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1055 Long-Term Bleeding Protection, Sustained FIX Activity, Reduction of FIX Consumption and Safety of Hemophilia B Gene Therapy: Results from the HOPE-B Trial 3 Years after Administration of a Single Dose of Etranacogene Dezaparvovec in Adult Patients with Severe or Moderately Severe Hemophilia B

Program: Oral and Poster Abstracts
Type: Oral
Session: 801. Gene Therapies: The Long and the Short of Clinical Trials in Blood Disorders
Hematology Disease Topics & Pathways:
Bleeding and Clotting, Research, clinical trials, Biological therapies, adult, hemophilia, Clinical Research, Diseases, Gene Therapy, Therapies, Study Population, Human
Monday, December 11, 2023: 5:30 PM

Steven Pipe, MD1, Paul van der Valk, MD2*, Peter Verhamme3*, Peter Kampmann4*, Frank W.G. Leebeek, MD, PhD5, Michiel Coppens, MD6,7*, Karina Meijer, MD, PhD8*, Priyanka Raheja9*, Nigel S. Key, MD10, Nathan Visweshwar, MD11, Guy Young, MD12, Richard S. Lemons, MD, PhD13*, Robert Klamroth, MD14*, Wolfgang Miesbach, MD15*, Jan Astermark16,17, Niamh O'Connell18*, Rashid Saeed Kazmi, MBBS, FRCP, FRCPath19*, Nicholas Galante, PhD20*, Sandra LeQuellec, PhD20*, Paul Monahan20 and Cedric R. Hermans, MD, PhD21

1University of Michigan, Ann Arbor, MI
2Van Creveldkliniek, University Medical Center Utrecht, Utrecht, Netherlands
3University Hospitals Leuven, Belgium, Leuven, Belgium
4Rigshospitalet, Copenhagen, Denmark
5Department of Haematology, Erasmus University Medical Center-Erasmus MC, Rotterdam, Rotterdam, Netherlands
6Amsterdam University Medical Centers, Department of Vascular Medicine, University of Amsterdam, Amsterdam, Netherlands
7Amsterdam Cardiovascular Sciences, Pulmonary Hypertension & Thrombosis, Amsterdam, Netherlands
8Department of Hematology, University Medical Center Groningen, Groningen, Groningen, Netherlands
9Royal London Haemophilia Centre, Bart health NHS trust, London, United Kingdom
10UNC Blood Reserach Center, Department of Medicine, University of North Carolina, Chapel Hill, NC
11University of South Florida, Tampa, FL
12Keck School of Medicine, University of Southern California, Los Angeles, CA
13University of Utah, Salt Lake City, UT
14Internal Medicine, Vascular Medicine and Coagulation Disorders, Vivantes Clinic Friedrichshain, Berlin, Germany
15Goethe University Hospital, Frankfurt, Germany
16Department of Hematology, Oncology and Radiation Physics, Skane University Hospital, Malmo, Sweden
17Department of Translational Medicine, Lund University, Malmö, Sweden
18National Coagulation Centre, St James’s Hospital, Dublin, Dublin, Ireland
19University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom
20CSL Behring, King of Prussia, PA
21Cliniques Universitaires Saint-Luc, Brussels, BEL

Introduction: Etranacogene dezaparvovec (formerly AMT-061) is the first approved gene therapy for hemophilia B in the US and Europe. It is an adeno-associated virus serotype 5 (AAV5) vector containing a codon-optimized, highly active factor IX (FIX) Padua R338L transgene under the control of the liver-specific promoter LP-1. The pivotal phase 3 HOPE-B clinical trial (NCT03569891) of etranacogene dezaparvovec demonstrated superiority of bleeding protection compared to standard of care FIX prophylaxis up to 24 months post-treatment; long-term follow-up from Year 2 post-administration onward is currently ongoing.

Aim: To report long-term efficacy and safety data of etranacogene dezaparvovec from the HOPE-B trial over a period of 3 years post-treatment.

Methods: In this pivotal phase 3 open-label, single-arm trial, adult male participants with severe or moderately severe hemophilia B (FIX ≤2%), with or without preexisting AAV5 neutralizing antibodies (NAbs), were infused with a single dose (2×1013 gc/kg) of etranacogene dezaparvovec, following a ≥6-month lead-in period of receiving their usual FIX prophylaxis. Efficacy (bleeding rates, aPTT-based FIX activity levels, FIX consumption) and safety data (adverse events [AEs]) during Years 1, 2, and 3 post-treatment with etranacogene dezaparvovec are reported.

