FDA Approval of Cardamyst Marks Milestone's Entry into Commercial Market

Milestone Pharmaceuticals has achieved a significant breakthrough with the FDA's approval of Cardamyst (etripamil), a novel nasal spray for treating paroxysmal supraventricular tachycardia (PSVT). This approval marks the company's transition from a development-stage biotech to a commercial entity, ending a long regulatory journey and introducing the first new PSVT treatment in over three decades.

Cardamyst: A Game-Changer for PSVT Management

Cardamyst, a calcium channel blocker, offers PSVT patients a self-administered alternative to emergency room visits for managing acute symptomatic episodes. The FDA's decision was based on data from the Phase III RAPID study, which demonstrated Cardamyst's superior efficacy compared to placebo.

Key findings from the study include:

• 64% of Cardamyst-treated patients converted to normal sinus rhythm within 30 minutes, versus 31% on placebo.
• Median time to heart rhythm normalization was 17 minutes for Cardamyst, compared to 54 minutes for placebo.

Joseph Oliveto, CEO of Milestone, highlighted the drug's potential impact: "Cardamyst gives patients the freedom to manage their episodes anytime and anywhere, addressing the unpredictable impact of PSVT."

Regulatory Challenges and Market Entry

Milestone's path to approval was not without obstacles. The FDA initially issued a refusal to file letter in late 2023, followed by a rejection in March 2025 due to manufacturing issues. These setbacks prompted Milestone to restructure datasets and address chemistry, manufacturing, and controls concerns.

With these hurdles now cleared, Milestone plans to launch Cardamyst in the U.S. market in the first quarter of 2026. The company's recent financial moves include securing $75 million from RTW Investments in exchange for tiered royalties, bolstering its commercialization efforts.

Future Prospects and Expansion Plans

While PSVT affects approximately 2 million people in the U.S., Milestone is already looking ahead to broader applications for Cardamyst. The company has completed a Phase II study (ReVeRA) for atrial fibrillation with rapid ventricular rate (AFib-RVR), a condition affecting 10-12 million U.S. patients.

Oliveto expressed optimism about the potential label expansion: "PSVT opens everything up for us to be transformative. It transforms us from a development company into a commercial company. It transforms us from a single indication to now starting the AFIB phase 3 indication."

The news of Cardamyst's approval has been well-received by investors, with Milestone's stock up more than 35% in premarket trading following the announcement.