Rhythm Pharmaceuticals announced on Mar. 20 that the United States Food and Drug Administration has approved its injectable weight-loss drug Imcivree for use in patients with acquired hypothalamic obesity, expanding the drug's indications despite a recent late-stage clinical trial failure.
The approval allows Imcivree to be used in patients aged four years and older who have this rare form of uncontrolled weight gain, which is linked to injury or dysfunction of the hypothalamus. Analysts estimate that this new indication could represent a market opportunity exceeding $2 billion.
Imcivree was first approved in late 2020 for managing body weight in patients with obesity due to POMC, PCSK1, or LEPR deficiency, and again in 2022 for Bardet-Biedl syndrome. The latest approval is based on data from the Phase 3 TRANSCEND study, which enrolled about 120 patients. According to Rhythm Pharmaceuticals, the study showed an 18.4% reduction in body mass index at 52 weeks compared to placebo. Adults experienced a 19.2% reduction while pediatric patients under age 18 saw a 20.2% decrease.
The company said Imcivree was generally well-tolerated among participants with hypothalamic obesity, with common side effects including nausea, vomiting, headache, and skin hyperpigmentation. The drug works as a melanocortin 4 receptor agonist by lowering food intake and increasing energy expenditure.
The FDA accepted Rhythm’s application for this expanded use in August 2025 and initially set a target action date of Dec. 20, later extending its review period to examine additional sensitivity analyses. Stifel analysts said Thursday that “while approval was expected given the strength of the data, a less predictable FDA combined with their additional data requests . . . may have contributed to recent stock volatility ahead of the FDA’s decision.”
Earlier this week, Imcivree failed to outperform placebo in four key subpopulations during the EMANATE basket trial targeting genetic forms of obesity—a result Stifel called “disappointing.” However, analysts described this as only a minor setback since those indications represented about $300 million in risk-adjusted sales by 2034 compared to the larger potential for hypothalamic obesity.
