Abstract: Introduction. Valoctocogene roxaparvovec (AAV5-hFVIII-SQ) is an adeno-associated virus gene therapy that transfers a B-domain deleted factor VIII (FVIII) cDNA to hepatocytes. The open-label, single-arm, multicenter phase 3 GENEr8-1 trial (NCT03370913) evaluated valoctocogene roxaparvovec in 134 men with severe hemophilia A (HA) and demonstrated an 83.8% reduction in annualized treated bleeding rate (ABR) and superiority to FVIII prophylaxis (P & lt;0.001). The relationship between baseline FVIII activity and ABR was estimated in congenital HA (den Uijl, et al. Haemophilia 2011;17[1]:41-4); it is unknown if a similar relationship exists after gene transfer. We present here post-hoc analyses of transgene-derived FVIII activity and bleeds in GENEr8-1. Methods. Men ≥18 years of age with severe HA previously on FVIII prophylaxis who were negative for FVIII inhibitors and anti-AAV5 antibodies received one 6x10 13 vg/kg infusion of valoctocogene roxaparvovec. FVIII activity was measured by chromogenic substrate (CSA; lower limit of quantitation [LLOQ], 3.0 IU/dL) and one stage assays (OSA; LLOQ, 1.0 IU/dL); median FVIII activity in every 4- or 6-week window was assessed. Self-reported treated bleeds were counted after week 4, when routine prophylaxis was scheduled to end. The relationship between number of treated joint bleeds and matched median FVIII activity levels in each 4- or 6-week window was modeled using negative binomial regression. Results. As of the data cut date, mean follow-up was 71.6 weeks; 1 participant was lost to follow-up at week 66. At weeks 49-52 (latest time with data for all participants; intent-to-treat population), 9% (12/134) had CSA FVIII activity & lt;3 IU/dL, 3% (4/134) had median FVIII activity ≥3- & lt;5 IU/dL, 17% (23/134) had median FVIII activity ≥5- & lt;15 IU/dL, and 71% (95/134) had median FVIII activity ≥15 IU/dL. While on FVIII prophylaxis prior to gene transfer, 32% of participants (43/134) had an ABR of 0. Following gene transfer, 75% of participants (101/134) were bleed-free through their last follow-up prior to the data cut. The remaining 33 participants reported 149 treated bleeds total, 62% (93/149) as traumatic and 38% (56/149) as spontaneous. By location, 53% (79/149) occurred in joints, 19% (28/149) in muscle, 14% (21/149) in soft tissue, and 14% (21/149) in other or unspecified locations. Relative to FVIII level, 54% of treated bleeds (80/149) occurred when CSA FVIII was & lt;3 IU/dL (LLOQ), 12% (18/149) when FVIII was ≥3- & lt;5 IU/dL, 23% (35/149) when FVIII was ≥5- & lt;15 IU/dL, and 11% (16/149) when FVIII was ≥15 IU/dL. Of 16 treated bleeds that occurred when FVIII was ≥15 IU/dL, 13 were traumatic. Treated joint bleeds followed a similar pattern: 51% (40/79) occurred when FVIII was & lt;3 IU/dL, 15% (12/79) when FVIII was ≥3- & lt;5 IU/dL, 27% (21/79) when FVIII was ≥5- & lt;15 IU/dL, and 8% (6/79) when FVIII was ≥15 IU/dL. A negative binomial regression model based on these data and matched FVIII activity levels predicts & lt;1 treated joint bleed in 2 years for individuals treated with valoctocogene roxaparvovec with FVIII activity ≥15 IU/dL (CSA; Figure). Clinical value of the CSA at low FVIII levels is limited by its LLOQ of 3 IU/dL. Of 12 participants with median FVIII levels below the CSA LLOQ at weeks 49-52, 9 had improved or the same ABR post-gene therapy relative to prophylaxis. The OSA, with its LLOQ of 1 IU/dL, provided important information here. By OSA, 1 had FVIII & lt;1 IU/dL, 5 had FVIII ≥1- & lt;5 IU/dL, and 3 had FVIII ≥5 IU/dL. The remaining 3 participants who had increased ABR after gene transfer had FVIII levels by OSA of 0, 2.1, and 4.8 IU/dL. For participants with OS FVIII & lt;5 IU/dL at week 52 (n = 11), median (IQR) ABR was 1.2 (0-7.9), similar to the median (IQR) ABR of 1.6 (0.6-3.5) reported for people with moderate HA (Abdi, et al. J Throm Haemost 2020;18[12]:3203-10). Conclusions. Gene transfer with valoctocogene roxaparvovec led to sustained