and ATG compared to cyclophosphamide alone or in combination with ATG in patients over age 30 undergoing sibling HSCT.⁹ There was a nonsignificant improvement in 5-year OS in the fludarabine arm compared to controls (77% ± 8% versus 60% ± 3%, P = 0.14) in the pooled analysis, but when adjusted for age the fludarabine arm had a significantly lower relative risk (RR) of death (RR, 0.44; P = 0.04) compared to the control arm. Shin et al reported outcomes with fludarabine/cyclophosphamide/ATG, with excellent overall outcomes and no difference in patients older or younger than 40 years.²⁹ In addition, Kim et al evaluated their experience with patients older than 40 years of age receiving matched related donors, finding comparable outcomes in those aged 41 to 50 years compared to younger patients. Outcomes did decline in those over the age of 50 years.³⁰ Long-term data for matched related donor transplant for aplastic anemia shows excellent long-term outcomes, with minimal chronic GVHD and good performance status.³¹ Hence, these factors support the role of matched related donor transplant as the initial treatment in SAA and VSAA.

Regarding the role of transplant for patients who lack a matched related donor, a growing body of literature demonstrating identical outcomes between matched related and matched unrelated donor (MUD) transplants for pediatric patients^32,33 supports recent recommendations for upfront unrelated donor transplantation for aplastic anemia.^34,35

Immunosuppressive Therapy

For patients without an HLA-matched sibling donor or those who are older than 50 years of age, immunosuppressive therapy is the first-line therapy. ATG and cyclosporine A are the treatments of choice.³⁶ The potential effectiveness of immunosuppressive therapy in treating aplastic anemia was initially observed in patients in whom autologous transplant failed but who still experienced hematopoietic reconstitution despite the failed graft; this observation led to the hypothesis that the conditioning regimen may have an effect on hematopoiesis.^16,36,37

Anti-thymocyte globulin. Immunosuppressive therapy with ATG has been used for the treatment of aplastic anemia since the 1980s.³⁸ Historically, rabbit ATG had been used, but a 2011 study of horse ATG demonstrated superior hematological response at 6 months compared to rabbit ATG (68% versus 37%).¹⁶ Superior survival was also seen with horse ATG compared to rabbit ATG (3-year OS: 96% versus 76%). Due to these results, horse ATG is preferred over rabbit ATG. ATG should be used in combination with cyclosporine A to optimize outcomes.

Cyclosporine A. Early studies also demonstrated the efficacy of cyclosporine A in the treatment of aplastic anemia, with response rates equivalent to that of ATG monotherapy.³⁹ Recent publications still note the efficacy of cyclosporine A in the treatment of aplastic anemia. Its role as an affordable option for single-agent therapy in developing countries is intriguing.³⁹

The combination of the ATG and cyclosporine A was proven superior to either agent alone in a study by Frickhofen et al.³⁷ In this study patients were randomly assigned to a control arm that received ATG plus methylprednisolone or to an arm that received ATG plus cyclosporine A and methylprednisolone. At 6 months, 70% of patients in the cyclosporine A arm had a complete remission (CR) or partial remission compared to 46% in the control arm.⁴⁰ Further work confirmed the long-term efficacy of this regimen, reporting a 7-year OS of 55%.⁴¹ Among a pediatric population, immunosuppressive therapy was associated with an 83% 10-year OS.⁴²

It is recommended that patients remain on cyclosporine therapy for a minimum of 6 months, after which a gradual taper may be considered, although there is variation among practitioners, with some continuing immunosuppressive therapy for a minimum of 12 months due to a proportion of patients being cyclosporine dependent.^42,43 A study found that within a population of patients who responded to immunosuppressive therapy, 18% became cyclosporine dependent.⁴² The median duration of cyclosporine A treatment at full dose was 12 months, with tapering completed over a median of 19 months after patients had been in a stable CR for a minimum of 3 months. Relapse occurred more often when patients were tapered quickly (decrease ≥ 0.8 mg/kg/month) compared to slowly (0.4-0.7 mg/kg/month) or very slowly (< 0.3 mg/kg/month).

Immunosuppressive therapy plus eltrombopag. Townsley and colleagues recently investigated incorporating the use of the thrombopoietin receptor agonist eltrombopag with immunosuppressive therapy as first-line therapy in aplastic anemia.⁴⁴ When given at a dose of 150 mg daily in patients aged 12 years and older or 75 mg daily in patients younger than 12 years, in conjunction with cyclosporine A and ATG, patients demonstrated markedly improved hematological response compared to historical treatment with standard immunosuppressive therapy alone.⁴⁴ In the patient cohort administered eltrombopag starting on day 1 and continuing for 6 months, the complete response rate was 58%. Eltrombopag led to improvement in all cell lines among all treatment subgroups, and OS (censored for patients who proceeded to transplant) was 99% at 2 years.⁴⁵ Overall, toxicities associated with this therapy were low, with liver enzyme elevations most commonly observed.⁴⁴ Recently, a phase 2 trial of immunosuppressive therapy with or without eltrombopag was reported. Of the 38 patients enrolled, overall response, complete response, and time to response were not statistically different.⁴⁶ With this recent finding, the role of eltrombopag in addition to immunosuppressive therapy is not clearly defined, and further studies are warranted.

OS for patients who do not respond to immunosuppressive therapy is approximately 57% at 5 years, largely due to improved supportive measures among this patient population.^4,22 Therefore, it is important to recognize those patients who have a low chance of response so that second-line therapy can be pursued to improve outcomes.

Matched Unrelated Donor Transplant

For patients with refractory disease following immunosuppressive therapy who lack a matched sibling donor, MUD HSCT is considered standard therapy given the marked improvement in overall outcomes with modulating conditioning regimens and high-resolution HLA typing. A European Society for Blood and Marrow Transplantation analysis comparing matched sibling HSCT to MUD HSCT noted significantly higher rates of acute grade II-IV and grade III-V GVHD (grade II-IV 13% versus 25%, grade III-IV 5% versus 10%) among patients undergoing MUD transplant.⁴⁷ Chronic GVHD rates were 14% in the sibling group, as compared to 26% in the MUD group. Additional benefits seen in this analysis included improved survival when transplanted under age 20 years (84% versus 72%), when transplanted within 6 months of diagnosis (85% versus 72%), the use of ATG in the conditioning regimen (81% versus 73%), and when the donor and recipient were cytomegalovirus-negative compared to other combinations (82% versus 76%).⁴⁷ Interestingly, this study demonstrated that OS was not significantly increased when using a sibling HSCT compared to a MUD HSCT, likely as a result of improved understanding of conditioning regimens, GVHD prophylaxis, and supportive care.

Additional studies of MUD HSCT have shown outcomes similar to those seen in sibling HSCT.^4,43 A French study found a significant increase in survival in patients undergoing MUD HSCT compared to historical cohorts (2000-2005: OS 52%; 2006-2012: OS 74%).³³ The majority of patients underwent conditioning with cyclophosphamide or a combination of busulfan and cyclophosphamide, with or without fludarabine; 81% of patients included underwent in vivo T-cell depletion, and a bone marrow donor source was utilized. OS was significantly lower in patients over age 30 years undergoing MUD HSCT (57%) compared to those under age 30 years (70%). Improved OS was also seen when patients underwent transplant within 1 year of diagnosis and when a 10/10 matched donor (compared to a 9/10 mismatched donor) was utilized.⁴ A 2015 study investigated the role of MUD HSCT as frontline therapy instead of immunosuppressive therapy in patients without a matched sibling donor.³³ The 2-year OS was 96% in the MUD HSCT cohort compared to 91%, 94%, and 74% in historical cohorts of sibling HSCT, frontline immunosuppressive therapy, and second-line MUD HSCT following failed immunosuppressive therapy, respectively. Additionally, event-free survival in the MUD HSCT cohort (defined by the authors as death, lack of response, relapse, occurrence of clonal evolution/clinical paroxysmal nocturnal hemoglobinuria, malignancies developing over follow‐up, and transplant for patients receiving immunosuppressive therapy frontline) was similar compared to sibling HSCT and superior to frontline immunosuppressive therapy and second-line MUD HSCT. Furthermore, Samarasinghe et al highlighted the importance of in vivo T-cell depletion with either ATG or alemtuzumab (anti-CD52 monoclonal antibody) in the prevention of acute and chronic GVHD in both sibling HSCT and MUD HSCT.⁴⁸

With continued improvement of less toxic and more immunomodulating conditioning regimens, utilization of bone marrow as a donor cell source, in vivo T-cell depletion, and use of GVHD and antimicrobial prophylaxis, more clinical evidence supports elevating MUD HSCT in the treatment plan for patients without a matched sibling donor.⁴⁹ However, there is still a large population of patients without matched sibling or unrelated donor options. In an effort to expand the transplant pool and thus avoid clonal hematopoiesis, clinically significant paroxysmal nocturnal hemoglobinuria, and relapsed aplastic anemia, more work continues to recognize the expanding role of alternative donor transplants (cord blood and haploidentical) as another viable treatment strategy for aplastic anemia after immunosuppressive therapy failure.⁵⁰

Summary

Aplastic anemia is a rare but potentially life-threatening disorder characterized by pancytopenia and a marked reduction in the hematopoietic stem cell compartment. Treatment should be instituted as soon as the dignosis of aplastic anemia is established. Treatment outcomes are excellent with modern supportive care and the current approach to allogeneic transplantation, and therefore referral to a bone marrow transplant program to evaluate for early transplantation is the new standard of care.

Aplastic anemia is a rare hematologic disorder marked by pancytopenia and a hypocellular marrow. Aplastic anemia results from either inherited or acquired causes, and the treatment approach varies significantly between the 2 causes. This article reviews the treatment of inherited and acquired forms of aplastic anemia. The approach to evaluation and diagnosis of aplastic anemia is reviewed in a separate article.

Inherited Aplastic Anemia

First-line treatment options for patients with inherited marrow failure syndromes (IMFS) are androgen therapy and hematopoietic stem cell transplant (HSCT). When evaluating patients for HSCT, it is critical to identify the presence of an IMFS, as the risk and mortality associated with the conditioning regimen, stem cell source, graft-versus-host disease (GVHD), and secondary malignancies differ between patients with IMFS and those with acquired marrow failure syndromes or hematologic malignancies.

Potential sibling donors need to be screened for donor candidacy as well as for the inherited defect.¹ Among patients with Fanconi anemia or a telomere biology disorder, the stem cell source must be considered, with bone marrow demonstrating lower rates of acute GVHD than a peripheral blood stem cell source.^2-4 In IMFS patients, the donor cell type may affect the choice of conditioning regimen.^5,6 Reduced-intensity conditioning in lieu of myeloablative conditioning without total body irradiation has proved feasible in patients with Fanconi anemia, and is associated with a reduced risk of secondary malignancies.^5,6 Incorporation of fludarabine in the conditioning regimen of patients without a matched sibling donor is associated with superior engraftment and survival^2,5,7 compared to cyclophosphamide conditioning, which was historically used in matched related donors.^6,8 The addition of fludarabine appears to be especially beneficial in older patients, in whom its use is associated with lower rates of graft failure, likely due to increased immunosuppression at the time of engraftment.^7,9 Fludarabine has also been incorporated into conditioning regimens for patients with a telomere biology disorder, but outcomes data is limited.⁵

For patients presenting with acute myeloid leukemia (AML) or a high-risk myelodysplastic syndrome (MDS) who are subsequently diagnosed with an IMFS, treatment can be more complex, as these patients are at high risk for toxicity from standard chemotherapy. Limited data suggests that induction therapy and transplantation are feasible in this group of patients, and this approach is associated with increased overall survival (OS) despite lower OS rates than those of IMFS patients who present prior to the development of MDS or AML.^10,11 Further work is needed to determine the optimal induction regimen that balances the risks of treatment-related mortality and complications associated with conditioning regimens, risk of relapse, and risk of secondary malignancies, especially in the cohort of patients diagnosed at an older age.

Acquired Aplastic Anemia

Supportive Care

While the workup and treatment plan is being established, attention should be directed at supportive care for prevention of complications. The most common complications leading to death in patients with significant pancytopenia and neutropenia are opportunistic infections and hemorrhagic complications.¹²

Transfusion support is critical to avoid symptomatic anemia and hemorrhagic complications related to thrombocytopenia, which typically occur with platelet counts lower than 10,000 cells/µL. However, transfusion carries the risk of alloimmunization (which may persist for years following transfusion) and transfusion-related graft versus host disease (trGVHD), and thus use of transfusion should be minimized when possible.^13,14 Transfusion support is often required to prevent complications associated with thrombocytopenia and anemia; all blood products given to patients with aplastic anemia should be irradiated and leukoreduced to reduce the risk of both alloimmunization and trGVHD. Guidelines from the British Society for Haematology recommend routine screening for Rh and Kell antibodies to reduce the risk of alloimmunization.¹⁵ Infectious complications remain a common cause of morbidity and mortality in patients with aplastic anemia who have prolonged neutropenia (defined as an absolute neutrophil count [ANC] < 500 cells/µL).^16-19 Therefore, patients should receive broad-spectrum antibiotics with antipseudomonal coverage. In a study by Tichelli and colleagues evaluating the role of granulocyte-colony stimulating factor (G-CSF) in patients with SAA receiving immunosuppressive therapy, 55% of all patient deaths were secondary to infection.²⁰ There was no OS benefit seen in patients who received G-CSF, though a significantly lower rate of infection was observed in the G-CSF arm compared to those not receiving G-CSF (56% versus 81%, P = 0.006).This difference was largely driven by a decrease in infectious episodes in patients with very severe aplastic anemia (VSAA) treated with G-CSF as compared to those who did not receive this therapy (22% versus 48%, P = 0.014).²⁰

Angio-invasive pulmonary aspergillosis and Zygomycetes (eg, Rhizopus, Mucor species) remain major causes of mortality related to opportunistic mycotic infections in patients with aplastic anemia.¹⁸ The infectious risk is directly related to the duration and severity of neutropenia, with one study demonstrating a significant increase in risk in AML patients with neutropenia lasting longer than 3 weeks.²¹ Invasive fungal infections carry a high mortality in patients with severe neutropenia, though due to earlier recognition and empiric antifungal therapy with extended-spectrum azoles, overall mortality secondary to invasive fungal infections is declining.^19,22

While neutropenia related to cytotoxic chemotherapy is commonly associated with gram-negative bacteria due to disruption of mucosal barriers, patients with aplastic anemia have an increased incidence of gram-positive bacteremia with staphylococcal species compared to other neutropenic populations.^18,19 This appears to be changing with time. Valdez and colleagues demonstrated a decrease in prevalence of coagulase-negative staphylococcal infections, increased prevalence of gram-positive bacilli bacteremia, and no change in prevalence of gram-negative bacteremia in patients with aplastic anemia treated between 1989 and 2008.²² Gram-negative bacteremia caused by Stenotrophomonas maltophila, Escherichia coli, Klebsiella pneumoniae, Citrobacter, and Proteus has also been reported.¹⁹ Despite a lack of clinical trials investigating the role of antifungal and antibacterial prophylaxis for patients with aplastic anemia, most centers initiate antifungal prophylaxis in patients with severe aplastic anema (SAA) or VSAA with an anti-mold agent such as voriconazole or posaconazole (which has the additional benefit compared to voriconazole of covering Mucor species).^17,23 This is especially true for patients who have received ATG or undergone HSCT. For antimicrobial prophylaxis, a fluoroquinolone antibiotic with a spectrum of activity against Pseudomonas should be considered for patients with an ANC < 500 cells/µL.¹⁷ Acyclovir or valacyclovir prophylaxis is recommended for varicella-zoster virus and herpes simplex virus. Cytomegalovirus reactivation is minimal in patients with aplastic anemia, unless multiple courses of ATG are used.

