Gene Therapy improves functional measures in XLRP

Beacon Therapeutics announced positive results from their phase 2 gene therapy trial for X-linked retinitis pigmentosa (XLRP) caused by mutations in the RPGR gene.

The treatment, called AGT-501, is an injection delivered to the retina, and led to improved visual function and retinal sensitivity in some trial participants  with X-linked RP after a 12 month follow up.

Specifically, 17% of patients in the low dose group and 63% of patients in the high dose group saw improvements in visual field measurements at 12 moths, compared to their baseline measurements. In functional vision tests, which included navigating a maze at various lighting levels, nine of the 14 participants saw improvements in their treated eye, compared to no improvements, and some worsening, in their untreated eyes.

AGT—501 was associated with a range of mild to moderate adverse effects. One case of glaucoma (increased eye pressure that can damage the optic nerve) emerged associated with the corticosterioids participants were required to take as part of the study’s protocol. However, this was treated with medications and resolved before the end of the study. One case of visual impairment also emerged associated with injection procedure, which is currently being investigated. Other adverse effects associated with the treatment included eye pain, metamorphopsia (straight objects appearing curvy or wavy), photopsia (severe sensitivity of the eyes to light), vitritis (inflammation of the gel in the middle of the eye ) and reduced visual acuity. All effects associated with the treatment were largely non-serious and mild to moderate in severity, and were similar between both high and low dose treatment groups.

X-linked RP is an inherited condition which causes progressive vision loss,  usually in men although women can also be affected.  It currently has no approved treatment, so AGT-501 has the potential to provide an important step forward.