Biogen have released topline results from its Phase2/3 Xirius study of cotoretigene toliparvovec (BIIB112) as a gene therapy for patients with X-linked retinitis pigmentosa (XLRP), falling short of its primary endpoint.
The study did not demonstrate statistically significant improvement in the proportion of treated study eyes, with ≥7 dB improvement from baseline at ≥5 of the 16 central loci of the 10-2 grid, as assessed by Macular Integrity Assessment (MAIA) microperimetry.
However, positive trends were observed across several clinically relevant prespecified secondary endpoints.
Katherine Dawson, MD, Head of the Therapeutics Development unit at Biogen, said: “Although the Phase 2/3 Xirius study of cotoretigene toliparvovec did not meet its primary endpoint, we are encouraged by positive trends in other pre-specified clinically relevant endpoints, such as a measure of visual acuity under low light conditions.
“XLRP is a serious, early-onset form of retinitis pigmentosa, and people living with it face almost certain blindness by the end of the fourth decade, commonly leading to loss of independence, depression and unemployment. We are working to further evaluate the data from the Xirius study before communicating potential next steps for the cotoretigene toliparvovec clinical development programme.”
The study was assessed after 12 months and compared to the study eye of patients randomised to the untreated control group. Most adverse events found were ocular in nature, mild-to-moderate in severity, and resolved.
Complete analysis of the study is ongoing and Biogen stated that detailed results will be shared in a future scientific forum.
XLRP is a rare, inherited retinal disease that is associated with progressive vision loss as the light-sensing cells of the retina gradually deteriorate. Initial symptoms are difficulty seeing at night, followed by restriction of the field of vision and eventually blindness in most people by the age of 40.
There are currently no approved treatments for XLRP.
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