Sangamo's Fabry gene therapy clears early clinical test, firing starting gun on preparations for phase 3

Safety and tolerability data for Sangamo Therapeutics's gene therapy look clean at this stage, with no treatment-related adverse events higher than Grade 1. (LionFive/Pixabay)

Sangamo Therapeutics has posted clinical data on a therapy it hopes will shake up the Fabry disease market. The gene therapy showed encouraging safety and efficacy signs in the small study, prompting Sangamo to start preparations for a phase 3 clinical trial. 

Today, Fabry patients receive enzyme replacement therapies (ERTs) such as Sanofi’s Fabrazyme and, in some ex-U.S. markets, Takeda’s Replagal. However, the biweekly infusions are a burden, leading gene therapy developers including Avrobio and Freeline to try to develop one-shot treatments for the disease.

Sangamo showed its hand Thursday, presenting data on the first four patients to receive ST-920 across two dose cohorts. The gene therapy, also known as isaralgagene civaparvovec, uses an AAV vector to get a copy of the GLA gene to the liver, thereby driving production of an enzyme needed by Fabry patients. 

All four patients experienced increased enzyme activity, ranging from two- to 15-fold above mean normal. Two of the patients were on ERT at baseline. Investigators have withdrawn ERT from one of the patients and plan to stop treatment of the second subject. One patient had elevated levels of lyso-Gb3, a Fabry biomarker, at baseline. Their lyso-Gb3 levels fell by around 40% after treatment.

RELATED: Avrobio plans head-to-head Fabrazyme trial after FDA changes path to market

The effects of the gene therapy on enzyme activity and lyso-Gb3 appear to be durable so far. The first patient to receive ST-920 had maintained elevated enzyme activity for one year as of the September cutoff. Lyso-Gb3 in the patient with an elevated level at baseline remained down and stable 32 weeks after treatment with ST-920.

Sangamo also highlighted changes relevant to quality of life. Three patients reported improvements in their ability to sweat, which Sangamo said could lift a limit on their ability to tolerate strenuous tasks and exercise. Safety and tolerability look clean at this stage, with no treatment-related adverse events higher than Grade 1.

The phase 1/2 clinical trial is continuing, with Sangamo recently dosing the first patient in the third dose cohort, but attention is already starting to turn to further development. Sangamo has started phase 3 planning. 

Shares in the biotech jumped nearly 24% in mid-morning trading Thursday at 10am ET.