Results: Of 54 participants who received etranacogene dezaparvovec, 52 completed 36 months of follow-up.

Mean annualized bleeding rate (ABR) for all bleeds during Months 7-36 post-treatment was significantly reduced by 64% (mean ABR 1.52) compared with the ≥6-month lead-in period (mean ABR 4.17; P=0.0004). Total number of bleeds (all types) were 136 during the ≥6-month lead-in period and decreased to 55 during Year 1, 48 during Year 2, and 37 during Year 3 post-treatment. Median [range] bleeds per participant decreased from 2.0 [0-10] during the lead-in period and remained stable to 0.0 [0-4] during Year 1, 0.0 [0-10] during Year 2, and 0.0 [0-8] during Year 3. Superior bleeding protection was in line with the level of transgene-derived endogenous FIX expression.

The mean±SD (median; range) endogenous FIX activity level (ie. in the absence of exogenous FIX exposure) of participants was 41.5 IU/dL ±21.7 (39.9; 5.9-113, n=50) at Year 1, 36.7 IU/dL ±19.0 (33.9; 4.7-99.2, n=50) at Year 2, and sustained at 38.6 IU/dL ±17.8 (36.0; 4.8-80.3, n=48) at Year 3 post-treatment. Pharmacodynamic profile was not significantly different in participants with AA5 NAb undetected or titer ≤1:678.

At 3 years post-treatment, 51 (94%) remained free of continuous FIX prophylaxis. One participant who lacked efficacy (highest AAV5 NAbs titer of 1:3212) and 1 who received a 10% partial dose of treatment did not discontinue prophylaxis; 1 participant eventually had his FIX levels declined to 2-5% range; his bleeding phenotype returned, and he resumed prophylaxis per protocol at month 30 post-treatment. During Year 2 and Year 3 post-treatment, 37 (70%) and 39 (75%) participants received no FIX infusion, respectively. Overall mean annualized FIX consumption decreased by 96% over 3 years post-treatment compared to the ≥6-month lead-in period (–246,763 IU/kg/participant, including those receiving FIX prophylaxis post-treatment; P<0.0001).

During the 3 years post-dose, all participants experienced at least 1 treatment-emergent AE (TEAE); of 709 events, 541 (76%) were mild, 137 (19%) were moderate, and 31 (4%) were severe. There were no serious AEs related to treatment [a serious AE of hepatocellular carcinoma (HCC) and a death were reported previously before Year 2 and determined to be unrelated to treatment]. A total of 38/54 (70%) participants experienced 96 treatment-related TEAEs, of which 95% occurred before 6 months post-treatment. The most common AE was an increase in alanine transaminase (ALT), for which 9 (16.7%) participants received supportive care with reactive corticosteroids for a mean duration of 81.4 days (SD: 28.6; range: 51-130 days). No new deaths, no new HCC, and no late treatment-related ALT elevations or thromboembolic events were reported.

Conclusion: Long-term follow-up during the HOPE-B trial has shown that a single-dose of etranacogene dezaparvovec resulted in long-term endogenous FIX Padua expression and superior bleeding protection compared to FIX prophylaxis in participants without or with AAV NAb titer ≤1:678, with a favorable safety profile over 3 years post-administration.

