MONTREAL and CHARLOTTE, N.C., Nov. 02, 2026 (GLOBE NEWSWIRE) — Milestone® Pharmaceuticals Inc. (Nasdaq: MIST), a biopharmaceutical company focused on the development and commercialization of innovative cardiovascular medicines, today announced new data showing that CARDAMYST® (etripamil) nasal spray converted approximately two-thirds of patients who experienced recurrent symptomatic paroxysmal supraventricular tachycardia (PSVT) after a prior catheter ablation to normal heart rhythm within 30 minutes. The subgroup analysis of the Phase 3 RAPID clinical trial will be presented by David Bharucha, MD, Ph.D., FACC, Chief Medical Officer of Milestone Pharmaceuticals in a moderated poster session at the American Heart Association (AHA) Scientific Sessions 2026 on Saturday, November 7. CARDAMYST is FDA-approved for the conversion of acute symptomatic episodes of PSVT to sinus rhythm in adults.

“Most patients do well after ablation but a subset continues to have episodes, and we have had limited options to offer them for treating an episode outside of an emergency room setting,” said James E. Ip, MD, Professor of Medicine and Director of Cardiac Pacing and Implantable Devices at Weill Cornell Medicine, a cardiac electrophysiologist at New York-Presbyterian/Weill Cornell Medical Center, and lead author of the analysis. “These data, although from a small group, are encouraging because the response to etripamil nasal spray in patients with a prior ablation is similar to what we observed across the broader RAPID population. For patients considering a repeat procedure, having a self-administered option to treat an episode should be a meaningful part of the conversation they have with their cardiologist.”

Catheter ablation is a procedure intended to treat PSVT, a common type of rapid heart rhythm, and it is successful for most patients. A small proportion of patients continue to have episodes afterward, and treatment options for these patients are limited.

Data Highlights

  • Prior ablation was reported in 6.6% of all randomized patients (46 of 692) in RAPID and in 6.0% of those with adjudicated, confirmed PSVT in the efficacy population (11 of 184), confirming that a subset of patients continue to experience confirmed PSVT recurrences after ablation.
  • In the prior-ablation subgroup (N=11), 66.7% of etripamil-treated patients (n=6) converted to sinus rhythm at 30 minutes, compared with 20.0% of placebo-treated patients (n=5), consistent with the conversion observed in the overall RAPID efficacy population. These are descriptive data, and this subgroup analysis was not powered for between-group comparison.
  • Safety in the prior-ablation subgroup was assessed using continuous ECG recordings and adverse-event reporting, including monitoring for AV block and prolonged pauses.

The authors concluded that etripamil should be considered a potential treatment option for patients who have incomplete resolution after ablation or who are considered high risk for a repeat procedure.

“In this analysis from the RAPID trial, patients with recurrent PSVT after a prior ablation responded to etripamil in a manner consistent with the overall trial population,” said David Bharucha, MD, Ph.D., FACC. “Thus, we believe these findings reinforce the overall data which show etripamil to be a safe and effective treatment option, and support this drug to be used as a self-administered treatment for patients who may have continued episodes of PSVT after ablation.”

The subgroup analysis draws on the overall RAPID trial, which met its primary endpoint. In the prior-ablation efficacy subgroup (N=11), patients had a mean age of 50.9 years, 82% were female, and 54.5% were taking an oral AV nodal-acting medication. Six patients received etripamil and five received placebo.

RAPID (NCT03464019) was a randomized, double-blind, event-driven, placebo-controlled Phase 3 study evaluating a single or repeat 70 mg dose of etripamil, self-administered by patients during a perceived PSVT episode, with a repeat dose permitted per protocol. Episodes were adjudicated from ambulatory ECG recordings. The efficacy population included patients who self-administered study drug during an adjudicated, confirmed, AV nodal-dependent PSVT episode; patients with post-conversion dosing, non-AV nodal-dependent events, or substantial ECG signal loss were excluded. To enroll, patients with a prior PSVT ablation were required to have documented ECG evidence of recurrent PSVT after the procedure.

CARDAMYST Product Theater

Milestone will also host a Product Theater at AHA Scientific Sessions 2026 titled “How Can CARDAMYST, the first and only FDA-approved, self-administered treatment for PSVT in adults, be used in a Health Care Professional’s practice?” on Saturday, November 7, from 9:30 to 10:15 am CT. The presenter will be Matthew Budoff, MD, FACC, FAHA, of the Department of Medicine, Lundquist Institute at Harbor-UCLA.

About CARDAMYST 

CARDAMYST® (etripamil) nasal spray is approved by the U.S. Food and Drug Administration (FDA) for the conversion of acute symptomatic episodes of paroxysmal supraventricular tachycardia (PSVT) to sinus rhythm in adults. It is a novel calcium channel blocker nasal spray designed as a self-administered rapid response therapy for patients, thereby bypassing the need for immediate medical oversight. The product is intended to provide health care providers with a new treatment option to enable on-demand care and patient self-management. This portable treatment may provide patients with active management and a greater sense of control over their condition. CARDAMYST is well studied with a robust clinical trial program that includes a completed Phase 3 clinical-stage program for the treatment of PSVT. Currently, etripamil is in Phase 2 development for treatment of PSVT in pediatric patients and Phase 3 development for control of acute atrial fibrillation with rapid ventricular rate (AFib-RVR) in adults. For more information, please visit CARDAMYST.com. 

U.S. FDA Indication
CARDAMYST is indicated for the conversion of acute symptomatic episodes of paroxysmal supraventricular tachycardia (PSVT) to sinus rhythm in adults.

