The FDA had previously turned back the heart rhythm nasal spray twice, once in late 2023 with a refusal to file letter and again in March this year, when it flagged manufacturing issues.
More than two years after its first filing, Milestone Pharmaceuticals has finally won the FDA’s approval for its calcium channel blocker nasal spray Cardamyst, which the FDA on Friday cleared for the treatment of irregular heartbeat in adults.
Specifically, Cardamyst is indicated to help normalize the heart rhythm of patients suffering from acute symptomatic episodes of paroxysmal supraventricular tachycardia (PSVT), or fast heartbeat. Cardamyst is the first novel approved treatment for PSVT in more than 30 years, Milestone claimed in its news release.
The FDA’s decision was supported by data from the Phase III RAPID study, which showed that 64% of patients who used Cardamyst converted back to sinus rhythm within 30 minutes of dosing, as opposed to 31% on placebo. Onset of action was likewise faster with Cardamyst, with patients taking a median of 17 minutes before their heartbeats normalized, versus 54 minutes in controls.
Milestone plans to make Cardamyst available in the U.S. in the first quarter of 2026. The drug, CEO Joseph Oliveto said in the company’s statement, gives patients “the freedom to manage their episodes anytime and anywhere,” allowing them to address the “unpredictable impact of PSVT.”
Oliveto also called Cardamyst’s approval a “watershed moment” for Milestone. The biotech has been trying to get the drug over the regulatory finish line since 2023. But in December of that year, the FDA handed Milestone a refusal to file letter, determining that the Cardamyst application “was not sufficiently complete to permit substantive review.”
Milestone tried again a few months later, filing its resubmission in March 2024 with restructured datasets that better characterized the timelines for adverse events. The company did not include additional efficacy or safety findings. In March of this year, however, the FDA again rejected Cardamyst, this time after a full review. The agency flagged chemistry, manufacturing and controls issues but did not find problems with the drug’s safety or efficacy.
Cardamyst is a calcium channel blocker designed to match the efficacy of intravenous therapies while also carrying the convenience of a nasal spray, Oliveto told BioSpace in an interview in March. Milestone is also testing the drug for atrial fibrillation with rapid ventricular rate, for which it has completed the Phase II ReVeRA study. Cardamyst is set to enter late-stage development for this indication, according to the Friday release, though Milestone did not provide a timeline.
