Tesamorelin

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Snapshot

Chemistry and make-up

Tesamorelin is a 44-amino-acid peptide, essentially the full native human GHRH(1-44) sequence, made resistant to breakdown by attaching a trans-3-hexenoyl (hexenoic acid) group to the N-terminal tyrosine [A][B]. That single lipid-like modification is the whole design point: native GHRH is destroyed within minutes by dipeptidyl peptidase-4 (DPP-4), which clips the N-terminus, so capping it with the hexenoyl group blunts that cleavage and extends the working half-life while keeping full GHRH-receptor activity [A]. This is a lipidation-style N-terminal modification, not a mid-chain change.

Being 44 residues long, it is a genuinely large peptide (~5.1 kDa) with one methionine (the single sulfur in the formula) and no cysteine, so no disulfide bridges. It is supplied and formulated as the acetate salt; the marketed drug is a lyophilised powder reconstituted before use. For QC the identity challenge is different from a short peptide: at this length, HPLC purity alone can miss deletion or oxidation variants (the Met is an oxidation liability), so identity really needs mass spec plus the N-terminal hexenoyl confirmation, and the CoA should state salt/counterion because trifluoroacetate versus acetate changes the mass and the water content.

What it is studied for (evidence)

• Mechanism [A]: Tesamorelin is a GHRH-receptor (GHRHR) agonist. It acts on the somatotroph cells of the anterior pituitary via the GHRH receptor (a class-B G-protein-coupled receptor, cAMP signalling) to stimulate synthesis and pulsatile release of endogenous growth hormone, which raises IGF-1. This is a different receptor and pathway from ghrelin-receptor GHRPs like ipamorelin, and because it works through the physiological GHRH axis it preserves negative feedback (somatostatin still restrains excess). GHRH-analogue plus GHRP combinations are synergistic for exactly this reason.
• Established (good evidence, and it is an approved medicine) [A][B]: In two large randomised placebo-controlled Phase III trials in HIV-associated lipodystrophy, tesamorelin produced roughly a 15 to 18% reduction in visceral adipose tissue (VAT) versus placebo, with improved lipids, and this is the basis of its FDA approval (Egrifta 2010; Egrifta SV 2019; Egrifta WR 2025) to reduce excess abdominal fat in HIV patients on antiretroviral therapy [A][B].
• Emerging / thin / preclinical only: In HIV-associated NAFLD, a randomised double-blind trial (61 patients, 12 months) reported a ~31% relative reduction in hepatic fat fraction and reduced fibrosis progression (Lancet HIV 201930338-8/abstract)) [A]. Further work covers VAT/liver fat in integrase-inhibitor-treated HIV [A] and an exploratory line on neurocognition in HIV with abdominal obesity, which remains weak and preliminary. Almost all high-quality data are in HIV populations; general-population body-composition, “anti-aging” and athletic uses are not established.
• Marketing claims vs data: Vendors extend the HIV visceral-fat and liver-fat findings into broad fat-loss, metabolic and anti-aging promises for healthy people. The controlled evidence is specific to HIV lipodystrophy/NAFLD; extrapolating it to the general population is unsupported. Any dosing content is outside our scope.
• Human clinical status: FDA-approved medicine for one indication (HIV lipodystrophy). Note the EU/UK contrast in section 5.

Handling, format and stability

Supplied lyophilised and reconstituted before use (research handling only, no dosing guidance here). As a large peptide with a methionine, it is sensitive to oxidation and to hydrolysis in solution, so the lyophilised powder should be kept cold and protected from light and heat, and reconstituted material is cold-chain dependent and short-lived. The approved product is a single-use lyophilised vial, which is a useful benchmark for how fragile the reconstituted form is. Because counterion (acetate vs trifluoroacetate) affects mass and residual solvent, CoAs should state it.

