Is Bivamelagon legal in the United Kingdom?

An oral MC4R agonist being developed as a tablet counterpart to injected setmelanotide. A 28 person phase 2 in hypothalamic obesity completed in February 2026 with no results posted, and there is no peer reviewed publication on the compound at all.

Bivamelagon is an oral agonist of the melanocortin-4 receptor, the same receptor that setmelanotide activates by daily injection. It was discovered by LG Chem under the code LB54640 and licensed to Rhythm Pharmaceuticals, which is developing it for hypothalamic obesity, the weight gain that follows damage to the hypothalamus from tumours or their treatment.

Mechanism: In human pharmacology of the class, MC4R activation in the hypothalamus reduces appetite; this is the pathway that loss of function mutations in POMC, PCSK1 and LEPR disrupt upstream of the receptor, and that setmelanotide restores. Bivamelagon is described by its developer as a selective MC4R agonist that is orally bioavailable.

Regulatory history: Not FDA approved. Investigational; phase 2 complete in hypothalamic obesity with no results posted, open label extension enrolling (September 2026).

Licenses medicines for the UK market. A compound without a marketing authorisation is an unlicensed medicine, which can only lawfully be supplied for human use through a prescriber under the specials scheme, not sold as a research product.

The classification above is the The Longevity Archive reading of Medicines and Healthcare products Regulatory Agency listings for Bivamelagon at the reviewed date, not a legal opinion. Rules change, and importing, prescribing and possessing a compound can each be treated differently. Check the regulator directly before acting on anything here.