Idorsia announces the results of REACT a Phase 3 study of clazosentan in patients following aneurysmal subarachnoid hemorrhage

Ad hoc announcement pursuant to Art. 53 LR

Allschwil, Switzerland – February 6, 2023

Idorsia Ltd (SIX: IDIA) today announces the initial findings of REACT, a Phase 3 study which investigated the efficacy and safety of clazosentan in preventing clinical deterioration due to delayed cerebral ischemia, in patients following aneurysmal subarachnoid hemorrhage (aSAH). The study did not meet the primary endpoint. The company will fully analyze the efficacy and safety data to understand this unexpected result.

Jean-Paul Clozel, MD and Chief Executive Officer of Idorsia, commented:
“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.”

The company will publish the data and interpretation in scientific literature in due course.

About the REACT study¹ NCT03585270
REACT, a multicenter, double-blind, randomized, placebo-controlled, parallel-group, Phase 3 study with clazosentan in patients with aneurysmal subarachnoid hemorrhage (aSAH), assessed the efficacy and safety of clazosentan in preventing clinical deterioration due to delayed cerebral ischemia, in adult patients following aSAH. REACT included patients aged 18 to 70 years with World Federation of Neurological Societies grades 1-4 after recovery from the aneurysm-securing procedure and “thick and diffuse clots” on the admission CT scan. REACT randomized 409 patients – treated either with microsurgical clipping or endovascular coiling aneurysm securing procedures – in a 1:1 ratio to receive placebo or clazosentan 15 mg/h. Patients were enrolled in the REACT study at 74 sites in 15 countries across North America and Europe. 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.

Notes to the editor

Clazosentan in aSAH^2-4
An aSAH involves sudden life-threatening bleeding occurring in the subarachnoid space. It is caused by the rupture of an aneurysm – a weak, bulging spot on the wall of a cerebral artery. An emergency procedure (endovascular coiling or microsurgical clipping) is required to secure the aneurysm to prevent rebleeding.