Iron overload is another complication the provider must be aware of in the setting of increased transfusions in aplastic anemia patients. Lee and colleagues demonstrated that iron chelation therapy using deferasirox is effective at reducing serum ferritin levels in patients with aplastic anemia (median ferritin level: 3254 ng/mL prior to therapy, 1854 ng/mL following), and is associated with no serious adverse events (most common adverse events included nausea, diarrhea, vomiting, and rash).²⁴ Approximately 25% of patients in this trial demonstrated an increase in creatinine, with patients taking concomitant cyclosporine more affected than those on chelation therapy alone.²⁴ For patients following HSCT or with improved hematopoiesis following immunosuppressive therapy, phlebotomy can be used to treat iron overload in lieu of chelation therapy.¹⁵

Approach to Therapy

The main treatment options for SAA and VSAA include allogeneic bone marrow transplant and immunosuppression. The deciding factors as to which treatment is best initially depends on the availability of HLA-matched related donors and age (Figure 1 and Figure 2). Survival is decreased in patients with SAA or VSAA who delay initiation of therapy, and therefore prompt referral for HLA typing and evaluation for bone marrow transplant is a very important first step in managing aplastic anemia.

Matched Sibling Donor Transplant

Current standards of care recommend HLA-matched sibling donor transplant for patients with SAA or VSAA who are younger than 50 years of age, with the caveat that integration of fludarabine and reduced cyclophosphamide dosing along with ATG shows the best overall outcomes. Locasciulli and colleagues examined outcomes in patients given either immunosuppressive therapy or sibling HSCT between 1991-1996 and 1997-2002, respectively, and found that sibling HSCT was associated with a superior 10-year OS compared to immunosuppressive therapy (73% versus 68%).²⁵ Interestingly in this study, there was no OS improvement seen with immunosuppressive therapy alone (69% versus 73%) between the 2 time periods, despite increased OS in both sibling HSCT (74% and 80%) and matched unrelated donor HSCT (38% and 65%).²⁵ Though total body irradiation has been used in the past, it is typically not included in current conditioning regimens for matched related donor transplants.²⁶

Current conditioning regimens typically use a combination of cyclophosphamide and ATG^27,28 with or without fludarabine. Fludarabine-based conditioning regimens have shown promise in patients undergoing sibling HSCT. Maury and colleagues evaluated the role of fludarabine in addition to low-dose cyclophosphamide and ATG compared to cyclophosphamide alone or in combination with ATG in patients over age 30 undergoing sibling HSCT.⁹ There was a nonsignificant improvement in 5-year OS in the fludarabine arm compared to controls (77% ± 8% versus 60% ± 3%, P = 0.14) in the pooled analysis, but when adjusted for age the fludarabine arm had a significantly lower relative risk (RR) of death (RR, 0.44; P = 0.04) compared to the control arm. Shin et al reported outcomes with fludarabine/cyclophosphamide/ATG, with excellent overall outcomes and no difference in patients older or younger than 40 years.²⁹ In addition, Kim et al evaluated their experience with patients older than 40 years of age receiving matched related donors, finding comparable outcomes in those aged 41 to 50 years compared to younger patients. Outcomes did decline in those over the age of 50 years.³⁰ Long-term data for matched related donor transplant for aplastic anemia shows excellent long-term outcomes, with minimal chronic GVHD and good performance status.³¹ Hence, these factors support the role of matched related donor transplant as the initial treatment in SAA and VSAA.

Regarding the role of transplant for patients who lack a matched related donor, a growing body of literature demonstrating identical outcomes between matched related and matched unrelated donor (MUD) transplants for pediatric patients^32,33 supports recent recommendations for upfront unrelated donor transplantation for aplastic anemia.^34,35

Immunosuppressive Therapy

For patients without an HLA-matched sibling donor or those who are older than 50 years of age, immunosuppressive therapy is the first-line therapy. ATG and cyclosporine A are the treatments of choice.³⁶ The potential effectiveness of immunosuppressive therapy in treating aplastic anemia was initially observed in patients in whom autologous transplant failed but who still experienced hematopoietic reconstitution despite the failed graft; this observation led to the hypothesis that the conditioning regimen may have an effect on hematopoiesis.^16,36,37

Anti-thymocyte globulin. Immunosuppressive therapy with ATG has been used for the treatment of aplastic anemia since the 1980s.³⁸ Historically, rabbit ATG had been used, but a 2011 study of horse ATG demonstrated superior hematological response at 6 months compared to rabbit ATG (68% versus 37%).¹⁶ Superior survival was also seen with horse ATG compared to rabbit ATG (3-year OS: 96% versus 76%). Due to these results, horse ATG is preferred over rabbit ATG. ATG should be used in combination with cyclosporine A to optimize outcomes.

Cyclosporine A. Early studies also demonstrated the efficacy of cyclosporine A in the treatment of aplastic anemia, with response rates equivalent to that of ATG monotherapy.³⁹ Recent publications still note the efficacy of cyclosporine A in the treatment of aplastic anemia. Its role as an affordable option for single-agent therapy in developing countries is intriguing.³⁹

The combination of the ATG and cyclosporine A was proven superior to either agent alone in a study by Frickhofen et al.³⁷ In this study patients were randomly assigned to a control arm that received ATG plus methylprednisolone or to an arm that received ATG plus cyclosporine A and methylprednisolone. At 6 months, 70% of patients in the cyclosporine A arm had a complete remission (CR) or partial remission compared to 46% in the control arm.⁴⁰ Further work confirmed the long-term efficacy of this regimen, reporting a 7-year OS of 55%.⁴¹ Among a pediatric population, immunosuppressive therapy was associated with an 83% 10-year OS.⁴²

It is recommended that patients remain on cyclosporine therapy for a minimum of 6 months, after which a gradual taper may be considered, although there is variation among practitioners, with some continuing immunosuppressive therapy for a minimum of 12 months due to a proportion of patients being cyclosporine dependent.^42,43 A study found that within a population of patients who responded to immunosuppressive therapy, 18% became cyclosporine dependent.⁴² The median duration of cyclosporine A treatment at full dose was 12 months, with tapering completed over a median of 19 months after patients had been in a stable CR for a minimum of 3 months. Relapse occurred more often when patients were tapered quickly (decrease ≥ 0.8 mg/kg/month) compared to slowly (0.4-0.7 mg/kg/month) or very slowly (< 0.3 mg/kg/month).

Immunosuppressive therapy plus eltrombopag. Townsley and colleagues recently investigated incorporating the use of the thrombopoietin receptor agonist eltrombopag with immunosuppressive therapy as first-line therapy in aplastic anemia.⁴⁴ When given at a dose of 150 mg daily in patients aged 12 years and older or 75 mg daily in patients younger than 12 years, in conjunction with cyclosporine A and ATG, patients demonstrated markedly improved hematological response compared to historical treatment with standard immunosuppressive therapy alone.⁴⁴ In the patient cohort administered eltrombopag starting on day 1 and continuing for 6 months, the complete response rate was 58%. Eltrombopag led to improvement in all cell lines among all treatment subgroups, and OS (censored for patients who proceeded to transplant) was 99% at 2 years.⁴⁵ Overall, toxicities associated with this therapy were low, with liver enzyme elevations most commonly observed.⁴⁴ Recently, a phase 2 trial of immunosuppressive therapy with or without eltrombopag was reported. Of the 38 patients enrolled, overall response, complete response, and time to response were not statistically different.⁴⁶ With this recent finding, the role of eltrombopag in addition to immunosuppressive therapy is not clearly defined, and further studies are warranted.

OS for patients who do not respond to immunosuppressive therapy is approximately 57% at 5 years, largely due to improved supportive measures among this patient population.^4,22 Therefore, it is important to recognize those patients who have a low chance of response so that second-line therapy can be pursued to improve outcomes.

Matched Unrelated Donor Transplant

For patients with refractory disease following immunosuppressive therapy who lack a matched sibling donor, MUD HSCT is considered standard therapy given the marked improvement in overall outcomes with modulating conditioning regimens and high-resolution HLA typing. A European Society for Blood and Marrow Transplantation analysis comparing matched sibling HSCT to MUD HSCT noted significantly higher rates of acute grade II-IV and grade III-V GVHD (grade II-IV 13% versus 25%, grade III-IV 5% versus 10%) among patients undergoing MUD transplant.⁴⁷ Chronic GVHD rates were 14% in the sibling group, as compared to 26% in the MUD group. Additional benefits seen in this analysis included improved survival when transplanted under age 20 years (84% versus 72%), when transplanted within 6 months of diagnosis (85% versus 72%), the use of ATG in the conditioning regimen (81% versus 73%), and when the donor and recipient were cytomegalovirus-negative compared to other combinations (82% versus 76%).⁴⁷ Interestingly, this study demonstrated that OS was not significantly increased when using a sibling HSCT compared to a MUD HSCT, likely as a result of improved understanding of conditioning regimens, GVHD prophylaxis, and supportive care.

Additional studies of MUD HSCT have shown outcomes similar to those seen in sibling HSCT.^4,43 A French study found a significant increase in survival in patients undergoing MUD HSCT compared to historical cohorts (2000-2005: OS 52%; 2006-2012: OS 74%).³³ The majority of patients underwent conditioning with cyclophosphamide or a combination of busulfan and cyclophosphamide, with or without fludarabine; 81% of patients included underwent in vivo T-cell depletion, and a bone marrow donor source was utilized. OS was significantly lower in patients over age 30 years undergoing MUD HSCT (57%) compared to those under age 30 years (70%). Improved OS was also seen when patients underwent transplant within 1 year of diagnosis and when a 10/10 matched donor (compared to a 9/10 mismatched donor) was utilized.⁴ A 2015 study investigated the role of MUD HSCT as frontline therapy instead of immunosuppressive therapy in patients without a matched sibling donor.³³ The 2-year OS was 96% in the MUD HSCT cohort compared to 91%, 94%, and 74% in historical cohorts of sibling HSCT, frontline immunosuppressive therapy, and second-line MUD HSCT following failed immunosuppressive therapy, respectively. Additionally, event-free survival in the MUD HSCT cohort (defined by the authors as death, lack of response, relapse, occurrence of clonal evolution/clinical paroxysmal nocturnal hemoglobinuria, malignancies developing over follow‐up, and transplant for patients receiving immunosuppressive therapy frontline) was similar compared to sibling HSCT and superior to frontline immunosuppressive therapy and second-line MUD HSCT. Furthermore, Samarasinghe et al highlighted the importance of in vivo T-cell depletion with either ATG or alemtuzumab (anti-CD52 monoclonal antibody) in the prevention of acute and chronic GVHD in both sibling HSCT and MUD HSCT.⁴⁸

With continued improvement of less toxic and more immunomodulating conditioning regimens, utilization of bone marrow as a donor cell source, in vivo T-cell depletion, and use of GVHD and antimicrobial prophylaxis, more clinical evidence supports elevating MUD HSCT in the treatment plan for patients without a matched sibling donor.⁴⁹ However, there is still a large population of patients without matched sibling or unrelated donor options. In an effort to expand the transplant pool and thus avoid clonal hematopoiesis, clinically significant paroxysmal nocturnal hemoglobinuria, and relapsed aplastic anemia, more work continues to recognize the expanding role of alternative donor transplants (cord blood and haploidentical) as another viable treatment strategy for aplastic anemia after immunosuppressive therapy failure.⁵⁰

Summary

Aplastic anemia is a rare but potentially life-threatening disorder characterized by pancytopenia and a marked reduction in the hematopoietic stem cell compartment. Treatment should be instituted as soon as the dignosis of aplastic anemia is established. Treatment outcomes are excellent with modern supportive care and the current approach to allogeneic transplantation, and therefore referral to a bone marrow transplant program to evaluate for early transplantation is the new standard of care.

Aplastic anemia is a rare hematologic disorder marked by pancytopenia and a hypocellular marrow. Aplastic anemia results from either inherited or acquired causes, and the treatment approach varies significantly between the 2 causes. This article reviews the treatment of inherited and acquired forms of aplastic anemia. The approach to evaluation and diagnosis of aplastic anemia is reviewed in a separate article.

Inherited Aplastic Anemia

First-line treatment options for patients with inherited marrow failure syndromes (IMFS) are androgen therapy and hematopoietic stem cell transplant (HSCT). When evaluating patients for HSCT, it is critical to identify the presence of an IMFS, as the risk and mortality associated with the conditioning regimen, stem cell source, graft-versus-host disease (GVHD), and secondary malignancies differ between patients with IMFS and those with acquired marrow failure syndromes or hematologic malignancies.

