Sangamo’s ‘Positive’ Phase I/II Data for Fabry Gene Therapy Opens Path to FDA

Sangamo Therapeutics’ investigational gene therapy isaralgagene civaparvovec improved kidney function in patients with Fabry disease, according to a Phase I/II readout from the company on Tuesday. Sangamo plans to use these results to build a case for an accelerated approval of the gene therapy.

This news comes after an earlier data release, slim on details, from the biotech last month, announcing that it had met a “key milestone” for a regulatory filing for isaralgagene civaparvovec. At the time, analysts at H.C. Wainwright said that data from this pivotal trial would be a “significant catalyst” for Fabry, one that could “accelerate the timeline to a potential partnership agreement.”

“Overall, we continue to view [isaralgagene civaparvovec] as a potential best-in-class gene therapy for Fabry disease,” the analysts said in their May 28 note. The asset, they continued, is “supported by long-term α-Gal A expression, ERT [enzyme replacement therapy] discontinuation, renal function stabilization, and improvements in quality of life.”

Fabry disease is a rare lysosomal storage disorder that manifests as skin blemishes, eye problems and the inability to sweat. In its more progressed forms, Fabry can lead to kidney problems, heart failure, mood disturbances and pain. The disease is caused by mutations in the galactosidase alpha, which isaralgagene civaparvovec addresses by delivering a functioning copy of the gene to the liver.

According to its Q1 earnings presentation, Sangamo expects to file a biologics license application (BLA) for isaralgagene civaparvovec as early as the first quarter of 2026. The biotech is also currently “engaged in potential commercialization partner negotiations.”

“In speaking with the company, the expectation is that they will secure Fabry partnership and will submit the BLA together with their Fabry partner,” Truist Securities analysts wrote to investors on Tuesday.

Tuesday’s readout comes from the pivotal STAAR study, which enrolled 33 adult patients with Fabry disease regardless of ERT status. Fifty-two weeks after receiving isaralgagene civaparvovec, patients saw a mean annualized slope of 1.965 mL/min/1.73m² per year in their estimated glomerular filtration rate (eGFR)—a common measure of kidney function. The positive slope indicates that their kidney function improved over time.

According to Sangamo, the FDA has agreed to consider eGFR as an intermediate clinical endpoint for accelerated approval.

Sangamo also plans to run a meta-analysis of published studies to compare the gene therapy’s annualized mean eGFR slope against that of already-approved Fabry therapies, like Takeda’s Replagal, Sanofi’s Fabrazyme and Amicus’ Galafold—a move that was recommended by the FDA.

“We believe these data support the potential for isaralgagene civaparvovec as a one-time, durable treatment for Fabry disease that can improve patient outcomes,” Sangamo said on Tuesday.

Aside from improving kidney function, isaralgagene civaparvovec also “demonstrated a range of other clinical benefits,” according to the company, including significant improvements in quality of life, social functioning, general health and physical function. The gene therapy likewise significantly eased gastrointestinal symptoms, while also reducing or outright eliminating the need for pain medication in some patients.

Truist analysts were positive on the results but raised the issue of price. “While the data support potential for the one-time therapy for Fabry disease, which is also competitive with existing options (such as Replagal, Fabrazyme and Galafold), one key question is how it will be priced and reimbursed for uptake in the backdrop of slow gene therapy launches in market such as Biomarin’s (BMRN, Buy, Lee) Roctavian for Hem A and BlueBird Bio’s (private) Zynteglo and Lyfgenia for sickle-cell disease and Skysona for cerebral adrenoleukodystrophy.”