Rare Daily Staff

Biogen reported that topline results from the phase 3 STAR study of its experimental gene therapy for the rare eye disease choroideremia failed to meet its primary endpoint.

The company said the study of the experimental gene therapy known as timrepigene emparvovec also failed to demonstrate efficacy on key secondary endpoints. Biogen began developing the gene therapy as a result of its 2019 acquisition of Nightstar Therapeutics for $800 million.

Choroideremia is a rare, inherited retinal disease resulting in progressive vision loss, ultimately leading to blindness. Choroideremia is an X-linked recessive chorioretinal disease that is caused by loss of function mutations in the choroideremia gene resulting in decreased Rab escort protein-1 (REP-1) expression, which leads to degeneration of the retinal pigment epithelium, photoreceptors and choroid. Initially, patients with choroideremia experience poor night vision and over time, slow, progressive visual loss ultimately leads to blindness. Visual impairments due to choroideremia are associated with emotional, functional, and economic burden.

Timrepigene emparvovec is an experimental recombinant AAV2 vector designed to deliver a functional version of the human choroideremia gene into the retinal pigment epithelium and photoreceptor cells that aims to address the underlying genetic cause of choroideremia.

STAR was a Phase 3, multicenter, randomized, three-arm, parallel-controlled group study that enrolled 169 adult males with a genetically confirmed diagnosis of choroideremia. The study evaluated the safety and efficacy of a single subretinal injection of timrepigene emparvovec. The primary endpoint was the proportion of patients with an improvement of at least 15 letters from baseline in best corrected visual acuity (BCVA) at 12 months post-treatment as measured by the Early Treatment Diabetic Retinopathy Study (ETDRS) chart.

“While we are disappointed by the results of the STAR study, we are hopeful that the clinical insights gleaned from this study may help to shape therapeutic innovation for inherited retinal diseases including choroideremia, so that in the future there may be treatment options for the community affected by these debilitating disorders,” said Katherine Dawson, head of the Therapeutics Development Unit at Biogen.

Biogen said it will evaluate the complete data set before confirming next steps for the therapy clinical development program. Detailed results of this study will be made available at a future scientific forum.

Photo: Katherine Dawson, head of the Therapeutics Development Unit at Biogen

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