endogenous FVIII production and reduced ABR in this phase 3 trial. After gene transfer, the majority of bleeds were traumatic. When FVIII was ≥15 IU/dL, reports of treated bleeds, including joint bleeds, were rare. CSA FVIII activity was predictive of bleeding risk post-gene transfer, as for epidemiologic congenital HA results. At FVIII levels below the CSA LLOQ, the OSA provided clinically relevant information; bleeding with OSA FVIII & lt;5 IU/dL was similar to observations in people with moderate HA, though further exploration with more data is needed. Figure 1 Figure 1. Disclosures Pipe: Biomarin: Consultancy, Other: Clinical trial investigator; Regeneron/ Intellia: Consultancy; uniQure: Consultancy, Other; Spark Therapeutics: Consultancy; Takeda: Consultancy; Sanofi: Consultancy, Other; Sangamo Therapeutics: Consultancy; Roche/Genentech: Consultancy, Other; Pfizer: Consultancy; Novo Nordisk: Consultancy; Freeline: Consultancy, Other: Clinical trial investigator; HEMA Biologics: Consultancy; CSL Behring: Consultancy; Catalyst Biosciences: Consultancy; Genventiv: Consultancy; Grifols: Consultancy; Bayer: Consultancy; ASC Therapeutics: Consultancy; Apcintex: Consultancy; Octapharma: Consultancy; Shire: Consultancy. Ozelo: BioMarin Pharmaceutical Inc.: Consultancy, Other: Clinical trial investigator, Speakers Bureau; Bayer: Consultancy, Speakers Bureau; Novo Nordisk: Consultancy, Other: Clinical trial investigator, Travel support, Speakers Bureau; Pfizer: Consultancy, Other: Clinical trial investigator, Research Funding; Roche: Consultancy, Other: Clinical trial investigator, Travel support, Research Funding, Speakers Bureau; Sanofi: Consultancy, Other: Clinical trial investigator; Takeda: Consultancy, Other: Clinical trial investigator, Travel support, Research Funding, Speakers Bureau; Grifols: Other: Grants review. Kenet: Takeda: Consultancy; Roche: Consultancy; Novo Nordisk: Consultancy; Shire: Research Funding; Pfizer: Consultancy, Research Funding; Opko Biologics: Research Funding; Bayer: Consultancy, Research Funding; Alnylam: Consultancy, Research Funding. Reding: Bayer, CSL Behring, Sanofi Genzyme, Takeda: Speakers Bureau; Bayer, Biomarin (institutional research funding): Research Funding; Bayer, CSL Behring, NovoNordisk, Sanofi Genzyme, Takeda: Honoraria; Bayer, CSL Behring, NovoNordisk, Sanofi Genzyme, Takeda (advisory committees): Membership on an entity's Board of Directors or advisory committees. Mason: BioMarin Pharmaceutical Inc.: Other: Participation as a clinical trial investigator; Roche: Other: Participation as a clinical trial investigator, Travel support, Speakers Bureau. Leavitt: Syntimmune: Research Funding; Sangamo Therapeutics: Research Funding; Pfizer: Research Funding; Merck: Consultancy; CSL DOVA: Consultancy; Catalys: Consultancy; BioMarin: Consultancy, Research Funding; BPL: Consultancy; Behring: Consultancy; HEMA Biologics: Consultancy; Rigel: Consultancy. Laffan: Shire: Membership on an entity's Board of Directors or advisory committees; Leo-Pharma: Speakers Bureau; Alexion: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda: Speakers Bureau; AstraZeneca: Consultancy; Sobi: Membership on an entity's Board of Directors or advisory committees, Other: Travel support; Bayer: Other: Travel support, Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BioMarin Pharmaceutical Inc.: Research Funding. Quon: Orthopaedic Institute for Children: Current Employment. von Drygalski: Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Hematherix, Inc: Membership on an entity's Board of Directors or advisory committees, Patents & Royalties: Super FVa; Novo Nordisk: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Research Funding; CSL Behring: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Biomarin: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; uniQure: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Genentech: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Chou: Bayer: Other: Clinical