Sangamo's Fabry Disease Gene Therapy Shows Promise in Phase I/II Trial

Sangamo Therapeutics has reported positive results from its Phase I/II STAAR study of isaralgagene civaparvovec, a potential gene therapy for Fabry disease. The data, released on Tuesday, demonstrate improvements in kidney function and quality of life for patients, potentially paving the way for an accelerated FDA approval pathway.

Promising Clinical Results

Isaralgagene civaparvovec, which delivers a functioning copy of the galactosidase alpha gene to the liver, showed significant benefits in the 33-patient study. Fifty-two weeks post-treatment, patients experienced a mean annualized improvement in estimated glomerular filtration rate (eGFR) of 1.965 mL/min/1.73m² per year, indicating enhanced kidney function over time.

Beyond renal improvements, the gene therapy demonstrated a range of other clinical benefits. Patients reported significant enhancements in quality of life, social functioning, general health, and physical function. Additionally, the treatment alleviated gastrointestinal symptoms and reduced or eliminated the need for pain medication in some patients.

Regulatory Strategy and Market Potential

Sangamo plans to use these pivotal Phase I/II data to build a case for accelerated approval of isaralgagene civaparvovec. The FDA has agreed to consider eGFR as an intermediate clinical endpoint for this purpose, potentially expediting the therapy's path to market.

The company expects to file a biologics license application (BLA) as early as the first quarter of 2026. Analysts at H.C. Wainwright have labeled isaralgagene civaparvovec a "potential best-in-class gene therapy for Fabry disease," citing its long-term α-Gal A expression, ability to discontinue enzyme replacement therapy (ERT), renal function stabilization, and quality of life improvements.

Competitive Landscape and Commercial Considerations

As Sangamo prepares for potential commercialization, the company is actively engaged in partnership negotiations. According to Truist Securities analysts, Sangamo is expected to secure a Fabry disease partner and submit the BLA jointly.

The gene therapy's performance will be compared to existing Fabry treatments, including Takeda's Replagal, Sanofi's Fabrazyme, and Amicus' Galafold, through a meta-analysis of published studies. This comparison, recommended by the FDA, will help position isaralgagene civaparvovec in the competitive landscape.

However, analysts have raised questions about pricing and reimbursement strategies, particularly in light of slow uptake for other gene therapies in the market, such as Biomarin's Roctavian for hemophilia A and BlueBird Bio's treatments for sickle cell disease and cerebral adrenoleukodystrophy. The success of isaralgagene civaparvovec may depend on navigating these commercial challenges effectively.