Tesamorelin
Also known as: TH9507, Egrifta, Egrifta SV, GRF(1-44) analog
A stabilized analog of the full-length growth hormone-releasing factor, GRF(1-44), studied for its ability to reduce visceral fat by restoring the body's own pulsatile growth hormone release.
Molecular Data
- Class
- GHRH analog / Growth hormone-releasing factor (GRF) analog
- Molecular Weight
- 5,135.9 Da (free base)
- Molecular Formula
- C₂₂₁H₃₆₆N₇₂O₆₇S (free base)
- Half-Life
- ~26–38 minutes (subcutaneous)
- Sequence / Structure
- N-(trans-3-hexenoyl)-[Tyr¹]-hGRF(1–44) amide — a 44-amino-acid GHRH analog with an N-terminal trans-3-hexenoyl modification (CAS 218949-48-5)
Mechanism of Action
Tesamorelin is a synthetic analog of human growth hormone-releasing factor (GRF, also called GHRH). Unlike shorter GHRH analogs that use only the first 29 amino acids, tesamorelin is built on the complete 44-amino-acid sequence, hGRF(1–44), with a trans-3-hexenoyl group attached to the N-terminal tyrosine.
Stabilizing modification: The N-terminal trans-3-hexenoyl group protects the peptide from rapid inactivation by dipeptidyl peptidase-IV (DPP-IV) and other plasma proteases, giving it a usable pharmacological profile where native GHRH is degraded almost immediately.
Pituitary GHRH receptor activation: Tesamorelin binds GHRH receptors on somatotroph cells in the anterior pituitary, stimulating the synthesis and pulsatile secretion of growth hormone. Because it works one step upstream of GH itself, it preserves the natural pulsatile rhythm of GH release and the somatostatin negative-feedback loop — a different profile from administering exogenous growth hormone directly.
Downstream effects studied: - Increased pulsatile GH secretion and a corresponding rise in IGF-1 (insulin-like growth factor 1) - Preferential reduction of visceral (intra-abdominal) adipose tissue — the deep fat around the organs — rather than subcutaneous fat - Reductions in liver fat, studied in the context of non-alcoholic fatty liver disease (NAFLD)
Research History
Tesamorelin was developed by Theratechnologies under the code name TH9507. Its pivotal Phase III program, led by Falutz and colleagues and published in the New England Journal of Medicine in 2007, randomized 412 people with HIV-associated abdominal fat accumulation to 2 mg of tesamorelin or placebo by daily subcutaneous injection for 26 weeks. Tesamorelin produced a significant reduction in visceral adipose tissue and raised IGF-1 relative to placebo.
On the strength of that program, tesamorelin was approved by the FDA in 2010 (marketed as Egrifta, later Egrifta SV) for the reduction of excess abdominal fat in HIV-infected patients with lipodystrophy. It remains the only growth hormone axis agent with a specific regulatory approval for a visceral-fat indication.
Later research extended the picture to the liver. A 2014 randomized trial by Stanley and colleagues in JAMA showed that tesamorelin reduced both visceral fat and liver fat, and a 2019 Lancet HIV trial found it reduced liver fat and slowed the progression of fibrosis in people with HIV and NAFLD.
Tesamorelin's approved use is narrow and specific to HIV-associated lipodystrophy; it is not approved for general weight loss, athletic performance, or anti-aging, and the peptide continues to be studied primarily as a tool for understanding the growth hormone axis and visceral-fat biology.
Notable Studies
Falutz J, Allas S, Blot K, et al. · New England Journal of Medicine
Pivotal Phase III trial (n=412) in which 2 mg of tesamorelin daily for 26 weeks significantly reduced visceral adipose tissue and increased IGF-1 versus placebo, with a favorable effect on lipid markers. This trial supported the FDA approval.
Stanley TL, Feldpausch MN, Oh J, et al. · JAMA
Randomized, double-blind trial (n=50) showing tesamorelin reduced visceral fat (net −42 cm² vs placebo) and liver fat fraction (net −2.9%) over 6 months, linking the compound's GH-axis effect to reductions in ectopic fat.
Stanley TL, Fourman LT, Feldpausch MN, et al. · The Lancet HIV
12-month randomized trial (n=61) in HIV-associated NAFLD in which tesamorelin reduced liver fat content and lowered the rate of fibrosis progression versus placebo — the first agent shown to affect NAFLD in this population.
Research Protocols
The following protocols describe doses used in published research studies. They are not prescriptions or recommendations for human use.
Falutz 2007 NEJM Phase III (HIV lipodystrophy)
- Dose
- 2 mg
- Route
- Subcutaneous injection
- Frequency
- Once daily
- Duration
- 26 weeks
The regimen used in the pivotal visceral-fat trial and reflected in the approved label. Cited as published clinical-trial data, not usage guidance.
Stanley 2014 JAMA / 2019 Lancet HIV (liver fat, NAFLD)
- Dose
- 2 mg
- Route
- Subcutaneous injection
- Frequency
- Once daily
- Duration
- 6–12 months
Same daily dose extended over longer periods to study effects on liver fat and fibrosis.