At its peak, Imcivree’s sales in hypothalamic obesity could reach over $2 billion worldwide, according to analysts at Stifel.
Just days after a disappointing late-stage showing, Rhythm Pharmaceuticals’ injectable weight-loss drug Imcivree has secured a key approval from the FDA, allowing its use in hypothalamic obesity, an indication that analysts estimate could unlock a market opportunity of over $2 billion.
Imcivree can now be used to treat patients aged four years and older with acquired hypothalamic obesity, a rare form of uncontrolled weight gain linked to an injury to or dysfunction of the hypothalamus, according to a Thursday press release. The drug was first approved in late 2020 to help manage body weight in patients with obesity due to POMC, PCSK1 or LEPR deficiency, and then again in 2022 for Bardet-Biedl syndrome, a rare genetic disease that includes obesity as a key symptom.
This most recent approval was supported by data from the Phase 3 TRANSCEND study, a double-blinded and randomized trial that enrolled some 120 patients. Here, Imcivree showed an 18.4% reduction in body mass index (BMI) at 52 weeks on a placebo-adjusted basis, according to Rhythm’s release. A readout last year provided a breakdown of Imcivree’s efficacy according to age subgroups: Adults saw a 19.2% placebo-adjusted drop in BMI, while pediatric patients younger than 18 years experienced a 20.2% reduction.
As for safety, Imcivree was generally well-tolerated for hypothalamic obesity, Rhythm said. The most common side effects included nausea, vomiting, headache and skin hyperpigmentation.
Imcivree is a melanocortin 4 receptor agonist that works by lowering food intake and increasing energy expenditure.
The FDA accepted Rhythm’s data package for Imcivree’s expansion in August 2025, setting an initial target action date of Dec. 20, 2025. In November, however, the agency extended its review period to better review additional sensitivity analyses.
Stifel analysts pointed to this extension in a note on Thursday, saying 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.”
The approval represents something of a comeback for Imcivree. On Monday, the drug failed the late-stage EMANATE basket trial, unable to significantly outperform placebo in four key subpopulations of patients with obesity linked to specific genetic mutations.
“Candidly we had thought that at least one sub-population in the EMANATE basket study could’ve resulted in a fileable dataset,” Stifel wrote in a Monday note, calling the outcome “disappointing.”
Nevertheless, the firm considered EMANATE’s failure to be a relatively minor setback for Rhythm, with all four indications tested accounting for around $300 million in risk-adjusted sales by 2034. Hypothalamic obesity, Stifel continued, is larger opportunity, with potential peak global sales exceeding $2 billion.
