The subjective experience of patients appeared to be reflected in objective measures. When the two groups were compared for interventions in an emergency room, the need was reduced by about half (12.1% vs. 24.5%; P = .051) among those treated with etripamil. Although this just missed the conventional measure of statistical significance, it was close. Similarly, patients randomized to etripamil required numerically fewer rescue medications (14.0% vs. 26.5%; P = .059).
Adenosine was the most common of the rescue medications, according to Dr. Stambler. He said there was no difference between the groups in use of rescue oral therapies.
When comparing etripamil and placebo in the subgroup that did visit an emergency room for PSVT, there was a delay in ER visits among those randomized to etripamil (116 vs. 79 minutes; P < 0.05), suggesting that this agent reduced the sense of urgency when PSVT symptoms develop, according to Dr. Stambler.
On average, the patients who enrolled in this trial had a PSVT history of about 1.5 years. In the year prior to enrollment, the mean number of ER visits was about nine.
In the trial design, patients were required to take a test dose of etripamil under observation by a physician before being sent home with their assigned therapy, but Dr. Stambler does not believe that the requirement, if the drug is approved, will be in the label.
Unexpectedly, many patients had symptom relief even without converting to sinus rhythm, Dr. Stambler acknowledged. He speculated that the reduction in heart rate associated with etripamil might have provided a relief of symptoms sufficient to relieve anxiety, producing the relative advantage for patient satisfaction.
Jodie L. Hurwitz, MD, director of the electrophysiology lab at Medical City Hospital, Dallas, indicated that there is a need for new options for PSVT. An expert panelist during the session where these data were presented, she was particularly interested in rapid symptom relief.
“It would be great to have a therapy that could be self-administered at home. Patients would like it, too,” she said.
Mary N. Walsh, MD, a heart failure specialist affiliated with Indiana University, Indianapolis, sees a potential role of a self-administered therapy like etripamil in conjunction with wearable devices. She noted that the proportion of patients using these devices to monitor arrhythmias is increasing, providing a role for an easily transportable therapy that could be used quickly when symptoms develop.
However, after the negative phase 3 trial, more data must now be collected to satisfy the regulatory authorities that this agent is safe and effective. Dr. Stambler said that the developer is now committed to pursue these studies.
Dr. Stambler has a financial relationship with Milestone Pharmaceuticals, which is developing etripamil nasal spray and was the sponsor of this trial. Dr. Walsh and Dr. Hurwitz have no potential relevant conflicts of interest.