Metreleptin

Metreleptin is a lab-made copy of leptin, the hormone that fat tissue normally releases to tell the brain how much energy is stored in the body. It is a prescription medicine for a rare condition called generalized lipodystrophy, in which a person is missing most or all of their body fat. Without fat tissue there is almost no leptin, the brain reads that as starvation, and hunger and metabolic problems follow. Metreleptin replaces the missing hormone.

In people with generalized lipodystrophy, replacing the missing hormone improved blood sugar control and brought down very high blood fat levels, and those improvements held up over years of treatment. The main study behind its approval gave the drug to everyone taking part, with no comparison group, and people were allowed to change their other medicines during it, so the results show what happened rather than proving how much of it the drug caused on its own. Research has also looked at people with partial lipodystrophy, where only some fat tissue is missing, and the medicine is not approved for that group.

FDA-approved prescription drug (Myalept, Chiesi). Approved as an adjunct to diet as replacement therapy to treat the complications of leptin deficiency in patients with congenital or acquired generalized lipodystrophy — a rare disease in which the body lacks fat tissue. It is not a weight-loss drug, and general obesity is a formal CONTRAINDICATION on its label, not merely an unapproved use. The label carries a boxed warning covering anti-metreleptin antibodies with neutralizing activity and the risk of lymphoma, and the product is available only through a restricted program under a Risk Evaluation and Mitigation Strategy (REMS). WADA status: metreleptin and leptin are not named anywhere on the 2026 WADA Prohibited List (checked directly against the list text, 2026-09-10); because metreleptin holds regulatory approval for human therapeutic use, S0 does not capture it. Not DEA-scheduled (prescription, non-controlled).

This is a prescription medicine for a rare disease, and it is not a weight-loss treatment. It carries the most serious warning label US regulators issue, covering two problems: the body can make antibodies against the medicine that block both it and the person's own leptin, and a type of blood cancer called T-cell lymphoma has been reported in people with one form of this condition, both those who took the medicine and those who did not. Because of these risks it can only be supplied through a restricted program with extra safety requirements. It is not on the banned list for drug-tested sport. VialWise is a research and educational reference, not medical advice — consult a licensed professional.

⚠️ Boxed warning, and a restricted distribution program. The label carries a boxed warning — the most serious warning the FDA issues — headed "WARNING: RISK OF ANTI-METRELEPTIN ANTIBODIES WITH NEUTRALIZING ACTIVITY AND RISK OF LYMPHOMA."[¹] Anti-metreleptin antibodies with neutralizing activity have been identified in treated patients; the consequences are not well characterized but could include inhibition of endogenous leptin action and/or loss of efficacy, and severe infection and/or worsening metabolic control have been reported.[¹] T-cell lymphoma has been reported in patients with acquired generalized lipodystrophy, both treated and not treated with MYALEPT.[¹] Because of these risks, the product is available only through a restricted program under a Risk Evaluation and Mitigation Strategy (REMS) called the myalept rems program.[¹]

⚠️ Metreleptin is an approved prescription medicine. Information in this entry is informational, not medical advice.

⚠️ This is not a weight-loss drug, and that is not a technicality. Metreleptin is approved to treat the complications of leptin deficiency in people with congenital or acquired generalized lipodystrophy — a rare disease in which the body lacks adipose tissue. Its label states plainly that MYALEPT is contraindicated in patients with general obesity not associated with congenital leptin deficiency, and that it has not been shown to be effective in treating general obesity.[¹] A contraindication is stronger than an absence of approval: it is the label instructing that the drug not be used in that group at all. If you arrived at this entry because "leptin" sounds like an appetite or weight-management tool, this is the finding that matters and the rest of the entry does not soften it.

⚠️ Note on evidence quality. The pivotal clinical experience behind the approval is an open-label, single-arm study in 48 patients — no control group, no blinding — and concomitant antihyperglycemic and lipid-altering medication regimens were not held constant during the study.[¹] Some patients had insulin increased, others had large reductions or discontinuation.[¹] This is normal and largely unavoidable in a disease this rare, but it means the reported changes describe what happened to a treated cohort rather than isolating the drug's independent effect.

