OC 01.5 - Innate and Adaptive Immune Responses to Adeno-Associated Viral Gene Therapy in the Severe Hemophilia A Dog Model

Saturday, July 9, 2022

2:00 PM – 2:15 PM

Location: S11A

Presentation Format: In-Person

Presenting Author(s)

Paul Batty, MBBS, PhD

Adjunct Assistant Professor
Queen's University
Kingston, Ontario, Canada

Co-Author(s)

AM

Aomei M. Mo

Research Assistant
Queen's University
Kingston, Ontario, Canada
AI

Ashrafali M. Ismail

Senior Scientist 1
BioMarin Pharmaceutical
Novato, California, United States
BY

Bridget Yates

Scientist 2
BioMarin Pharmaceutical
Novato, California, United States
AG

Alyssa Gonzalez

Research Associate 2
BioMarin Pharmaceutical, USA
Novato, California, United States
BH

Britta Handyside

Senior Scientist 2
BioMarin Pharmaceutical, USA
Novato, California, United States
LH

Lorianne Harpell

Research Associate
Queen's University
Kingston, Ontario, Canada
DH

David Hurlbut

Associate Professor
Queen's University, Canada
Kingston, Ontario, Canada
AM

Alexandre Menard

Interventional Radiologist
Kingston Health Sciences Center
Kingston, Ontario, Canada
AP

Abbey Pender

Veterinary Technician
Queen's University
Kingston, Ontario, Canada
LR

Lisa Razon

Research Associate 2
BioMarin Pharmaceutical, USA
Novato, California, United States
CS

Choong-Ryoul Sihn

Senior Scientist 1
BioMarin Pharmaceutical, USA
Novato, California, United States
AW

Andrew Winterborn

University Veterinarian
Queen's University
Kingston, Ontario, Canada
SF

Sylvia Fong, MD

Senior Director
BioMarin Pharmaceutical
Novato, California, United States
David Lillicrap, MD

Professor
Department of Pathology and Molecular Medicine, Queen's University
Kingston, Ontario, Canada

Background: Adeno-associated viral (AAV) gene therapy is under investigation for the treatment of severe hemophilia. The predominant adverse event in clinical trials has been elevation of alanine aminotransferase (ALT) levels. Although capsid directed cytotoxic T-cell responses have been reported, the underlying mechanism(s) remain unclear.

Aims: To evaluate the early immune response to AAV5-cFVIII in the severe hemophilia dog model.

Methods: Severe hemophilia A dogs were treated using one of three AAV5-B-domain deleted canine Factor VIII constructs with a hybrid liver promoter (AAV5-HLP-cFVIII, Table 1). Capsid immune responses were evaluated using total antibody and ELISPOT assays. Serum innate immune responses were evaluated using a cytokine array (n=16) and complement function. Vector genome (VG) copies and cFVIII mRNA were quantified in liver biopsies at baseline and 3-months post-treatment using ddPCR.

Results: Ten male hemophilia dogs (median = 4.3 years, 0.8 – 9.0 years) received a single AAV5-HLP-cFVIII infusion (dose = 6.0e13 – 2.0e14 vg/kg). FVIII expression was seen for dogs treated with the codon-optimized constructs (n=7). Dose response was seen at 3 months post-treatment, with higher one-stage FVIII:C in the high-dose (2e14 vg/kg, mean=15.6±0.3 IU/dL) compared to the low-dose cohort (6-8e13 vg/kg, mean=6.2±1.0 IU/dL). Liver biopsies at 3-months demonstrated AAV5-HLP-cFVIII in all animals, with correlation between VG and cFVIII mRNA copies (r=0.8, p=0.01). Anti-AAV5 capsid antibodies were detected starting day 7 post-treatment. No new FVIII inhibitors were detected. Dogs displayed variable serum cytokine profiles, with no change in mean levels 24-hours post-dosing. Higher baseline and post-dose levels of TNF-alpha, IL2, IL6, IL7, IL15 and IL18 were observed in the dog with a FVIII inhibitor history (MEM2018). No capsid specific T-cell responses or complement activation was detected.

Conclusion(s): FVIII expression was seen using co-AAV5-HLP-cFVIII vectors in the hemophilia dog model. No blood biomarkers of innate immune activation were detected, with further liver studies ongoing.