Sangamo cues up Fabry gene therapy filing on STAAR data

A gene therapy for Fabry disease could be on the horizon, after a clinical trial readout for Sangamo Therapeutics' ST-920 hit its safety and efficacy endpoints.
The STAAR trial showed that a one-shot dose of ST-920 – now known as isaralgagene civaparvovec – was able to improve kidney function in Fabry patients over 52 weeks of follow-up and allowed patients to be weaned off standard therapies for the disease, which are given either by intravenous infusion every two weeks or as a daily oral therapy.
Fabry disease is a form of lysosomal storage disorder caused by a defective gene (GLA) that causes a deficiency in the enzyme alpha-galactosidase A, which in turn leads to the build-up of a toxic metabolite (Gb3) that damages the kidneys and other organs. ST-920 is designed to deliver a working copy of the GLA gene to cells using an adeno-associated virus (AAV) vector.
Sangamo has reported top-line results from STAAR, in 32 patients, which reveal a reduction in kidney function decline measured by the mean annualised estimated glomerular filtration rate (eGFR) slope, an indicator of kidney health that the FDA has agreed can be used as a surrogate marker for accelerated approval, over 52 weeks. Armed with the data, Sangamo now expects to file for approval of ST-920 in 2026.
Improvements were also recorded in a subgroup of 19 patients who had completed two years of follow-up, pointing to a durable effect for the gene therapy, according to Sangamo. Meanwhile, all 18 patients in the trial who were being treated with enzyme replacement therapy (ERT) at the start of the trial were able to have that treatment withdrawn, with Gb3 levels staying "generally stable."
At the moment, ERT treatment is delivered by intravenous infusion every two weeks using drugs like Takeda's Replagal (agalsidase alfa) and Sanofi's Fabrazyme or Amicus Therapeutics' oral option Galafold (migalastat), which is only suitable for some Fabry patients with an amenable GLA mutation.
As it prepares for the regulatory filing, Sangamo is still hoping to line up a commercial partner for ST-920. The company has been in something of a retreat in the last couple of years, marked by staffing reductions and cuts to its R&D programmes, and suffered a major blow earlier this year when Pfizer pulled out of an alliance for an experimental haemophilia A gene therapy.
With cash reserves dwindling, Sangamo was thrown a lifeline by Eli Lilly, which paid $18 million upfront in April to secure rights to use an AAV capsid designed to deliver gene therapies into the central nervous system in a deal that could be worth up to $1.4 billion. It ended the first quarter with $25 million in cash reserves, down from $42 million at the end of last year, which it said was enough to fund operations into the third quarter of 2025.
Another gene therapy for Fabry, concentrating on preventing the cardiomyopathy that is another clinical manifestation of the disease, has been developed by 4D Molecular Therapeutics (4DMT) and reached phase 1/2 testing.
That 4D-310 programme has been placed on hiatus, however, pending additional financing or a partnership as the company focuses on other projects.