trial investigator, Speakers Bureau; Novo Nordisk: Consultancy, Other: Clinical trial investigator, Speakers Bureau; BioMarin: Other: Clinical trial investigator; Sanofi: Consultancy, Other: Clinical trial investigator, Speakers Bureau; Chugai: Consultancy, Other: Clinical trial investigator, Speakers Bureau; Pfizer: Other: Clinical trial investigator, Speakers Bureau; CSL: Consultancy, Other: Clinical trial investigator, Speakers Bureau. Shapiro: Sobi: Consultancy; Shire: Consultancy; Pfizer: Consultancy, Speakers Bureau; Bayer: Other: Travel support, Speakers Bureau; Takeda: Speakers Bureau; Roche: Speakers Bureau; CSL Behring: Other: travel support. Dunn: Genentech/Roche: Consultancy, Speakers Bureau; ATHN: Research Funding; Biomarin: Consultancy, Research Funding; Freeline: Research Funding; Takeda: Research Funding; World Federation of Hemophilia USA: Membership on an entity's Board of Directors or advisory committees; CSL Behring: Consultancy; Uniqure: Consultancy; Sanofi: Research Funding; Kedrion: Consultancy. Wang: Bioverativ: Consultancy, Other: Clinical trial investigator; CSL Behring: Consultancy, Other: Clinical trial investigator; Novo Nordisk: Consultancy, Other: Clinical trial investigator; Genentech: Consultancy, Other: Clinical trial investigator; Takeda: Consultancy, Other: Clinical trial investigator; Hema Biologics: Consultancy, Other: Clinical trial investigator; uniQure: Consultancy, Other: Clinical trial investigator; Pfizer/Spark: Other: clinical trial investigator; Octapharma: Other; Bayer: Consultancy, Other: Clinical trial investigator; BioMarin: Consultancy, Other: Clinical trial investigator. Key: Grifols: Research Funding; Takeda: Research Funding; BioMarin: Honoraria, Other: Participation as a clinical trial investigator; Sanofi: Consultancy; Uniqure: Consultancy, Other: Participation as a clinical trial investigator. Kaczmarek: Bayer: Research Funding. Symington: Biomarin: Research Funding; CSL Behring: Other: Travel support; Novonordisk: Other: Travel support. Lawal: BioMarin Pharmaceutical Inc.: Current equity holder in publicly-traded company, Ended employment in the past 24 months. Mahajan: BioMarin Pharmaceutical: Current Employment, Current equity holder in publicly-traded company. Chavele: BioMarin Pharmaceutical: Current Employment, Current equity holder in publicly-traded company. Reddy: BioMarin Pharmaceutical: Current Employment, Current equity holder in publicly-traded company. Yu: BioMarin Pharmaceutical: Current Employment, Current equity holder in publicly-traded company. Wong: BioMarin Pharmaceutical Inc.: Current Employment, Current equity holder in publicly-traded company. Robinson: BioMarin Pharmaceutical Inc.: Current Employment, Current equity holder in publicly-traded company. Kim: BioMarin Pharmaceutical Inc.: Current Employment, Current equity holder in publicly-traded company.

Abstract: Introduction. Severe hemophilia A (HA) negatively impacts health-related quality of life (HRQOL) through joint pain and disability, treatment burden, and effects on mental and emotional health; chronic pain and mental health are core outcomes for hemophilia gene therapy trials (Iorio, et al. Haemophilia 2018;24[4]:e167-72). In the phase 3 trial GENEr8-1 (NCT03370913), men with severe HA who received valoctocogene roxaparvovec (AAV5-hFVIII-SQ) gene therapy experienced a significant increase in endogenous FVIII activity that resulted in reduced bleeding events and FVIII utilization from baseline through 52 weeks (Ozelo, et al. Res Pract Thromb Haemost 2021;5). Here, we analyzed the impact of valoctocogene roxaparvovec on HRQOL. Methods. Men ≥18 years of age with FVIII ≤1 IU/dL previously receiving standard-of-care FVIII prophylaxis and without history of FVIII inhibitors received one 6x10 13 vg/kg valoctocogene roxaparvovec infusion. This analysis included HIV-negative participants who completed the weeks 49-52 visit. Participants completed QOL questionnaires at baseline and weeks 4, 12, 