Mixed Ph III results for Milestone Pharma’s etripamil for at-home acute PSVT treatment

Shares of Canadian drug developer Milestone Pharmaceuticals (Nasdaq: MIST) were down a massive 75% at $10.51 in pre-market trading today, after its announcement on Monday of disappointing top-line results from its Phase III, multicenter, randomized, double-blind, placebo-controlled NODE-301 trial of its investigational new drug, etripamil nasal spray, the company's novel short-acting calcium channel blocker, in patients with paroxysmal supraventricular tachycardia (PSVT).

The NODE-301 trial, which enrolled a total of 431 patients across 65 sites in the USA and Canada, is an event-driven Phase III efficacy trial of etripamil for terminating supraventricular tachycardia (SVT) episodes in the at-home setting.

Etripamil (70mg) did not achieve its primary endpoint of time to conversion of SVT to sinus rhythm (SR) compared to placebo over the five-hour period following study drug administration (median time to conversion of 25 minutes [95% CI: 16, 43] for etripamil versus 50 minutes [95% CI: 31,101] for placebo, p=0.12). Despite early activity, including the conversion of 61% of etripamil patients vs 45% of placebo patients by 45 minutes (p=0.02), a time period consistent with etripamil's known pharmacological activity, results from the latter part of the analysis confounded the statistical analysis of the primary endpoint.