Rhythm Pharma To Present Preliminary Phase 2 Data Of Setmelanotide In Prader-Willi Syndrome Today

Rhythm Pharmaceuticals will present preliminary Phase 2 data for Setmelanotide in Prader-Willi syndrome on Dec. 11, 2025 — a key readout for a drug already marketed as IMCIVREE for select genetic obesity disorders and supported by an sNDA for acquired hypothalamic obesity with an FDA decision due March 20, 2025 — that could materially expand its addressable market given PWS’s high unmet need. The company is also advancing a broader MC4R agonist portfolio, with RM-718 in Phase I, Bivamelagon planned for a pivotal Phase III in 2026 pending regulatory alignment, and preclinical programs for congenital hyperinsulinism. Rhythm reported Q3 2025 IMCIVREE net product revenue of $51.3 million (U.S. sales $38.2 million, up 19% sequentially), holds $416.1 million in cash and equivalents to fund development, and has seen recent positive stock moves (closed $104.77, up 4.0%, $108.80 after-hours), underscoring market interest ahead of the PWS data release.

Analysis

Rhythm Pharmaceuticals will release preliminary exploratory Phase 2 data for Setmelanotide in Prader-Willi syndrome (PWS) via a live webcast on December 11, 2025; Setmelanotide (commercialized as IMCIVREE) is already approved in the U.S. and 15+ other countries for select genetic obesity disorders, so positive PWS data could materially expand its labeled indications and addressable market given PWS’s high unmet need.

The company reported Q3 2025 net product revenue of $51.3 million, with U.S. sales of $38.2 million up 19% sequentially, and held $416.1 million in cash, cash equivalents and short-term investments as of September 30, 2025, providing a meaningful runway to fund ongoing development. The stock has traded between $45.90 and $116.00 over the past year and showed a near-term market reaction, closing at $104.77 (+4.03%) with after-hours strength to $108.80 (+3.85%), indicating investor sensitivity to readouts and regulatory catalysts.

Beyond PWS, Rhythm has an sNDA for acquired hypothalamic obesity with an FDA decision due March 20, 2025, RM-718 in Phase I, and a planned pivotal Phase III for Bivamelagon in 2026 pending regulatory alignment. Key risks are the exploratory nature of the PWS data, ex-U.S. ordering variability affecting revenue, and regulatory/timing uncertainty for broader label expansion and pivotal programs.

Key Decisions for Investors

• Consider reducing directional exposure or buying short-term hedges ahead of the Dec. 11 preliminary PWS readout given its exploratory, binary nature
• If the PWS data are clearly positive, consider adding or initiating exposure to capture potential label expansion and IMCIVREE upside, but require confirmatory pivotal data or regulatory guidance before increasing position size materially
• Monitor the FDA sNDA outcome for acquired hypothalamic obesity (Mar. 20, 2025) and milestones around Bivamelagon Phase III alignment as key medium-term catalysts
• Use the $416.1 million cash runway and sequential U.S. sales growth ($38.2 million, +19% sequentially) as a partial risk buffer and size positions conservatively to account for ex-U.S. ordering variability and execution risk