Regulatory and trade status

• Medicine “by function” and the real RUO risk [B]: This is the key flag for AxYn. Tesamorelin is an approved active pharmaceutical ingredient (Egrifta, FDA 2010, still marketed and reformulated as recently as Egrifta WR in 2025). A substance that is a licensed medicine’s active is far more exposed to being treated as a “medicinal product by function” by the MHRA than a never-approved research peptide. Selling it RUO in the UK demands especially disciplined, strictly non-therapeutic copy; any human-benefit language is high-risk.
• UK / EU status: There is no EU marketing authorisation. Ferrer Internacional withdrew its centralised EMA application for Egrifta in 2012 because the CHMP did not consider the benefit-risk positive (EMA withdrawal notice) [B]. So in the UK/EU it is not an authorised medicine, yet it is approved in the US, which is exactly the awkward middle ground: unapproved here, a known drug substance globally.
• US: FDA-approved (Egrifta line). Not a lawful “research chemical” for human use; the approved-drug status also constrains compounding.
• WADA (sport): Prohibited at all times under S2.2 (Growth Hormone, its fragments and releasing factors) as a GHRH analogue, named explicitly in the 2026 List alongside CJC-1293, CJC-1295 and sermorelin [B]. Banned in and out of competition.
• Customs: As a known approved-drug active, misdescribed shipments carry medicines-regulation as well as identity risk.

Sources

• [A] Falutz J. et al., Phase III tesamorelin in HIV lipodystrophy (VAT reduction) — summarised in FDA review, NDA 22-505 — https://www.accessdata.fda.gov/drugsatfda_docs/nda/2010/022505Orig1s000SumR.pdf
• [A] Stanley T.L. et al., “Effects of tesamorelin on non-alcoholic fatty liver disease in HIV”, *Lancet HIV* 2019 — https://www.thelancet.com/journals/lanhiv/article/PIIS2352-3018(19)30338-8/abstract
• [A] Tesamorelin reduces VAT and liver fat in INSTI-treated HIV, *Open Forum Infect Dis* 2023 — https://academic.oup.com/ofid/article/10/Supplement_2/ofad500.1334/7447395
• [B] FDA CDER review, Egrifta (tesamorelin) NDA 22-505 (structure, hexenoyl modification, DPP-4 rationale, approval) — https://www.accessdata.fda.gov/drugsatfda_docs/nda/2010/022505Orig1s000SumR.pdf
• [B] EMA, Ferrer withdrawal of Egrifta marketing authorisation application (2012) — https://www.ema.europa.eu/en/documents/press-release/ferrer-internacional-sa-withdraws-its-marketing-authorisation-application-egrifta-tesamorelin_en.pdf
• [B] WADA Prohibited List, S2.2 (GHRH analogues incl. tesamorelin) — https://www.drugs.com/wada/s2-peptide-hormones-growth-factors-and-related-substances.html
• [B] PubChem CID 16137828 (formula C221H366N72O67S, MW ~5136) — https://pubchem.ncbi.nlm.nih.gov/compound/16137828
• [D] Wikipedia, Tesamorelin (aliases TH-9507, approval timeline) — https://en.wikipedia.org/wiki/Tesamorelin

Plain summary

Tesamorelin is a stabilised, full-length copy of the natural hormone GHRH: it is the same 44 amino acids as human GHRH with a small fatty cap on the front end that stops the enzyme DPP-4 from destroying it, and it works by telling the pituitary through the GHRH receptor to make its own growth hormone (a different route from ghrelin peptides like ipamorelin, which is why the two are combined). It is unusual for a research peptide because it is a real approved medicine (Egrifta, FDA-approved for HIV-related belly fat), which makes it much easier for UK regulators to treat as a “medicine by function”, so it must be sold strictly research-use-only with no health claims; it is also banned in sport (WADA S2). Note the split status: FDA-approved in the US but never authorised in the EU/UK (the application was withdrawn in 2012), and as a large 44-residue peptide with an oxidation-prone methionine its CoA needs mass-spec identity, the N-terminal cap confirmed, and the salt form stated.

For laboratory and research use only (RUO). Not for human or veterinary use, not for consumption, and not a medicine. Information is a research summary, not medical advice, and contains no dosing guidance.

For laboratory research use only. Not for human or veterinary use, not for consumption, and not a medicine. This is a research summary, not medical advice, and contains no dosing guidance.