Tesamorelin: the GHRH analogue aimed at deep belly fat

A drug for one particular kind of fat

Not all fat is equal. The fat under the skin is mostly a storage depot. Visceral fat, packed around the organs inside the abdomen, behaves differently and is linked with higher cardiovascular risk. Many people treated for HIV with antiretroviral therapy accumulate it, and researchers noticed that people with excess visceral fat also secrete less growth hormone ^[1,5].

Tesamorelin was built to address that gap. Rather than giving growth hormone (GH) directly, it nudges the pituitary to make more of its own. The result can look like a paradox: a drug that shrinks visceral fat while its label describes it as "weight neutral" and explicitly not for weight loss ^[8].

From Montreal: a cap against molecular scissors

Tesamorelin began life at Theratechnologies in Montreal under the code name TH9507 ^[7]. Its starting point was the releasing hormone that two laboratories isolated from pancreatic tumours in 1982, a story we tell in our sermorelin article, along with how the whole GH axis works.

Natural GHRH has a fatal flaw as a medicine. An enzyme in blood, dipeptidyl peptidase-4 (DPP-4), clips off its first two amino acids and leaves an almost inactive fragment; intact GHRH injected into a vein has a half-life of under 7 minutes ^[12]. Theratechnologies' chemists made one small change. They attached a trans-3-hexenoyl group, a six-carbon chain with one double bond, to the tyrosine at the front of the molecule ^[7,8].

In preclinical work the modified peptide resisted DPP-4, broke down more slowly in rat, dog and human plasma, and raised GH and IGF-1 in pigs, rats and dogs ^[7]. Those studies also gave an early warning: dogs given prolonged high exposure showed reversible liver and kidney findings and anaemia, which the authors attributed to sustained supraphysiological GH and IGF-1 ^[7].

How it works

DPP-4 acts like a pair of scissors that can only cut at the very front of a peptide. The hexenoyl group works like the plastic tip on a shoelace: a small cap that stops the front end being snipped, while the rest of the molecule is unchanged. In laboratory tests, tesamorelin binds and activates human GHRH receptors with a potency similar to the natural hormone ^[8].

The cap does not make the drug long-lived. After a single dose of the current formulation in healthy volunteers, the mean elimination half-life was 11 minutes ^[8]. What lasts is the downstream signal. In 13 healthy men treated daily for two weeks, tesamorelin raised mean overnight GH, the size of GH pulses and basal secretion, and lifted IGF-1 by 181 µg/L, while insulin-stimulated glucose uptake did not change ^[5].

GH breaks down stored fat, and IGF-1 carries many of its other effects ^[8]. A striking feature of the trials is selectivity: visceral fat fell while fat under the skin of the abdomen did not change significantly ^[2].

What the research shows

Visceral fat in HIV-associated lipodystrophy

The first phase 3 trial, published in 2007, randomised 412 people with HIV and abdominal fat accumulation (86% men) to daily tesamorelin or placebo for 26 weeks ^[1]. Visceral fat measured by CT fell by 15.2% with tesamorelin and rose by 5.0% with placebo. Triglycerides fell by 50 mg/dl against a 9 mg/dl rise, and IGF-1 rose by 81% ^[1]. Overall adverse events did not differ, but more people on tesamorelin withdrew because of one, and glucose measures did not differ significantly ^[1].

A pooled analysis of both phase 3 trials covered 806 patients randomised 2:1 ^[2]. At 26 weeks the treatment effect on visceral fat was −15.4%, triglycerides and the cholesterol-to-HDL ratio improved, and patients rated their belly appearance as less distressing. In those who stayed on tesamorelin to 52 weeks, visceral fat remained 17.5% below baseline ^[2].

Fat in the liver

Because visceral fat and liver fat travel together, researchers at Massachusetts General Hospital tested whether tesamorelin also reaches the liver. In a 6-month trial of 50 patients, it reduced visceral fat by 34 cm² against an 8 cm² rise on placebo, and modestly reduced liver fat ^[3]. Fasting glucose rose at 2 weeks but the difference had disappeared by 6 months ^[3].

The follow-up trial, funded by the US National Institutes of Health, enrolled 61 people with HIV and non-alcoholic fatty liver disease for 12 months ^[4]. Liver fat fell by 4.1 percentage points more than with placebo, a 37% relative reduction. In a secondary biopsy analysis, fibrosis progressed in 2 tesamorelin patients (10.5%) against 9 placebo patients (37.5%), P=0.04 ^[4].

In a year-long trial in people with HIV and fatty liver, 35% of the tesamorelin group ended below the 5% liver-fat threshold that defines fatty liver, against 4% of the placebo group ^[4].

Beyond HIV: thinking and memory

One trial looked at the brain. In 152 adults aged 55 to 87, including 66 with mild cognitive impairment, 20 weeks of tesamorelin had a favourable effect on a combined cognitive score (P=0.03), with the clearest effect on executive function ^[6]. IGF-1 rose by 117% and body fat fell by 7.4%. Adverse events, mostly mild, were reported by 68% of the tesamorelin group and 36% of the placebo group ^[6]. It remains a single trial.

What we don't know yet

• Heart outcomes. Visceral fat and triglycerides fall, but the label states that long-term cardiovascular safety has not been established ^[8]. No trial has shown fewer heart attacks or strokes.
• Long-term IGF-1. The label warns that the effects of prolonged IGF-1 elevation are unknown and requires IGF-1 monitoring ^[8]. European assessors listed possible cancer risk and worsening of diabetic eye disease among their concerns ^[10]. Our IGF-1 LR3 article reviews the epidemiology.
• Glucose. The label warns that glucose intolerance or diabetes may develop ^[8], even though the large trials found no significant glycaemic differences ^[1,2].
• Other side effects. Fluid retention, joint pain and carpal tunnel syndrome are listed warnings, and active malignancy is a contraindication ^[8].
• Who benefits. Assessors questioned how to separate lipodystrophy fat from ordinary obesity, and whether trial patients matched European patients, who tend to have less abdominal fat ^[10].
• Liver and brain results. Both rest on small trials that have not yet been confirmed at scale ^[4,6].

Regulatory status

• United States. Approved on 10 November 2010 for the reduction of excess abdominal fat in HIV-infected adults with lipodystrophy ^[8,9]. Its original new drug application was deemed a biologics licence application on 23 March 2020 ^[9]. After a complete response letter in January 2024 focused on manufacturing questions ^[13], the FDA approved a new formulation, Egrifta WR, on 25 March 2025; it coexists with Egrifta SV and the two are not interchangeable ^[8,9].
• European Union. The applicant, Ferrer Internacional, withdrew its marketing application on 21 June 2012. At that point the CHMP's provisional view was that the drug could not be approved, because the benefits did not outweigh the risks ^[10].
• Sport. GHRH analogues, tesamorelin named among them, are prohibited at all times under S2.2.4 of the WADA Prohibited List ^[11].

In the lab: handling and storage

Research-grade tesamorelin comes as a lyophilised powder. Common practice is long-term storage at −20 °C, with 2–8 °C acceptable for short periods, protected from light and moisture. The approved medicine gives a useful stability benchmark: its lyophilised vials are stored at room temperature, and once reconstituted the solution is labelled for use within 7 days ^[8]. Research material is formulated differently, so standard cold storage and single-use aliquots remain the safer default; our storage guide covers the details. The expected molecular weight of the free peptide is 5,135.9 Da ^[8].

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