Research and Development


There are no FDA-approved self-administered pharmaceutical treatment options to stop PSVT episodes when they occur.  Milestone’s lead product etripamil (MSP-2017) was developed to address a significant unmet medical need for self-administered products to terminate PSVT episodes in the outpatient setting.

Etripamil is a proprietary small molecule new chemical entity that was conceived, discovered and optimized by Milestone. Etripamil is currently being tested in Phase 3 trials.  It is administered intra-nasally to allow for rapid systemic drug delivery.  Etripamil has been designed to be short-acting due to a transient blood half-life measured in minutes.

Clinical Studies


A Phase 1 clinical trial was successfully completed in healthy volunteers and was designed to assess the safety, pharmacokinetic profile, and cardiac pharmacology of intra-nasally administered etripamil in a randomized, placebo-controlled, single ascending dose design. These results showed rapid absorption into the blood stream and modulation of the AV node as measured by prolongation of the PR interval via ECG. The Phase 1 results supported the selection of 4 doses of etripamil into Phase 2 development.

node-1 logoA Phase 2 study (NODE-1) was successfully completed in PSVT patients in the electrophysiology (EP) laboratory setting. NODE-1 was a multi-center, randomized, double-blind, placebo-controlled study conducted in the United States and Canada to evaluate the effects of 4 different doses of etripamil in patients with PSVT. Subjects were randomized to yield 104 evaluable subjects distributed into 5 groups of at least 20 subjects each. Each group received a different intra-nasally administered dose of etripamil (35 mg, 70 mg, 105 mg, 140 mg) or placebo at the time of EP lab intervention. The primary objective of this study was to demonstrate the superiority of at least one dose of intranasal etripamil over placebo in terminating PSVT induced in an electrophysiology (EP) lab in patients who were scheduled to undergo an EP study and catheter ablation. The secondary objectives were to determine the minimal effective dose of etripamil, to establish a dose-related trend for etripamil, and to evaluate the safety of etripamil in a clinical setting. The primary endpoint was the conversion of PSVT to normal sinus rhythm within 15 minutes after administration of the investigational product.

See a description of our phase II clinical trial on