Gene therapy could treat FVII deficiency

Beagle

Photo by Julien Valroff

Gene therapy can safely and effectively treat factor VII (FVII) deficiency in dogs, according to research published in Blood.

Three of the 4 dogs treated expressed levels of FVII that would be therapeutic in humans, with long-term stability.

In one dog, the effects have persisted for more than 2.5 years and are ongoing.

In addition, researchers said the therapy appears safe, based on kidney function, liver function, and blood measurements.

The team believes this success in large animals holds considerable potential for a safe, effective, and long-lasting new treatment in humans with FVII deficiency.

“Our finding has great clinical relevance for patients with FVII deficiency,” said Paris Margaritis, DPhil, of The Children’s Hospital of Philadelphia in Pennsylvania.

“These dogs have the type of mutation found in the majority of patients with this disorder, so this approach could lead to a sustained gene therapy in people.”

Dr Margaritis and his colleagues studied dogs with a G96E missense FVII mutation (FVII-G96E), which have less than 1% FVII activity. The researchers said these dogs had undetectable plasmatic antigen by Western blot and therefore represent the most prevalent type of human FVII deficiency.

“We developed a unique animal model of this disease after identifying dogs with naturally occurring FVII deficiency,” Dr Margaritis said. “Our investigations enabled us to design the corrective gene to insert into our virus vector in the current study.”

The researchers tested liver-directed, adeno-associated viral (AAV) serotype 8 vector delivery of a canine FVII zymogen transgene (cFVII) in 4 FVII-G96E dogs, known as Otis, N22, N24, and N25.

The animals received escalating doses of AAV8-cFVII, ranging from 2E11 vg/kg to 4.95E13 vg/kg.

Efficacy

At baseline, all dogs had less than 1% cFVII activity levels. After receiving AAV8-cFVII, they experienced a reduction in prothrombin time that reached a plateau:

• From 121.1± 1.0s to 22.1 ± 3.2s in N24 (4.95E13 vg/kg)
• From 83.5 ± 18.4s to 25.0 ± 3.6s in N22 (2E12 vg/kg)
• From 96.0 ± 5.8s to 28.7 ± 3.7s in N25 (6E11 vg/kg)
• From 124.8 ± 4.6s to 50.4 ± 4.0s in Otis (2E11 vg/kg).

The researchers also observed an increase in cFVII expression for all of the dogs but Otis. Levels of cFVII antigen reached plateaus of:

• 8320 ± 1800 ng/ml in N24, which is 770 ± 167 percent of normal
• 307 ± 56 ng/ml in N22, which is 29.7 ± 6.2 percent of normal
• 170 ± 62 ng/ml in N25, which is 15.7 ± 5.7 percent of normal.

These clinically therapeutic cFVII antigen levels have, thus far, persisted for more than 1 year in N22 and N25 and for 2.6 years in N24.

Safety

The researchers found that measures of liver and kidney function were within the normal range in all of the dogs. Likewise, D-dimer and fibrinogen levels were within the normal range.

The team said these results suggest that continuous cFVII expression—even in N24, which averaged 8.3 μg/ml for 2.6 years—did not result in evident activation of the endogenous coagulation system or induce a chronic pathological state.

N24 did exhibit a transient elevation of anti-cFVII IgG2. However, this response was not inhibitory and did not affect the transgene expression plateau.

The researchers did not detect anti-cFVII IgG2 in the other 3 dogs, nor did the team detect anti-cFVII IgG1 in any of the dogs studied.

“This work is very exciting and promising,” said study author Timothy Nichols, MD, of The University of North Carolina at Chapel Hill.

“The FVII-deficient dogs tolerated the initial gene therapy infusions very well and have had no adverse side effects over several years of follow-up. In other related studies in dogs with hemophilia B, similar positive findings have translated to people with hemophilia B.”

Beagle

Photo by Julien Valroff

Gene therapy can safely and effectively treat factor VII (FVII) deficiency in dogs, according to research published in Blood.

Three of the 4 dogs treated expressed levels of FVII that would be therapeutic in humans, with long-term stability.

In one dog, the effects have persisted for more than 2.5 years and are ongoing.

In addition, researchers said the therapy appears safe, based on kidney function, liver function, and blood measurements.

The team believes this success in large animals holds considerable potential for a safe, effective, and long-lasting new treatment in humans with FVII deficiency.

“Our finding has great clinical relevance for patients with FVII deficiency,” said Paris Margaritis, DPhil, of The Children’s Hospital of Philadelphia in Pennsylvania.

“These dogs have the type of mutation found in the majority of patients with this disorder, so this approach could lead to a sustained gene therapy in people.”

Dr Margaritis and his colleagues studied dogs with a G96E missense FVII mutation (FVII-G96E), which have less than 1% FVII activity. The researchers said these dogs had undetectable plasmatic antigen by Western blot and therefore represent the most prevalent type of human FVII deficiency.

“We developed a unique animal model of this disease after identifying dogs with naturally occurring FVII deficiency,” Dr Margaritis said. “Our investigations enabled us to design the corrective gene to insert into our virus vector in the current study.”

The researchers tested liver-directed, adeno-associated viral (AAV) serotype 8 vector delivery of a canine FVII zymogen transgene (cFVII) in 4 FVII-G96E dogs, known as Otis, N22, N24, and N25.

The animals received escalating doses of AAV8-cFVII, ranging from 2E11 vg/kg to 4.95E13 vg/kg.