26, and 52 post-gene therapy infusion. Change from baseline was assessed with a two-sided t-test without multiplicity control. Missing data were not imputed. Measures included the hemophilia-specific Haemo-QOL-A questionnaire, which consists of 6 domain scores (Physical Functioning, Role Functioning, Consequences of Bleeding, Worry, Emotional Impact, Treatment Concern) and Total Score ranging from 0-100 (Rentz, et al. Haemophilia 2008;14[5]:1023-34); and the EQ-5D-5L, a general measure of HRQOL that assesses functional dimensions (Mobility, Self-Care, Usual Activities) as well as Pain/Discomfort and Anxiety/Depression (Herdman, et al. Qual Life Res 2011;20[10] :1727-36). EQ-5D-5L results are reported as visual analog scale (VAS; range, 0-100) and Utility Index Score (range, 0-1), which is calculated from population norms (Janssen, et al. Qual Life Res 2013;22[7]:171-27). Higher scores indicate better HRQOL. The anchor-based clinically important differences (CID) used for the Haemo-QOL-A were 5.5 for Total Score and 6 for domain scores (Quinn, et al. Abstract, Hemophilia Federation of America Virtual Conference, Aug 2020). For the EQ-5D-5L Index, 0.03 was considered a CID (Kaplan. COPD 2005;2[1] :91-7). However, use of general population norms, together with the presence of a disability paradox in hemophilia, causes the EQ-5D-5L to underestimate the negative impact of hemophilia on HRQOL (O'Hara, et al. Haemophilia 2021;27[2]:245-52), likely leading to underestimation of changes in HRQOL. Results. This analysis included 132 participants. At baseline, mean ± standard deviation (SD) Haemo-QOL-A Total Score was 75.7 ± 16.7 (n = 130); at weeks 26 and 52, mean change from baseline in Total Score demonstrated improvement (P & lt;0.0001) at or above the CID threshold (Table). Improvement in Total Score was noted as early as 4 weeks (change from baseline, 3.0 ± 8.5; P = 0.0001) and by week 12 had reached the CID (5.5 ± 8.4; P & lt;0.0001). Domain scores for Physical Function, Role Functioning, and Consequences of Bleeding also improved from baseline (P & lt;0.0001), exceeding the CID at weeks 26 and 52 (Table). Treatment Concern demonstrated improvement from baseline (P & lt;0.001) at weeks 26 and 52, exceeding the CID at week 52. Improvements below the CID were noted for Worry at weeks 26 and 52 (P & lt;0.01) and Emotional Impact at week 52 (P & lt;0.05; Table). At baseline, EQ-5D-5L VAS mean ± SD was 80.1 ± 15.3 (n = 131), which increased by 2.5 ± 13.7 (n = 129) at week 26 and 4.5 ± 13.3 (n = 129) at week 52. Mean ± SD EQ-5D-5L Index Score at baseline was 0.78 ± 0.17 (n = 131); mean ± SD changes from baseline at both week 26 (0.04 ± 0.14 [n = 128]) and 52 (0.04 ± 0.16 [n = 129] ) demonstrated improvement (P ≤0.002), exceeding the CID of 0.03. Conclusions. These data demonstrate improvement in core outcomes of mental health (EQ-5D-5L Anxiety/Depression, Haemo-QOL-A Consequences of Bleeding) and pain and discomfort (EQ-5D-5L Pain/Discomfort, Haemo-QOL-A Physical Functioning) as well as ability to perform activities of daily living (EQ-5D-5L Self-Care and Mobility, Haemo-QOL-A Physical Functioning and Role Functioning) for participants with HA following treatment with valoctocogene roxaparvovec compared with their values on standard-of-care FVIII prophylaxis. Figure 1 Figure 1. Disclosures O'Mahony: Freeline: Consultancy; Uniqure: Speakers Bureau; BioMarin Pharmaceutical Inc.: Consultancy. Mahlangu: Baxalta: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Catalyst Biosciences: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; CSL Behring: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novo Nordisk: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Biomarin: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Univeristy of the Witwatersrand: Current Employment; Spark: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Research Funding; Pfizer: Research Funding; Unique: Research Funding; Sanofi: Research Funding, Speakers