Potential sibling donors need to be screened for donor candidacy as well as for the inherited defect.¹ Among patients with Fanconi anemia or a telomere biology disorder, the stem cell source must be considered, with bone marrow demonstrating lower rates of acute GVHD than a peripheral blood stem cell source.^2-4 In IMFS patients, the donor cell type may affect the choice of conditioning regimen.^5,6 Reduced-intensity conditioning in lieu of myeloablative conditioning without total body irradiation has proved feasible in patients with Fanconi anemia, and is associated with a reduced risk of secondary malignancies.^5,6 Incorporation of fludarabine in the conditioning regimen of patients without a matched sibling donor is associated with superior engraftment and survival^2,5,7 compared to cyclophosphamide conditioning, which was historically used in matched related donors.^6,8 The addition of fludarabine appears to be especially beneficial in older patients, in whom its use is associated with lower rates of graft failure, likely due to increased immunosuppression at the time of engraftment.^7,9 Fludarabine has also been incorporated into conditioning regimens for patients with a telomere biology disorder, but outcomes data is limited.⁵

For patients presenting with acute myeloid leukemia (AML) or a high-risk myelodysplastic syndrome (MDS) who are subsequently diagnosed with an IMFS, treatment can be more complex, as these patients are at high risk for toxicity from standard chemotherapy. Limited data suggests that induction therapy and transplantation are feasible in this group of patients, and this approach is associated with increased overall survival (OS) despite lower OS rates than those of IMFS patients who present prior to the development of MDS or AML.^10,11 Further work is needed to determine the optimal induction regimen that balances the risks of treatment-related mortality and complications associated with conditioning regimens, risk of relapse, and risk of secondary malignancies, especially in the cohort of patients diagnosed at an older age.

Acquired Aplastic Anemia

Supportive Care

While the workup and treatment plan is being established, attention should be directed at supportive care for prevention of complications. The most common complications leading to death in patients with significant pancytopenia and neutropenia are opportunistic infections and hemorrhagic complications.¹²

Transfusion support is critical to avoid symptomatic anemia and hemorrhagic complications related to thrombocytopenia, which typically occur with platelet counts lower than 10,000 cells/µL. However, transfusion carries the risk of alloimmunization (which may persist for years following transfusion) and transfusion-related graft versus host disease (trGVHD), and thus use of transfusion should be minimized when possible.^13,14 Transfusion support is often required to prevent complications associated with thrombocytopenia and anemia; all blood products given to patients with aplastic anemia should be irradiated and leukoreduced to reduce the risk of both alloimmunization and trGVHD. Guidelines from the British Society for Haematology recommend routine screening for Rh and Kell antibodies to reduce the risk of alloimmunization.¹⁵ Infectious complications remain a common cause of morbidity and mortality in patients with aplastic anemia who have prolonged neutropenia (defined as an absolute neutrophil count [ANC] < 500 cells/µL).^16-19 Therefore, patients should receive broad-spectrum antibiotics with antipseudomonal coverage. In a study by Tichelli and colleagues evaluating the role of granulocyte-colony stimulating factor (G-CSF) in patients with SAA receiving immunosuppressive therapy, 55% of all patient deaths were secondary to infection.²⁰ There was no OS benefit seen in patients who received G-CSF, though a significantly lower rate of infection was observed in the G-CSF arm compared to those not receiving G-CSF (56% versus 81%, P = 0.006).This difference was largely driven by a decrease in infectious episodes in patients with very severe aplastic anemia (VSAA) treated with G-CSF as compared to those who did not receive this therapy (22% versus 48%, P = 0.014).²⁰

Angio-invasive pulmonary aspergillosis and Zygomycetes (eg, Rhizopus, Mucor species) remain major causes of mortality related to opportunistic mycotic infections in patients with aplastic anemia.¹⁸ The infectious risk is directly related to the duration and severity of neutropenia, with one study demonstrating a significant increase in risk in AML patients with neutropenia lasting longer than 3 weeks.²¹ Invasive fungal infections carry a high mortality in patients with severe neutropenia, though due to earlier recognition and empiric antifungal therapy with extended-spectrum azoles, overall mortality secondary to invasive fungal infections is declining.^19,22

While neutropenia related to cytotoxic chemotherapy is commonly associated with gram-negative bacteria due to disruption of mucosal barriers, patients with aplastic anemia have an increased incidence of gram-positive bacteremia with staphylococcal species compared to other neutropenic populations.^18,19 This appears to be changing with time. Valdez and colleagues demonstrated a decrease in prevalence of coagulase-negative staphylococcal infections, increased prevalence of gram-positive bacilli bacteremia, and no change in prevalence of gram-negative bacteremia in patients with aplastic anemia treated between 1989 and 2008.²² Gram-negative bacteremia caused by Stenotrophomonas maltophila, Escherichia coli, Klebsiella pneumoniae, Citrobacter, and Proteus has also been reported.¹⁹ Despite a lack of clinical trials investigating the role of antifungal and antibacterial prophylaxis for patients with aplastic anemia, most centers initiate antifungal prophylaxis in patients with severe aplastic anema (SAA) or VSAA with an anti-mold agent such as voriconazole or posaconazole (which has the additional benefit compared to voriconazole of covering Mucor species).^17,23 This is especially true for patients who have received ATG or undergone HSCT. For antimicrobial prophylaxis, a fluoroquinolone antibiotic with a spectrum of activity against Pseudomonas should be considered for patients with an ANC < 500 cells/µL.¹⁷ Acyclovir or valacyclovir prophylaxis is recommended for varicella-zoster virus and herpes simplex virus. Cytomegalovirus reactivation is minimal in patients with aplastic anemia, unless multiple courses of ATG are used.

Iron overload is another complication the provider must be aware of in the setting of increased transfusions in aplastic anemia patients. Lee and colleagues demonstrated that iron chelation therapy using deferasirox is effective at reducing serum ferritin levels in patients with aplastic anemia (median ferritin level: 3254 ng/mL prior to therapy, 1854 ng/mL following), and is associated with no serious adverse events (most common adverse events included nausea, diarrhea, vomiting, and rash).²⁴ Approximately 25% of patients in this trial demonstrated an increase in creatinine, with patients taking concomitant cyclosporine more affected than those on chelation therapy alone.²⁴ For patients following HSCT or with improved hematopoiesis following immunosuppressive therapy, phlebotomy can be used to treat iron overload in lieu of chelation therapy.¹⁵

Approach to Therapy

The main treatment options for SAA and VSAA include allogeneic bone marrow transplant and immunosuppression. The deciding factors as to which treatment is best initially depends on the availability of HLA-matched related donors and age (Figure 1 and Figure 2). Survival is decreased in patients with SAA or VSAA who delay initiation of therapy, and therefore prompt referral for HLA typing and evaluation for bone marrow transplant is a very important first step in managing aplastic anemia.

Matched Sibling Donor Transplant

Current standards of care recommend HLA-matched sibling donor transplant for patients with SAA or VSAA who are younger than 50 years of age, with the caveat that integration of fludarabine and reduced cyclophosphamide dosing along with ATG shows the best overall outcomes. Locasciulli and colleagues examined outcomes in patients given either immunosuppressive therapy or sibling HSCT between 1991-1996 and 1997-2002, respectively, and found that sibling HSCT was associated with a superior 10-year OS compared to immunosuppressive therapy (73% versus 68%).²⁵ Interestingly in this study, there was no OS improvement seen with immunosuppressive therapy alone (69% versus 73%) between the 2 time periods, despite increased OS in both sibling HSCT (74% and 80%) and matched unrelated donor HSCT (38% and 65%).²⁵ Though total body irradiation has been used in the past, it is typically not included in current conditioning regimens for matched related donor transplants.²⁶

Current conditioning regimens typically use a combination of cyclophosphamide and ATG^27,28 with or without fludarabine. Fludarabine-based conditioning regimens have shown promise in patients undergoing sibling HSCT. Maury and colleagues evaluated the role of fludarabine in addition to low-dose cyclophosphamide and ATG compared to cyclophosphamide alone or in combination with ATG in patients over age 30 undergoing sibling HSCT.⁹ There was a nonsignificant improvement in 5-year OS in the fludarabine arm compared to controls (77% ± 8% versus 60% ± 3%, P = 0.14) in the pooled analysis, but when adjusted for age the fludarabine arm had a significantly lower relative risk (RR) of death (RR, 0.44; P = 0.04) compared to the control arm. Shin et al reported outcomes with fludarabine/cyclophosphamide/ATG, with excellent overall outcomes and no difference in patients older or younger than 40 years.²⁹ In addition, Kim et al evaluated their experience with patients older than 40 years of age receiving matched related donors, finding comparable outcomes in those aged 41 to 50 years compared to younger patients. Outcomes did decline in those over the age of 50 years.³⁰ Long-term data for matched related donor transplant for aplastic anemia shows excellent long-term outcomes, with minimal chronic GVHD and good performance status.³¹ Hence, these factors support the role of matched related donor transplant as the initial treatment in SAA and VSAA.

Regarding the role of transplant for patients who lack a matched related donor, a growing body of literature demonstrating identical outcomes between matched related and matched unrelated donor (MUD) transplants for pediatric patients^32,33 supports recent recommendations for upfront unrelated donor transplantation for aplastic anemia.^34,35

Immunosuppressive Therapy

For patients without an HLA-matched sibling donor or those who are older than 50 years of age, immunosuppressive therapy is the first-line therapy. ATG and cyclosporine A are the treatments of choice.³⁶ The potential effectiveness of immunosuppressive therapy in treating aplastic anemia was initially observed in patients in whom autologous transplant failed but who still experienced hematopoietic reconstitution despite the failed graft; this observation led to the hypothesis that the conditioning regimen may have an effect on hematopoiesis.^16,36,37

Anti-thymocyte globulin. Immunosuppressive therapy with ATG has been used for the treatment of aplastic anemia since the 1980s.³⁸ Historically, rabbit ATG had been used, but a 2011 study of horse ATG demonstrated superior hematological response at 6 months compared to rabbit ATG (68% versus 37%).¹⁶ Superior survival was also seen with horse ATG compared to rabbit ATG (3-year OS: 96% versus 76%). Due to these results, horse ATG is preferred over rabbit ATG. ATG should be used in combination with cyclosporine A to optimize outcomes.

Cyclosporine A. Early studies also demonstrated the efficacy of cyclosporine A in the treatment of aplastic anemia, with response rates equivalent to that of ATG monotherapy.³⁹ Recent publications still note the efficacy of cyclosporine A in the treatment of aplastic anemia. Its role as an affordable option for single-agent therapy in developing countries is intriguing.³⁹

The combination of the ATG and cyclosporine A was proven superior to either agent alone in a study by Frickhofen et al.³⁷ In this study patients were randomly assigned to a control arm that received ATG plus methylprednisolone or to an arm that received ATG plus cyclosporine A and methylprednisolone. At 6 months, 70% of patients in the cyclosporine A arm had a complete remission (CR) or partial remission compared to 46% in the control arm.⁴⁰ Further work confirmed the long-term efficacy of this regimen, reporting a 7-year OS of 55%.⁴¹ Among a pediatric population, immunosuppressive therapy was associated with an 83% 10-year OS.⁴²

It is recommended that patients remain on cyclosporine therapy for a minimum of 6 months, after which a gradual taper may be considered, although there is variation among practitioners, with some continuing immunosuppressive therapy for a minimum of 12 months due to a proportion of patients being cyclosporine dependent.^42,43 A study found that within a population of patients who responded to immunosuppressive therapy, 18% became cyclosporine dependent.⁴² The median duration of cyclosporine A treatment at full dose was 12 months, with tapering completed over a median of 19 months after patients had been in a stable CR for a minimum of 3 months. Relapse occurred more often when patients were tapered quickly (decrease ≥ 0.8 mg/kg/month) compared to slowly (0.4-0.7 mg/kg/month) or very slowly (< 0.3 mg/kg/month).

Immunosuppressive therapy plus eltrombopag. Townsley and colleagues recently investigated incorporating the use of the thrombopoietin receptor agonist eltrombopag with immunosuppressive therapy as first-line therapy in aplastic anemia.⁴⁴ When given at a dose of 150 mg daily in patients aged 12 years and older or 75 mg daily in patients younger than 12 years, in conjunction with cyclosporine A and ATG, patients demonstrated markedly improved hematological response compared to historical treatment with standard immunosuppressive therapy alone.⁴⁴ In the patient cohort administered eltrombopag starting on day 1 and continuing for 6 months, the complete response rate was 58%. Eltrombopag led to improvement in all cell lines among all treatment subgroups, and OS (censored for patients who proceeded to transplant) was 99% at 2 years.⁴⁵ Overall, toxicities associated with this therapy were low, with liver enzyme elevations most commonly observed.⁴⁴ Recently, a phase 2 trial of immunosuppressive therapy with or without eltrombopag was reported. Of the 38 patients enrolled, overall response, complete response, and time to response were not statistically different.⁴⁶ With this recent finding, the role of eltrombopag in addition to immunosuppressive therapy is not clearly defined, and further studies are warranted.

OS for patients who do not respond to immunosuppressive therapy is approximately 57% at 5 years, largely due to improved supportive measures among this patient population.^4,22 Therefore, it is important to recognize those patients who have a low chance of response so that second-line therapy can be pursued to improve outcomes.

Matched Unrelated Donor Transplant

For patients with refractory disease following immunosuppressive therapy who lack a matched sibling donor, MUD HSCT is considered standard therapy given the marked improvement in overall outcomes with modulating conditioning regimens and high-resolution HLA typing. A European Society for Blood and Marrow Transplantation analysis comparing matched sibling HSCT to MUD HSCT noted significantly higher rates of acute grade II-IV and grade III-V GVHD (grade II-IV 13% versus 25%, grade III-IV 5% versus 10%) among patients undergoing MUD transplant.⁴⁷ Chronic GVHD rates were 14% in the sibling group, as compared to 26% in the MUD group. Additional benefits seen in this analysis included improved survival when transplanted under age 20 years (84% versus 72%), when transplanted within 6 months of diagnosis (85% versus 72%), the use of ATG in the conditioning regimen (81% versus 73%), and when the donor and recipient were cytomegalovirus-negative compared to other combinations (82% versus 76%).⁴⁷ Interestingly, this study demonstrated that OS was not significantly increased when using a sibling HSCT compared to a MUD HSCT, likely as a result of improved understanding of conditioning regimens, GVHD prophylaxis, and supportive care.

