Spk-9001: Adeno-Associated Virus Mediated Gene Transfer For Hemophilia B-1 Year Follow Up And Impact Of Baseline Characteristics On Transgene-Derived Factor Ix Activity And Persistence

Background : Prior work demonstrated long term expression of factor IX (mean FIX:C ~5.1%) after AAV8-mediated gene transfer in hemophilia B (Nathwani et al., 2014), but transgene-derived FIX:C fell short of trough values obtained by long-acting FIX prophylaxis (Santagostino et al . 2016) and natural history data supporting levels of ~12% sufficiently eliminate spontaneous hemarthroses (den Uijl et al. 2011). We developed an efficient capsid and expression cassette that could be administered at low doses to achieve FIX:C adequate to prevent bleeding without use of exogenous FIX. Here we report 1 year follow up data in 7 subjects following SPK-9001 infusion at a dose of 5 x 10 11 vg/kg. These data represent the largest cohort of hemophilia B subjects treated with gene transfer using the same vector and dose with available 1 year follow up data. We additionally report observations of subject baseline pre-vector characteristics relative to steady-state transgene-derived FIX:C and clinical outcomes. Objective: To obtain long term transgene-derived FIX:C u003e 12% able to prevent spontaneous bleeding without the need for prophylactic FIX infusions with consistent and predictable results among all subjects, irrespective of baseline characteristics. Methods : The study vector, SPK-9001, consists of a liver specific, bioengineered AAV capsid (Spark100) and a single-stranded codon optimized expression cassette encoding FIX-Padua. FIX-Padua is a naturally occurring variant that confers ~8-12-fold greater specific activity compared to wild-type FIX (Simioni et al. 2009, Crudele et al. 2015). Subject baseline characteristics were determined at study screening. FIX:C and clinical data were prospectively collected after vector infusion. Results : To date, 7 subjects completed 1 year follow up after SPK-9001 infusion at a dose of 5 x10 11 vg/kg. No subjects developed a FIX inhibitor or experienced vector related adverse events (AEs). Subject mean FIX:C following vector infusion through 52 weeks is outlined in figure 1. Subjects were males ages 18-52 yrs with FIX:C ≤2%. One subject had a Spark 100 neutralizing antibody (NAb) of 1:1 and the remaining were Conclusion : As of 8/1/17, we report the highest, most consistent and sustained vector derived FIX:C following gene transfer. Despite heterogenous baseline characteristics, all subjects achieved consistent clinical results, including no vector related AEs, improved QoL, termination of prophylaxis, near complete elimination of bleeding and factor use. Low grade liver fibrosis and prior HCV exposure did not appear to affect steady-state FIX:C. Individual subject data may imply effects of CRM status and NAb titer on achieved FIX, but the current dataset is too small to define the relationship. In summary, these preliminary data suggest SPK-9001 safely, consistently, and independent of subject baseline characteristics, achieved FIX:C able to substantially ameliorate clinical manifestations of hemophilia. Disclosures George: Pfizer: Consultancy; Spark Therapeutics: Other: Principal Investigator of Ongoing Phase I/II Gene Therapy Trials for Hemophilia A and B. Ducore: Octapharma: Research Funding; Bayer, Shire, HemaBiologics, Bioverativ, Octapharma, Spark Therapeutics: Other: Advisory board. Cuker: T2 Biosystems: Research Funding; Spark Therapeutics: Research Funding. Von Mackensen: LFB: Honoraria. McGuinn: Shire / Baxalta, Spark, Biogen, Roche/Genetehc: Research Funding; Shire/Baxalta: Consultancy. Wright: Spark Therapeutics: Employment, Equity Ownership, Patents u0026 Royalties. Dasen: Spark Therapeutics: Employment. Barber: Spark Therapeutics: Employment. Chen: Spark Therapeutics: Employment. Hui: Spark Therapeutics: Employment. Patel: Spark Therapeutics: Employment. Liu: Spark Therapeutics: Employment. Wachtel: Spark Therapeutics: Employment. Takefman: Spark Therapeutics: Employment. Couto: Spark Therapeutics: Employment. Reape: Spark Therapeutics: Employment. Carr: Spark Therapeutics: Employment. Anguela: Spark Therapeutics: Employment, Equity Ownership, Patents u0026 Royalties. High: Spark Therapeutics: Employment, Equity Ownership, Patents u0026 Royalties.