Disclosures: Pipe: Takeda: Consultancy; Sanofi: Consultancy; Regeneron/Intellia: Consultancy; Roche/Genentech: Consultancy; Pfizer: Consultancy; Novo Nordisk: Consultancy; LFB: Consultancy; Freeline: Consultancy; HEMA Biologics: Consultancy; GenVentiv: Consultancy; Equilibra Bioscience: Consultancy; CSL Behring: Consultancy; BioMarin: Consultancy; Bayer: Consultancy; ASC Therapeutics: Consultancy; Apcintex: Consultancy; Spark Therapeutics: Consultancy; uniQure: Consultancy. van der Valk: Bayer: Consultancy. Verhamme: CSL Behring, Roche, CAP-DCF, Bayer HealthCare; LeoPharma; Boehringer Ingelheim; Daiichi Sankyo; Pfizer; Sanofi-Aventis; ThromboGenics: Consultancy. Kampmann: BioMarin Pharmaceuticals, CSL Behring, NovoNordisk AS: Consultancy; CSL Behring: Speakers Bureau. Leebeek: CSL Behring, Takeda, UniQure: Consultancy, Research Funding; Sobi: Research Funding; Biomarin: Consultancy; Roche: Membership on an entity's Board of Directors or advisory committees. Coppens: Anthos, Bayer, CSL Behring/uniQure, Novo Nordisk and Roche: Research Funding; Alexion/AstraZeneca, Bayer, CSL Behring, Daiichi Sankyo, Sobi and Viatris: Consultancy, Honoraria. Meijer: Octapharma: Membership on an entity's Board of Directors or advisory committees; UniQure: Consultancy; Bayer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Alexion and CSL Behring: Speakers Bureau. Key: Biomarin: Consultancy, Ended employment in the past 24 months, Honoraria; Novo Nordisk: Consultancy, Other: Chair of hemophilia grants study section; Uniqure/CSL: Consultancy, Ended employment in the past 24 months, Other: HOPE-B trial (hemophilia gene therapy) Steering Committee; Genentech: Consultancy. Visweshwar: Biogen Idec: Consultancy. Young: Takeda: Consultancy, Research Funding; Genentech/Roche: Consultancy; Hema Biologics/LFB: Consultancy; Spark: Consultancy, Speakers Bureau; Sanofi Genzyme: Consultancy, Speakers Bureau; Genentech, Inc.: Research Funding; Hema Biologics: Speakers Bureau; CSL Behring: Consultancy, Speakers Bureau; Novo Nordisk: Consultancy; Viatris: Patents & Royalties. Lemons: CSL Behring, NovoNordisk: Consultancy. Klamroth: Sobi: Honoraria, Other: Advisory board; Sanofi: Honoraria, Other: Advisory board; Roche/Chugai: Honoraria, Other: Advisory board; Pfizer: Honoraria, Other: Advisory board; Octapharma: Honoraria, Other: Advisory board; Bayer: Honoraria, Other: Advisory board; BioMarin: Honoraria, Other: Advisory board; Takeda: Honoraria, Other: Advisory board; Novo Nordisk: Honoraria, Other: Advisory board; Grifols: Honoraria, Other: Advisory board; Biotest: Honoraria, Other: Advisory board; CSL Behring: Honoraria, Other: Advisory board. Miesbach: Bayer: Consultancy, Research Funding, Speakers Bureau; Regeneron: Consultancy; uniQure: Consultancy; Sanofi: Consultancy; Roche: Consultancy, Speakers Bureau; LFB: Consultancy, Research Funding, Speakers Bureau; CSL Behring: Consultancy, Research Funding, Speakers Bureau; Biotest: Consultancy, Research Funding, Speakers Bureau; Freeline: Consultancy; Chugai: Consultancy, Speakers Bureau; BioMarin: Consultancy, Speakers Bureau; Takeda/Shire: Consultancy, Research Funding, Speakers Bureau; Pfizer: Consultancy, Research Funding, Speakers Bureau; Octapharma: Consultancy, Research Funding, Speakers Bureau; Novo Nordisk: Consultancy, Research Funding, Speakers Bureau. Astermark: BioMarin: Honoraria, Speakers Bureau; Takeda: Honoraria, Speakers Bureau; CSL Behring: Honoraria, Speakers Bureau; Sanofi: Honoraria; Roche: Honoraria, Speakers Bureau; Bayer: Honoraria, Speakers Bureau; Novo Nordisk: Honoraria, Speakers Bureau; Pfizer: Honoraria, Speakers Bureau; Octapharma: Honoraria, Speakers Bureau; SOBI: Honoraria, Speakers Bureau. O'Connell: Sobi: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Freeline: Membership on an entity's Board of Directors or advisory committees; Novo Nordisk: Speakers Bureau; UniQure: Membership on an entity's Board of Directors or advisory committees; F. Hoffmann-La Roche Ltd: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Kazmi: BioMarin Pharmaceuticals, CSL Behring: Consultancy. Galante: CSL Behring: Current Employment. LeQuellec: CSL Behring: Current Employment. Monahan: CSL Behring: Current Employment. Hermans: Bayer, Takeda, Roche, CSL Behring, Novo Nordisk, Pfizer, Sobi, LFB, OctaPharma, Uniqure and Biomarin: Consultancy.

*signifies non-member of ASH