Supernus Pharmaceuticals announced Tuesday that its investigational drug SPN-820 failed to achieve its primary endpoint in a Phase IIb clinical trial for treatment-resistant depression, leading to a significant market response with the company's stock dropping approximately 20% in pre-market trading.
The oral mTORC activator showed only a modest improvement over placebo, with treated patients experiencing a 12.3-point reduction in Montgomery-Åsberg Depression Rating Scale (MADRS) scores after four weeks, compared to an 11.9-point improvement in the placebo group. The 0.4-point difference failed to reach statistical significance, dampening hopes for a new treatment option in the challenging field of treatment-resistant depression.
Secondary endpoints similarly showed no meaningful treatment difference between SPN-820 and placebo, further complicating the drug's development pathway.
Previous Success in Major Depression
The failed trial comes as a particular disappointment following SPN-820's promising performance in an October 2024 Phase II study for major depressive disorder. In that trial, the drug demonstrated clinically meaningful improvements when administered once every three days as an adjunct to existing antidepressant therapy, with benefits observed as early as four hours post-dosing.
Market Impact and Strategic Focus
Jack Khattar, CEO of Supernus, expressed disappointment with the results but indicated that the company would continue analyzing the data while discussing future development options with their partner, Navitor Pharmaceuticals.
Jefferies analysts, who had anticipated the market reaction, noted that successful crossover between major depressive disorder and treatment-resistant depression treatments is rare. Despite the setback, they maintain some optimism about Supernus's overall prospects, particularly regarding their non-stimulant ADHD medication Qelbree.
Commercial Outlook
The company is now expected to concentrate on growing its core central nervous system (CNS) portfolio, with particular emphasis on Qelbree. Analysts project the ADHD drug to exceed fourth-quarter 2024 sales expectations and potentially reach peak sales of at least $500 million, providing a stable foundation for the company despite the recent clinical setback.
