Acadia Pharmaceuticals has ceased development of its intranasal drug ACP-101 for treating hyperphagia in Prader-Willi syndrome after a 12-week Phase III trial failed to meet its primary endpoint of statistically significant symptom improvement versus placebo. The trial outcome, announced in September 2025, dampens prospects for an alternative to Soleno Therapeutics’ approved Vykat XR. Acadia’s stock dropped following the announcement, while Soleno’s shares surged amid its market-leading position.