Milestone Pharmaceuticals has announced new data showing that its 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—the company’s chief medical officer—in a moderated poster session at the 2026 American Heart Association (AHA) Scientific Sessions (7–9 November, Chicago, USA).
Cardamyst is US Food and Drug Administration (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 Ip (New York-Presbyterian/Weill Cornell Medical Center, New York City, USA), 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.”
While catheter ablation is successful in the treatment of PSVT for most patients, a small proportion of patients continue to have episodes afterward—and treatment options for these patients are limited.
Milestone states in a press release that prior ablation was reported in 6.6% of all randomised patients (46 out of 692) in RAPID and in 6% of those with adjudicated, confirmed PSVT in the efficacy population (11 out of 184), indicating that a subset of patients continue to experience confirmed PSVT recurrences after ablation. The overall RAPID trial met its primary endpoint, the company also notes.
Across the 11 patients in the prior-ablation subgroup (mean age, 50.9 years; 82% female; 54.5% taking oral atrioventricular [AV] nodal-acting medication), 66.7% of six etripamil-treated patients converted to sinus rhythm at 30 minutes, compared with 20% of five placebo-treated patients, which is 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, Milestone notes.
Safety in the prior-ablation subgroup was also assessed using continuous electrocardiogram (ECG) recordings and adverse-event reporting, including monitoring for AV block and prolonged pauses.
The authors of the analysis conclude 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,” Bharucha commented. “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.”
