Applied Genetic Technologies Corporation (AGTC), a leading developer of gene therapies, has reported the six-month follow-up data in all patients treated with its gene therapy for X-linked retinoschisis (XLRS) in its Phase 1/2 clinical trial. The company reported that no consistently significant clinical activity from the treatment was observed after six months. AGTC will continue to analyze all of the XLRS trial data and complete all visits specified in the clinical protocol. However, if the data at additional follow-up data visits are consistent with the current six-month findings, the company has stated that they will not further develop the product.
A total of 27 subjects were treated, and all completed study visits through at least six months. Thirteen adult participants received the high dose of the treatment. The study subjects also included five pediatric patients who received the medium dose, and nine adults who received medium and low doses of the gene therapy. All participants will continue to be evaluated until the 12-month endpoint and annually thereafter.
Two of the 13 adult patients treated at the high dose showed some improvements in retinal structure as measured by optical coherence tomography (OCT), an imaging technology that provides a side view of the layers of the retina.
The company also reported that the treatment was safe and well-tolerated in the clinical trial.
“Of course, we had hoped that XLRS gene therapy would lead to vision improvements and/or improvements in retinal structure for most patients, but like many clinical trials of new treatment approaches, the XLRS trial is early, first-in-human research. These results underscore the importance of conducting small, well-designed trials, such as the AGTC XLRS Phase 1/2 clinical trial before evaluating novel treatment approaches in larger groups of patients,” says Stephen Rose, PhD, chief scientific officer, Foundation Fighting Blindness. “The good news is that the study affirms the strong overall safety profile for retinal gene therapies and intravitreal injections. Also, the results for XLRS have no impact on AGTC’s development of gene therapies for X-linked retinitis pigmentosa (XLRP) or achromatopsia. Those trials continue full steam ahead.”
The Foundation Fighting Blindness funded critical, preclinical research that made the XLRS and XLRP gene therapy trials possible.
XLRS, which, as an X-linked condition, primarily affects males, causes a splitting of the layers of the retina, resulting in significant vision loss. It affects about 35,000 patients in the U.S. and Europe.
Also, prior to the release of the XLRS trial six-month results, Biogen announced termination of its collaboration agreement with AGTC in March 2019.
“We appreciate our collaboration with Biogen and the support they have provided in advancing our joint efforts,” says Sue Washer, chief executive officer at AGTC. “We will regain full rights to the XLRP Phase 1/2 clinical program, which has completed its dose escalation phase ahead of our previous guidance and is moving directly to an expansion phase in 2019.”
AGTC’s two ongoing clinical programs in achromatopsia (for mutations in the genes CNGA3 and CNGB3) and XLRP are proceeding as previously reported. The company is expecting data reports from the XLRP and achromatopsia trials in 2019.