Nightstar Therapeutics has released preliminary data from a Phase 1/2 study of an experimental gene therapy designed to treat X-linked retinitis pigmentosa. For more detailed information you can view the source press release at Nightstar’s website by clicking here.
About treat X-Linked Retinitis Pigmentosa (XLRP)
XLRP is a form of retinitis pigmentosa that follows an X-linked inheritance pattern. Retinitis pigmentosa causes progressive loss of vision and typically affects the retina of the eye (a type of light-sensitive tissue). According to the NIH, people with retinitis pigmentosa often begin to lose their night vision at an early stage, and, later on, may develop blind spots, particularly in the peripheral vision, and vision loss can progress over time.
Nightstar’s press release says that an estimated 70% of cases of XLRP are caused by variations in the genes that produce RPGR. RPGR plays an important role in moving proteins that are needed to maintain photoreceptor cells, and if RPGR isn’t functioning properly, it can lead to a progressive reduction in photoreceptors, and, as a result, vision.
About NSR-RPGR and the ‘Xirius’ Study
An investigational gene therapy called NSR-RPGR is being researched as a potential treatment for XLRP in patients who have the RPGR variation. It is an AAV8 vector that contains cDNA, which has been developed to produce RPGR. It is being investigated in a Phase 1/2 ‘Xirus’ clinical trial taking place in the US and UK. The study will involve eighteen patients divided into six groups (cohorts), with three patients in each group. The dosage of the therapy will increase from group 1, who receive the smallest dose, to group 6, who receive the largest.
Nightstar Therapeutics has released preliminary data from this study, which they say is “encouraging.” According to their press release, NSR-RPGR showed proof of concept and dose-related improvements in microperimetry analyses (a measure of change of visual function). Furthermore, some patients were found to show durable improvements in overall macula sensitivity.
Importantly, Nightstar says that, so far, NSR-RPGR has been “well-tolerated”, and that there have not been any dose-limiting toxicities or serious adverse events related to treatment. A Xirius expansion study is expected to begin later this year.