Tesamorelin: what it is, how it works and what studies have found

Tesamorelin is a stabilised analogue of human growth hormone-releasing hormone (GHRH). It keeps the hormone’s full 44-amino-acid sequence and adds a trans-3-hexenoyl group to the N-terminal tyrosine, which protects it from the enzyme that inactivates native GHRH [1] [2]. The US FDA approved it on 10 November 2010 for reducing excess abdominal fat in HIV-infected adults with lipodystrophy [3] [1].

This overview covers tesamorelin’s structure, mechanism and pharmacokinetics, the phase 3 programme behind the approval, the later liver-fat (NAFLD) and cognition studies, and how it compares with sermorelin and CJC-1295. It is written for researchers and is not medical guidance.

What is tesamorelin?

Endogenous GHRH is a 44-residue amidated hypothalamic peptide, first sequenced in 1982 from a pancreatic tumour that had caused acromegaly [4]. Native GHRH is cleared within minutes: in human plasma, a dipeptidyl aminopeptidase removes Tyr1-Ala2 to give GHRH(3-44), which has less than one-thousandth of the parent’s activity [5].

Tesamorelin (development code TH9507) was designed around that weakness. Adding a trans-3-hexenoyl moiety to Tyr1 made the peptide resistant to dipeptidyl aminopeptidase-IV, slowed its degradation in rat, dog and human plasma in vitro, and prolonged its plasma elimination in animals [2]. The rest of the molecule is the unmodified human sequence.

Tesamorelin structure, sequence and molecular weight

Property	Tesamorelin
INN	Tesamorelin (tesamorelin acetate in the approved product)
Development code	TH9507 [2]
CAS number	218949-48-5 [6]
Molecular formula	C221H366N72O67S (free base) [1]
Molecular weight	5135.9 Da as free base equivalent [1]
Salt form	Acetate, approximately 7 acetate per molecule [1]
Sequence	(trans-3-hexenoyl)-YADAIFTNSYRKVLGQLSARKLLQDIMSRQQGESNQERGARARL-NH2 [6] [4]
Length	44 residues
Modification	Hexenoyl group (C6 chain, double bond at position 3) on the N-terminal Tyr [1]
PubChem CID	16137828 [6]

The backbone is identical to human GHRH(1-44)-NH2 [4], so the first 29 residues are the same as sermorelin’s. The only chemical difference from the natural hormone is the N-terminal acyl group. Like sermorelin, the sequence contains a single methionine (Met27), a potential oxidation site.

Tesamorelin mechanism of action

According to the US label, tesamorelin binds and stimulates human GRF receptors in vitro with potency similar to endogenous GRF. GHRH acts on pituitary somatotroph cells to stimulate the synthesis and pulsatile release of endogenous growth hormone, which is both anabolic and lipolytic; some of growth hormone’s effects are mediated by IGF-1 produced in the liver and peripheral tissues [1]. The receptor is GHRHR (UniProt Q02643), a G protein-coupled receptor that activates adenylyl cyclase and stimulates growth hormone gene transcription and secretion [7].

Because tesamorelin works through the pituitary, its effect depends on an intact hypothalamic-pituitary axis. The label contraindicates it in patients with disruption of that axis from hypophysectomy, hypopituitarism, pituitary tumour or surgery, head irradiation or head trauma [1].

Tesamorelin half-life and pharmacokinetics

Parameter (US label, healthy subjects unless stated)	Value	Ref
Absolute subcutaneous bioavailability	Less than 4%	[1]
Median Tmax	0.15 h	[1]
Mean volume of distribution	4.8 ± 1.9 L/kg	[1]
Mean elimination half-life	8 minutes	[1]
Exposure in HIV-infected patients	AUC 34% higher than healthy subjects; Cmax similar	[1]
Formal human metabolism studies	None performed	[1]
Apparent half-life in dogs (immunoreactive)	21–45 minutes	[2]

The short plasma half-life looks at odds with a once-daily product, but the pharmacodynamic markers outlast the peptide. In the first phase 3 trial, IGF-I rose on average by 81.0% after 26 weeks of once-daily treatment [8]. The non-clinical work described tesamorelin as having enhanced potency and duration of action compared with native GHRH, alongside its resistance to dipeptidyl aminopeptidase-IV [2].

Development history and timeline

Date	Event	Ref
1982	Human GHRH(1-44) isolated and sequenced	[4]
2007	Non-clinical pharmacology and toxicology of TH9507 published by Theratechnologies scientists	[2]
Dec 2007	First phase 3 trial (NCT00123253) published in NEJM, 412 patients	[8]
Jan 2007 to Oct 2008	Second phase 3 trial with safety extension, 404 patients	[9]
10 Nov 2010	FDA approval, application 022505	[3]
21 Jun 2012	EU marketing authorisation application (applicant Ferrer Internacional) withdrawn after CHMP concerns	[10]
2014 and 2019	Liver-fat trials in HIV (JAMA 2014; Lancet HIV 2019)	[11] [12]
23 Mar 2020	Former NDA deemed a biologics licence application (BLA 022505)	[3]
29 Jul 2026	Current version of the US prescribing information published on DailyMed	[1]

