Pfizer Inc. (NYSE: PFE) and Sangamo Therapeutics, Inc.Pfizer Inc. (NYSE:PFE) and Sangamo Therapeutics, Inc. (NASDAQ:SGMO), a genomic medicines company, today announced updated follow-up data from the Phase 1/2 Alta study of giroctocogene fitelparvovec, an investigational gene therapy for patients with moderately severe to severe hemophilia A. The Alta study data, in patients with severe hemophilia A, are being presented today at the 63rd American Society for Hematology Annual Meeting and Exposition taking place from December 11-14 virtually and in Atlanta, GA. The oral presentation slides, which include follow-up data up to 195 weeks for the longest-treated patient, are available on Sangamo’s website in the Investors and Media section under Events and Presentations.

At 104 weeks, the five patients in the highest dose 3e13 vg/kg cohort had mean factor VIII (FVIII) activity of 25.4% via chromogenic clotting assay. In this cohort, mean annualized bleeding rate (ABR) was 0.0 in the first year post-infusion and was 1.4 throughout the total duration of follow-up as of the October 1, 2021 cutoff date. All bleeding events occurred after week 69 post-infusion. Two patients experienced bleeding events necessitating treatment with exogenous FVIII. No participants in the highest dose cohort have resumed prophylaxis.

“These latest results further suggest the potential of this investigational therapy to bring transformational benefit to eligible patients living with severe hemophilia A, if confirmed in ongoing clinical trials,” said Seng H. Cheng, Senior Vice President and Chief Scientific Officer, Pfizer Rare Disease.

“We continue to be encouraged by findings from the Phase 1/2 Alta study in patients with severe hemophilia A,” said Rob Schott, M.D., M.P.H, F.A.C.C, Head of Development at Sangamo. “We believe these two-year results demonstrate the potential of this gene therapy candidate to minimize significant symptoms associated with hemophilia A and become an alternative to the current burden of disease management.”

Giroctocogene fitelparvovec was generally well-tolerated in this Phase 1/2 study. Among the five patients in the highest dose cohort, four received corticosteroids for liver enzyme (ALT/AST) elevations. All elevations fully resolved with oral corticosteroids. As previously reported, one patient in the highest dose cohort had a treatment-related serious adverse event of hypotension (grade 3) and fever (grade 2), with symptoms of headache and tachycardia, which occurred six hours post-infusion with giroctocogene fitelparvovec and resolved approximately 12 hours post-infusion. Across all four cohorts, 26 treatment-related adverse events occurred in six patients as of the October 1, 2021 cutoff date. No other treatment-related serious adverse events were reported as of the cutoff date. Additionally, no confirmed FVIII inhibitor development occurred, and no thrombotic events were reported.

The Phase 3 AFFINE clinical trial of giroctocogene fitelparvovec in patients with hemophilia A has started and is over 50% enrolled. Following the observation of FVIII levels greater than 150% in some treated patients, Pfizer voluntarily paused screening and dosing of additional patients in the trial to implement a protocol amendment to provide clinical management guidance for elevated FVIII levels. Subsequently, on November 3, 2021, the U.S. Food and Drug Administration (FDA) informed Pfizer that this trial has been placed on clinical hold while the protocol amendment and associated documents are reviewed.