Bureau; Takeda: Speakers Bureau; WFH: Speakers Bureau; ISTH: Speakers Bureau; Springer: Speakers Bureau. Peerlinck: SOBI: Consultancy, Research Funding; Octapharma: Consultancy; NovoNordisk: Consultancy, Research Funding; Pfizer: Consultancy; Roche: Other: Clinical trial investigator, Research Funding; CSL Behring: Research Funding; Uniqure: Other: Clinical trial investigator; BIoMarin: Other: Clinical trial investigator. Lowe: Biomarin: Research Funding; Novartis: Honoraria; Sobi: Honoraria; Leo: Honoraria; Alexion: Honoraria; Takeda: Honoraria; NovoNordisk: Honoraria. Giermasz: Bayer: Consultancy; ATHN: Consultancy; NovoNordisk: Consultancy; UniQure: Consultancy, Research Funding; Sanofi Genzyme: Consultancy; Bioverativ/Sanofi: Consultancy, Research Funding, Speakers Bureau; Sangamo Therapeutics,: Research Funding; Pfizer: Consultancy; Genentech/Roche: Consultancy, Research Funding, Speakers Bureau; BioMarin: Consultancy, Research Funding. Cockrell: Takeda: Consultancy; CSL Behring: Consultancy; HEMA Biologics: Consultancy; Sanofi: Consultancy; BioMarin: Consultancy; Novo Nordisk: Consultancy; Genentech: Consultancy, Speakers Bureau. Pepperell: Pfizer: Other: Travel support. Chambost: Bayer: Consultancy; BioMarin: Consultancy, Other: Clinical trial investigator; travel support, Speakers Bureau; Roche: Consultancy, Other: Clinical trial investigator; travel support, Speakers Bureau; Sobi: Consultancy, Other: Clinical trial investigator; travel support, Speakers Bureau; Bioverativ: Other: Clinical trial investigator; CSL Behring: Other: Clinical trial investigator; travel support; LFB: Other: Clinical trial investigator; Octapharma: Other: Clinical trial investigator; travel support; Pfizer: Other: clinical trial investigator, Speakers Bureau. Majerus: BioMarin Pharmaceutical Inc.: Consultancy, Other: Clinical trial investigator, Travel support. Skinner: Bayer: Consultancy; BioMarin: Consultancy, Research Funding; Pfizer (DMC): Consultancy; Roche/Genentech: Consultancy, Research Funding; Sanofi: Consultancy; Spark (DMC): Consultancy; Takeda: Consultancy, Research Funding; Freeline: Research Funding; uniQure: Research Funding. Klamroth: Bayer: Consultancy, Other: Clinical trial investigator, Travel support, Research Funding, Speakers Bureau; CSL Behring: Consultancy, Other: Clinical trial investigator, Travel support, Research Funding, Speakers Bureau; Novo Nordisk: Consultancy, Other: Clinical trial investigator, Travel support, Research Funding, Speakers Bureau; Pfizer: Consultancy, Other: Clinical trial investigator, Travel support, Research Funding, Speakers Bureau; Shire (a Takeda company): Consultancy, Other: Clinical trial investigator, Travel support, Research Funding, Speakers Bureau; BioMarin: Consultancy, Other: Clinical trial investigator, Travel support, Speakers Bureau; Biotest: Consultancy, Other: Travel support, Speakers Bureau; Roche/Cugai: Consultancy, Other: Clinical trial investigator, Travel support, Speakers Bureau; Octapharma: Consultancy, Other: Clinical trial investigator, Travel support, Speakers Bureau; Sanofi: Consultancy, Other: Clinical trial investigator, Travel support, Speakers Bureau; Sobi: Consultancy, Other, Speakers Bureau; Uniqure: Consultancy, Other; LEO: Other, Research Funding, Speakers Bureau; Daiichi Sankyo: Other, Speakers Bureau; Grifols: Speakers Bureau. Quinn: BioMarin Pharmaceutical: Current Employment, Current equity holder in publicly-traded company. Yu: BioMarin Pharmaceutical: Current Employment, Current equity holder in publicly-traded company. Wong: BioMarin Pharmaceutical Inc.: Current Employment, Current equity holder in publicly-traded company. Lawal: BioMarin Pharmaceutical Inc.: Current equity holder in publicly-traded company, Ended employment in the past 24 months. Robinson: BioMarin Pharmaceutical Inc.: Current Employment, Current equity holder in publicly-traded company. Kim: BioMarin Pharmaceutical Inc.: Current Employment, Current equity holder in publicly-traded company.