ST-920 Gene Therapy Demonstrates Positive Slope in eGFR Data Ahead of WORLD Symposium 2026 Presentations

Sangamo Therapeutics has revealed encouraging clinical results from its Phase 1/2 STAAR study evaluating isaralgagene civaparvovec (ST-920), a gene therapy candidate for Fabry disease treatment. The data showcases a positive slope in estimated glomerular filtration rate (eGFR) measurements, indicating meaningful improvements in kidney function among study participants. The company will present these findings across four platform presentations and multiple poster sessions at the 22nd Annual WORLD Symposium, scheduled for San Diego, CA, February 2-6, 2026.

Clinical Data Reveals Sustained Improvements in Renal Function With Positive eGFR Slope

The STAAR study’s primary endpoint demonstrated robust positive slope outcomes. As of the April 10, 2025 data cut-off, all 32 dosed patients showed a mean annualized positive eGFR slope of 1.965 mL/min/1.73m²/year at the 52-week mark. Among the 19 patients who completed 104 weeks of follow-up, a mean annualized eGFR slope of 1.747 mL/min/1.73m²/year (95% CI: -0.106, 3.601) was documented.

This positive slope trajectory is significant because eGFR decline typically characterizes Fabry disease progression—a condition where kidney function deteriorates as fatty substances accumulate in various organs. Reversing or slowing this decline represents a transformative therapeutic achievement. The study enrolled diverse patient populations, including those on Enzyme Replacement Therapy (ERT), patients who had discontinued ERT for at least six months, and treatment-naïve individuals, strengthening the generalizability of results.

Beyond renal function improvements, ST-920 demonstrated cardiovascular stability. Participants maintained consistent cardiac function over one year, with stable cardiac structural measures across clinical and demographic subgroups—a critical finding since cardiac complications represent a major health concern in Fabry disease management.

Long-Term Durability Demonstrated: Gene Expression Maintained for Over 4.5 Years

A defining characteristic of gene therapy success lies in treatment durability. The STAAR study data confirmed that elevated alpha-galactosidase A (a-Gal A) enzyme activity—the deficient enzyme in Fabry disease—remained sustainably elevated for up to 4.5 years in the longest-treated patient cohort. This sustained expression of the therapeutic enzyme directly correlates with the positive slope improvements observed in kidney function metrics.

The durability profile is particularly noteworthy because it suggests ST-920 requires no ongoing redosing or maintenance therapy, potentially offering a single-administration solution to a chronic progressive disease. Additionally, ST-920 demonstrated a favorable safety and tolerability profile without requiring preconditioning—a distinct advantage over some competing therapeutic approaches.

Accelerated FDA Approval Pathway Opens Market Opportunity in Growing Fabry Disease Treatment Sector

Recognizing ST-920’s potential, the FDA granted multiple expedited designations: Orphan Drug status, Fast Track designation, and Regenerative Medicine Advanced Therapy (RMAT) classification. Most significantly, the FDA established an accelerated approval pathway, agreeing that positive slope data from the STAAR study—specifically the mean annualized eGFR slope at 52 weeks—can serve as the primary basis for approval, bypassing lengthy traditional review processes.

This regulatory achievement enabled Sangamo to initiate a rolling Biologics License Application (BLA) submission to the FDA in December 2025. A rolling submission allows the company to submit data sequentially as it becomes available, potentially expediting the approval timeline.

From a market perspective, this approval momentum arrives amid substantial industry growth. According to Grandview Research, the global Fabry disease treatment market was valued at $2.54 billion in 2023 and is projected to reach $4.93 billion by 2030, representing a 9.9% compound annual growth rate from 2024 to 2030. ST-920’s positive slope efficacy data positions Sangamo competitively within this expanding therapeutic landscape, addressing an unmet need in a patient population with limited treatment options.

“We are pleased to have initiated a rolling submission of a BLA to the FDA seeking approval of ST-920,” stated Nathalie Dubois-Stringfellow, Ph.D., Chief Development Officer at Sangamo, underscoring the company’s commitment to bringing this gene therapy to Fabry disease patients as rapidly as possible.

The upcoming WORLD Symposium presentations will provide the global medical community with detailed analysis of the positive slope trajectory, long-term safety data, and clinical implications—further validating ST-920’s therapeutic promise in addressing a devastating rare genetic disorder.