Additional studies of MUD HSCT have shown outcomes similar to those seen in sibling HSCT.^4,43 A French study found a significant increase in survival in patients undergoing MUD HSCT compared to historical cohorts (2000-2005: OS 52%; 2006-2012: OS 74%).³³ The majority of patients underwent conditioning with cyclophosphamide or a combination of busulfan and cyclophosphamide, with or without fludarabine; 81% of patients included underwent in vivo T-cell depletion, and a bone marrow donor source was utilized. OS was significantly lower in patients over age 30 years undergoing MUD HSCT (57%) compared to those under age 30 years (70%). Improved OS was also seen when patients underwent transplant within 1 year of diagnosis and when a 10/10 matched donor (compared to a 9/10 mismatched donor) was utilized.⁴ A 2015 study investigated the role of MUD HSCT as frontline therapy instead of immunosuppressive therapy in patients without a matched sibling donor.³³ The 2-year OS was 96% in the MUD HSCT cohort compared to 91%, 94%, and 74% in historical cohorts of sibling HSCT, frontline immunosuppressive therapy, and second-line MUD HSCT following failed immunosuppressive therapy, respectively. Additionally, event-free survival in the MUD HSCT cohort (defined by the authors as death, lack of response, relapse, occurrence of clonal evolution/clinical paroxysmal nocturnal hemoglobinuria, malignancies developing over follow‐up, and transplant for patients receiving immunosuppressive therapy frontline) was similar compared to sibling HSCT and superior to frontline immunosuppressive therapy and second-line MUD HSCT. Furthermore, Samarasinghe et al highlighted the importance of in vivo T-cell depletion with either ATG or alemtuzumab (anti-CD52 monoclonal antibody) in the prevention of acute and chronic GVHD in both sibling HSCT and MUD HSCT.⁴⁸

With continued improvement of less toxic and more immunomodulating conditioning regimens, utilization of bone marrow as a donor cell source, in vivo T-cell depletion, and use of GVHD and antimicrobial prophylaxis, more clinical evidence supports elevating MUD HSCT in the treatment plan for patients without a matched sibling donor.⁴⁹ However, there is still a large population of patients without matched sibling or unrelated donor options. In an effort to expand the transplant pool and thus avoid clonal hematopoiesis, clinically significant paroxysmal nocturnal hemoglobinuria, and relapsed aplastic anemia, more work continues to recognize the expanding role of alternative donor transplants (cord blood and haploidentical) as another viable treatment strategy for aplastic anemia after immunosuppressive therapy failure.⁵⁰

Summary

Aplastic anemia is a rare but potentially life-threatening disorder characterized by pancytopenia and a marked reduction in the hematopoietic stem cell compartment. Treatment should be instituted as soon as the dignosis of aplastic anemia is established. Treatment outcomes are excellent with modern supportive care and the current approach to allogeneic transplantation, and therefore referral to a bone marrow transplant program to evaluate for early transplantation is the new standard of care.

In children with sickle cell anemia, matched sibling donor transplants improved an indicator of stroke risk in a multicenter French study, suggesting that this intervention may improve outcomes related to cerebral vasculopathy.

Matched sibling donor hematopoietic stem cell transplantation (MSD-HSCT) was linked to significantly lower transcranial Doppler (TCD) velocities at one year compared to standard care in the 9-center study, investigators reported in JAMA.

The study enrolled children with sickle cell anemia who required chronic transfusion due to persistently high TCD velocities, which are associated with increased stroke risk, researchers said.

“Further research is warranted to assess the effects of MSD-HSCT on clinical outcomes and over longer follow-up,” said the researchers, led by Françoise Bernaudin, MD, of Centre Hospitalier Intercommunal de Créteil, Créteil, France

In the non-randomized, prospective DREPAGREFFE study by Dr. Bernaudin and colleagues, 32 children with sickle cell anemia who had a matched sibling donor underwent transplantation, while another 35 children received standard therapy. The primary end point of the study was time-averaged mean of maximum velocities (TAMV) in cerebral arteries at one year.

The highest TAMV at one year was on average 129.6 cm/s in the MSD-HSCT group, versus 170.4 cm/s in the standard care group, for a difference of -40.8 cm/s (P less than .001), Dr. Bernaudin and co-investigators reported.

The improvement persisted at 3 years, with a TAMV of 112.4 cm/s in the transplantation group and 156.7 cm/s in the standard care group (P less than .001), which they also reported as a secondary outcome of the study.

These findings indicate that MSD-HSCT may allow patients with a history of abnormal TCD velocities to stop transfusions and hydroxyurea, Dr. Bernaudin and colleagues said.

The improvement in TCD velocities may be due in part to anemia correction, but also to the “exclusive presence” of normal red blood cells following transplantation, as opposed to simultaneous presence of normal and sickled cells as would be seen after transfusion, they added.

This study wasn’t powered to determine whether a 40 cm/s reduction in TCD velocities would translate into clinical benefits such as reduction in stenosis and silent infarct, or improved cognitive function, they said. Even so, there were no infarcts or stenoses in the MSD-HSCT group, whereas those event occurred in 9% and 6% of patients in the standard care group, respectively, they added.

Dr. Bernaudin reported disclosures related to Addmedica and bluebird bio. Co-authors reported disclosures with Addmedica, Novartis, Alexion, Amgen, Jazz Pharmaceuticals, and others.

SOURCE: Bernaudin F, et al. JAMA. 2019;321(3):266-276.

In children with sickle cell anemia, matched sibling donor transplants improved an indicator of stroke risk in a multicenter French study, suggesting that this intervention may improve outcomes related to cerebral vasculopathy.

Matched sibling donor hematopoietic stem cell transplantation (MSD-HSCT) was linked to significantly lower transcranial Doppler (TCD) velocities at one year compared to standard care in the 9-center study, investigators reported in JAMA.

The study enrolled children with sickle cell anemia who required chronic transfusion due to persistently high TCD velocities, which are associated with increased stroke risk, researchers said.

“Further research is warranted to assess the effects of MSD-HSCT on clinical outcomes and over longer follow-up,” said the researchers, led by Françoise Bernaudin, MD, of Centre Hospitalier Intercommunal de Créteil, Créteil, France

In the non-randomized, prospective DREPAGREFFE study by Dr. Bernaudin and colleagues, 32 children with sickle cell anemia who had a matched sibling donor underwent transplantation, while another 35 children received standard therapy. The primary end point of the study was time-averaged mean of maximum velocities (TAMV) in cerebral arteries at one year.

The highest TAMV at one year was on average 129.6 cm/s in the MSD-HSCT group, versus 170.4 cm/s in the standard care group, for a difference of -40.8 cm/s (P less than .001), Dr. Bernaudin and co-investigators reported.

The improvement persisted at 3 years, with a TAMV of 112.4 cm/s in the transplantation group and 156.7 cm/s in the standard care group (P less than .001), which they also reported as a secondary outcome of the study.

These findings indicate that MSD-HSCT may allow patients with a history of abnormal TCD velocities to stop transfusions and hydroxyurea, Dr. Bernaudin and colleagues said.

The improvement in TCD velocities may be due in part to anemia correction, but also to the “exclusive presence” of normal red blood cells following transplantation, as opposed to simultaneous presence of normal and sickled cells as would be seen after transfusion, they added.

This study wasn’t powered to determine whether a 40 cm/s reduction in TCD velocities would translate into clinical benefits such as reduction in stenosis and silent infarct, or improved cognitive function, they said. Even so, there were no infarcts or stenoses in the MSD-HSCT group, whereas those event occurred in 9% and 6% of patients in the standard care group, respectively, they added.

Dr. Bernaudin reported disclosures related to Addmedica and bluebird bio. Co-authors reported disclosures with Addmedica, Novartis, Alexion, Amgen, Jazz Pharmaceuticals, and others.

SOURCE: Bernaudin F, et al. JAMA. 2019;321(3):266-276.

In children with sickle cell anemia, matched sibling donor transplants improved an indicator of stroke risk in a multicenter French study, suggesting that this intervention may improve outcomes related to cerebral vasculopathy.

Matched sibling donor hematopoietic stem cell transplantation (MSD-HSCT) was linked to significantly lower transcranial Doppler (TCD) velocities at one year compared to standard care in the 9-center study, investigators reported in JAMA.

The study enrolled children with sickle cell anemia who required chronic transfusion due to persistently high TCD velocities, which are associated with increased stroke risk, researchers said.

“Further research is warranted to assess the effects of MSD-HSCT on clinical outcomes and over longer follow-up,” said the researchers, led by Françoise Bernaudin, MD, of Centre Hospitalier Intercommunal de Créteil, Créteil, France

In the non-randomized, prospective DREPAGREFFE study by Dr. Bernaudin and colleagues, 32 children with sickle cell anemia who had a matched sibling donor underwent transplantation, while another 35 children received standard therapy. The primary end point of the study was time-averaged mean of maximum velocities (TAMV) in cerebral arteries at one year.

The highest TAMV at one year was on average 129.6 cm/s in the MSD-HSCT group, versus 170.4 cm/s in the standard care group, for a difference of -40.8 cm/s (P less than .001), Dr. Bernaudin and co-investigators reported.

The improvement persisted at 3 years, with a TAMV of 112.4 cm/s in the transplantation group and 156.7 cm/s in the standard care group (P less than .001), which they also reported as a secondary outcome of the study.

These findings indicate that MSD-HSCT may allow patients with a history of abnormal TCD velocities to stop transfusions and hydroxyurea, Dr. Bernaudin and colleagues said.

The improvement in TCD velocities may be due in part to anemia correction, but also to the “exclusive presence” of normal red blood cells following transplantation, as opposed to simultaneous presence of normal and sickled cells as would be seen after transfusion, they added.

This study wasn’t powered to determine whether a 40 cm/s reduction in TCD velocities would translate into clinical benefits such as reduction in stenosis and silent infarct, or improved cognitive function, they said. Even so, there were no infarcts or stenoses in the MSD-HSCT group, whereas those event occurred in 9% and 6% of patients in the standard care group, respectively, they added.

Dr. Bernaudin reported disclosures related to Addmedica and bluebird bio. Co-authors reported disclosures with Addmedica, Novartis, Alexion, Amgen, Jazz Pharmaceuticals, and others.

SOURCE: Bernaudin F, et al. JAMA. 2019;321(3):266-276.

Aplastic anemia is a clinical and pathological entity of bone marrow failure that causes progressive loss of hematopoietic progenitor stem cells (HPSC), resulting in pancytopenia.¹ Patients may present along a spectrum, ranging from being asymptomatic with incidental findings on peripheral blood testing to having life-threatening neutropenic infections or bleeding. Aplastic anemia results from either inherited or acquired causes, and the pathophysiology and treatment approach vary significantly between these 2 causes. Therefore, recognition of inherited marrow failure diseases, such as Fanconi anemia and telomere biology disorders, is critical to establishing the management plan. This article reviews the epidemiology, pathophysiology, clinical presentation, and diagnosis of aplastic anemia. Treatment of aplastic anemia is reviewed in a separate article.

Epidemiology

Aplastic anemia is a rare disorder, with an incidence of approximately 1.5 to 7 cases per million individuals per year.^2,3 A recent Scandinavian study reported that the incidence of aplastic anemia among the Swedish population is 2.3 cases per million individuals per year, with a median age at diagnosis of 60 years and a slight female predominance (52% versus 48%, respectively).² This data is congruent with prior observations made in Barcelona, where the incidence was 2.34 cases per million individuals per year, albeit with a slightly higher incidence in males compared to females (2.54 versus 2.16, respectively).⁴ The incidence of aplastic anemia varies globally, with a disproportionate increase in incidence seen among Asian populations, with rates as high as 8.8 per million individuals per year.^3-5 This variation in incidence in Asia versus other countries has not been well explained. There appears to be a bimodal distribution, with incidence peaks seen in young adults and in older adults.^2,3,6

Pathophysiology

Acquired Aplastic Anemia

The leading hypothesis as to the cause of most cases of acquired aplastic anemia is that a dysregulated immune system destroys hematopoietic progenitor cells. Inciting etiologies implicated in the development of acquired aplastic anemia include pregnancy, infection, medications, and exposure to certain chemicals, such as benzene.^1,7 The historical understanding of acquired aplastic anemia implicates cytotoxic T-lymphocyte–mediated destruction of CD34+ hematopoietic stem cells.^1,8,9 This hypothesis served as the basis for treatment of acquired aplastic anemia with immunosuppressive therapy, predominantly anti-thymocyte globulin (ATG) combined with cyclosporine A.^1,8 More recent work has focused on cytokine interactions, particularly the suppressive role of interferon (IFN)-γ on hematopoietic stem cells independent of T-lymphocyte–mediated hematopoietic destruction, which has been demonstrated in a murine model.⁸ The interaction of IFN-γ with the hematopoietic stem cells pool is dynamic. IFN-γ levels are elevated during an acute inflammatory response such as a viral infection, providing further basis for the immune-mediated nature of the acquired disease.¹⁰ Specifically, in vitro studies suggest the effects of IFN-γ on HPSC may be secondary to interruption of thrombopoietin and its respective signaling pathways, which play a key role in hematopoietic stem cell renewal.¹¹ Eltrombopag, a thrombopoietin receptor antagonist, has shown promise in the treatment of refractory aplastic anemia, with studies indicating that its effectiveness is independent of IFN-γ levels.^11,12

Inherited Aplastic Anemia

The inherited marrow failure syndromes (IMFSs) are a group of disorders characterized by cellular maintenance and repair defects, leading to cytopenias, increased cancer risk, structural defects, and risk of end organ damage, such as liver cirrhosis and pulmonary fibrosis.^13-15 The most common diseases include Fanconi anemia, dyskeratosis congenita/telomere biology disorders, Diamond-Blackfan anemia, and Shwachman-Diamond syndrome, but with the advent of whole exome sequencing new syndromes continue to be discovered. While classically these disorders present in children, adult presentations of these syndromes are now commonplace. Broadly, the pathophysiology of inherited aplastic anemia relates to the defective hematopoietic progenitor cells and an accelerated decline of the hematopoietic stem cell compartment.

The most common IMFS, Fanconi anemia and telomere biology disorders, are associated with numerous mutations in DNA damage repair pathways and telomere maintenance pathways. TERT, DKC, and TERC mutations are most commonly associated with dyskeratosis congenita, but may also be found infrequently in patients with aplastic anemia presenting at an older age in the absence of the classic phenotypical features.^1,16,17 The recognition of an underlying genetic disorder or telomere biology disorder leading to constitutional aplastic anemia is significant, as these conditions are associated not only with marrow failure, but also endocrinopathies, organ fibrosis, and solid organ malignancies.^13-15 In particular, mutations in the TERT and TERC genes have been associated with dyskeratosis congenita as well as pulmonary fibrosis and cirrhosis.^18,19 The implications of early diagnosis of an IMFS lie in the approach to treatment and prognosis.

