Idorsia’s Clazosentan Does Not Meet Endpoint in Phase 3 REACT Study of Patients After aSAH

February 6, 2023—Idorsia Ltd., a Switzerland-based pharmaceutical company, announced the initial findings of the REACT study, which did not meet the primary endpoint. The data and interpretation of the study will be published in scientific literature in due course. Additionally, the company will fully analyze the efficacy and safety data to understand this unexpected result, noted the press release.

REACT is a phase 3 study investigating the efficacy and safety of clazosentan in preventing clinical deterioration caused by delayed cerebral ischemia (DCI) in patients after aneurysmal subarachnoid hemorrhage (aSAH). REACT is a multicenter, double-blind, randomized, placebo-controlled, parallel-group study.

According to the company, clazosentan is a fast-acting, endothelin A receptor antagonist that Idorsia developed as a continuous intravenous infusion for the prevention of clinical deterioration caused by DCI in patients after aSAH. Clazosentan is approved for the prevention of cerebral vasospasm, vasospasm-related cerebral infarction, and cerebral ischemic symptoms after aSAH in Japan.

REACT was composed of 409 patients ages 18 to 70 years with World Federation of Neurological Societies grades 1 to 4 after recovery from the aneurysm-securing procedure and “thick and diffuse clots” on the admission CT scan. Patients were enrolled at 74 sites in 15 countries across North America and Europe.

The study randomized the patients—who were treated either with microsurgical clipping or endovascular coiling aneurysm securing procedures—in a 1:1 ratio to receive placebo or clazosentan 15 mg/h. In general, the standard of care for managing aSAH was allowed, and the administration of nimodipine (oral or intravenous) was permitted if it was routine standard of care at the site.

Jean-Paul Clozel, MD, and Chief Executive Officer of Idorsia, commented in the company’s press release, “I am very disappointed with the negative result of REACT. The study was based on strong scientific and medical rationale and executed diligently by a committed team of experts at Idorsia and by the investigators. On behalf of everyone at Idorsia, I’d like to thank the investigator teams and expert advisors for their tireless support to conduct this study in such a challenging medical condition.”