On December 26, 2023, before the market opened, Milestone Pharmaceuticals, Inc. announced that it had received a Refuse to File (“RTF”) letter from the U.S. Food and Drug Administration (“FDA”) for its recently submitted new drug application for its lead investigational product, Etripamil, a self-administered nasal spray for the treatment of paroxysmal supraventricular tachycardia. In the RTF, the FDA noted that Milestone had not provided the agency with sufficient information to permit substantive review, and sought additional information related to the timing of adverse events in Etripamil’s Phase 3 trial.

On this news, Milestone’s stock fell $0.89 per share, or 30.90%, to close at $1.99 per share on December 26, 2023.