Fabry treatment ST-920 boosts kidney, heart function in trial
Sangamo says treatment on path for accelerated approval application
A one-time infusion of gene therapy ST-920 (isaralgagene civaparvovec) improved kidney function and stabilized heart function in adults with Fabry disease for up to two years after treatment, according to new data from a Phase 1/2 clinical trial.
Kidney functional improvements in the STAAR study (NCT04046224) were observed regardless of sex, previous use of enzyme replacement therapy (ERT), type of Fabry disease, or degree of kidney impairment before gene therapy, the data showed.
Sangamo Therapeutics, the therapy’s developer, said it met with the U.S. Food and Drug Administration (FDA) and agreed on a proposed efficacy and safety data package to support an approval pathway for the treatment. The company said it expects to submit an application for accelerated approval as soon as early 2026.
The FDA previously said that STAAR data could serve as a basis for accelerated approval, a type of conditional authorization that allows the FDA to bring a therapy to market before all confirmatory data are available. Full approval depends on the outcomes of additional studies that verify the treatment delivers meaningful clinical benefits to patients.
“The announcement of detailed clinical data from our registrational STAAR study in Fabry disease, alongside our recent FDA meeting, marked important steps forward on the path to an anticipated regulatory submission for this program,” Sandy Macrae, CEO of Sangamo, said in a company press release.
Data follow promising early results
The data were presented recently at the International Congress of Inborn Errors of Metabolism 2025 (ICIEM2025) in Kyoto, Japan.
Fabry is caused by mutations in the GLA gene that reduce the activity of the enzyme alpha-galactosidase A (alpha-Gal A). As a result, fatty molecules accumulate to toxic levels in cells, leading to organ damage, particularly in the heart and kidneys.
Administered by a one-time infusion into the bloodstream, ST-920 works by delivering a healthy copy of the GLA gene to liver cells. It’s expected to boost production of a working alpha-Gal A, which can break down and clear fatty molecules from cells, thereby preventing organ damage and easing Fabry symptoms.
STAAR enrolled men and women, ages 18 and older, with Fabry who were previously treated with ERT, had been off ERT for at least six months, or had never received ERT.
Top-line data reported last June showed that among the 32 Fabry patients treated with ST-920, there was an increase in eGFR rate, or an improvement in kidney function, one year after the infusion. The results were similar to those of 19 patients who had been followed for two years.
All 18 patients who began the study on ERT had stopped and remained off ERT after ST-920 treatment. Their blood levels of lyso-Gb3, a marker of Fabry disease, remained generally stable thereafter.
Researchers also noted improvements in measures of disease severity, gastrointestinal symptoms, and quality of life.
The newly reported data showed that patients saw ST-920-induced improvements in the mean annualized eGFR, regardless of sex, previous ERT status, Fabry disease type, and pre-gene therapy eGFR values.
Heart function remained stable for at least one year, as assessed by various imaging measures, including left ventricular mass, the size of the heart’s pumping chamber, left ventricular strain, and blood volumes in the heart before and after it contracts.
Before ST-920, 10 participants had measurable levels of antibodies against alpha-Gal A associated with previous ERT use, which can limit the treatment’s efficacy. After ST-920, antibody levels decreased markedly in nine patients and eventually became undetectable in eight.
Sangamo also reported on a Fabry patient who had withdrawn from ERT during the study, but restarted ERT as directed by a physician. The patient received ST-920 more than two and a half years ago, and maintained higher-than-normal levels of alpha-Gal A activity and stable levels of lyso-Gb3.
The most common adverse events reported during STAAR were fever, COVID-19, the common cold, and headache, all of which were resolved with standard medical treatments.
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