Sangamo reports positive Phase 1/2 data for AAV gene therapy ST-920 in Fabry disease

RICHMOND, Calif., Feb. 03, 2026 (GLOBE NEWSWIRE) — Sangamo Therapeutics reported detailed clinical results from its registrational Phase 1/2 STAAR study of isaralgagene civaparvovec (ST-920), an investigational AAV-based gene therapy for Fabry disease, timed to presentations at the 22nd Annual WORLDSymposium in San Diego. The update included data from 33 patients treated with the AAV gene therapy as of an April 10, 2025 cutoff, with 32 patients having at least 52 weeks of follow-up and all eligible participants enrolled into a long-term extension.

The completed Phase 1/2 trial showed that the AAV therapy ST-920 was generally well tolerated without preconditioning. Most adverse events were mild to moderate, with only one treatment-related serious adverse event, no thrombotic microangiopathy, no treatment-related discontinuations, and no deaths reported following AAV administration.

Efficacy data demonstrated sustained normal to supraphysiological α-galactosidase A (α-Gal A) activity following AAV gene transfer, along with reductions or stabilization of lyso-Gb3. Notably, all 18 patients who entered the study on enzyme replacement therapy were able to discontinue chronic therapy under medical supervision after receiving the AAV gene therapy, while maintaining biochemical control in most cases. Antibody titers against α-Gal A decreased or became undetectable in the majority of patients with preexisting antibodies following AAV treatment.

Renal outcomes, assessed by mean annualized eGFR slope at 52 and 104 weeks, were positive and compared favorably with historical data from approved Fabry therapies. Cardiac structure and function remained stable over 52 weeks following AAV delivery, and patients experienced statistically significant improvements in disease severity measures, quality of life, and gastrointestinal symptoms.

On the regulatory front, the U.S. Food and Drug Administration agreed in October 2025 that data from the Phase 1/2 STAAR study could serve as the primary basis for potential approval of the AAV gene therapy ST-920 under the Accelerated Approval Program, using 52-week eGFR slope as an intermediate clinical endpoint. Sangamo initiated a rolling Biologics License Application submission in December 2025, positioning ST-920 as an AAV gene therapy alternative to lifelong enzyme replacement therapy and marking a key milestone in the company’s rare-disease AAV gene therapy strategy.