Metreleptin is a recombinant analogue of human leptin — the adipocyte-derived hormone that signals energy sufficiency to the hypothalamus. It occupies an unusual position on a site otherwise dominated by grey-market research compounds: it is a genuinely licensed peptide medicine, not a research reagent.
Leptin is a protein hormone secreted mainly by white adipose tissue. Circulating leptin concentration broadly tracks fat mass, and the hormone acts on the arcuate nucleus to restrain appetite and permit energy expenditure when stores are adequate. Where adipose tissue is almost absent, leptin is very low, and the downstream consequences are severe: ectopic fat deposition in liver and muscle, marked hypertriglyceridaemia, and pronounced insulin resistance.
The product, and its authorisation
The clinical agent is not leptin itself but metreleptin, an N-methionyl recombinant human leptin analogue. Because the number of patients with the generalised forms of lipodystrophy is small, the condition is classified as rare: metreleptin received an EU orphan designation on 17 July 2012. A marketing authorisation valid throughout the EU was granted on 30 July 2018 under exceptional circumstances — a route reserved for medicines whose complete data set cannot be assembled because the patient population is too small, and which carries an obligation to gather further data after authorisation.
In the UK, Myalepta appears in the electronic medicines compendium (emc) as a prescription-only medicine (POM), supplied by Chiesi Limited in three strengths — 3 mg, 5.8 mg and 11.3 mg powder for solution for injection. The licensed indication is narrow and specific: as an adjunct to diet, as replacement therapy for the complications of leptin deficiency, in confirmed congenital generalised lipodystrophy (Berardinelli–Seip syndrome) or acquired generalised lipodystrophy (Lawrence syndrome) from age two; and in confirmed familial or acquired partial lipodystrophy (Barraquer–Simons syndrome) from age twelve where standard treatments have failed to achieve adequate metabolic control.
What the pivotal studies reported
The EU authorisation rests on two main studies in 107 adults and children with generalised or partial lipodystrophy. There was no active comparator. After twelve months, mean triglyceride concentrations fell from roughly 15 mmol/l to roughly 5 mmol/l in generalised disease, and from roughly 16 mmol/l to roughly 6 mmol/l in partial disease. Glycated haemoglobin, a marker of longer-term glycaemic control, fell from 8.6% to 6.4% in generalised lipodystrophy, and from 8.8% to 8.0% in partial lipodystrophy. These are studied outcomes reported in the assessment; they are not a claim that the medicine reverses lipodystrophy, and it does not restore subcutaneous fat.
Where the evidence is thinner
Response is not universal. In partial lipodystrophy — where leptin deficiency is relative rather than absolute — endogenous leptin concentrations poorly predict who will respond, and the variable response may be partly attributable to the development of anti-leptin antibodies (Meral et al., 2022). Because metreleptin was authorised under exceptional circumstances, the marketing authorisation holder is required to maintain a patient registry and to conduct further studies, including on the potential to trigger antibody production. The most common adverse reactions, affecting more than one in ten patients, are hypoglycaemia and weight loss.
Beyond the licensed indication
Metreleptin has been studied in settings outside its licence. An open-label series examined its use in non-alcoholic steatohepatitis in two clinical settings (Akinci et al., 2021), and short-term treatment has been explored in anorexia nervosa, where a small study reported rapid cognitive, emotional and behavioural changes (Milos et al., 2020). Both remain research questions, not licensed indications, and neither supports use outside a supervised clinical setting.
The UK regulatory line
Metreleptin sits on the licensed side of the medicines boundary. As a prescription-only medicine it may be supplied only against a prescription, and the Medicines Act 1968 and the Human Medicines Regulations 2012 govern its authorisation, supply and promotion; advertising a POM to the public is prohibited. That is the opposite of the 'research use only' grey-market framing: a compound that is independently regulated, prescribed and monitored — and which cannot lawfully be sold as a general research reagent where it is plainly intended for human use.
The bottom line
Metreleptin is the exception that tests the rule that peptides in wide online circulation are unlicensed. It is a ligand-replacement therapy with a marketing authorisation, a narrow rare-disease indication, and a pivotal evidence base that is open-label. The evidence in generalised lipodystrophy is the stronger; the partial-lipodystrophy evidence is less uniform, and the long-term antibody question is unresolved. Everything here describes licensed regulatory status and published research. This site does not provide consumption or dosing guidance, and no peptide is described as treating, curing or preventing any condition.
This article is AI-researched and editorially reviewed. It is provided for research and educational purposes only and is not medical advice. Research peptides are not licensed for human consumption in the UK.