Sangamo's Fabry Disease Gene Therapy Shows Promise in Phase 1/2 Trial, FDA Submission Planned

Sangamo Therapeutics has announced positive topline results from its registrational phase 1/2 STAAR trial evaluating isaralgagene civaparvovec (ST-920), a gene therapy for Fabry disease. The company plans to use these data to support an FDA submission via the accelerated approval pathway as early as the first quarter of 2026.

Improved Kidney Function and Patient Outcomes

The open-label study, which included 32 patients with Fabry disease, demonstrated a mean annualized estimated glomerular filtration rate (eGFR) slope of 1.965 mL/min/1.73m2/year at 52 weeks across all dosed patients. For 19 patients with two years of follow-up, the mean annualized eGFR slope was 1.747 mL/min/1.73m2/year.

These results are particularly significant as the FDA has previously agreed that eGFR slope can serve as an intermediate clinical endpoint for an accelerated approval submission. The agency has accepted this measure in the past as a way to assess the rate of decline in kidney function.

All 18 patients who began the study on enzyme replacement therapy (ERT) have discontinued and remain off the treatment. Additionally, the trial reported a stabilization in cardiac endpoints.

Safety Profile and Next Steps

Isaralgagene civaparvovec, which does not require preconditioning, demonstrated a favorable safety and tolerability profile. Most adverse events were mild, with fever and COVID-19 being the most common treatment-emergent adverse events. No safety-related study discontinuations were reported.

Sangamo plans to conduct a meta-analysis of published studies to compare the eGFR slope data against approved Fabry treatments. The company noted that estimated mean annualized eGFR slopes for existing therapies such as Takeda's Replagal, Sanofi's Fabrazyme, and Amicus Therapeutics' Galafold range from -2.2 to -0.4 mL/min/1.73m2/year.

Commercialization and Financial Considerations

As Sangamo prepares for an FDA submission, the company is actively engaging in business development negotiations for a potential Fabry commercialization agreement. This partnership appears crucial for the cash-strapped biotech to bring the gene therapy to market.

Sangamo's financial position has been challenging, with only $25.1 million in cash and cash equivalents reported as of March 31, 2025. However, a recent $18 million upfront deal with Eli Lilly for the use of Sangamo's neurotropic adeno-associated virus capsid has provided some financial relief. The company expects its current funds, combined with the Lilly deal, to support operations into the third quarter of 2025.