Sangamo Therapeutics is continuing to enroll and treat patients with a rare genetic condition called Fabry disease in an early clinical trial of a gene therapy it is developing, announcing Tuesday updated results from the first 11 study participants.
Data to date has shown Sangamo’s medicine to be safe, with no serious treatment-related adverse reactions, and suggests the gene therapy is working as intended. As a result, Sangamo has begun the “dose expansion” phase of the trial, enrolling new patients to receive the fourth and highest dose tested in the initial “dose escalation” cohort.
Sangamo, which has a pipeline of experimental cell, gene replacement and gene editing therapies, is already planning for a potential Phase 3 study, should results from the current trial continue to prove positive. It, along with Freeline Therapeutics, have the most advanced gene therapies in clinical development for Fabry, which is one of an array of inherited conditions known as lysosomal storage disorders.
In Fabry, mutations in a gene called GLA lead to low levels of an enzyme that’s needed to prevent the buildup of a certain toxin in cells, causing a constellation of symptoms that over time can become severe and life-threatening. Sangamo’s therapy is designed to deliver a functional copy of the GLA gene into the body via a type of modified virus that acts as a courier of sorts.
The updated trial results released Thursday show that, among the five earliest treated patients, enzyme levels rose to several times a normal average. In three, enzyme levels were 10 to 17 times higher. Notably, in one patient with the highest toxin level pre-treatment, the gene therapy led to a 40% decline in toxin levels within 10 weeks after dosing.
Five patients have been able to discontinue standard drugs, which in the case of Fabry is an enzyme replacement therapy that must be taken chronically to control toxin levels.
According to Sangamo, there were no treatment-related side effects rated by investigators as more significant than “mild,” and no patient experienced elevations in liver enzymes that can sometimes signal broader safety concerns.
In the next part of the trial, Sangamo plans to enroll up to six participants in six different cohorts.
Sangamo and Freeline were previously joined by Avrobio in developing a Fabry gene therapy. But in February Avrobio announced it would stop work on its program after disappointing findings and prioritize research elsewhere. Amicus Therapeutics and UniQure also have Fabry gene therapy programs, although Amicus recently had to pivot after plans to spin out its gene therapy business fell apart.