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
Authors: Pipe Steven , Giermasz Adam , Castaman Giancarlo , Key Nigel S. , Lattimore Susan U , Leebeek Frank , Miesbach Wolfgang , Recht Michael , Gomez Esteban , Long Alison , Gut Robert , von Drygalski Annette 
Published: November 2019

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.

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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; Baxalta/Shire: Research Funding; uniQure BV: Consultancy, 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.