Milestone Pharmaceuticals Receives Refusal to File Letter from U.S. FDA for New Drug Application for Etripamil in the Treatment of PSVT

MONTREAL and CHARLOTTE, N.C., Dec. 26, 2023 (GLOBE NEWSWIRE) -- Milestone Pharmaceuticals Inc. (Nasdaq: MIST) announced today that the Company received a Refusal to File (RTF) letter from the U.S. Food and Drug Administration (FDA) for the New Drug Application (NDA) for self-administered etripamil nasal spray for the treatment of paroxysmal supraventricular tachycardia (PSVT).

Upon preliminary review, the FDA determined that the NDA, submitted in October 2023, was not sufficiently complete to permit substantive review. The FDA requested clarification about the time of data recorded for adverse events in Phase 3 clinical trials; FDA did not express concerns about the nature or severity of adverse events. Milestone will seek clarification and is in the process of planning a meeting with the FDA.

"We intend to work with the FDA to better understand the open issues and to agree on a path forward," said Joseph Oliveto, President, and Chief Executive Officer of Milestone Pharmaceuticals. "We are committed to advancing etripamil nasal spray as a first-of-its kind portable and fast acting solution that would allow patients with episodic cardiovascular conditions to actively self-manage their condition outside of the healthcare setting.”

About Pivotal RAPID Phase 3 Trial
Recently published in The Lancet, RAPID is a global, randomized, double-blind Phase 3 clinical trial of etripamil versus placebo in patients with PSVT. The trial was designed to evaluate the safety and efficacy of self-administered etripamil for treating PSVT. RAPID achieved its primary endpoint with 64% of patients who self-administered etripamil converting from supraventricular tachycardia (SVT) to sinus rhythm within 30 minutes compared to 31% on placebo (HR = 2.62, p<0.001). At one hour, the benefit was demonstrated in 73% of patients. In addition, significant reductions in time to conversion in patients who took etripamil were evident early and durable, with a median time to conversion of 17 minutes (95% CI: 13.4, 26.5) for patients treated with etripamil versus 54 minutes (95% CI: 38.7, 87.3) for patients treated with placebo. Data demonstrated statistically significant improvement in multiple defined symptoms of PSVT in patients receiving etripamil compared to placebo, using a patient-reported outcome (PRO) questionnaire. The safety and tolerability profile of etripamil is supportive of the NDA submission.