-Author name in bold denotes the presenting author
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3348 One Year Data from a Phase 2b Trial of AMT-061 (AAV5-Padua hFIX variant), an Enhanced Vector for Gene Transfer in Adults with Severe or Moderate-Severe Hemophilia B

Program: Oral and Poster Abstracts
Session: 801. Gene Therapy and Transfer: Poster II
Hematology Disease Topics & Pathways:
Adult, Biological, Hemophilia, Diseases, Therapies, Bleeding and clotting, gene therapy, Study Population, Clinically relevant
Sunday, December 8, 2019, 6:00 PM-8:00 PM
Hall B, Level 2 (Orange County Convention Center)

Steven Pipe, MD1, Adam Giermasz, MD, PhD2, Giancarlo Castaman, MD3*, Nigel S. Key, MBChB, FRCP4, Susan U Lattimore5*, Frank W.G. Leebeek, MD, PhD6, Wolfgang Miesbach, MD, PhD7*, Michael Recht, MD, PhD5, Esteban Gomez, MD8, Alison Long9*, Robert Gut10* and Annette von Drygalski, MD, PharmD11

1University of Michigan, Ann Arbor
2University of California Davis, Sacramento, CA
3Azienda Ospedaliera Universitaria Careggi, Florence, Italy
4University of North Carolina, Chapel Hill
5Oregon Health & Science University, Portland
6Erasmus University Medical Center, Rotterdam, Netherlands
7University Hospital Frankfurt, Frankfurt, Germany
8Phoenix Children's HOspital, Phoenix
9UniQure Inc, Lexington, MA
10Uniqure Inc, Lexington, MA
11Department of Medicine, Division of Hematology/Oncology, University of California San Diego, San Diego, CA

Background: Gene therapy for hemophilia offers the possibility of ameliorating the disease severity to a milder or functionally curative state through a single treatment. AMT-061 is an investigational gene therapy for hemophilia B comprising an adeno-associated virus serotype 5 (AAV5) vector containing a codon-optimized Padua variant human factor IX (FIX) gene with liver-specific promoter.
Aims: Confirm that a single dose of AMT-061 will provide a minimum-therapeutic response of FIX activity 6-weeks post-dose in participants with severe or moderate-severe hemophilia B. Here, 1 year of follow-up will be presented for the first time.

Methods: Phase 2b, open-label, multi-center trial (NCT03489291) in adult males with FIX ≤2% and without active hepatitis or uncontrolled HIV. Participants were not excluded based on neutralizing antibodies to AAV5. Participants received a single intravenous dose of AMT-061 (2x1013 gc/kg) and will be followed for 5-years. The primary endpoint was FIX activity at Week 6. Secondary endpoints include e-diary recordings of bleeds and FIX concentrate use, laboratory parameters, joint health, patient-reported outcomes, and adverse events (AEs).

Results: All participants had FIX ≤1% (severe or moderately-severe FIX deficiency), required routine FIX prophylaxis, and had neutralizing activity to AAV5 at baseline. Following AMT-061 treatment, FIX activity increased rapidly (Figure) to a mean of 31% at Week 6. At Week 36, mean FIX activity increased further to 45% with FIX activity levels of 54%, 30% and 51% in participants 1-3 respectively. As of 36 weeks, there were no bleeds post-treatment and no requirement for FIX replacement aside from protocol-specified use for perioperative management in participant 3. There were no clinically significant elevations in liver enzymes and no participants required steroids related to the treatment. One participant experienced 2 mild AEs possibly related to treatment shortly after dosing (self-limiting headache and slightly elevated CRP). One patient had hip surgery due to worsening of pre-existing avascular necrosis deemed unrelated by investigator to AMT-061 and received FIX per protocol according to standard clinical practice. No participant developed inhibitors to FIX. Updated results to 52 weeks of follow-up will be presented.

Conclusions: Sustained elevation of FIX activity into the mild-to-normative range were observed in all participants 36 weeks after treatment with AMT-061. AMT-061 was safe and well-tolerated with no requirement for immunosuppression. These data support the ongoing Phase 3 study.

Disclosures: Pipe: Novo Nordisk: Consultancy; Apcintex: Consultancy; Roche/Genentech: Consultancy; BioMarin: Consultancy; Shire: Consultancy; Sanofi: Consultancy; uniQure: Consultancy; Pfizer: Consultancy; HEMA Biologics: Consultancy; Catalyst Bioscience: Consultancy; Freeline: Consultancy; CSL Behring: Consultancy; Bayer: Consultancy; Spark Therapeutics: Consultancy. Giermasz: Genentech/Roche: Consultancy, Other: Research, Speakers Bureau; Sangamo: Other: Research; BioMarin: Consultancy, Other: Research; uniQure: Consultancy, Other: Research; Bioverativ/Sanofi: Consultancy, Speakers Bureau. Castaman: Roche: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Kedrion: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sanofi: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda (SHIRE): Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; CSL Behring: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Uniqure: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Werfen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Bayer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novo Nordisk: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Research Funding; Sobi: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Key: Uniqure BV: Research Funding. Leebeek: CSL Behring: Research Funding; uniQure BV: Consultancy, Research Funding; Baxalta/Shire: Research Funding. Miesbach: Bayer, Chugai, Novo Nordisk, Octapharma, Pfizer, Takeda/Shire, UniQure: Speakers Bureau; Bayer, BioMarin, CSL Behring, Chugai, Freeline, Novo Nordisk, Octapharma, Pfizer, Roche, Takeda/Shire, UniQure: Consultancy; Bayer, Novo Nordisk, Octapharma, Pfizer, Takeda/Shire: Research Funding. Recht: Bioverativ, CSL Behring, Genentech, Kedrion, NovoNordisk, Pfizer, Shire, Uniqure: Consultancy; American Thorombosis & Hemostasis Network: Other: Immediate Past Chair; Bioverativ, Genentech, NovoNordisk Shire: Research Funding. Gomez: Alnylam: Consultancy; Novo Nordisk, Novartis, Pfizer, Sanofi, Takeda, UniQure: Research Funding. Long: Uniqure BV: Employment. Gut: Uniqure BV: Employment. von Drygalski: University of California San Diego: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties; UniQure, Bayer, Bioverativ/Sanofi, Pfizer, Novo Nordisk, Biomarin, Shire, CSL Behring: Consultancy; Hematherix Inc.: Membership on an entity's Board of Directors or advisory committees, Other: Founder.

*signifies non-member of ASH