Acadia's Prader-Willi Syndrome Drug Fails Phase 3 Trial, Leaving Soleno as Sole Market Player

Acadia Pharmaceuticals has announced the discontinuation of its intranasal carbetocin program for the treatment of hyperphagia in patients with Prader-Willi Syndrome (PWS) following disappointing phase 3 trial results. This development leaves Soleno Therapeutics as the only company with an approved treatment for the condition, solidifying its market position.

Trial Failure and Program Termination

Acadia's phase 3 trial, which enrolled 175 children and adults aged 5 to 30 with PWS, failed to meet its primary endpoint. The study aimed to demonstrate a statistically significant improvement on the Hyperphagia Questionnaire for Clinical Trials (HQ-CT) over placebo after 12 weeks of treatment. Participants in the treatment group received three 3.2-mg doses of intranasal carbetocin daily.

Dr. Elizabeth Thompson, Acadia's R&D chief, stated, "We are committed to sharing a summary of the data in the future to ensure learning for the PWS community. However, given these results, we do not intend to investigate intranasal carbetocin any further."

Market Implications and Soleno's Position

The failure of Acadia's candidate has significant implications for the PWS treatment landscape:

1. Soleno Therapeutics remains the sole provider of an FDA-approved treatment for hyperphagia in PWS patients.
2. Soleno's drug, Vykat XR, approved by the FDA in March, has shown strong market performance with second-quarter sales reaching $33 million.
3. Vykat XR, a once-daily, extended-release tablet, carries an annual list price of $466,200.

The market responded swiftly to the news, with Soleno's share price increasing by 11%, while Acadia's stock tumbled by 9% following the announcement.

Acadia's Future Outlook

Despite this setback, Acadia's CEO Catherine Owen Adams remains optimistic about the company's future:

1. Acadia expects to generate more than $1 billion in revenue this year from its two approved products.
2. The company plans to initiate seven phase 2 or phase 3 trials next year.
3. Four data readouts are anticipated by the end of 2027.

"Despite this disappointment, Acadia is well-positioned to deliver long-term, sustainable growth," Adams stated, emphasizing the company's diverse pipeline and ongoing research efforts.