Milestone Pharmaceuticals has received approval from the U.S. Food and Drug Administration (FDA) for its nasal spray Cardamyst, a calcium channel blocker intended to treat irregular heartbeat in adults. The FDA’s decision marks the end of a long regulatory process that began with Milestone’s initial application more than two years ago.
Cardamyst is indicated for adults experiencing acute symptomatic episodes of paroxysmal supraventricular tachycardia (PSVT), which is characterized by sudden episodes of rapid heart rate. According to Milestone, this is the first novel treatment for PSVT to be approved in over 30 years.
The approval was based on results from the Phase III RAPID study. In this trial, 64% of patients who received Cardamyst returned to normal heart rhythm within 30 minutes, compared with 31% of those given a placebo. The median time for normalization was 17 minutes with Cardamyst versus 54 minutes in the control group.
Milestone plans to launch Cardamyst in the United States during the first quarter of 2026. CEO Joseph Oliveto stated that the medication provides patients “the freedom to manage their episodes anytime and anywhere,” addressing what he called “the unpredictable impact of PSVT.” He also described Cardamyst’s approval as a “watershed moment” for Milestone.
The regulatory journey included several setbacks. In December 2023, Milestone received an FDA refusal to file letter because its original submission was deemed incomplete. The company resubmitted its application in March 2024 with improved data structuring related to adverse event timelines but without new efficacy or safety data. After a full review, the FDA rejected the drug again due to issues concerning chemistry, manufacturing, and controls; however, it did not raise concerns about safety or efficacy.
Oliveto told BioSpace in March that Cardamyst aims to deliver similar effectiveness as intravenous treatments but offers greater convenience as a nasal spray. The company is also investigating Cardamyst for use in atrial fibrillation with rapid ventricular rate and has completed Phase II studies for this indication. Late-stage development is planned but no timeline has been announced.