Clonal Disorders and Secondary Malignancies

Myelodysplastic syndrome (MDS) and secondary acute myeloid leukemia (AML) are 2 clonal disorders that may arise from a background of aplastic anemia.^9,20,21 Hypoplastic MDS can be difficult to differentiate from aplastic anemia at diagnosis based on morphology alone, although recent work has demonstrated that molecular testing for somatic mutations in ASXL1, DNMT3A, and BCOR can aid in differentiating a subset of aplastic anemia patients who are more likely to progress to MDS.²¹ Clonal populations of cells harboring 6p uniparental disomy are seen in more than 10% of patients with aplastic anemia on cytogenetic analysis, which can help differentiate the diseases.⁹ Yoshizato and colleagues found lower rates of ASXL1 and DNMT3A mutations in patients with aplastic anemia as compared with patients with MDS or AML. In this study, patients with aplastic anemia had higher rates of mutations in PIGA (reflecting the increased paroxysmal nocturnal hemoglobinuria [PNH] clonality seen in aplastic anemia) and BCOR.⁹ Mutations were also found in genes commonly mutated in MDS and AML, including TET2, RUNX1, TP53, and JAK2, albeit at lower frequencies.⁹ These mutations as a whole have not predicted response to therapy or prognosis. However, when performing survival analysis in patients with specific mutations, those commonly encountered in MDS/AML (ASXL1, DNMT3A, TP53, RUNX1, CSMD1) are associated with faster progression to overt MDS/AML and decreased overall survival (OS),^20,21 suggesting these mutations may represent early clonality that can lead to clonal evolution and the development of secondary malignancies. Conversely, mutations in BCOR and BCORL appear to identify patients who may have a favorable outcome in response to immunosuppressive therapy and, similar to patients with PIGA mutations, improved OS.⁹

Paroxysmal Nocturnal Hemoglobinuria

In addition to having an increased risk of myelodysplasia and malignancy due to the development of a dominant pre-malignant clone, patients with aplastic anemia often harbor progenitor cell clones associated with PNH.^1,17 PNH clones have been identified in more than 50% of patients with aplastic anemia.^22,23 PNH represents a clonal disorder of hematopoiesis in which cells harbor X-linked somatic mutations in the PIGA gene; this gene encodes a protein responsible for the synthesis of glycosylphosphatidylinositol (GPI) anchors on the cell surface.^22,24 The lack of these cell surface proteins, specifically CD55 (also known as decay accelerating factor) and CD59 (also known as membrane inhibitor of reactive lysis), predisposes red cells to increased complement-mediated lysis.²⁵ The exact mechanism for the development of these clones in patients with aplastic anemia is not fully understood. Current theories hypothesize that these clones are protected from the immune-mediated destruction of normal hematopoietic stem cells due to the absence of the cell surface proteins.^1,20 The role of these clones over time in patients with aplastic anemia is less clear, though recent work demonstrated that despite differences in clonality over the disease course, aplastic anemia patients with small PNH clones are less likely to develop overt hemolysis and larger PNH clones compared to patients harboring larger (≥ 50%) PNH clones at diagnosis.^23,26,27 Additionally, PNH clones in patients with aplastic anemia infrequently become clinically significant.²⁷ It should be noted that these conditions exist along a continuum; that is, patients with aplastic anemia may develop PNH clones, while conversely patients with PNH may develop aplastic anemia.²⁰ Patients with PNH clones should be followed via peripheral blood flow cytometry in addition to complete blood count to track clonal stability and identify clinically significant PNH among aplastic anemia patients.²⁸

Patients with aplastic anemia typically are diagnosed either due to asymptomatic cytopenias found on peripheral blood sampling, symptomatic anemia, bleeding secondary to thrombocytopenia, or wound healing and infectious complications related to neutropenia.²⁹ A thorough history to understand the timing of symptoms, recent infectious symptoms/exposure, habits, and chemical or toxin exposures (including medications, travel, and supplements) helps guide diagnostic testing. Family history is also critical, with attention given to premature graying, pulmonary, renal, and liver disease, and blood disorders.

Patients with an IMFS, (eg, Fanconi anemia or dyskeratosis congenita) may have associated phenotypical findings such as urogenital abnormalities or short stature; in addition, those with dyskeratosis congenita may present with the classic triad of oral leukoplakia, lacy skin pigmentation, and dystrophic nails.⁷ However, in patients with IMFS, classic phenotypical findings may be lacking in up to 30% to 40% of patients.⁷ As described previously, while congenital malformations are common in Fanconi anemia and dyskeratosis congenita, a third of patients may have no or only subtle phenotypical abnormalities, including alterations in skin or hair pigmentation, skeletal and growth abnormalities, and endocrine disorders.³⁰ The International Fanconi Anemia Registry identified central nervous system, genitourinary, skin and musculoskeletal, ophthalmic, and gastrointestinal system malformations among children with Fanconi anemia.^31,32 Patients with dyskeratosis congenita may present with pulmonary fibrosis, hepatic cirrhosis, or premature graying, as highlighted in a recent study by DiNardo and colleagues.³³ Therefore, physicians must have a heightened index of suspicion in patients with subtle phenotypical findings and associated cytopenias.

Diagnosis

Differential Diagnosis

The diagnosis of aplastic anemia should be suspected in any patient presenting with pancytopenia. Aplastic anemia is a diagnosis of exclusion.³⁴ Other conditions associated with peripheral blood pancytopenia should be considered including infections (HIV, hepatitis, parvovirus B19, cytomegalovirus, Epstein-Barr virus, varicella-zoster virus), nutritional deficiencies (vitamin B12, folate, copper, zinc), autoimmune disease (systemic lupus erythematosus, rheumatoid arthritis, hemophagocytic lymphohistiocytosis), hypersplenism, marrow-occupying diseases (eg, leukemia, lymphoma, MDS), solid malignancies, and fibrosis (Table).⁷

Diagnostic Evaluation

The workup for aplastic anemia should include a thorough history and physical exam to search simultaneously for alternative diagnoses and clues pointing to potential etiologic agents.⁷ Diagnostic tests to be performed include a complete blood count with differential, reticulocyte count, immature platelet fraction, flow cytometry (to rule out lymphoproliferative disorders and atypical myeloid cells and to evaluate for PNH), and bone marrow biopsy with subsequent cytogenetic, immunohistochemical, and molecular testing.³⁵ The typical findings in aplastic anemia include peripheral blood pancytopenia without dysplastic features and bone marrow biopsy demonstrating a hypocellular marrow.⁷ A relative lymphocytosis in the peripheral blood is common.⁷ In patients with a significant PNH clone, a macrocytosis along with elevated lactate dehydrogenase and elevated reticulocyte and granulocyte counts may be present.³⁶

The diagnosis (based on the Camitta criteria³⁷ and modified Camitta criteria³⁸ for severe aplastic anemia) requires 2 of the following findings on peripheral blood samples:

• Absolute neutrophil count (ANC) < 500 cells/µL
• Platelet count < 20,000 cells/µL
• Reticulocyte count < 1% corrected or < 20,000 cells/µL.³⁵

In addition to peripheral blood findings, bone marrow biopsy is essential for the diagnosis, and should demonstrate a markedly hypocellular marrow (cellularity < 25%), occasionally with an increase in T lymphocytes.^7,39 Because marrow cellularity varies with age and can be challenging to assess, additional biopsies may be needed to confirm the diagnosis.²⁹ A 1- to 2-cm core biopsy is necessary to confirm hypocellularity, as small areas of residual hematopoiesis may be present and obscure the diagnosis.³⁵

Excluding Hypocellular MDS and IMFS

A diagnostic challenge is the exclusion of hypocellular MDS, especially in the older adult presenting with aplastic anemia, as patients with aplastic anemia may have some degree of erythroid dysplasia on bone marrow morphology.³⁶ The presence of a PNH clone on flow cytometry can aid in diagnosing aplastic anemia and excluding MDS,³⁴ although PNH clones can be present in refractory anemia MDS. Patients with aplastic anemia have a lower ratio of CD34+ cells compared to those with hypoplastic MDS, with one study demonstrating a mean CD34+ percentage of < 0.5% in aplastic anemia versus 3.7% in hypoplastic MDS.⁴⁰ Cytogenetic and molecular testing can also aid in making this distinction by identifying mutations commonly implicated in MDS.⁷ The presence of monosomy 7 (-7) in aplastic anemia patients is associated with a poor overall prognosis.^34,41

Peripheral blood screening using chromosome breakage analysis (done using either mitomycin C or diepoxybutane as in vitro DNA-crosslinking agents) and telomere length testing (of peripheral blood leukocytes) is necessary to exclude the main IMFS, Fanconi anemia and telomere biology disorders, respectively. Ruling out these conditions is imperative, as the approach to treatment varies significantly between IMFS and aplastic anemia. Patients with shortened telomeres should undergo genetic screening for mutations in the telomere maintenance genes to evaluate the underlying defect leading to shortened telomeres. Patients with increased peripheral blood breakage should have genetic testing to detect mutations associated with Fanconi anemia.

Classification

Once the diagnosis of aplastic anemia has been made, the patient should be classified according to the severity of their disease. Disease severity is determined based on peripheral blood ANC:³⁴ non-severe aplastic anemia (NSAA), ANC > 500 polymorphonuclear neutrophils (PMNs)/µL; severe aplastic anemia (SAA), 200–500 PMNs/µL; and very severe (VSAA), 0–200 PMNs/µL.^4,34 Disease classification is important, as VSAA is associated with a decreased OS compared to SAA.² Disease classification may affect treatment decisions, as patients with NSAA may be observed for a short period of time, while conversely patients with SAA have a worse prognosis with delays in therapy.^42-44

Summary

Aplastic anemia is a rare but potentially life-threatening disorder characterized by pancytopenia and a marked reduction in the hematopoietic stem cell compartment. It can be acquired or associated with an IMFS, and the treatment and prognosis vary dramatically between these 2 etiologies. Work-up and diagnosis involves investigating IMFSs and ruling out malignant or infectious etiologies for pancytopenia. After aplastic anemia has been diagnosed, the patient should be classified according to the severity of their disease based on peripheral blood ANC.

Aplastic anemia is a clinical and pathological entity of bone marrow failure that causes progressive loss of hematopoietic progenitor stem cells (HPSC), resulting in pancytopenia.¹ Patients may present along a spectrum, ranging from being asymptomatic with incidental findings on peripheral blood testing to having life-threatening neutropenic infections or bleeding. Aplastic anemia results from either inherited or acquired causes, and the pathophysiology and treatment approach vary significantly between these 2 causes. Therefore, recognition of inherited marrow failure diseases, such as Fanconi anemia and telomere biology disorders, is critical to establishing the management plan. This article reviews the epidemiology, pathophysiology, clinical presentation, and diagnosis of aplastic anemia. Treatment of aplastic anemia is reviewed in a separate article.

Epidemiology

Aplastic anemia is a rare disorder, with an incidence of approximately 1.5 to 7 cases per million individuals per year.^2,3 A recent Scandinavian study reported that the incidence of aplastic anemia among the Swedish population is 2.3 cases per million individuals per year, with a median age at diagnosis of 60 years and a slight female predominance (52% versus 48%, respectively).² This data is congruent with prior observations made in Barcelona, where the incidence was 2.34 cases per million individuals per year, albeit with a slightly higher incidence in males compared to females (2.54 versus 2.16, respectively).⁴ The incidence of aplastic anemia varies globally, with a disproportionate increase in incidence seen among Asian populations, with rates as high as 8.8 per million individuals per year.^3-5 This variation in incidence in Asia versus other countries has not been well explained. There appears to be a bimodal distribution, with incidence peaks seen in young adults and in older adults.^2,3,6

Pathophysiology

Acquired Aplastic Anemia

The leading hypothesis as to the cause of most cases of acquired aplastic anemia is that a dysregulated immune system destroys hematopoietic progenitor cells. Inciting etiologies implicated in the development of acquired aplastic anemia include pregnancy, infection, medications, and exposure to certain chemicals, such as benzene.^1,7 The historical understanding of acquired aplastic anemia implicates cytotoxic T-lymphocyte–mediated destruction of CD34+ hematopoietic stem cells.^1,8,9 This hypothesis served as the basis for treatment of acquired aplastic anemia with immunosuppressive therapy, predominantly anti-thymocyte globulin (ATG) combined with cyclosporine A.^1,8 More recent work has focused on cytokine interactions, particularly the suppressive role of interferon (IFN)-γ on hematopoietic stem cells independent of T-lymphocyte–mediated hematopoietic destruction, which has been demonstrated in a murine model.⁸ The interaction of IFN-γ with the hematopoietic stem cells pool is dynamic. IFN-γ levels are elevated during an acute inflammatory response such as a viral infection, providing further basis for the immune-mediated nature of the acquired disease.¹⁰ Specifically, in vitro studies suggest the effects of IFN-γ on HPSC may be secondary to interruption of thrombopoietin and its respective signaling pathways, which play a key role in hematopoietic stem cell renewal.¹¹ Eltrombopag, a thrombopoietin receptor antagonist, has shown promise in the treatment of refractory aplastic anemia, with studies indicating that its effectiveness is independent of IFN-γ levels.^11,12

Inherited Aplastic Anemia

The inherited marrow failure syndromes (IMFSs) are a group of disorders characterized by cellular maintenance and repair defects, leading to cytopenias, increased cancer risk, structural defects, and risk of end organ damage, such as liver cirrhosis and pulmonary fibrosis.^13-15 The most common diseases include Fanconi anemia, dyskeratosis congenita/telomere biology disorders, Diamond-Blackfan anemia, and Shwachman-Diamond syndrome, but with the advent of whole exome sequencing new syndromes continue to be discovered. While classically these disorders present in children, adult presentations of these syndromes are now commonplace. Broadly, the pathophysiology of inherited aplastic anemia relates to the defective hematopoietic progenitor cells and an accelerated decline of the hematopoietic stem cell compartment.

The most common IMFS, Fanconi anemia and telomere biology disorders, are associated with numerous mutations in DNA damage repair pathways and telomere maintenance pathways. TERT, DKC, and TERC mutations are most commonly associated with dyskeratosis congenita, but may also be found infrequently in patients with aplastic anemia presenting at an older age in the absence of the classic phenotypical features.^1,16,17 The recognition of an underlying genetic disorder or telomere biology disorder leading to constitutional aplastic anemia is significant, as these conditions are associated not only with marrow failure, but also endocrinopathies, organ fibrosis, and solid organ malignancies.^13-15 In particular, mutations in the TERT and TERC genes have been associated with dyskeratosis congenita as well as pulmonary fibrosis and cirrhosis.^18,19 The implications of early diagnosis of an IMFS lie in the approach to treatment and prognosis.

