Milestone Electronics and Milestone Pharmaceuticals today announced that CARDAMYST™ (etripamil) nasal spray has received FDA authorization as the first and only self-administered treatment for adults experiencing paroxysmal supraventricular tachycardia (PSVT). This milestone marks the first FDA-endorsed therapy for PSVT in over 30 years, offering a rapid, on-demand option for millions of Americans. CARDAMYST is expected to hit retail pharmacies in Q1 2026.
CARDAMYST is a novel, fast-acting calcium channel blocker delivered as needed to interrupt often dramatic PSVT episodes and restore normal sinus rhythm. With this approval, patients can prepare to manage episodes outside traditional healthcare settings, providing a greater feeling of control over their condition.
Milestone’s leadership highlighted that CARDAMYST represents a watershed moment for the company and a meaningful advancement for patients, clinicians, and researchers who contributed to its development. The approval was celebrated as a significant step forward for those living with PSVT who typically faced stressful treks to emergency departments for treatment.
Dr. James Ip, M.D., FACC, FHRS and etripamil study investigator, emphasized that CARDAMYST empowers patients to intervene early, potentially avoiding hospital visits or emergency service use during PSVT episodes.
Clinical Evidence and Safety
The FDA decision is underpinned by a robust clinical program, drawing safety data from more than 1,800 participants and over 2,000 PSVT episodes. The pivotal RAPID Phase 3 trial compared CARDAMYST with placebo in a global, randomized, double-blind design. In the trial, 64% of self-administered CARDAMYST users converted to sinus rhythm within 30 minutes, versus 31% for placebo (hazard ratio 2.62; p<0.001) with 73% showing benefit at one hour. The median time to conversion was 17 minutes for CARDAMYST, compared with 54 minutes for placebo. These effects were consistent across subgroups, including individuals also taking beta blockers or calcium channel blockers.
Reported adverse events were generally mild to moderate and transient, including local nasal discomfort, congestion, runny nose, throat irritation, and nosebleeds. Discontinuation due to adverse events occurred in fewer than 2% of participants.
Additional safety details are available in the product’s Important Safety Information, and the latest availability information is on Milestone’s website.
Commercial Readiness and Financing
Milestone stated it is well-positioned financially to launch CARDAMYST, supported by existing cash, equivalents, and short-term investments totaling $82.6 million as of September 30, 2025. In 2023, Milestone entered into a Royalty Purchase Agreement with RTW Investments, LP and affiliates, securing a $75 million upfront payment contingent on FDA approval of etripamil by December 31, 2025, in exchange for a tiered royalty on U.S. net product sales. An amendment extended the approval date to accommodate regulatory timelines. Milestone expects to receive the $75 million payment after meeting the specified conditions.
A conference call and live webcast with slides are planned for December 15, 2025, at 8:00 a.m. ET to discuss the FDA approval. Dial-in details and the webcast link are provided in Milestone’s investor communications.
About PSVT and AFib-RVR
PSVT affects an estimated two million people in the United States and is marked by sudden episodes of rapid heart rate. Attacks can be highly disruptive and may prompt anxiety due to their unpredictability and potential to limit daily activities. Prior treatments often required IV administration in clinical settings, resulting in stress, cost, and time away from daily life. CARDAMYST introduces a new self-administered option to address PSVT at onset.
Milestone also envisions a development path for AFib-RVR (atrial fibrillation with rapid ventricular rate). Building on positive ReVeRA Phase 2 results and in line with FDA guidance, Milestone plans a Phase 3 program to evaluate etripamil for AFib-RVR, with a potential supplemental New Drug Application (sNDA) following a pivotal study.
Indication and Safety Information
CARDAMYST is indicated for converting acute symptomatic PSVT episodes to sinus rhythm in adults. It is not established as safe or effective in children. Patients should avoid CARDAMYST if they have certain heart conduction issues, severe heart failure, or a history of specific arrhythmias, unless advised otherwise by their clinician. The full Prescribing Information contains details about ingredients, dosing, contraindications, precautions, potential drug interactions, and reported adverse events. Consultation with a healthcare provider is essential to ensure suitability and safe use.
Thought-Provoking Takeaways
CARDAMYST introduces a self-administered, rapid-acting treatment for PSVT, representing a shift in how patients manage episodic tachycardias. The door is opened for broader use cases and potential indications, such as AFib-RVR, but with regulatory and practical challenges to navigate. How might self-administered therapies alter emergency department dynamics, health economics, and patient outcomes in rhythm disorders? Are there scenarios where a widely accessible inhaled or nasal agent could change other acute cardiovascular conditions? Share your thoughts in the comments on where this approach could go next.
