Highlights From the ISTH 2020 Virtual Congress
Frequency, Location and Nature of AAV Vector Insertions After Long-term Follow-up of FVIII Transgene Delivery in a Hemophilia A Dog Model
Paul Batty1, Sylvia Fong2, Matteo Franco3, Irene Gil-Farina3, Aomei Mo1, Lorianne Harpell1, Christine Hough1, David Hurlbut1, Abbey Pender1, Sofia Sardo Infirri1, Andrew Winterborn4, Manfred Schmidt3 and David Lillicrap1
1Department of Pathology and Molecular Medicine, Queen's University, Kingston, Ontario, Canada.
2BioMarin Pharmaceutical, Novato, CA, USA.
3GeneWerk GmbH, Heidelberg, Germany.
3Animal Care Services, Queen's University, Kingston, Ontario, Canada.
Key Data Points
- FREQUENCY AND LOCATION OF INTEGRATION EVENTS
- EPISOMAL AND INTEGRATED AAV-FVIII COPIES
- COMMON INTEGRATION SITES
The table on the left shows dose, capsid serotype, FVIII levels, and number of integration sites (IS) for the 8 dogs included in the study. Ten years after infusion, FVIII levels in 2 of the 8 animals were < 1% and ranged from 2.9% to 8.6% in the other 6 animals. Integration sites were analyzed using 2 methods (target-enrichment sequencing, TES, and linear amplification-mediated PCR, LAM-PCR). The graph on the right shows the relative distribution of IS for each animal.
Genomic DNA from 2 hepatic sites for each animal was analyzed for vector-genome integration. Integration forms (vector-genome) accounted for 4.6% and episomal forms (vector-vector) accounted for 95.4% of the read counts. These results indicate that the expression vectors maintained predominantly an episomal form 10+ years after infusion.
This table shows the 10 most common integration sites (chromosome, size, gene, and location) based on the TES method. Based on both sequencing methods, the most common integration sites were found in proximity to the KCNIP2, CLIC2, ABCB1, and F8 genes.