Clonal Disorders and Secondary Malignancies

Myelodysplastic syndrome (MDS) and secondary acute myeloid leukemia (AML) are 2 clonal disorders that may arise from a background of aplastic anemia.^9,20,21 Hypoplastic MDS can be difficult to differentiate from aplastic anemia at diagnosis based on morphology alone, although recent work has demonstrated that molecular testing for somatic mutations in ASXL1, DNMT3A, and BCOR can aid in differentiating a subset of aplastic anemia patients who are more likely to progress to MDS.²¹ Clonal populations of cells harboring 6p uniparental disomy are seen in more than 10% of patients with aplastic anemia on cytogenetic analysis, which can help differentiate the diseases.⁹ Yoshizato and colleagues found lower rates of ASXL1 and DNMT3A mutations in patients with aplastic anemia as compared with patients with MDS or AML. In this study, patients with aplastic anemia had higher rates of mutations in PIGA (reflecting the increased paroxysmal nocturnal hemoglobinuria [PNH] clonality seen in aplastic anemia) and BCOR.⁹ Mutations were also found in genes commonly mutated in MDS and AML, including TET2, RUNX1, TP53, and JAK2, albeit at lower frequencies.⁹ These mutations as a whole have not predicted response to therapy or prognosis. However, when performing survival analysis in patients with specific mutations, those commonly encountered in MDS/AML (ASXL1, DNMT3A, TP53, RUNX1, CSMD1) are associated with faster progression to overt MDS/AML and decreased overall survival (OS),^20,21 suggesting these mutations may represent early clonality that can lead to clonal evolution and the development of secondary malignancies. Conversely, mutations in BCOR and BCORL appear to identify patients who may have a favorable outcome in response to immunosuppressive therapy and, similar to patients with PIGA mutations, improved OS.⁹

Paroxysmal Nocturnal Hemoglobinuria

In addition to having an increased risk of myelodysplasia and malignancy due to the development of a dominant pre-malignant clone, patients with aplastic anemia often harbor progenitor cell clones associated with PNH.^1,17 PNH clones have been identified in more than 50% of patients with aplastic anemia.^22,23 PNH represents a clonal disorder of hematopoiesis in which cells harbor X-linked somatic mutations in the PIGA gene; this gene encodes a protein responsible for the synthesis of glycosylphosphatidylinositol (GPI) anchors on the cell surface.^22,24 The lack of these cell surface proteins, specifically CD55 (also known as decay accelerating factor) and CD59 (also known as membrane inhibitor of reactive lysis), predisposes red cells to increased complement-mediated lysis.²⁵ The exact mechanism for the development of these clones in patients with aplastic anemia is not fully understood. Current theories hypothesize that these clones are protected from the immune-mediated destruction of normal hematopoietic stem cells due to the absence of the cell surface proteins.^1,20 The role of these clones over time in patients with aplastic anemia is less clear, though recent work demonstrated that despite differences in clonality over the disease course, aplastic anemia patients with small PNH clones are less likely to develop overt hemolysis and larger PNH clones compared to patients harboring larger (≥ 50%) PNH clones at diagnosis.^23,26,27 Additionally, PNH clones in patients with aplastic anemia infrequently become clinically significant.²⁷ It should be noted that these conditions exist along a continuum; that is, patients with aplastic anemia may develop PNH clones, while conversely patients with PNH may develop aplastic anemia.²⁰ Patients with PNH clones should be followed via peripheral blood flow cytometry in addition to complete blood count to track clonal stability and identify clinically significant PNH among aplastic anemia patients.²⁸

Patients with aplastic anemia typically are diagnosed either due to asymptomatic cytopenias found on peripheral blood sampling, symptomatic anemia, bleeding secondary to thrombocytopenia, or wound healing and infectious complications related to neutropenia.²⁹ A thorough history to understand the timing of symptoms, recent infectious symptoms/exposure, habits, and chemical or toxin exposures (including medications, travel, and supplements) helps guide diagnostic testing. Family history is also critical, with attention given to premature graying, pulmonary, renal, and liver disease, and blood disorders.

Patients with an IMFS, (eg, Fanconi anemia or dyskeratosis congenita) may have associated phenotypical findings such as urogenital abnormalities or short stature; in addition, those with dyskeratosis congenita may present with the classic triad of oral leukoplakia, lacy skin pigmentation, and dystrophic nails.⁷ However, in patients with IMFS, classic phenotypical findings may be lacking in up to 30% to 40% of patients.⁷ As described previously, while congenital malformations are common in Fanconi anemia and dyskeratosis congenita, a third of patients may have no or only subtle phenotypical abnormalities, including alterations in skin or hair pigmentation, skeletal and growth abnormalities, and endocrine disorders.³⁰ The International Fanconi Anemia Registry identified central nervous system, genitourinary, skin and musculoskeletal, ophthalmic, and gastrointestinal system malformations among children with Fanconi anemia.^31,32 Patients with dyskeratosis congenita may present with pulmonary fibrosis, hepatic cirrhosis, or premature graying, as highlighted in a recent study by DiNardo and colleagues.³³ Therefore, physicians must have a heightened index of suspicion in patients with subtle phenotypical findings and associated cytopenias.

Diagnosis

Differential Diagnosis

The diagnosis of aplastic anemia should be suspected in any patient presenting with pancytopenia. Aplastic anemia is a diagnosis of exclusion.³⁴ Other conditions associated with peripheral blood pancytopenia should be considered including infections (HIV, hepatitis, parvovirus B19, cytomegalovirus, Epstein-Barr virus, varicella-zoster virus), nutritional deficiencies (vitamin B12, folate, copper, zinc), autoimmune disease (systemic lupus erythematosus, rheumatoid arthritis, hemophagocytic lymphohistiocytosis), hypersplenism, marrow-occupying diseases (eg, leukemia, lymphoma, MDS), solid malignancies, and fibrosis (Table).⁷

Diagnostic Evaluation

The workup for aplastic anemia should include a thorough history and physical exam to search simultaneously for alternative diagnoses and clues pointing to potential etiologic agents.⁷ Diagnostic tests to be performed include a complete blood count with differential, reticulocyte count, immature platelet fraction, flow cytometry (to rule out lymphoproliferative disorders and atypical myeloid cells and to evaluate for PNH), and bone marrow biopsy with subsequent cytogenetic, immunohistochemical, and molecular testing.³⁵ The typical findings in aplastic anemia include peripheral blood pancytopenia without dysplastic features and bone marrow biopsy demonstrating a hypocellular marrow.⁷ A relative lymphocytosis in the peripheral blood is common.⁷ In patients with a significant PNH clone, a macrocytosis along with elevated lactate dehydrogenase and elevated reticulocyte and granulocyte counts may be present.³⁶

The diagnosis (based on the Camitta criteria³⁷ and modified Camitta criteria³⁸ for severe aplastic anemia) requires 2 of the following findings on peripheral blood samples:

• Absolute neutrophil count (ANC) < 500 cells/µL
• Platelet count < 20,000 cells/µL
• Reticulocyte count < 1% corrected or < 20,000 cells/µL.³⁵

In addition to peripheral blood findings, bone marrow biopsy is essential for the diagnosis, and should demonstrate a markedly hypocellular marrow (cellularity < 25%), occasionally with an increase in T lymphocytes.^7,39 Because marrow cellularity varies with age and can be challenging to assess, additional biopsies may be needed to confirm the diagnosis.²⁹ A 1- to 2-cm core biopsy is necessary to confirm hypocellularity, as small areas of residual hematopoiesis may be present and obscure the diagnosis.³⁵

Excluding Hypocellular MDS and IMFS

A diagnostic challenge is the exclusion of hypocellular MDS, especially in the older adult presenting with aplastic anemia, as patients with aplastic anemia may have some degree of erythroid dysplasia on bone marrow morphology.³⁶ The presence of a PNH clone on flow cytometry can aid in diagnosing aplastic anemia and excluding MDS,³⁴ although PNH clones can be present in refractory anemia MDS. Patients with aplastic anemia have a lower ratio of CD34+ cells compared to those with hypoplastic MDS, with one study demonstrating a mean CD34+ percentage of < 0.5% in aplastic anemia versus 3.7% in hypoplastic MDS.⁴⁰ Cytogenetic and molecular testing can also aid in making this distinction by identifying mutations commonly implicated in MDS.⁷ The presence of monosomy 7 (-7) in aplastic anemia patients is associated with a poor overall prognosis.^34,41

Peripheral blood screening using chromosome breakage analysis (done using either mitomycin C or diepoxybutane as in vitro DNA-crosslinking agents) and telomere length testing (of peripheral blood leukocytes) is necessary to exclude the main IMFS, Fanconi anemia and telomere biology disorders, respectively. Ruling out these conditions is imperative, as the approach to treatment varies significantly between IMFS and aplastic anemia. Patients with shortened telomeres should undergo genetic screening for mutations in the telomere maintenance genes to evaluate the underlying defect leading to shortened telomeres. Patients with increased peripheral blood breakage should have genetic testing to detect mutations associated with Fanconi anemia.

Classification

Once the diagnosis of aplastic anemia has been made, the patient should be classified according to the severity of their disease. Disease severity is determined based on peripheral blood ANC:³⁴ non-severe aplastic anemia (NSAA), ANC > 500 polymorphonuclear neutrophils (PMNs)/µL; severe aplastic anemia (SAA), 200–500 PMNs/µL; and very severe (VSAA), 0–200 PMNs/µL.^4,34 Disease classification is important, as VSAA is associated with a decreased OS compared to SAA.² Disease classification may affect treatment decisions, as patients with NSAA may be observed for a short period of time, while conversely patients with SAA have a worse prognosis with delays in therapy.^42-44

Summary

Aplastic anemia is a rare but potentially life-threatening disorder characterized by pancytopenia and a marked reduction in the hematopoietic stem cell compartment. It can be acquired or associated with an IMFS, and the treatment and prognosis vary dramatically between these 2 etiologies. Work-up and diagnosis involves investigating IMFSs and ruling out malignant or infectious etiologies for pancytopenia. After aplastic anemia has been diagnosed, the patient should be classified according to the severity of their disease based on peripheral blood ANC.

Aplastic anemia is a clinical and pathological entity of bone marrow failure that causes progressive loss of hematopoietic progenitor stem cells (HPSC), resulting in pancytopenia.¹ Patients may present along a spectrum, ranging from being asymptomatic with incidental findings on peripheral blood testing to having life-threatening neutropenic infections or bleeding. Aplastic anemia results from either inherited or acquired causes, and the pathophysiology and treatment approach vary significantly between these 2 causes. Therefore, recognition of inherited marrow failure diseases, such as Fanconi anemia and telomere biology disorders, is critical to establishing the management plan. This article reviews the epidemiology, pathophysiology, clinical presentation, and diagnosis of aplastic anemia. Treatment of aplastic anemia is reviewed in a separate article.

Epidemiology

Aplastic anemia is a rare disorder, with an incidence of approximately 1.5 to 7 cases per million individuals per year.^2,3 A recent Scandinavian study reported that the incidence of aplastic anemia among the Swedish population is 2.3 cases per million individuals per year, with a median age at diagnosis of 60 years and a slight female predominance (52% versus 48%, respectively).² This data is congruent with prior observations made in Barcelona, where the incidence was 2.34 cases per million individuals per year, albeit with a slightly higher incidence in males compared to females (2.54 versus 2.16, respectively).⁴ The incidence of aplastic anemia varies globally, with a disproportionate increase in incidence seen among Asian populations, with rates as high as 8.8 per million individuals per year.^3-5 This variation in incidence in Asia versus other countries has not been well explained. There appears to be a bimodal distribution, with incidence peaks seen in young adults and in older adults.^2,3,6

Pathophysiology

Acquired Aplastic Anemia

The leading hypothesis as to the cause of most cases of acquired aplastic anemia is that a dysregulated immune system destroys hematopoietic progenitor cells. Inciting etiologies implicated in the development of acquired aplastic anemia include pregnancy, infection, medications, and exposure to certain chemicals, such as benzene.^1,7 The historical understanding of acquired aplastic anemia implicates cytotoxic T-lymphocyte–mediated destruction of CD34+ hematopoietic stem cells.^1,8,9 This hypothesis served as the basis for treatment of acquired aplastic anemia with immunosuppressive therapy, predominantly anti-thymocyte globulin (ATG) combined with cyclosporine A.^1,8 More recent work has focused on cytokine interactions, particularly the suppressive role of interferon (IFN)-γ on hematopoietic stem cells independent of T-lymphocyte–mediated hematopoietic destruction, which has been demonstrated in a murine model.⁸ The interaction of IFN-γ with the hematopoietic stem cells pool is dynamic. IFN-γ levels are elevated during an acute inflammatory response such as a viral infection, providing further basis for the immune-mediated nature of the acquired disease.¹⁰ Specifically, in vitro studies suggest the effects of IFN-γ on HPSC may be secondary to interruption of thrombopoietin and its respective signaling pathways, which play a key role in hematopoietic stem cell renewal.¹¹ Eltrombopag, a thrombopoietin receptor antagonist, has shown promise in the treatment of refractory aplastic anemia, with studies indicating that its effectiveness is independent of IFN-γ levels.^11,12

Inherited Aplastic Anemia

The inherited marrow failure syndromes (IMFSs) are a group of disorders characterized by cellular maintenance and repair defects, leading to cytopenias, increased cancer risk, structural defects, and risk of end organ damage, such as liver cirrhosis and pulmonary fibrosis.^13-15 The most common diseases include Fanconi anemia, dyskeratosis congenita/telomere biology disorders, Diamond-Blackfan anemia, and Shwachman-Diamond syndrome, but with the advent of whole exome sequencing new syndromes continue to be discovered. While classically these disorders present in children, adult presentations of these syndromes are now commonplace. Broadly, the pathophysiology of inherited aplastic anemia relates to the defective hematopoietic progenitor cells and an accelerated decline of the hematopoietic stem cell compartment.

