Milestone Pharmaceuticals announced that the FDA has declined to approve its new drug application for etripamil nasal spray (Cardamyst) to treat paroxysmal supraventricular tachycardia.

In a complete response letter, the FDA cited two chemistry, manufacturing, and control issues and requested an inspection of the facility responsible for release testing. The agency also requested additional data on nitrosamine impurities, referencing guidance issued after the application was submitted.

The FDA did not raise concerns related to safety or efficacy. The company stated that the self-administered nasal spray helped a significantly greater proportion of patients return to normal heart rhythm compared to placebo in a late-stage study.

Milestone previously received a refusal-to-file letter from the agency in December 2023 and subsequently resubmitted the application. The company estimates that approximately 2 million people in the U.S. have been diagnosed with paroxysmal supraventricular tachycardia.