PB0263 - Treatment of Canine Hemophilia A via Intraosseous Delivery of a Platelet-Specific Factor VIII-Lentiviral Vector

Sunday, June 23, 2024

13:45 – 14:45 ICT

Room: Exhibition Hall

Presenting Author(s)

CR

Cameron W. Rementer

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

Co-Author(s)

TN

Timothy Nichols

Director of the Francis Owen Blood Research Laboratory
Department of Pathology and Laboratory Medicine and Blood Research Center, University of North Carolina School of Medicine, Chapel Hill, NC USA.
Chapel Hill, North Carolina, United States
CL

Chong Li

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

Xiaohe Cai

Research Scientist
Seattle Children's Research Institute
Seattle, Washington, United States
Ting-Yen Chao

Research Scientist
Seattle Children's Research Institute
Everett, Washington, United States
Yuanyi Xu

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

Elizabeth Merricks

Research Specialist
Department of Pathology and Laboratory Medicine and Blood Research Center, University of North Carolina School of Medicine, Chapel Hill, NC USA.
Chapel Hill, North Carolina, United States
CM

Carol H. 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. Current AAV-mediated gene therapies produced decreasing levels of FVIII over time. 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. To facilitate clinical translation, we investigated the treatment of HemA dogs using this approach.

Aims: To investigate if IO delivery of LVs carrying FVIII gene (F8) driven by a megakaryocyte-specific promoter GP1bα (G) can produce FVIII protein in platelets and correct HemA phenotype in a canine model.

Methods: An LV vector containing the cFVIII gene was injected into the tibia/iliac bones of 6 HemA dogs (4 in Cohort #1, 2 in Cohort #2). Blood samples were taken at various timepoints post-procedure. For the dogs in Cohort #2, we incorporated several improvements, including performing injections in both the tibia and the iliac bone. Additionally, perioperative hemostasis was performed using bypassing agents to avoid inhibitor formation.

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 could be detected in platelets with the highest expression at 5-10 mU/108 platelets around 1-2 months post-procedure. The improvement of blood coagulation was evaluated by whole blood clotting time (WBCT) and was found to be shortened in multiple time points shortly after IO gene therapy, indicating improved hemostasis. Encouragingly, the dogs experienced fewer bleeding events per year after gene therapy treatment compared to baseline, indicating a partial phenotypic correction .

Conclusion(s): We have established an IO-LV gene therapy protocol to treat HemA dogs successfully with persistent effects of treatment over 2-5 years, including a phenotypic improvement. This represents a potential strategy for gene therapy in HemA patients.