NEW YORK, December 30, 2025, 13:33 ET — Regular session
- Rhythm Pharmaceuticals shares fell 4.2% to $107.85 in early afternoon trade.
- Biotech stocks lagged, with major biotech ETFs down more than 1% while the broader market was little changed.
- Investors remain focused on the next FDA decision date for an Imcivree label expansion.
Rhythm Pharmaceuticals shares were down 4.2% at $107.85 at 1:33 p.m. ET on Tuesday, after trading as low as $106.65.
The move matters because Rhythm is a single-product rare-disease biotech whose stock has tended to swing on regulatory and clinical milestones for Imcivree, its obesity drug. Investors are watching the company’s next U.S. Food and Drug Administration decision closely.
With the next major catalyst still ahead, the stock can move sharply on broader risk sentiment in biotech, even when there is no fresh company news.
The SPDR S&P Biotech ETF was down 1.4% and the iShares Nasdaq Biotechnology ETF fell 1.2%, while the S&P 500 ETF and Nasdaq 100 ETF were nearly flat.
Rhythm sells Imcivree (setmelanotide), an “MC4R agonist” — a drug that activates a brain pathway involved in hunger and weight regulation — for certain rare genetic forms of obesity.
On Dec. 11, the company said preliminary data from an exploratory Phase 2 trial in Prader-Willi syndrome (PWS) showed BMI and hyperphagia (extreme, persistent hunger) reductions in some patients, with 17 of 18 enrolled patients remaining on therapy, and it outlined plans to move setmelanotide into a Phase 3 trial. (Source: https://www.globenewswire.com/news-release…)
The PWS landscape has become more defined since Soleno Therapeutics won FDA approval in 2025 for Vykat XR to treat hyperphagia in PWS, raising the bar for new entrants seeking to carve out a role in the disorder. (Source: https://www.reuters.com/business/healthcare-pharmaceuticals/us-fda-greenlights-first-ever-treatment-rare-metabolic-disorder-2025-03-26/)
Beyond PWS, Rhythm’s nearer-term swing factor is the FDA review of a supplemental application to expand Imcivree into acquired hypothalamic obesity, a rare form of obesity linked to hypothalamus damage. The FDA extended the review deadline to March 20, 2026, and CEO David Meeker said, “We have every confidence that these additional sensitivity analyses confirm the strength of the data.” (A PDUFA goal date is the FDA’s target deadline for a decision.) (Source: https://www.reuters.com/business/healthcare-pharmaceuticals/us-fda-extends-review-rhythm-pharmas-drug-rare-form-obesity-2025-11-07/)
In corporate disclosures, Rhythm said in an 8-K filing that board member Camille L. Bedrosian resigned effective immediately. (Source: https://www.sec.gov/Archives/edgar/data/16…)
What investors are watching next includes additional PWS trial updates the company has pointed to for 2026, progress on its RM-718 study in PWS, and the March FDA decision for hypothalamic obesity. Rhythm is also expected to report results in late February based on past reporting patterns, according to Zacks’ earnings calendar. (Source: https://www.zacks.com/stock/research/RYTM/…)
On Tuesday, the stock opened at $111.97 and has ranged from $106.65 to $113.43, with about 470,000 shares traded by early afternoon.
The shares are also giving back some of the gains from earlier this month, when they hit a record high after the PWS update, according to Investor’s Business Daily. (Source: https://www.investors.com/news/technology/rhythm-pharmaceuticals-stock-prader-willi-syndrome-treatment/)
