Applied Genetic Technologies Corporation (AGTC), a developer of gene therapies for retinal degenerative diseases and other conditions, has reported positive, interim, three-month results for its Phase 2 Skyline gene-therapy clinical trial for people with X-linked retinitis pigmentosa (XLRP) caused by mutations in the gene RPGR. Skyline is an expansion of AGTC’s Phase ½ clinical trial, which also demonstrated encouraging results for the XLRP gene therapy. Combined, the results provide affirmation for the company’s planned Phase 2/3 Vista clinical trial. AGTC is currently pre-screening patients for the Vista trial.
In the Skyline trial, five of eight (62.5 percent) patients in Group B had improved visual sensitivity. In Group A, one of four (25 percent) patients had improved visual sensitivity after receiving the gene therapy. Patient responses were captured using microperimetry, which measures retinal sensitivity at various points in the central retina. Responders were those who had improvements of at least 7 decibels in retinal sensitivity at five points or more in the central retina. Improvements for some patients in best-corrected visual acuity and the ability to navigate a maze were also observed.
The Skyline trial included pediatric and adult male patients. Patients in the Skyline trial were younger and had better baseline visual acuity than those in the Phase ½ trial. Each patient had one eye treated.
“If Vista (Phase 2/3) data is consistent with Skyline and Phase ½ data, the company intends to prepare a BLA filing,” said Sue Washer, chief executive officer at AGTC. A BLA, or biologics license application, is submitted by therapy developers to gain approval from the US Food & Drug Administration to market their treatments.
Ms. Washer also noted that improvements in vision observed at three months in the Phase ½ clinical trial were maintained at 12 months, so the company believes vision improvements at three months in Skyline will be durable.
XLRP affects approximately 20,000 people in the US and EU. The condition causes constriction of vision, reduced vision in dark settings, and central vision loss, especially in later stages. Most people with XLRP are legally blind by the age of 45. XLRP usually affects males. Females are most often unaffected carriers but can be affected, as well.
The Foundation Fighting Blindness funded successful canine studies of XLRP gene therapy at the University of Pennsylvania School of Veterinary Medicine that helped make AGTC’s XLRP gene therapy clinical trial possible.
AGTC used the Foundation’s My Retina Tracker patient registry and genetic testing program to identify and recruit patients for its XLRP studies.
