FDA approves Imcivree for acquired hypothalamic obesity
A once-daily injection becomes the first FDA-approved treatment for a rare form of obesity caused by injury to the hypothalamus, which Rhythm estimates affects roughly 10,000 people in the US.
Rhythm Pharmaceuticals said the FDA widened the label for IMCIVREE (setmelanotide) on March 19, 2026, allowing it to be prescribed for acquired hypothalamic obesity in adults and children aged 4 and older [1][2]. No other medicine had been cleared for the condition.
This form of obesity is not the common kind. It follows physical damage to the hypothalamus, the brain region that helps govern hunger, energy use and body weight [1]. The most frequent trigger is a craniopharyngioma, astrocytoma or another tumor near the hypothalamus and pituitary, or the surgery and radiation used to treat it; traumatic brain injury, stroke and inflammation are other listed causes [1]. Such damage can reduce production of alpha-melanocyte-stimulating hormone, which weakens signaling along the MC4R pathway and drives weight upward [1]. Gain is rapid and lasting, and can begin as soon as six months after the injury [1]. Drawing on the medical literature, tumor registries and insurance claims, Rhythm puts the number of Americans with the disorder at about 10,000 [1].
The decision rests on TRANSCEND, a global phase 3 study that enrolled 142 people with acquired hypothalamic obesity [1]. Of those, 94 received setmelanotide and 48 received a placebo. At 52 weeks, BMI had dropped an average of 15.8 percent in the treatment group and risen an average of 2.6 percent in the placebo group, a placebo-adjusted difference of 18.4 percentage points (p<0.0001) [1]. The company said the drug was generally well tolerated, with the most common side effects, seen in more than one in five participants, being skin hyperpigmentation, nausea, vomiting and headache [1].
"Patients treated with setmelanotide experienced meaningful reductions in BMI and hunger, demonstrating the therapy's ability to deliver clinically significant outcomes in both children and adult patients," said Ashley Shoemaker, M.D., MSCI, associate professor of pediatrics at Vanderbilt Health [1].
Some risks stand out in this patient group. Among participants who also had secondary adrenal insufficiency, serious reactions related to acute adrenal insufficiency occurred in 5 percent of those taking setmelanotide and none of those taking placebo [1][2]. In patients with central diabetes insipidus, low sodium was reported in 6 percent of the treatment group versus 2 percent of the placebo group, and high sodium in 5 percent versus 4 percent; the label calls for monitoring sodium [1][2].
The prescribing information also warns about depression and suicidal thoughts, serious allergic reactions including anaphylaxis, and changes to the skin: generalized darkening, darkening of existing moles and new moles, which require a full-body skin exam before treatment starts and periodically afterward [1][2]. Disturbances in sexual arousal can occur, and the label tells patients to seek emergency care for an erection lasting more than four hours [1][2]. Across all approved uses, the most common adverse reactions listed are skin hyperpigmentation, injection site reactions, nausea, headache, diarrhea, abdominal pain, vomiting, depression and spontaneous penile erection [2].
Setmelanotide is an MC4 receptor agonist given as a shot under the skin. It is not a GLP-1 medicine such as semaglutide or tirzepatide [1][2]. The FDA first approved it in 2020 for Bardet-Biedl syndrome and for certain POMC, PCSK1 or LEPR deficiencies in patients aged 2 and older [2]. The label states it is not indicated for other types of obesity, including general polygenic obesity [2].
Why it matters for patients
People with acquired hypothalamic obesity previously had no approved drug, even as the condition pushed weight up through a specific injury to the body's weight-regulating circuitry [1]. "IMCIVREE is now the first and only FDA-approved therapy for acquired HO, offering a targeted approach that addresses the underlying biology of this disease," Rhythm chief executive David Meeker said [1]. Amy Wood, executive director of the Raymond A. Wood Foundation, described relentless hunger and accelerating weight gain and called a therapy for these families potentially transformational [1].
The new use is narrower than a general weight-loss approval. It applies only to patients a clinician has diagnosed with acquired hypothalamic obesity, and the label's limitations section rules out ordinary obesity [2]. The drug is available in the US now, and Rhythm's InTune program offers insurance navigation, injection support and education [1]. Dosing steps up over several weeks and differs for adults and children, with the youngest patients dosed partly by body weight [2]. What the medicine will cost for this use, and what insurers will cover, has not been disclosed [1].
What happens next
Rhythm held a conference call at 7 p.m. ET on March 19, 2026 to discuss the approval, with an archived webcast posted about two hours later and available for 30 days [1]. Whether regulators outside the US will add acquired hypothalamic obesity to setmelanotide's approved uses has not been reported [1].
Sources
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