The most common IMFS, Fanconi anemia and telomere biology disorders, are associated with numerous mutations in DNA damage repair pathways and telomere maintenance pathways. TERT, DKC, and TERC mutations are most commonly associated with dyskeratosis congenita, but may also be found infrequently in patients with aplastic anemia presenting at an older age in the absence of the classic phenotypical features.^1,16,17 The recognition of an underlying genetic disorder or telomere biology disorder leading to constitutional aplastic anemia is significant, as these conditions are associated not only with marrow failure, but also endocrinopathies, organ fibrosis, and solid organ malignancies.^13-15 In particular, mutations in the TERT and TERC genes have been associated with dyskeratosis congenita as well as pulmonary fibrosis and cirrhosis.^18,19 The implications of early diagnosis of an IMFS lie in the approach to treatment and prognosis.

Clonal Disorders and Secondary Malignancies

Myelodysplastic syndrome (MDS) and secondary acute myeloid leukemia (AML) are 2 clonal disorders that may arise from a background of aplastic anemia.^9,20,21 Hypoplastic MDS can be difficult to differentiate from aplastic anemia at diagnosis based on morphology alone, although recent work has demonstrated that molecular testing for somatic mutations in ASXL1, DNMT3A, and BCOR can aid in differentiating a subset of aplastic anemia patients who are more likely to progress to MDS.²¹ Clonal populations of cells harboring 6p uniparental disomy are seen in more than 10% of patients with aplastic anemia on cytogenetic analysis, which can help differentiate the diseases.⁹ Yoshizato and colleagues found lower rates of ASXL1 and DNMT3A mutations in patients with aplastic anemia as compared with patients with MDS or AML. In this study, patients with aplastic anemia had higher rates of mutations in PIGA (reflecting the increased paroxysmal nocturnal hemoglobinuria [PNH] clonality seen in aplastic anemia) and BCOR.⁹ Mutations were also found in genes commonly mutated in MDS and AML, including TET2, RUNX1, TP53, and JAK2, albeit at lower frequencies.⁹ These mutations as a whole have not predicted response to therapy or prognosis. However, when performing survival analysis in patients with specific mutations, those commonly encountered in MDS/AML (ASXL1, DNMT3A, TP53, RUNX1, CSMD1) are associated with faster progression to overt MDS/AML and decreased overall survival (OS),^20,21 suggesting these mutations may represent early clonality that can lead to clonal evolution and the development of secondary malignancies. Conversely, mutations in BCOR and BCORL appear to identify patients who may have a favorable outcome in response to immunosuppressive therapy and, similar to patients with PIGA mutations, improved OS.⁹

Paroxysmal Nocturnal Hemoglobinuria

In addition to having an increased risk of myelodysplasia and malignancy due to the development of a dominant pre-malignant clone, patients with aplastic anemia often harbor progenitor cell clones associated with PNH.^1,17 PNH clones have been identified in more than 50% of patients with aplastic anemia.^22,23 PNH represents a clonal disorder of hematopoiesis in which cells harbor X-linked somatic mutations in the PIGA gene; this gene encodes a protein responsible for the synthesis of glycosylphosphatidylinositol (GPI) anchors on the cell surface.^22,24 The lack of these cell surface proteins, specifically CD55 (also known as decay accelerating factor) and CD59 (also known as membrane inhibitor of reactive lysis), predisposes red cells to increased complement-mediated lysis.²⁵ The exact mechanism for the development of these clones in patients with aplastic anemia is not fully understood. Current theories hypothesize that these clones are protected from the immune-mediated destruction of normal hematopoietic stem cells due to the absence of the cell surface proteins.^1,20 The role of these clones over time in patients with aplastic anemia is less clear, though recent work demonstrated that despite differences in clonality over the disease course, aplastic anemia patients with small PNH clones are less likely to develop overt hemolysis and larger PNH clones compared to patients harboring larger (≥ 50%) PNH clones at diagnosis.^23,26,27 Additionally, PNH clones in patients with aplastic anemia infrequently become clinically significant.²⁷ It should be noted that these conditions exist along a continuum; that is, patients with aplastic anemia may develop PNH clones, while conversely patients with PNH may develop aplastic anemia.²⁰ Patients with PNH clones should be followed via peripheral blood flow cytometry in addition to complete blood count to track clonal stability and identify clinically significant PNH among aplastic anemia patients.²⁸

Patients with aplastic anemia typically are diagnosed either due to asymptomatic cytopenias found on peripheral blood sampling, symptomatic anemia, bleeding secondary to thrombocytopenia, or wound healing and infectious complications related to neutropenia.²⁹ A thorough history to understand the timing of symptoms, recent infectious symptoms/exposure, habits, and chemical or toxin exposures (including medications, travel, and supplements) helps guide diagnostic testing. Family history is also critical, with attention given to premature graying, pulmonary, renal, and liver disease, and blood disorders.

Patients with an IMFS, (eg, Fanconi anemia or dyskeratosis congenita) may have associated phenotypical findings such as urogenital abnormalities or short stature; in addition, those with dyskeratosis congenita may present with the classic triad of oral leukoplakia, lacy skin pigmentation, and dystrophic nails.⁷ However, in patients with IMFS, classic phenotypical findings may be lacking in up to 30% to 40% of patients.⁷ As described previously, while congenital malformations are common in Fanconi anemia and dyskeratosis congenita, a third of patients may have no or only subtle phenotypical abnormalities, including alterations in skin or hair pigmentation, skeletal and growth abnormalities, and endocrine disorders.³⁰ The International Fanconi Anemia Registry identified central nervous system, genitourinary, skin and musculoskeletal, ophthalmic, and gastrointestinal system malformations among children with Fanconi anemia.^31,32 Patients with dyskeratosis congenita may present with pulmonary fibrosis, hepatic cirrhosis, or premature graying, as highlighted in a recent study by DiNardo and colleagues.³³ Therefore, physicians must have a heightened index of suspicion in patients with subtle phenotypical findings and associated cytopenias.

Diagnosis

Differential Diagnosis

The diagnosis of aplastic anemia should be suspected in any patient presenting with pancytopenia. Aplastic anemia is a diagnosis of exclusion.³⁴ Other conditions associated with peripheral blood pancytopenia should be considered including infections (HIV, hepatitis, parvovirus B19, cytomegalovirus, Epstein-Barr virus, varicella-zoster virus), nutritional deficiencies (vitamin B12, folate, copper, zinc), autoimmune disease (systemic lupus erythematosus, rheumatoid arthritis, hemophagocytic lymphohistiocytosis), hypersplenism, marrow-occupying diseases (eg, leukemia, lymphoma, MDS), solid malignancies, and fibrosis (Table).⁷

Diagnostic Evaluation

The workup for aplastic anemia should include a thorough history and physical exam to search simultaneously for alternative diagnoses and clues pointing to potential etiologic agents.⁷ Diagnostic tests to be performed include a complete blood count with differential, reticulocyte count, immature platelet fraction, flow cytometry (to rule out lymphoproliferative disorders and atypical myeloid cells and to evaluate for PNH), and bone marrow biopsy with subsequent cytogenetic, immunohistochemical, and molecular testing.³⁵ The typical findings in aplastic anemia include peripheral blood pancytopenia without dysplastic features and bone marrow biopsy demonstrating a hypocellular marrow.⁷ A relative lymphocytosis in the peripheral blood is common.⁷ In patients with a significant PNH clone, a macrocytosis along with elevated lactate dehydrogenase and elevated reticulocyte and granulocyte counts may be present.³⁶

The diagnosis (based on the Camitta criteria³⁷ and modified Camitta criteria³⁸ for severe aplastic anemia) requires 2 of the following findings on peripheral blood samples:

• Absolute neutrophil count (ANC) < 500 cells/µL
• Platelet count < 20,000 cells/µL
• Reticulocyte count < 1% corrected or < 20,000 cells/µL.³⁵

In addition to peripheral blood findings, bone marrow biopsy is essential for the diagnosis, and should demonstrate a markedly hypocellular marrow (cellularity < 25%), occasionally with an increase in T lymphocytes.^7,39 Because marrow cellularity varies with age and can be challenging to assess, additional biopsies may be needed to confirm the diagnosis.²⁹ A 1- to 2-cm core biopsy is necessary to confirm hypocellularity, as small areas of residual hematopoiesis may be present and obscure the diagnosis.³⁵

Excluding Hypocellular MDS and IMFS

A diagnostic challenge is the exclusion of hypocellular MDS, especially in the older adult presenting with aplastic anemia, as patients with aplastic anemia may have some degree of erythroid dysplasia on bone marrow morphology.³⁶ The presence of a PNH clone on flow cytometry can aid in diagnosing aplastic anemia and excluding MDS,³⁴ although PNH clones can be present in refractory anemia MDS. Patients with aplastic anemia have a lower ratio of CD34+ cells compared to those with hypoplastic MDS, with one study demonstrating a mean CD34+ percentage of < 0.5% in aplastic anemia versus 3.7% in hypoplastic MDS.⁴⁰ Cytogenetic and molecular testing can also aid in making this distinction by identifying mutations commonly implicated in MDS.⁷ The presence of monosomy 7 (-7) in aplastic anemia patients is associated with a poor overall prognosis.^34,41

Peripheral blood screening using chromosome breakage analysis (done using either mitomycin C or diepoxybutane as in vitro DNA-crosslinking agents) and telomere length testing (of peripheral blood leukocytes) is necessary to exclude the main IMFS, Fanconi anemia and telomere biology disorders, respectively. Ruling out these conditions is imperative, as the approach to treatment varies significantly between IMFS and aplastic anemia. Patients with shortened telomeres should undergo genetic screening for mutations in the telomere maintenance genes to evaluate the underlying defect leading to shortened telomeres. Patients with increased peripheral blood breakage should have genetic testing to detect mutations associated with Fanconi anemia.

Classification

Once the diagnosis of aplastic anemia has been made, the patient should be classified according to the severity of their disease. Disease severity is determined based on peripheral blood ANC:³⁴ non-severe aplastic anemia (NSAA), ANC > 500 polymorphonuclear neutrophils (PMNs)/µL; severe aplastic anemia (SAA), 200–500 PMNs/µL; and very severe (VSAA), 0–200 PMNs/µL.^4,34 Disease classification is important, as VSAA is associated with a decreased OS compared to SAA.² Disease classification may affect treatment decisions, as patients with NSAA may be observed for a short period of time, while conversely patients with SAA have a worse prognosis with delays in therapy.^42-44

Summary

Aplastic anemia is a rare but potentially life-threatening disorder characterized by pancytopenia and a marked reduction in the hematopoietic stem cell compartment. It can be acquired or associated with an IMFS, and the treatment and prognosis vary dramatically between these 2 etiologies. Work-up and diagnosis involves investigating IMFSs and ruling out malignant or infectious etiologies for pancytopenia. After aplastic anemia has been diagnosed, the patient should be classified according to the severity of their disease based on peripheral blood ANC.

Low-dose treatment with plerixafor, a CXC chemokine receptor 4 antagonist, was well tolerated and markedly improved severe presentations of warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome in three patients who could not receive granulocyte colony-stimulating factor therapy, investigators reported.

“Myelofibrosis, panleukopenia, anemia, and thrombocytopenia were ameliorated, the wart burden and frequency of infection declined, human papillomavirus–associated oropharyngeal squamous-cell carcinoma stabilized, and quality of life improved markedly,” David H. McDermott, MD, of the National Institute of Allergy and Infectious Diseases and his colleagues wrote in the New England Journal of Medicine.

WHIM syndrome is a primary immunodeficiency disorder characterized by panleukopenia and caused by autosomal dominant gain-of-function mutations in CXC chemokine receptor 4 (CXCR4). Granulocyte colony-stimulating factor (G-CSF) therapy improves neutropenia in these patients, but not other cytopenias.

Previously, the investigators treated three WHIM syndrome patients with plerixafor (Mozobil), which was well tolerated and led to sustained increases in circulating neutrophils, lymphocytes, and monocytes. The current report is of three patients with advanced WHIM syndrome who received open-label plerixafor because they were ineligible for a randomized trial of this drug.

After treatment initiation, infection frequency dropped by 85% in one patient and declined markedly in all three patients. Lymphocyte counts improved the most in two patients while neutrophils were most responsive in the third patient. Warts partially resolved in two patients, of which one patient also experienced partial resolution of head and neck squamous cell carcinoma. This patient later died of a multidrug-resistant Pseudomonas aeruginosa infection after undergoing a 9-hour surgery.

In the third patient, plerixafor therapy led to clearance of TSPyV and 17 human papillomavirus (HPV) infections, with consequent resolution of chronic, progressive, multifocal eczematoid and follicular lesions, the researchers reported. The study dose was relatively low – about 10% of the stem-cell mobilization dose – and did not cause bone pain or other treatment-emergent adverse events, despite the relatively long treatment course (19-52 months).

A separate, phase 3 trial (NCT02231879) has enrolled 19 patients. Primary results are expected in 2020.

The National Institutes of Health funded the work. Dr. McDermott reported a pending patent to reduce CXCR4 expression and/or function to enhance engraftment of hematopoietic stem cells.

SOURCE: McDermott DH et al. N Engl J Med. 2019;380:163-70.
 

Low-dose treatment with plerixafor, a CXC chemokine receptor 4 antagonist, was well tolerated and markedly improved severe presentations of warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome in three patients who could not receive granulocyte colony-stimulating factor therapy, investigators reported.

“Myelofibrosis, panleukopenia, anemia, and thrombocytopenia were ameliorated, the wart burden and frequency of infection declined, human papillomavirus–associated oropharyngeal squamous-cell carcinoma stabilized, and quality of life improved markedly,” David H. McDermott, MD, of the National Institute of Allergy and Infectious Diseases and his colleagues wrote in the New England Journal of Medicine.

WHIM syndrome is a primary immunodeficiency disorder characterized by panleukopenia and caused by autosomal dominant gain-of-function mutations in CXC chemokine receptor 4 (CXCR4). Granulocyte colony-stimulating factor (G-CSF) therapy improves neutropenia in these patients, but not other cytopenias.

Previously, the investigators treated three WHIM syndrome patients with plerixafor (Mozobil), which was well tolerated and led to sustained increases in circulating neutrophils, lymphocytes, and monocytes. The current report is of three patients with advanced WHIM syndrome who received open-label plerixafor because they were ineligible for a randomized trial of this drug.

