Sangamo AAV Gene Therapy Shows Positive Clinical Benefits for Fabry Disease Patients

RICHMOND, Calif. September 4, 2025 — Sangamo Therapeutics, a genomic medicine company, has announced detailed positive data from its Phase 1/2 STAAR study of isaralgagene civaparvovec (ST-920), an investigational gene therapy for adults with Fabry disease. The results, presented at a recent medical congress in Kyoto, Japan, suggest that a single dose of the therapy provides meaningful and durable clinical benefits with a favorable safety profile.

Fabry disease is a rare genetic disorder caused by a lack of the alpha-galactosidase A (α-Gal A) enzyme, leading to a buildup of a fatty substance that can damage vital organs. ST-920 is a one-time gene therapy delivered using a recombinant adeno-associated virus (AAV) vector. Specifically, it uses an AAV 2/6 vector to deliver a functional copy of the GLA gene to the liver, enabling the body to produce its own working α-Gal A enzyme.

Key Clinical Findings

The study included 32 patients, with the longest-treated patient now having 4.5 years of follow-up.

• Improved Kidney Function: The study showed a positive mean annualized eGFR (estimated glomerular filtration rate) slope after 52 weeks, a key measure of kidney function. This result compares favorably to approved Fabry disease treatments.
• Stable Cardiac Function: The therapy was associated with stable cardiac function, including key measures like left ventricular mass and global longitudinal strain, which typically decline in Fabry patients.
• Long-Term Durability: The therapy has maintained elevated levels of the α-Gal A enzyme for up to 4.5 years in the longest-treated patient, demonstrating a durable effect.
• Discontinuation of Existing Therapy: All 18 patients who were on enzyme replacement therapy (ERT) at the start of the study were able to safely discontinue their ERT and have remained off the burdensome treatment.
• Improved Quality of Life: Patients reported statistically and clinically significant improvements in several quality-of-life measures, including physical function, bodily pain, and social functioning.
• Favorable Safety Profile: The therapy was well-tolerated without the need for preconditioning. The most common side effects were mild to moderate, and no patients discontinued the study due to a safety-related event.

According to Sangamo, these data support the potential for isaralgagene civaparvovec as a one-time, durable treatment that could provide significant benefits over current standards of care. The company plans to submit a Biologics License Application (BLA) under the Accelerated Approval pathway as early as the first quarter of 2026.