⚠️ Approved for generalized, not partial, lipodystrophy. The label's Limitations of Use state that safety and effectiveness have not been established for the complications of partial lipodystrophy, or for liver disease including nonalcoholic steatohepatitis (NASH), and that the drug is not indicated in HIV-related lipodystrophy or in patients with metabolic disease — including diabetes mellitus and hypertriglyceridemia — without concurrent evidence of generalized lipodystrophy.[¹]

Metreleptin is a recombinant analog of human leptin that binds to and activates the human leptin receptor (ObR), a Class I cytokine-family receptor that signals through the JAK/STAT pathway.[¹] It is marketed in the US as Myalept under BLA 125390, originally approved 24 February 2014, currently sponsored by Chiesi Farmaceutici S.p.A. and listed as a prescription product in the FDA's application record (checked 2026-09-10).

Why leptin replacement makes sense in this disease, and only in this disease. Adipocytes store lipids to meet the fuel requirements of non-adipose tissues during fasting.[¹] In generalized lipodystrophy, the deficiency of adipose tissue leads to hypertriglyceridemia and ectopic deposition of fat in non-adipose tissues such as liver and muscle, contributing to insulin resistance.[¹] Leptin is secreted predominantly by adipose tissue and informs the central nervous system about the status of the body's energy stores; when there is no adipose tissue, there is almost no leptin, and that deficiency contributes to excess caloric intake, which worsens the metabolic abnormalities.[¹] Metreleptin replaces the missing hormone.

This is the mechanistic reason it does not transfer to common obesity. In generalized lipodystrophy the problem is an absence of leptin. In common obesity, leptin levels are typically high rather than low, and the limiting factor is resistance to leptin's action — the contrast the PYY literature drew on explicitly when it argued that obesity does not blunt the response to PYY, "in common with the adipocyte hormone leptin… in obesity there is a marked resistance to the action of leptin, which greatly limits its therapeutic effectiveness."[³] Replacing a hormone that is already abundant does not address resistance to it. See [pyy.md](./pyy.md) for that comparison in its original context, and [setmelanotide.md](./setmelanotide.md) for the downstream leptin–melanocortin pathway, where a different rare, genetically defined defect is treated by acting below the leptin step.

What the pivotal study reported. An open-label, single-arm study evaluated metreleptin in patients with congenital or acquired generalized lipodystrophy who had diabetes mellitus, hypertriglyceridemia, and/or increased fasting insulin.[¹] Of the 48 patients enrolled, 32 (67%) had congenital and 16 (33%) had acquired generalized lipodystrophy; 36 (75%) were female; median age at baseline was 15 years (range 1–68), with 35 (73%) under 18.[¹] Median duration of treatment was 2.7 years (range 3.6 months – 10.9 years).[¹] At 12 months, mean HbA1c fell by 2.0 percentage points (SD 1.5) from a baseline of 8.5% (n=35); mean fasting glucose fell by 49 mg/dL (SD 75) from 174 (n=37); and median fasting triglycerides fell by 184 mg/dL from a median baseline of 348, a median −55% change (n=36).[¹] Among the 28 patients with baseline HbA1c ≥7% and month-12 data, mean baseline HbA1c was 9.3% and the mean reduction was 2.4%.[¹] Among the 12 patients with baseline triglycerides ≥500 mg/dL and month-12 data, median baseline was 1527 mg/dL and the median reduction was 1117 mg/dL.[¹] These are single-arm, open-label results with background medications changing during the study, and the label reports them as such.[¹]

Longer-term and comparative reports. A prospective, single-arm, open-label study conducted at the National Institutes of Health compared response in generalized versus partial lipodystrophy in patients treated for six months or longer.[²] At 12 months, HbA1c fell in both groups — to 6.4% ± 1.5% in 55 patients with generalized lipodystrophy (P<.001) and 7.3% ± 1.6% in 31 with partial lipodystrophy (P=.004) — and triglycerides fell in both.[²] The paper's own framing is that metreleptin was approved in the United States for generalized but not partial lipodystrophy, and its object was to test efficacy in partial versus generalized disease.[²] A separate report of long-term treatment in 55 patients (36 generalized, 19 partial) at the same centre described sustained reductions in HbA1c and triglycerides across a 3-year treatment period, alongside reductions in elevated ALT and AST.[³] Both are uncontrolled: one is explicitly a prospective single-arm open-label study,[²] the other describes an observed patient population within an ongoing trial.[³]

Regulatory status (US). FDA-approved as Myalept under BLA 125390 (original approval 24 February 2014), sponsor Chiesi Farmaceutici S.p.A., current label effective 25 March 2024, marketing status Prescription.[¹] Because this is a biologic licensed under a BLA, the Orange Book is the wrong database for it — approval and marketing status here are taken from the FDA labeling and application records. Distribution is restricted through the myalept rems program.[¹] not DEA-scheduled.

