Milestone Pharmaceuticals (NASDAQ:MIST) shares jumped roughly 35% after the U.S. Food and Drug Administration approved CARDAMYST, the first nasal spray that patients can self-administer to treat paroxysmal supraventricular tachycardia (PSVT).
The decision introduces the first new treatment option in more than three decades for the estimated 2 million people in the U.S. affected by PSVT, a condition marked by sudden episodes of rapid heart rate. CARDAMYST is intended to quickly terminate these episodes and restore normal heart rhythm, potentially reducing the need for emergency room visits.
Clinical studies showed that patients treated with CARDAMYST were twice as likely to convert from PSVT to normal sinus rhythm compared with placebo, and achieved conversion more than three times faster. The FDA’s approval was supported by data from more than 1,800 patients across multiple trials, including the successful Phase 3 RAPID study published in The Lancet last year.
“CARDAMYST is a novel at-the-ready treatment option that addresses the unpredictable impact of PSVT by offering patients the freedom to manage episodes anytime and anywhere,” said Joseph Oliveto, President and CEO of Milestone Pharmaceuticals.
Milestone expects CARDAMYST to reach retail pharmacies in the first quarter of 2026. Beyond PSVT, the company is advancing etripamil — the active ingredient in CARDAMYST — for use in atrial fibrillation with rapid ventricular rate (AFib-RVR), and plans to seek approval via a supplemental New Drug Application following completion of a Phase 3 program.
Reported side effects in clinical trials were generally mild to moderate and temporary, with the most common including nasal discomfort, congestion and throat irritation. Milestone said it has sufficient capital and royalty-based financing in place to support the launch and commercialization of CARDAMYST.