Milestone Pharmaceuticals announces FDA acceptance of response to Cardamyst nasal spray CRL

Milestone Pharmaceuticals announced that the U.S. Food and Drug Administration (FDA) has accepted for review the company’s response to the Complete Response Letter (CRL) for cardamyst (etripamil) nasal spray, an investigational therapy for paroxysmal supraventricular tachycardia (PSVT). The FDA has set a new Prescription Drug User Fee Act (PDUFA) target action date of December 13, 2025.

Alongside this FDA update, Milestone also announced the extension of its $75 million Royalty Purchase Agreement with RTW Investments and its affiliates until December 31, 2025. The proceeds from this agreement are expected to support the planned launch of cardamyst for PSVT, pending FDA approval and other closing conditions.

“The FDA’s acceptance of our response is a key step for cardamyst, and we look forward to working with the Agency toward a potential approval later this year,” said Joe Oliveto, President and CEO of Milestone Pharmaceuticals. “We’re also pleased to extend our agreement with RTW, which reinforces their ongoing support. The anticipated funds will help us prepare for the commercial launch and make cardamyst available to patients with PSVT who need new treatment options.”

Milestone first entered into the Royalty Purchase Agreement with RTW in March 2023, under which RTW agreed to purchase the rights to receive tiered royalty payments on annual U.S. sales of etripamil following FDA approval, in exchange for $75 million. The original agreement required FDA approval by September 30, 2025. On July 10, 2025, the agreement was amended to extend this deadline to December 31, 2025. Milestone must also meet other customary conditions to receive the funds. This represents a potential future source of funding for the company.

Milestone Pharmaceuticals announced on July 11, 2025, that the US FDA accepted their response to the Complete Response Letter (CRL) for Cardamyst (etripamil) nasal spray, a novel therapy for treating paroxysmal supraventricular tachycardia (PSVT). The FDA assigned a new PDUFA target action date of December 13, 2025.

Key Details:

– Product: Cardamyst (etripamil) nasal spray
– Indication: Paroxysmal supraventricular tachycardia (PSVT)
– Company: Milestone Pharmaceuticals Inc. (Nasdaq: MIST)
– PDUFA Date: December 13, 2025

Response to CRL:

Milestone Pharmaceuticals received a CRL from the FDA in March 2025 and held a Type A meeting with the Agency in early June 2025 to clarify outstanding items. The company submitted its response to the CRL on June 13, 2025, which included results from additional in-vitro studies conducted to meet updated FDA guidance on nitrosamines ¹.

Financial Update:

Concurrent with the FDA acceptance, Milestone announced the extension of its $75 million purchase and sale agreement with RTW Investments, LP until December 31, 2025. The proceeds are expected to support a successful planned launch of Cardamyst in PSVT following FDA approval ¹