Regulatory status (sport — WADA). Metreleptin and leptin are not named anywhere on the 2026 WADA Prohibited List (checked directly against the list text, 2026-09-10). S0 (Non-Approved Substances) does not capture metreleptin, because S0 reaches only substances "with no current approval by any governmental regulatory health authority for human therapeutic use" and metreleptin holds such approval. This is the same reasoning applied in [setmelanotide.md](./setmelanotide.md). Athletes should verify current status with their National Anti-Doping Organization.

Serious

• Anti-metreleptin antibodies with neutralizing activity. Identified in treated patients. Consequences are not well characterized but could include inhibition of endogenous leptin action and/or loss of efficacy. Severe infection and/or worsening metabolic control have been reported. The label directs testing for neutralizing antibodies in patients who develop severe infections or show signs suspicious for loss of efficacy during treatment.
• T-cell lymphoma, reported in patients with acquired generalized lipodystrophy — both treated and not treated with metreleptin. The label directs careful consideration of benefits and risks in patients with significant hematologic abnormalities and/or acquired generalized lipodystrophy.

Contraindications, verbatim in substance from the label:[¹]

General obesity not associated with congenital leptin deficiency. Metreleptin has not been shown to be effective in treating general obesity, and the development of anti-metreleptin antibodies with neutralizing activity has been reported in obese patients treated with it.

Hypersensitivity to metreleptin — prior severe hypersensitivity reactions to metreleptin or any product component.

Limitations of use, from the label:[¹]

Safety and effectiveness not established for complications of partial lipodystrophy.

Safety and effectiveness not established for liver disease, including NASH.

Not indicated in HIV-related lipodystrophy.

Not indicated in patients with metabolic disease, including diabetes mellitus and hypertriglyceridemia, without concurrent evidence of congenital or acquired generalized lipodystrophy.

Access: available only through the myalept rems program.[¹] There is no legitimate supply route outside it.

Leptin

A hormone released by fat tissue that tells the brain how much energy the body has stored. Low levels read to the brain as not enough food.

Generalized lipodystrophy

A rare condition in which the body is missing most or all of its fat tissue, either from birth or acquired later.

Leptin deficiency

Having too little leptin. In this condition it happens because the fat tissue that would make it is not there.

Replacement therapy

Giving back a substance the body cannot make enough of, rather than adding a drug that does something new.

Neutralizing antibodies

Proteins the immune system can make against a medicine, which can stop it working and, here, can also block the body's own version of the hormone.

1. US Food and Drug Administration. MYALEPT (metreleptin) for injection, for subcutaneous use — Prescribing Information. BLA 125390; label version effective 2024-03-25; sponsor Chiesi Farmaceutici S.p.A. (US labeler Chiesi USA, Inc.); NDC 10122-210; unii tl60c27rlh; SPL set id d3b50bbd-140b-425c-b5ec-d4682aad62bc. Retrieved 2026-09-10 from the openFDA drug label API (api.fda.gov/drug/label.json, raw JSON saved); approval history and marketing status cross-checked the same day against the openFDA
2. Diker-Cohen T, Cochran E, Gorden P, Brown RJ. (2015). Partial and generalized lipodystrophy: comparison of baseline characteristics and response to metreleptin. The Journal of Clinical Endocrinology and Metabolism, 100(5):1802–1810.(PMID 25734254)
3. Chan JL, Lutz K, Cochran E, Huang W, Peters Y, Weyer C, Gorden P. (2011). Clinical effects of long-term metreleptin treatment in patients with lipodystrophy. Endocrine Practice, 17(6):922–932.(PMID 22068254)
4. World Anti-Doping Agency. The 2026 Prohibited List, International Standard (effective 1 January 2026). Canonical PDF: wada-ama.org; local archival copy at docs/legal/wada-2026-prohibited-list.pdf.

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