After treatment initiation, infection frequency dropped by 85% in one patient and declined markedly in all three patients. Lymphocyte counts improved the most in two patients while neutrophils were most responsive in the third patient. Warts partially resolved in two patients, of which one patient also experienced partial resolution of head and neck squamous cell carcinoma. This patient later died of a multidrug-resistant Pseudomonas aeruginosa infection after undergoing a 9-hour surgery.

In the third patient, plerixafor therapy led to clearance of TSPyV and 17 human papillomavirus (HPV) infections, with consequent resolution of chronic, progressive, multifocal eczematoid and follicular lesions, the researchers reported. The study dose was relatively low – about 10% of the stem-cell mobilization dose – and did not cause bone pain or other treatment-emergent adverse events, despite the relatively long treatment course (19-52 months).

A separate, phase 3 trial (NCT02231879) has enrolled 19 patients. Primary results are expected in 2020.

The National Institutes of Health funded the work. Dr. McDermott reported a pending patent to reduce CXCR4 expression and/or function to enhance engraftment of hematopoietic stem cells.

SOURCE: McDermott DH et al. N Engl J Med. 2019;380:163-70.
 

Low-dose treatment with plerixafor, a CXC chemokine receptor 4 antagonist, was well tolerated and markedly improved severe presentations of warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome in three patients who could not receive granulocyte colony-stimulating factor therapy, investigators reported.

“Myelofibrosis, panleukopenia, anemia, and thrombocytopenia were ameliorated, the wart burden and frequency of infection declined, human papillomavirus–associated oropharyngeal squamous-cell carcinoma stabilized, and quality of life improved markedly,” David H. McDermott, MD, of the National Institute of Allergy and Infectious Diseases and his colleagues wrote in the New England Journal of Medicine.

WHIM syndrome is a primary immunodeficiency disorder characterized by panleukopenia and caused by autosomal dominant gain-of-function mutations in CXC chemokine receptor 4 (CXCR4). Granulocyte colony-stimulating factor (G-CSF) therapy improves neutropenia in these patients, but not other cytopenias.

Previously, the investigators treated three WHIM syndrome patients with plerixafor (Mozobil), which was well tolerated and led to sustained increases in circulating neutrophils, lymphocytes, and monocytes. The current report is of three patients with advanced WHIM syndrome who received open-label plerixafor because they were ineligible for a randomized trial of this drug.

After treatment initiation, infection frequency dropped by 85% in one patient and declined markedly in all three patients. Lymphocyte counts improved the most in two patients while neutrophils were most responsive in the third patient. Warts partially resolved in two patients, of which one patient also experienced partial resolution of head and neck squamous cell carcinoma. This patient later died of a multidrug-resistant Pseudomonas aeruginosa infection after undergoing a 9-hour surgery.

In the third patient, plerixafor therapy led to clearance of TSPyV and 17 human papillomavirus (HPV) infections, with consequent resolution of chronic, progressive, multifocal eczematoid and follicular lesions, the researchers reported. The study dose was relatively low – about 10% of the stem-cell mobilization dose – and did not cause bone pain or other treatment-emergent adverse events, despite the relatively long treatment course (19-52 months).

A separate, phase 3 trial (NCT02231879) has enrolled 19 patients. Primary results are expected in 2020.

The National Institutes of Health funded the work. Dr. McDermott reported a pending patent to reduce CXCR4 expression and/or function to enhance engraftment of hematopoietic stem cells.

SOURCE: McDermott DH et al. N Engl J Med. 2019;380:163-70.
 

The Food and Drug Administration has granted breakthrough therapy designation to crizanlizumab, a monthly infusion for the prevention of vasoocclusive crises in patients with sickle cell disease of all genotypes.

The designation allows the treatment to be reviewed on an expedited schedule.

Crizanlizumab, marketed by Novartis, is a humanized anti–P-selectin monoclonal antibody that has been shown to inhibit interactions between endothelial cells, platelets, red blood cells, sickled red blood cells, and leukocytes.

In the phase 2 SUSTAIN trial, crizanlizumab reduced the median annual rate of vasoocclusive crises that resulted in health care visits by about 45%, compared with placebo (1.63 vs. 2.98; P = .010). The drug also increased the percentage of patients who did not experience any vasoocclusive crises, compared with placebo (35.8% vs. 16.9%; P = .010).

The rates of treatment-emergent and serious adverse events was similar in the drug and placebo arms of the trial.

[email protected]

The Food and Drug Administration has granted breakthrough therapy designation to crizanlizumab, a monthly infusion for the prevention of vasoocclusive crises in patients with sickle cell disease of all genotypes.

The designation allows the treatment to be reviewed on an expedited schedule.

Crizanlizumab, marketed by Novartis, is a humanized anti–P-selectin monoclonal antibody that has been shown to inhibit interactions between endothelial cells, platelets, red blood cells, sickled red blood cells, and leukocytes.

In the phase 2 SUSTAIN trial, crizanlizumab reduced the median annual rate of vasoocclusive crises that resulted in health care visits by about 45%, compared with placebo (1.63 vs. 2.98; P = .010). The drug also increased the percentage of patients who did not experience any vasoocclusive crises, compared with placebo (35.8% vs. 16.9%; P = .010).

The rates of treatment-emergent and serious adverse events was similar in the drug and placebo arms of the trial.

[email protected]

The Food and Drug Administration has granted breakthrough therapy designation to crizanlizumab, a monthly infusion for the prevention of vasoocclusive crises in patients with sickle cell disease of all genotypes.

The designation allows the treatment to be reviewed on an expedited schedule.

Crizanlizumab, marketed by Novartis, is a humanized anti–P-selectin monoclonal antibody that has been shown to inhibit interactions between endothelial cells, platelets, red blood cells, sickled red blood cells, and leukocytes.

In the phase 2 SUSTAIN trial, crizanlizumab reduced the median annual rate of vasoocclusive crises that resulted in health care visits by about 45%, compared with placebo (1.63 vs. 2.98; P = .010). The drug also increased the percentage of patients who did not experience any vasoocclusive crises, compared with placebo (35.8% vs. 16.9%; P = .010).

The rates of treatment-emergent and serious adverse events was similar in the drug and placebo arms of the trial.

[email protected]

Photo by Rhoda Baer

Chemotherapy for solid tumors is associated with an increased risk of therapy-related myelodysplastic syndromes or acute myeloid leukemia (tMDS/AML), according to a retrospective analysis.

Long-term, population-based cohort data showed the risk of tMDS/AML was significantly elevated after chemotherapy for 22 solid tumor types.

The relative risk of tMDS/AML was 1.5- to 39.0-fold greater among patients treated for these tumors than among the general population.

Lindsay M. Morton, PhD, of the National Institutes of Health in Rockville, Maryland, and her colleagues reported these findings in JAMA Oncology.

“We undertook an investigation to quantify tMDS/AML risks after chemotherapy for solid tumors in the modern treatment era, 2000-2014, using United States cancer registry data from the National Cancer Institute’s Surveillance, Epidemiology, and End Results Program,” the investigators wrote.

They retrospectively analyzed data from 1619 patients with tMDS/AML who were diagnosed with an initial primary solid tumor from 2000 to 2013.

Patients were given initial chemotherapy and lived for at least 1 year after treatment. Subsequently, Dr. Morton and her colleagues linked patient database records with Medicare insurance claim information to confirm the accuracy of chemotherapy data.

“Because registry data do not include treatment details, we used an alternative database to provide descriptive information on population-based patterns of chemotherapeutic drug use,” the investigators noted.

The team found the risk of developing tMDS/AML was significantly increased following chemotherapy administration for 22 of 23 solid tumor types, excluding colon cancer.

The standardized incidence ratio (SIR) for tMDS/AML ranged from 1.5 to 39.0, and the excess absolute risk (EAR) ranged from 1.4 to 23.6 cases per 10,000 person-years.

SIRs were greatest in patients who received chemotherapy for malignancy of the bone (SIR=39.0, EAR=23.6), testis (SIR, 12.3, EAR=4.4), soft tissue (SIR=10.4, EAR=12.6), fallopian tube (SIR=8.7, EAR=16.0), small cell lung (SIR=8.1, EAR=19.9), peritoneum (SIR=7.5, EAR=15.8), brain or central nervous system (SIR=7.2, EAR=6.0), and ovary (SIR=5.8, EAR=8.2).

The investigators also found that patients who were given chemotherapy at a young age had the highest risk of developing tMDS/AML.

“For patients treated with chemotherapy at the present time, approximately three-quarters of tMDS/AML cases expected to occur within the next 5 years will be attributable to chemotherapy,” the investigators said.

They acknowledged a key limitation of this study was the limited data on patient-specific chemotherapy and dosing information. Given these limitations, Dr. Morton and her colleagues said, “the exact magnitude of our risk estimates, including the proportions of excess cases, should therefore be interpreted cautiously.”

This study was supported by the Intramural Research Program of the National Institutes of Health, National Cancer Institute, and the California Department of Public Health. The authors reported no conflicts of interest.

Photo by Rhoda Baer

Chemotherapy for solid tumors is associated with an increased risk of therapy-related myelodysplastic syndromes or acute myeloid leukemia (tMDS/AML), according to a retrospective analysis.

Long-term, population-based cohort data showed the risk of tMDS/AML was significantly elevated after chemotherapy for 22 solid tumor types.

The relative risk of tMDS/AML was 1.5- to 39.0-fold greater among patients treated for these tumors than among the general population.

Lindsay M. Morton, PhD, of the National Institutes of Health in Rockville, Maryland, and her colleagues reported these findings in JAMA Oncology.

“We undertook an investigation to quantify tMDS/AML risks after chemotherapy for solid tumors in the modern treatment era, 2000-2014, using United States cancer registry data from the National Cancer Institute’s Surveillance, Epidemiology, and End Results Program,” the investigators wrote.

They retrospectively analyzed data from 1619 patients with tMDS/AML who were diagnosed with an initial primary solid tumor from 2000 to 2013.

Patients were given initial chemotherapy and lived for at least 1 year after treatment. Subsequently, Dr. Morton and her colleagues linked patient database records with Medicare insurance claim information to confirm the accuracy of chemotherapy data.

“Because registry data do not include treatment details, we used an alternative database to provide descriptive information on population-based patterns of chemotherapeutic drug use,” the investigators noted.

The team found the risk of developing tMDS/AML was significantly increased following chemotherapy administration for 22 of 23 solid tumor types, excluding colon cancer.

The standardized incidence ratio (SIR) for tMDS/AML ranged from 1.5 to 39.0, and the excess absolute risk (EAR) ranged from 1.4 to 23.6 cases per 10,000 person-years.

SIRs were greatest in patients who received chemotherapy for malignancy of the bone (SIR=39.0, EAR=23.6), testis (SIR, 12.3, EAR=4.4), soft tissue (SIR=10.4, EAR=12.6), fallopian tube (SIR=8.7, EAR=16.0), small cell lung (SIR=8.1, EAR=19.9), peritoneum (SIR=7.5, EAR=15.8), brain or central nervous system (SIR=7.2, EAR=6.0), and ovary (SIR=5.8, EAR=8.2).

The investigators also found that patients who were given chemotherapy at a young age had the highest risk of developing tMDS/AML.

“For patients treated with chemotherapy at the present time, approximately three-quarters of tMDS/AML cases expected to occur within the next 5 years will be attributable to chemotherapy,” the investigators said.

They acknowledged a key limitation of this study was the limited data on patient-specific chemotherapy and dosing information. Given these limitations, Dr. Morton and her colleagues said, “the exact magnitude of our risk estimates, including the proportions of excess cases, should therefore be interpreted cautiously.”

This study was supported by the Intramural Research Program of the National Institutes of Health, National Cancer Institute, and the California Department of Public Health. The authors reported no conflicts of interest.

Photo by Rhoda Baer

Chemotherapy for solid tumors is associated with an increased risk of therapy-related myelodysplastic syndromes or acute myeloid leukemia (tMDS/AML), according to a retrospective analysis.

Long-term, population-based cohort data showed the risk of tMDS/AML was significantly elevated after chemotherapy for 22 solid tumor types.

The relative risk of tMDS/AML was 1.5- to 39.0-fold greater among patients treated for these tumors than among the general population.

Lindsay M. Morton, PhD, of the National Institutes of Health in Rockville, Maryland, and her colleagues reported these findings in JAMA Oncology.

“We undertook an investigation to quantify tMDS/AML risks after chemotherapy for solid tumors in the modern treatment era, 2000-2014, using United States cancer registry data from the National Cancer Institute’s Surveillance, Epidemiology, and End Results Program,” the investigators wrote.

They retrospectively analyzed data from 1619 patients with tMDS/AML who were diagnosed with an initial primary solid tumor from 2000 to 2013.

Patients were given initial chemotherapy and lived for at least 1 year after treatment. Subsequently, Dr. Morton and her colleagues linked patient database records with Medicare insurance claim information to confirm the accuracy of chemotherapy data.

“Because registry data do not include treatment details, we used an alternative database to provide descriptive information on population-based patterns of chemotherapeutic drug use,” the investigators noted.

The team found the risk of developing tMDS/AML was significantly increased following chemotherapy administration for 22 of 23 solid tumor types, excluding colon cancer.

The standardized incidence ratio (SIR) for tMDS/AML ranged from 1.5 to 39.0, and the excess absolute risk (EAR) ranged from 1.4 to 23.6 cases per 10,000 person-years.

SIRs were greatest in patients who received chemotherapy for malignancy of the bone (SIR=39.0, EAR=23.6), testis (SIR, 12.3, EAR=4.4), soft tissue (SIR=10.4, EAR=12.6), fallopian tube (SIR=8.7, EAR=16.0), small cell lung (SIR=8.1, EAR=19.9), peritoneum (SIR=7.5, EAR=15.8), brain or central nervous system (SIR=7.2, EAR=6.0), and ovary (SIR=5.8, EAR=8.2).

The investigators also found that patients who were given chemotherapy at a young age had the highest risk of developing tMDS/AML.

“For patients treated with chemotherapy at the present time, approximately three-quarters of tMDS/AML cases expected to occur within the next 5 years will be attributable to chemotherapy,” the investigators said.

They acknowledged a key limitation of this study was the limited data on patient-specific chemotherapy and dosing information. Given these limitations, Dr. Morton and her colleagues said, “the exact magnitude of our risk estimates, including the proportions of excess cases, should therefore be interpreted cautiously.”

This study was supported by the Intramural Research Program of the National Institutes of Health, National Cancer Institute, and the California Department of Public Health. The authors reported no conflicts of interest.