OC 02.1 - Kinetic profiles of anti-AAV5 antibody generation and clearance in neonatal, infant, and adult hemophilia A dogs

Saturday, June 22, 2024

13:00 – 13:15 ICT

Room: Ballroom B2

Presenting Author(s)

Paul Batty, MBBS PhD

Associate Professor
Cancer Institute, University College London, London, UK
London, England, United Kingdom

Co-Author(s)

BH

Britta Handyside

Associate Director
BioMarin Pharmaceutical, Novato, United States
Novato, California, United States
LS

Laura Swystun

Medical Writer
Department of Pathology and Molecular Medicine, Queen's University, Kingston, Canada
Kingston, Ontario, Canada
AM

Aomei Mo

Research Technologist
Department of Pathology and Molecular Medicine, Queen's University, Kingston, Canada
Kingston, Ontario, Canada
LH

Lori Harpell

Veterinary Technologist
Department of Pathology and Molecular Medicine, Queen's University, Kingston, Canada
Kingston, Ontario, Canada
AP

Abbey Pender

Veterinary Technologist
Department of Pathology and Molecular Medicine, Queen's University, Kingston, Canada
Kingston, Ontario, Canada
AW

Andrew Winterborn

Veterinarian
Animal Care Services, Queen's University, Kingston, Canada
Kingston, Ontario, Canada
Sylvia Fong

Executive Director, Head of Hematology Research
BioMarin Pharmaceutical
Novato, California, United States
David Lillicrap, MD

Professor Department of Pathology and Molecular Medicine
Molecular Hemostasis Research Group, Department of Pathology and Molecular Medicine, Queen's University, Kingston, ON, Canada.
Kingston, Ontario, Canada

Background: Hemophilia A dogs represent an important pre-clinical model for adeno-associated virus (AAV)-gene therapy. Anti-AAV antibodies are recognized to adversely affect the outcome of AAV-mediated gene delivery. Details of the anti-AAV5 antibody response in hemophilia dogs have not been studied.

Aims: To determine the kinetic profiles of anti-AAV5 total antibody generation and clearance in neonatal, infant, and adult severe hemophilia A dogs.

Methods: Neonatal (2-week, n=2), infant (2-month, n=3), and adult (mean=4.7 years, n=10) hemophilia A dogs received a single infusion of AAV5-canine FVIII (AAV-cFVIII) (dose=6.0e13-2.0e14 vg/kg). Two untreated neonates born to an AAV5-cFVIII-treated mother were also studied. Total anti-AAV5 antibodies were detected and quantified by ELISA. All plasma samples were tested at a dilution of 1 to 25. Results are reported as the signal-to-noise (S/N) ratio (positive >1.3). In the 2 neonates with passively acquired antibodies, anti-AAV antibody titers were derived.

Results: In all dogs treated with AAV5-cFVIII vectors, pre-treatment plasma samples were negative for anti-AAV5 total antibodies. All 10 adult dogs treated with AAV5-cFVIII developed high-level anti-AAV5 antibodies in the 4 weeks post-treatment (S/N ratios range 146-169). S/N ratios remained stable for the period of follow-up (12-45 months) (Figure 1). Similar results were seen in the 5 neonatal/infant dogs with peak S/N ratios of 165-189 that were stable over 18-27 months. There were no significant differences in antibody responses or kinetics with any vector dose or age cohort. One neonatal-treated dog (who did not express FVIII) experienced a 20% fall in anti-AAV5 antibodies by 22 months. The two neonates born to an AAV5-cFVIII treated mother had anti-AAV5 titers of 2,451 and 3,679 at 1 week of age that declined to 219 and 337 at 6 weeks (Figure 2).

Conclusion(s): Anti-AAV5 antibody responses in hemophilia dogs are robust and long-lasting. Passively acquired antibodies in newborn dogs show rapid clearance kinetics.