Acadia Discontinues Prader-Willi Drug After Phase 3 Trial Failure

Acadia Pharmaceuticals has announced the discontinuation of its drug candidate ACP-101 for treating hyperphagia associated with Prader-Willi syndrome following disappointing results from a Phase 3 clinical trial. The setback removes a potential competitor to Soleno Therapeutics' recently approved treatment, Vykat XR.

Trial Failure Leads to Program Termination

The 12-week Phase 3 study, which enrolled 175 patients with Prader-Willi syndrome, failed to demonstrate superiority of ACP-101 over placebo in reducing hyperphagia, the insatiable hunger characteristic of the rare genetic disorder. The drug did not show advantages on the primary endpoint, measured by a questionnaire assessing hunger levels, or any secondary endpoints.

As a result of this setback, Acadia has decided to terminate the development program for ACP-101. The company acquired the drug candidate through its 2022 purchase of Levo Therapeutics, which had previously faced challenges in securing FDA approval for the treatment.

Market Implications and Competitive Landscape

The news of ACP-101's failure had immediate market repercussions. Acadia's stock price dropped 11% in early trading following the announcement, while shares of rival Soleno Therapeutics surged 13%.

Soleno's Vykat XR, approved by the FDA in March 2023, currently stands as the first and only treatment specifically cleared for hyperphagia in Prader-Willi patients. The elimination of Acadia's competing drug from the development pipeline strengthens Soleno's position in this niche market.

However, Soleno faces its own challenges. Despite Vykat's strong initial sales performance, the company has recently encountered controversy. In August, short-selling firm Scorpion Capital published a report alleging serious safety concerns with Vykat, leading to a decline in Soleno's stock price.

Industry Outlook and Future Directions

For Acadia, the focus now shifts to other candidates in its pipeline. Analysts, including Leerink Partners' Marc Goodman, express optimism about upcoming late-stage data from other Acadia programs, particularly an experimental treatment for Alzheimer's disease psychosis.

The failure of ACP-101 underscores the inherent risks in drug development, especially for rare diseases. It also highlights the ongoing need for effective treatments for Prader-Willi syndrome, a complex genetic disorder affecting approximately 1 in 15,000 births.

As the pharmaceutical industry continues to navigate the challenges of developing treatments for rare diseases, the Prader-Willi syndrome market remains an area of unmet medical need and potential opportunity for innovative therapies.