ACAD Stock Down 10% Following Phase III Hyperphagia Study Failure

Acadia Pharmaceuticals (ACAD) shares dropped 9.9% after its Phase III COMPASS PWS study for ACP-101 failed to meet its primary endpoint for hyperphagia in Prader-Willi syndrome, leading to the program's discontinuation. This setback significantly strengthens Soleno Therapeutics' (SLNO) market position, whose recently FDA-approved Vykat XR now stands as the sole approved treatment for PWS hyperphagia, prompting a 13.5% surge in SLNO stock. Despite the pipeline failure, Acadia projects continued growth from its established products, Nuplazid and Daybue, which reported H1 2025 sales increases of 14% and 13% respectively, alongside other pipeline developments.

Analysis

Acadia Pharmaceuticals (ACAD) experienced a significant clinical setback as its Phase III candidate, ACP-101, failed to meet its primary endpoint in the COMPASS PWS study, leading to the program's termination and a 9.9% decline in its share price. This event directly benefits competitor Soleno Therapeutics (SLNO), whose stock surged 13.5% as its recently approved Vykat XR now stands as the sole FDA-approved treatment for hyperphagia in Prader-Willi syndrome, significantly strengthening its market position. Despite the pipeline failure, ACAD's investment thesis is now anchored by its commercial portfolio; its two approved drugs, Nuplazid and Daybue, demonstrated robust growth in the first half of 2025 with sales up 14% and 13% year-over-year, respectively, and are projected to surpass $1 billion in combined net sales by 2025. The company's future growth prospects hinge on continued commercial execution and its remaining pipeline, including a pending EU approval for Daybue in Q1 2026 and mid-2026 data for its Alzheimer's psychosis candidate, ACP-204.

Key Decisions for Investors

• For ACAD investors, the focus shifts entirely to the commercial performance of Nuplazid and Daybue; monitor their sales growth and patient uptake to validate the projected $1 billion revenue run-rate and weigh it against the now-higher risk profile of its development pipeline.
• Soleno Therapeutics (SLNO) now represents a clearer growth play with its uncontested market position for Vykat XR in PWS hyperphagia; investors should assess the drug's commercial adoption rate, which generated $32.7 million in its first full quarter, as the primary valuation driver.
• The divergent stock movements present a potential pairs trade opportunity, but investors should recognize that while SLNO's upside is now more defined, ACAD's downside is cushioned by its substantial and growing revenue base from its existing approved products.