Metreleptin
Metreleptin (Myalept), recombinant human leptin analogue
Written by Aaron CuhaReviewed Sep 2026
Also known as: Myalept, Recombinant methionyl human leptin, r-metHuLeptin
Transformative in people who make almost no leptin, and useless for ordinary obesity. The clearest case on this site of a hormone that only works as replacement.
Overview
When leptin was discovered in 1994, an obesity cure looked imminent: here was the hormone that tells the brain how much fat exists, and obese mice lacking it lost weight dramatically when given it back. Then it was given to people with ordinary obesity and did almost nothing, because their leptin was already high and the brain had stopped responding.
What survived is metreleptin, approved not for obesity but for generalised lipodystrophy, where patients have almost no fat tissue and therefore almost no leptin. In that population the effect is substantial, improving the severe insulin resistance, hypertriglyceridaemia and hepatic steatosis that come with having nowhere to store fat.
The page also carries a finding that complicates the simple version. In partial lipodystrophy, endogenous leptin concentration turned out to predict response poorly, which means even the replacement logic is not as clean as it sounds.
Mechanism of action
A recombinant analogue of human leptin, differing by an added methionine residue. Leptin is secreted by adipocytes in proportion to fat mass and acts at the leptin receptor on hypothalamic arcuate nucleus neurons, suppressing the orexigenic neuropeptide Y and agouti-related peptide neurons and stimulating the anorexigenic pro-opiomelanocortin neurons. It also signals nutritional sufficiency to the reproductive, thyroid and immune axes. In leptin deficiency all those signals read as starvation regardless of actual energy stores, which is why replacement does so much. In ordinary obesity leptin is already elevated and central resistance has developed, so adding more changes little.
Human evidence
An approved drug for a rare disease, with substantial metabolic benefit in true leptin deficiency, no benefit in ordinary obesity, and serious immunological risks.
- Approved for complications of leptin deficiency in generalised lipodystrophy, where it improves insulin resistance, triglycerides and hepatic steatosis.
- In ordinary obesity, leptin administration produced little effect, which is the foundational negative result of the field.
- In partial lipodystrophy, endogenous leptin concentration poorly predicted who responded, so the deficiency-replacement model is incomplete.
- Boxed warning for anti-metreleptin antibodies with neutralising activity, which can cause loss of effect and worsening metabolic control.
- Boxed warning for T-cell lymphoma, reported in patients with acquired generalised lipodystrophy both on and off treatment.
- Distribution is restricted, which is unusual and reflects both risks.
What this does not tell you: The population is very small and the evidence is not from large randomised trials but from open-label studies in a rare disease, which is the norm for conditions this uncommon. Nothing here supports leptin or leptin analogues for ordinary obesity; that question was asked and answered negatively decades ago. The neutralising antibody problem is the reason the newer leptin receptor agonist antibody mibavademab exists.
Reading the research record
Leptin is the most instructive failure in metabolic medicine and this page is where the lesson lives. The hormone was real, the mouse result was real, and the inference that supplying it would treat obesity was wrong because obesity is not a leptin deficiency. It is closer to the opposite.
That pattern recurs constantly on this site. A hormone declines or is low in a disease state, so supplying it looks like an obvious fix, and the fix works only in the people who genuinely lack it. Growth hormone, testosterone and thyroid hormone all have versions of the same story. The question to ask of any hormone therapy is not whether the hormone matters but whether you are short of it, which is the same rule the supplements section applies to nutrients.
The evidence, charted
Fig. 1 · evidence composition
1of 1 citation (100%) is in people
Every citation cited here is Human work; no other study type is cited on this page. This count is of our own citation list and understates any literature larger than the sources we cite.
Fig. 2 · evidence over time
Every citation here was published in 2022.
Too few distinct publication years on this page to plot as a timeline.
Fig. 3 · legal status at a glance
US
Approved
UK
Approved
AU
Approved
CA
Approved
Approved in all four jurisdictions shown. A jurisdiction's classification is a regulatory fact, not a verdict on the science; see Legal status below for the full text and any notes.
Fig. 4 · dose response
No human dose response curve exists
We draw this figure where the data supports it. For this compound in humans it does not, so the panel stays empty rather than borrowing an animal curve and implying it transfers.
Key studies & citations
- Human2022
Endogenous leptin concentrations poorly predict metreleptin response in patients with partial lipodystrophy
The finding that complicates the replacement story. In partial lipodystrophy, a patient's own leptin concentration was a poor predictor of whether they would respond to metreleptin. If replacement were the whole mechanism, baseline deficiency should predict benefit, and it did not.
Journal of Clinical Endocrinology and Metabolism
Frequently asked questions
Does leptin cause weight loss?
Only in people who are genuinely leptin deficient, which is rare and mostly means generalised lipodystrophy or congenital leptin deficiency. In ordinary obesity, leptin is already high, central resistance has developed, and giving more does almost nothing. That result is the foundation of modern obesity pharmacology.
Why is it restricted?
Two boxed warnings. Patients can develop antibodies that neutralise the drug, causing loss of effect and worsening metabolic control, and T-cell lymphoma has been reported in patients with acquired generalised lipodystrophy. Both are serious enough that distribution is controlled.
How does it relate to mibavademab?
Directly. Mibavademab is an antibody that activates the leptin receptor with or without leptin present, which means it can work in patients who have developed neutralising antibodies against metreleptin. This site carries a page for it, including its finding that it reduced weight only in people whose leptin was already low.