Sangamo Starts Putting BLA for Fabry Disease Gene Therapy Isa-Vec in Front of FDA

Sangamo Therapeutics has begun submission of a rolling biologics license application (BLA) application to the FDA for investigational Fabry disease gene therapy isaralgagene civaparvove (isa-vec, ST-920).¹

The BLA is supported by data from the phase 1/2 STAAR clinical trial (NCT04046224). Across all patients who were treated in STAAR, a positive mean annualized estimated glomerular filtration rate (eGFR) slop was observed at 52 weeks posttreatment. Notably, in an October 2025 meeting with Sangamo, the FDA onfirmed its agreement that eGFR slope can be used as an end point for the support of an accelerated approval pathway for isa-vec.² Shortly after this meeting, in November 2025, Sangamo received a green light from the FDA to begon submitting a rolling BLA for the therapy.

“The initiation of our BLA submission marks an important milestone for Sangamo and for Fabry patients in need,” Nathalie Dubois-Stringfellow, PhD, the chief development officer of Sangamo, said in a statement.¹ “The compelling data from our STAAR study shows the potential of ST-920 to provide safe and long-lasting clinical benefits to a wide range of Fabry disease patients. We look forward to working with the FDA as we continue to advance the regulatory process.”

Sangamo noted that it expects the rolling BLA submission, which is taking place under the accelerated approval pathway, will be finished in the second quarter of next year. Isa-vec has previously received orphan drug designation, fast track designation, and regenerative medicine advanced therapy designation from the FDA. From the European Medicines Agency, it has been granted orphan medicinal product designation and PRIority MEdicines eligibility. It has also received Innovative Licensing and Access Pathway designation from the United Kingdom's Medicines and Healthcare products Regulatory Agency.

Updated data from STAAR, with a cutoff date of April 10, 2025, were presented earlier this year at the International Congress of Inborn Errors of Metabolism (ICIEM), held in Kyoto, Japan, from September 2 to 6, 2025, and subsequently summarized key points in a press release.3 Across all 32 of the treated patients, a 1.965 mL/min/1.73m²/year (95% CI: -0.153, 4.083) mean annualized eGFR slope was seen at 52 weeks posttreatment, which Sangamo noted is favorable in comparison to a metaanalysis of publications covering approved treatment options for Fabry disease. It was also reported that for the 19 patients who had been followed for at least 104 weeks, the mean annualized eGFR slope was 1.747 mL/min/1.73m²/year (95% CI: -0.106, 3.601) at 104 weeks posttreatment.

“These STAAR study data demonstrate the potential for ST-920 to provide meaningful clinical benefits to Fabry disease patients,” STAAR investigator John Bernat, MD, PhD, of the University of Iowa, said in the press release.³ “The positive mean eGFR slope at both 1 and 2 years, which compares favorably to approved Fabry treatments, alongside stable cardiac function, are exciting developments, particularly given the decline in renal and cardiac function traditionally seen with Fabry patients. The ability for patients to discontinue the use of burdensome enzyme replacement therapies further supports the potential of ST-920 as a single-dose, durable treatment option for people living with Fabry disease.”

CGTLive® has previously spoken with Robert J. Hopkin, MD, associate professor, clinical pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, to learn more about isa-vec and future research for Fabry disease. In a 2024 interview, Hopkin discussed other investigations into novel therapies for Fabry, including ex vivo gene-edited cell therapy, and further research looking deeper into the biology of the disease itself.

“We know that the stored material causes problems,” Hopkin told CGTLive. “But one of the questions that we haven't understood very well is how does that cause problems? And we know that some of it is just the presence of this substance that builds up. But there's growing evidence that that the presence of distorted material causes distress to the cells, which leads to inflammation, as the body's defenses ramp up to protect the tissues. And there's now emerging data on how that works. And we're hoping that we will be able to find which biomarkers of inflammation are initiating that inflammatory response."

REFERENCES
1. Sangamo Therapeutics Initiates Rolling Submission of BLA to U.S. FDA for ST-920 in Fabry Disease. News release. Sangamo Therapeutics, Inc. December 18, 2025. Accessed December 19, 2025. https://investor.sangamo.com/news-releases/news-release-details/sangamo-therapeutics-initiates-rolling-submission-bla-us-fda-st
2. Sangamo Therapeutics Announces FDA Acceptance of BLA Rolling Submission Request for ST-920 in Fabry Disease. News release. Sangamo Therapeutics, Inc. November 21, 2025. Accessed December 19, 2025. https://investor.sangamo.com/news-releases/news-release-details/sangamo-therapeutics-announces-fda-acceptance-bla-rolling
3. Sangamo Therapeutics Presents Detailed Data from Registrational STAAR Study in Fabry Disease at International Congress of Inborn Errors of Metabolism 2025. News release. Sangamo Therapeutics, Inc. September 4, 2025. Accessed December 19, 2025. https://investor.sangamo.com/news-releases/news-release-details/sangamo-therapeutics-presents-detailed-data-registrational-staar