BOSTON, August 24, 2026
Rhythm Pharmaceuticals, Inc. announced that Japan’s Ministry of Health, Labour and Welfare (MHLW) has granted marketing authorization for IMCIVREE® (setmelanotide) for the treatment of patients with acquired hypothalamic obesity (HO). The approval represents an important regulatory milestone for the company because IMCIVREE is the first therapy approved in Japan for acquired hypothalamic obesity, a rare form of obesity caused by injury to the hypothalamus. Rhythm expects a commercial launch in Japan by the end of 2026, subject to final pricing determination. The company estimates that approximately 5,000 to 8,000 people in Japan are living with acquired HO, creating a defined population with a significant unmet treatment need.
IMCIVREE Targets the MC4R Pathway in Hypothalamic Obesity
IMCIVREE is a melanocortin-4 receptor (MC4R) agonist designed to address impaired signaling within the MC4R pathway, which plays an important role in regulating energy balance and body weight. Acquired hypothalamic obesity can develop after injury to the hypothalamus and is frequently associated with conditions such as craniopharyngioma, astrocytoma and other hypothalamic-pituitary tumors, as well as traumatic brain injury, stroke, infection or inflammation. Damage to the hypothalamus can disrupt production of alpha-melanocyte-stimulating hormone (α-MSH) and impair MC4R signaling, contributing to accelerated and sustained weight gain, hyperphagia and reduced energy expenditure. By targeting the MC4R pathway, IMCIVREE provides a treatment approach specifically directed at an underlying biological mechanism associated with acquired HO rather than treating obesity solely through general weight-management strategies.
Phase 3 TRANSCEND Data Supported Japanese Approval
The Japanese authorization was supported by results from the pivotal Phase 3 TRANSCEND trial, which evaluated setmelanotide in 142 patients with acquired hypothalamic obesity. The global study achieved its primary endpoint, demonstrating a statistically significant 18.8% placebo-adjusted reduction in body mass index (BMI). The data set included 12 patients from a Japanese cohort, together with 10 supplemental patients enrolled in addition to the primary 120-patient pivotal cohort. The TRANSCEND findings provide the clinical foundation for Rhythm’s expansion of IMCIVREE into Japan and support the company’s strategy of addressing rare neuroendocrine diseases through targeted therapies. The study results were also recently published in The New England Journal of Medicine, adding peer-reviewed evidence to the clinical development program. The Japanese approval follows the MHLW’s orphan drug designation for IMCIVREE in March 2025.
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Rhythm Expands Global Access to Rare Obesity Treatment
The Japan approval strengthens Rhythm Pharmaceuticals’ international commercial footprint for IMCIVREE and expands access to an MC4R-targeted treatment for patients with acquired HO. Rhythm already markets or has regulatory authorization for setmelanotide in other major markets for specific rare obesity conditions, while continuing to develop the therapy in additional rare diseases. The company is also advancing bivamelagon, RM-718 and other investigational programs targeting rare neuroendocrine and metabolic disorders. For Japan, the next major milestone will be final pricing determination followed by the planned commercial launch before the end of 2026. The approval therefore moves IMCIVREE from clinical development into the final stages of commercial preparation for Japanese patients with acquired hypothalamic obesity, while reinforcing Rhythm’s focus on rare, genetically or biologically defined forms of obesity.
Source:Rhythm Pharmaceuticals, press relese