IMPORTANT SAFETY INFORMATION FOR CARDAMYST (etripamil)

What is CARDAMYST?

CARDAMYST is a prescription medicine used to help restore normal sinus heart rhythm in adults who have symptoms of sudden episodes of fast heartbeat called paroxysmal supraventricular tachycardia (PSVT).

It is not known if CARDAMYST is safe and effective in children.

Do not use CARDAMYST if you:

  • are allergic to CARDAMYST or any of its ingredients. See the Patient Information for a complete list of ingredients in CARDAMYST.
  • have limitations in activities due to heart failure (moderate to severe heart failure).
  • have Wolff-Parkinson-White (WPW) syndrome, Lown-Ganong-Levine syndrome, or an abnormal heart rhythm pattern called pre-excitation (delta wave) on an electrocardiogram (ECG).
  • have sick sinus syndrome without a permanent pacemaker.
  • have second degree or higher atrioventricular (AV) block.

Before using CARDAMYST, tell your healthcare provider about all of your medical conditions, including if you:

  • have a history of fainting.
  • have low blood pressure.
  • are pregnant or plan to become pregnant. It is not known if CARDAMYST will harm your unborn baby.
  • are breastfeeding or plan to breastfeed. It is not known if CARDAMYST passes into your breast milk. You should stop breastfeeding for 12 hours after treatment with CARDAMYST. During this time, pump and throw away your breast milk. Talk to your healthcare provider about the best way to feed your baby after using CARDAMYST.

Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.

What are the possible side effects of CARDAMYST?

CARDAMYST may cause serious side effects, including:

  • Fainting due to CARDAMYST effects on blood pressure, heart rate, and electrical activity of the heart. CARDAMYST may cause dizziness and fainting, especially in people with a history of fainting and certain heart problems, or people with a history of fainting during an episode of PSVT. Use CARDAMYST while sitting in a safe area where you will not fall if you become dizzy or lightheaded. Lie down if you feel dizzy or lightheaded after using CARDAMYST. If fainting occurs after using CARDAMYST, caregivers should place you on your back and seek medical help.

The most common side effects of CARDAMYST include nasal discomfort, nasal congestion, runny nose, throat irritation, and nosebleed.

These are not all of the possible side effects for CARDAMYST. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Please see the full Prescribing Information 
https://milestonepharma.com/etripamilprescribinginformation.pdf for CARDAMYST.

About Milestone Pharmaceuticals
Milestone Pharmaceuticals Inc. (Nasdaq: MIST) is an emerging commercial-stage biopharmaceutical company advancing innovative cardiovascular medicines to benefit people living with certain heart conditions. Milestone’s lead product is CARDAMYST® (etripamil) nasal spray, a novel calcium channel blocker, which is FDA-approved for the conversion of acute symptomatic episodes of paroxysmal supraventricular tachycardia (PSVT) to sinus rhythm in adults. Etripamil is also in Phase 3 development for the control of symptomatic episodic attacks associated with AFib-RVR. https://milestonepharma.com/.

Cautionary Note on Forward-Looking Statements
This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Words such as “believe,” “continue,” “could,” “demonstrate,” “designed,” “develop,” “estimate,” “expect,” “may,” “pending,” “plan,” “potential,” “progress,” “will,” “intend” and similar expressions (as well as other words or expressions referencing future events, conditions, or circumstances) are intended to identify forward-looking statements. These forward-looking statements are based on Milestone’s expectations and assumptions as of the date of this press release. Each of these forward-looking statements involves risks and uncertainties. Actual results may differ materially from these forward-looking statements. Forward-looking statements contained in this press release include statements regarding: Milestone’s business strategy and plans; the commercialization and market adoption of CARDAMYST; expectations regarding the potential role of CARDAMYST as a self-administered treatment option for patients experiencing recurrent PSVT after catheter ablation; the anticipated presentations at AHA Scientific Sessions 2026; Milestone’s development plans for etripamil in additional indications and patient populations; and other statements not related to historical facts. Important factors that could cause actual results to differ materially from those in the forward-looking statements include, but are not limited to, the risks inherent in biopharmaceutical product development and clinical trials, including the lengthy and uncertain regulatory approval process; uncertainties related to the timing of initiation, enrollment, completion, evaluation and results of Milestone’s clinical trials; risks and uncertainty related to the complexity inherent in cleaning, verifying and analyzing trial data; and whether the clinical trials will validate the safety and efficacy of etripamil for PSVT or other indications, among others, general economic, political, and market conditions, including deteriorating market conditions due to investor concerns regarding inflation, international tariffs and conflicts, and overall fluctuations in the financial markets in the United States and abroad, risks related to pandemics and public health emergencies, and risks related to the sufficiency of Milestone’s capital resources and its ability to raise additional capital in the current economic climate. These and other risks are set forth in Milestone’s filings with the U.S. Securities and Exchange Commission (SEC), including in its annual report on Form 10-K for the year ended December 31, 2025, and its Quarterly Report on Form 10-Q for the quarter ended June 30, 2026, under the caption “Risk Factors,” as such discussions may be updated from time to time by subsequent filings Milestone may make with the SEC. Except as required by law, Milestone assumes no obligation to update any forward-looking statements contained herein to reflect any change in expectations, even as new information becomes available.

Contact:

Investor Relations
Kevin Gardner, kgardner@lifesciadvisors.com

Media Relations
Rebecca Novak, rnovak@milestonepharma.com 


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