OC 21.3 - Treatment of Canine Hemophilia A via Intraosseous Delivery of a Platelet-Specific Factor VIII-Lentiviral Vector

Sunday, July 10, 2022

3:15 PM – 3:30 PM

Location: ExCel Center, S11A

Presentation Format: In-Person

Presenting Author(s)

CR

Cameron W. Rementer, PhD

Postdoctoral Researcher
Seattle Children's Research Institute
Seattle, Washington, United States

Co-Author(s)

CL

Chong Li

Research Scientist
Seattle Children's Research Institute
Seattle, Washington, United States
TN

Timothy C. Nichols

Professor
Department of Medicine and Pathology and Lab Medicine, UNC
Chapel Hill, North Carolina, United States
XC

Xiaohe Cai

Research Scientist
Seattle Children's Research Institute
seattle, Washington, United States
JJ

Julia Joo

Research Scientist
Seattle Children's Research Institute
Seattle, Washington, United States
XW

Xuefeng Wang

Research Scientist
Seattle Children's Research Institute
Seattle, Washington, United States
EM

Elizabeth Merricks

Research Operations Manager
UNC Department of Pathology and Lab Medicine (FOBRL)
Chapel Hill, North Carolina, United States
HO

Hans Ochs

Principal Investigator
Seattle Children's Research Institute
Seattle, Washington, United States
DR

David Rawlings

Center Director
Seattle Children's Research Institute
Seattle, Washington, United States
CM

Carol Miao

Principal Investigator
Seattle Children's Research Institute
Seattle, Washington, United States

Background: Hemophilia A (HemA) is a genetic disease resulting from a factor VIII (FVIII) deficiency. Traditional protein infusion to treat HemA is costly and requires repeated dosing.

Aims: We demonstrated previously that intraosseous (IO) gene therapy via delivery of lentiviral vectors (LVs) into bone marrow targeting FVIII expression in platelets successfully treated HemA mice, including mice that had developed FVIII inhibitors. Here, we investigated the treatment of HemA dogs using this approach.

Methods: A lentiviral vector incorporating a platelet-specific promoter Gp1bα and canine FVIII gene was injected into the tibia or iliac bones of 4 HemA dogs. Prior to injection, the dogs were treated with an immune modulation regimen to minimize the immune response. Following the procedure, blood samples were taken at various timepoints.

Results: All dogs recovered well from the procedure and had blood chemistry values within normal ranges. Expression of cFVIII was examined in platelets and plasma isolated from LV-treated dogs by ELISA and aPTT assays. Canine FVIII can be detected in platelets with the highest expression at 5-10 mU/108 platelets around 1-2 months post-procedure and expression persisted for the experimental duration in all treated dogs. The correction of HemA phenotype was evaluated by whole blood clotting time (WBCT) and thromboelastography. WBCT was shortened in multiple time points shortly after IO gene therapy, indicating improved hemostasis. Furthermore, the IO gene therapy was well tolerated and did not produce any toxicity as evaluated by CBC and blood chemistry analysis. Encouragingly, the dogs experienced fewer bleeding events per year after gene therapy treatment compared with the baseline prior treatment.

Conclusion(s): We have established an IO-LV gene therapy protocol to treat HemA dogs successfully with persistent effects of treatment over 2-4 years. Our study demonstrated a potential strategy for safe and effective application of gene therapy in vivo for treating HemA patients.