Harmony Biosciences reported that its experimental drug EPX-100 reduced monthly seizures by about 50% in a Phase III trial involving patients with Dravet syndrome. The results were part of the open-label extension phase of the ARGUS study, which is a randomized, double-blind, placebo-controlled trial measuring countable motor seizures per 28 days (CMS-28).
Analysts at H.C. Wainwright & Co. commented on the findings: “These results increase our confidence in the EPX-100 program.” They described EPX-100 as “a cornerstone of Harmony’s strategy” to support its current product Wakix for excessive sleepiness.
The analysts further stated that this outcome “represents a de-risking event for a key pipeline asset” for Harmony. According to the study data, patients who had been taking EPX-100 for at least six months experienced an “approximately 50% reduction” in seizure frequency compared to baseline measurements.
All 29 participants from the double-blind portion continued into the open-label extension phase, which H.C. Wainwright noted reflects “a positive patient and physician view of the drug’s risk/benefit profile.” Additional details are expected to be presented at the American Epilepsy Society’s annual conference on December 8.
The safety evaluation during this phase found 28 drug-related side effects and 11 serious adverse events; one was considered “possibly” related to EPX-100. Despite these events, H.C. Wainwright characterized the overall safety profile as “favorable.”
“While from a small, open-label cohort, this clinically meaningful efficacy signal provides strong validation for the program” in Dravet syndrome, according to H.C. Wainwright analysts. Harmony is also conducting another Phase III trial called LIGHTHOUSE to test EPX-100 in Lennox-Gastaut syndrome—a rare form of childhood epilepsy—with both studies expected to report results next year.
This recent success comes after some setbacks for Harmony Biosciences earlier in the year. In September, their cannabidiol candidate ZYN002 did not meet endpoints in a late-stage study on fragile X syndrome due to what was described as a higher than anticipated placebo response rate. Additionally, in February, the FDA declined to review Harmony’s supplemental application seeking approval to expand Wakix use into idiopathic hypersomnia; no specific reasons were disclosed by either party.
