Supernus Pharma (SUPN) Reports Update on Results from Phase III Study (P301) of SPN-810 for Treatment of Impulsive Aggression in ADHD Patients

Supernus Pharmaceuticals, Inc. (NASDAQ: SUPN), a pharmaceutical company focused on developing and commercializing products for the treatment of central nervous system (CNS) diseases, is providing an update on the results from the first Phase III study (P301) of SPN-810, a novel treatment of Impulsive Aggression (IA) in patients with ADHD.

In early November 2019, the Company reported topline results from the Phase III P301 trial in patients 6 to 11 years. The study was a randomized, double-blind, placebo controlled, multicenter, parallel group clinical trial in patients diagnosed with ADHD. Patients receiving SPN-810 36mg showed a median percent reduction of 58.6% in the average weekly frequency of impulsive aggression episodes from baseline that was not statistically significant (p=0.092) compared to placebo. These results are based on the combined analysis of data from stages 1 and 2 in the study. In stage 1 (interim analysis stage), the median percent reduction was 60.0%, which was statistically significant (p=0.029) compared to placebo. However, in stage 2 of the P301 study, post the interim analysis, the increase in variability in the 36mg treatment arm seems to have adversely impacted the results in the combined analysis.

After conducting further analysis on the P301 data, the Company believes that the high variability in the 36mg treatment arm was primarily due to 6 patients out of 135 that had a mild IA condition with a baseline score of 6 episodes or less per week. In the placebo arm, there were 7 patients with the same mild IA condition. By excluding these subjects from the placebo and the 36mg treatment arm, the primary analysis (combined stage 1 and 2 data) of the P301 data on the primary endpoint results in a p value of 0.017 for the treatment arm compared to placebo. This positive result is also confirmed by the sensitivity analysis on the primary endpoint with a p value of 0.044.

Percent Change from Baseline (CFB) in the Frequency of IA BehaviorsTreatment Period - Primary Analysis (ITT Population)

The Company plans on finalizing the statistical plan (SAP) for the second Phase III P302 study in patients 6 to 11 years old taking into consideration the exclusion of patients with 6 or less episodes of IA per week. The Company will be submitting the SAP to the Food and Drug Administration (FDA) and expects data from the P302 study in the first quarter of 2020.

The P503 adolescent Phase III study in patients 12 to 17 years old had been designed from the outset with an exclusion criterion that excludes patients with a baseline score of 6 or less episodes per week.

“Based on this new analysis, we are hopeful that the second Phase III study will be positive, and if so, that future discussions with the FDA will be productive in progressing this potential novel treatment,” said Jack Khattar, President and CEO of Supernus. “While there are no assurances that SPN-810 will eventually progress forward and obtain FDA approval, we continue to believe that with a clinically meaningful reduction of approximately 60% in IA episodes, it can be a real treatment option for patients who currently have no proven products to help them manage their condition,” added Mr. Khattar.

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