Efficacy

At baseline, all dogs had less than 1% cFVII activity levels. After receiving AAV8-cFVII, they experienced a reduction in prothrombin time that reached a plateau:

• From 121.1± 1.0s to 22.1 ± 3.2s in N24 (4.95E13 vg/kg)
• From 83.5 ± 18.4s to 25.0 ± 3.6s in N22 (2E12 vg/kg)
• From 96.0 ± 5.8s to 28.7 ± 3.7s in N25 (6E11 vg/kg)
• From 124.8 ± 4.6s to 50.4 ± 4.0s in Otis (2E11 vg/kg).

The researchers also observed an increase in cFVII expression for all of the dogs but Otis. Levels of cFVII antigen reached plateaus of:

• 8320 ± 1800 ng/ml in N24, which is 770 ± 167 percent of normal
• 307 ± 56 ng/ml in N22, which is 29.7 ± 6.2 percent of normal
• 170 ± 62 ng/ml in N25, which is 15.7 ± 5.7 percent of normal.

These clinically therapeutic cFVII antigen levels have, thus far, persisted for more than 1 year in N22 and N25 and for 2.6 years in N24.

Safety

The researchers found that measures of liver and kidney function were within the normal range in all of the dogs. Likewise, D-dimer and fibrinogen levels were within the normal range.

The team said these results suggest that continuous cFVII expression—even in N24, which averaged 8.3 μg/ml for 2.6 years—did not result in evident activation of the endogenous coagulation system or induce a chronic pathological state.

N24 did exhibit a transient elevation of anti-cFVII IgG2. However, this response was not inhibitory and did not affect the transgene expression plateau.

The researchers did not detect anti-cFVII IgG2 in the other 3 dogs, nor did the team detect anti-cFVII IgG1 in any of the dogs studied.

“This work is very exciting and promising,” said study author Timothy Nichols, MD, of The University of North Carolina at Chapel Hill.

“The FVII-deficient dogs tolerated the initial gene therapy infusions very well and have had no adverse side effects over several years of follow-up. In other related studies in dogs with hemophilia B, similar positive findings have translated to people with hemophilia B.”

Beagle

Photo by Julien Valroff

Gene therapy can safely and effectively treat factor VII (FVII) deficiency in dogs, according to research published in Blood.

Three of the 4 dogs treated expressed levels of FVII that would be therapeutic in humans, with long-term stability.

In one dog, the effects have persisted for more than 2.5 years and are ongoing.

In addition, researchers said the therapy appears safe, based on kidney function, liver function, and blood measurements.

The team believes this success in large animals holds considerable potential for a safe, effective, and long-lasting new treatment in humans with FVII deficiency.

“Our finding has great clinical relevance for patients with FVII deficiency,” said Paris Margaritis, DPhil, of The Children’s Hospital of Philadelphia in Pennsylvania.

“These dogs have the type of mutation found in the majority of patients with this disorder, so this approach could lead to a sustained gene therapy in people.”

Dr Margaritis and his colleagues studied dogs with a G96E missense FVII mutation (FVII-G96E), which have less than 1% FVII activity. The researchers said these dogs had undetectable plasmatic antigen by Western blot and therefore represent the most prevalent type of human FVII deficiency.

“We developed a unique animal model of this disease after identifying dogs with naturally occurring FVII deficiency,” Dr Margaritis said. “Our investigations enabled us to design the corrective gene to insert into our virus vector in the current study.”

The researchers tested liver-directed, adeno-associated viral (AAV) serotype 8 vector delivery of a canine FVII zymogen transgene (cFVII) in 4 FVII-G96E dogs, known as Otis, N22, N24, and N25.

The animals received escalating doses of AAV8-cFVII, ranging from 2E11 vg/kg to 4.95E13 vg/kg.

Efficacy

At baseline, all dogs had less than 1% cFVII activity levels. After receiving AAV8-cFVII, they experienced a reduction in prothrombin time that reached a plateau:

• From 121.1± 1.0s to 22.1 ± 3.2s in N24 (4.95E13 vg/kg)
• From 83.5 ± 18.4s to 25.0 ± 3.6s in N22 (2E12 vg/kg)
• From 96.0 ± 5.8s to 28.7 ± 3.7s in N25 (6E11 vg/kg)
• From 124.8 ± 4.6s to 50.4 ± 4.0s in Otis (2E11 vg/kg).

The researchers also observed an increase in cFVII expression for all of the dogs but Otis. Levels of cFVII antigen reached plateaus of:

• 8320 ± 1800 ng/ml in N24, which is 770 ± 167 percent of normal
• 307 ± 56 ng/ml in N22, which is 29.7 ± 6.2 percent of normal
• 170 ± 62 ng/ml in N25, which is 15.7 ± 5.7 percent of normal.

These clinically therapeutic cFVII antigen levels have, thus far, persisted for more than 1 year in N22 and N25 and for 2.6 years in N24.

Safety

The researchers found that measures of liver and kidney function were within the normal range in all of the dogs. Likewise, D-dimer and fibrinogen levels were within the normal range.

The team said these results suggest that continuous cFVII expression—even in N24, which averaged 8.3 μg/ml for 2.6 years—did not result in evident activation of the endogenous coagulation system or induce a chronic pathological state.

N24 did exhibit a transient elevation of anti-cFVII IgG2. However, this response was not inhibitory and did not affect the transgene expression plateau.

The researchers did not detect anti-cFVII IgG2 in the other 3 dogs, nor did the team detect anti-cFVII IgG1 in any of the dogs studied.

“This work is very exciting and promising,” said study author Timothy Nichols, MD, of The University of North Carolina at Chapel Hill.

“The FVII-deficient dogs tolerated the initial gene therapy infusions very well and have had no adverse side effects over several years of follow-up. In other related studies in dogs with hemophilia B, similar positive findings have translated to people with hemophilia B.”