Slide 1: Human liver biopsy analysis shows decline in FVIII levels following AAV5-hFVIII-SQ gene therapy
World Federation of Hemophilia World Human liver biopsy analysis shows decline Congress 2024 in FVIII levels following AAV5-hFVIII-SQ gene therapy may be due to low RNA transcription levels despite persistence of full-length episomal vector genomes Bridget Yates1, Ashrafali M. Ismail1, Aras N. Matti
Slide 2: Disclosures
Disclosures • Bridget Yates is an employee and stockholder of BioMarin Pharmaceutical Inc. 2
Slide 3: FVIII activity declines over time following AAV-mediated gene therapy
FVIII activity declines over time following AAV-mediated gene therapy • Valoctocogene roxaparvovec (AAV5-hFVIII-SQ) is a gene therapy for hemophilia A that uses an AAV5 vector to deliver a B-domain-deleted hFVIII coding sequence controlled by a liver-selective promoter • A single infusion has provid
Slide 4: Study design
Study design • Optional sub-study of the phase 1/2, phase 3 GENEr8-1, and phase 3b GENEr8-3 trials, assessing the efficacy and safety of valoctocogene roxaparvovec in adult males with severe hemophilia A (FVIII ≤1 IU/dL) – Participants were administered 6x1013 vg/kg – Phase 3b trial incorporated the
Slide 5: Aims
Aims To examine liver histopathology To assess rAAV5-HLP-co-hFVIII-SQ vector transduction efficiency To characterize and quantify episomal forms of vector DNA To quantify transgene expression (hFVIII-SQ RNA) and correlate with FVIII activity FVIII, factor VIII; hFVIII-SQ, B-domain-deleted human FVII
Slide 6: Liver biopsy samples were collected from a wide variety of participants
Liver biopsy samples were collected from a wide variety of participants • Participants’ FVIII activity level varied from <3 to 87 IU/dL • Two participants originally had high FVIII activity, but it had since declined to <3 IU/dL • Four biopsy samples collected at the time of transaminitis (SoC) Red
Slide 7: Histopathology revealed no evidence of abnormal architecture or dysplasia
Histopathology revealed no evidence of abnormal architecture or dysplasia Histopathology sections stained with hematoxylin and eosin Steatosis score SoC samples Sub-study samples BMI >33 at enrollment % steatosis • Varying levels of steatosis were detected – 11/13 showed mild steatosis consistent wi
Slide 8: Efficient hepatocyte transduction of AAV5-hFVIII-SQ was detected regardless of corticosteroid treatment
Efficient hepatocyte transduction of AAV5-hFVIII-SQ was detected regardless of prophylactic corticosteroid treatment - prophylactic CS + prophylactic CS Hepatocyte transduction Phase 1/2 study FVIII DNA/FVIII RNA Phase 3 sub-study Phase 3 SoC samples Steroid regimen Bx #14 (wk 17) Bx #15 (wk 26) AAV
Slide 9: Circular full-length episomes persist through years of post-gene therapy follow-up
Circular full-length episomes persist through 4 years of post-gene therapy follow-up • AAV vector genomes persist as episomal DNA and are accountable for long-term gene expression1 • Circular full-length episomes did not decrease over time – Mean ± SD circular full-length episomes in the study parti
Slide 10: Full-length episomes and RNA transcript levels correlate with FVIII activity
Full-length episomes and RNA transcript levels correlate with FVIII activity Phase 1/2 study DNA vs FVIII activity RNA vs FVIII activity Phase 3 sub-study r = 0.78 Phase 3 SoC samples r = 0.63 P = 0.016 FVIII <3 IU/dL (phase 3) P = 0.02 FVIII activity was measured using chromogenic substrate assay.
Slide 11: FVIII-SQ RNA expression influences FVIII response
FVIII-SQ RNA expression influences FVIII response • Mean ± SD hFVIII-SQ RNA transcript levels in participants with FVIII >3 IU/dL were 78.5 ± 50.9* transcripts/ng RNA (n = 11) • Two participants’ FVIII activity declined to <3 IU/dL – Low RNA transcript levels (0.2 and 1.7 transcripts/ng RNA) – Level
Slide 12: Transcriptional efficiency contributes to low FVIII activity, suggesting transgene silencing
Transcriptional efficiency contributes to low FVIII activity, suggesting transgene silencing may mediate the decline of FVIII expression following AAV5-hFVIII-SQ treatment FVIII activity vs time Transcriptional efficiency Phase 1/2 study r = −0.1 Phase 3 sub-study P = 0.79 Phase 3 SoC samples FVIII
Slide 13: Conclusions
Conclusions Histopathology analysis shows no evidence of abnormal architecture findings or dysplasia Varying levels of steatosis were detected, similar to levels observed with high prevalence in normal male populations from developed countries No clinically relevant inflammation was observed Follow-
Slide 14: Acknowledgements
Acknowledgements Thank you to all the trial participants, their families, study-site personnel, and investigators • Funding for this study was provided by BioMarin Pharmaceutical Inc. Scan to view this presentation online 14