Key tesamorelin studies and findings

Study	Design / phase	Population	n	Duration	Primary endpoint	Main finding	Ref
Falutz 2007 (NCT00123253)	Phase 3 RCT, 2:1	HIV with abdominal fat accumulation on ART	412	26 weeks	% change in VAT (CT)	VAT −15.2% vs +5.0% placebo; IGF-I +81.0% vs −5.0%; no glycaemic differences	[8]
Falutz 2008	Extension, re-randomised	Completers of trial 1	315 re-randomised	52 weeks	Safety, VAT	VAT −18% sustained at 52 weeks; VAT reaccumulated after stopping	[13]
Falutz 2010 (JAIDS)	Phase 3 RCT, 2:1, with extension	HIV with excess abdominal fat	404	26 + 26 weeks	VAT	VAT −10.9% vs −0.6% at 6 months; about −18% at 12 months when continued	[9]
Falutz 2010 (JCEM)	Pooled analysis of both phase 3 trials	As above	806	26 + 26 weeks	% change in VAT	Treatment effect −15.4%; abdominal SAT unchanged	[14]
Stanley 2014 (NCT01263717)	RCT	HIV with abdominal fat accumulation	50	6 months	VAT and liver fat	VAT −34 vs +8 cm²; liver fat net −2.9% (lipid to water)	[11]
Stanley 2019 (NCT02196831)	Multicentre RCT, 1:1	HIV with NAFLD (HFF ≥5%)	61	12 months	Change in hepatic fat fraction	Absolute −4.1%, relative −37% vs placebo; 35% vs 4% reached HFF <5%	[12]
Baker 2012 (NCT00257712)	RCT	Adults 55–87, healthy or with MCI	152	20 weeks	Cognitive composites	Favourable effect on cognition (ITT P=.03), mainly executive function	[15]

The phase 3 programme in HIV-associated abdominal fat

The first phase 3 trial randomised 412 patients with HIV (86% men) who had accumulated abdominal fat on antiretroviral therapy to once-daily subcutaneous tesamorelin or placebo for 26 weeks. Visceral adipose tissue measured by CT fell by 15.2% with tesamorelin and rose by 5.0% with placebo, triglycerides and the total-to-HDL cholesterol ratio improved (P<0.001 for both comparisons), and IGF-I rose by 81.0% against a 5.0% fall. Adverse events did not differ significantly overall, but more tesamorelin patients withdrew because of an adverse event, and there were no significant differences in glycaemic measures [8].

In the 26-week extension, patients on tesamorelin were re-randomised to continue (154) or switch to placebo (50), and placebo patients switched to tesamorelin (111). The reduction in visceral fat was sustained at −18% over 52 weeks of continuous treatment, but visceral fat reaccumulated once tesamorelin was stopped [13]. The second phase 3 trial, in 404 patients between January 2007 and October 2008, reproduced the pattern: visceral fat fell 10.9% versus 0.6% with placebo at 6 months, by about 18% in those who continued for 12 months, and the early gains were rapidly lost in those switched to placebo [9].

The pooled analysis of both trials (543 tesamorelin, 263 placebo) gave a mean visceral fat change of −24 versus +2 cm² at week 26, a treatment effect of −15.4%, with no significant change in abdominal subcutaneous fat. Mean IGF-I rose by 108 versus −7 ng/mL, and there were no clinically meaningful differences in glucose parameters at weeks 26 and 52 [14]. A post hoc analysis found that patients whose visceral fat fell by at least 8% (the predefined responder threshold) had larger triglyceride reductions and better-preserved glucose homeostasis over 52 weeks than non-responders [16].

Liver fat and NAFLD

A single-centre trial in 50 HIV-infected adults with abdominal fat accumulation was designed to measure liver fat, an effect of tesamorelin that was then unknown. Over 6 months, tesamorelin reduced visceral fat (mean −34 versus +8 cm²) and liver fat (median lipid-to-water change −2.0% versus +0.9%), a net effect of −2.9%. Fasting glucose rose transiently at 2 weeks but the difference was not significant at 6 months [11]. A 2017 reanalysis of the phase 3 trials found that among patients with raised transaminases at baseline, visceral-fat responders had larger falls in ALT and AST than non-responders [17].

The dedicated NAFLD trial enrolled 61 people with HIV and a hepatic fat fraction of at least 5% by proton MR spectroscopy, randomised to tesamorelin or placebo for 12 months. Hepatic fat fraction fell by an absolute 4.1% more with tesamorelin (95% CI −7.6 to −0.7), a relative reduction of 37% from baseline, and 35% of tesamorelin patients versus 4% on placebo ended with a fat fraction below 5%. Fasting glucose and HbA1c did not differ between groups at 12 months; local administration-site complaints were more frequent with tesamorelin, none judged serious [12]. In paired biopsies from this trial, tesamorelin increased hepatic expression of oxidative phosphorylation gene sets and decreased gene sets linked to inflammation, tissue repair and cell division [18]. A 2024 subgroup analysis of 38 participants on integrase-inhibitor regimens reported significant falls in visceral and hepatic fat versus placebo, with a similar frequency of adverse events, including hyperglycaemia, in both groups [19]. These are small trials in a single population, and NAFLD is not an approved indication.

Cognition in older adults

In a 20-week randomised trial in 152 adults aged 55 to 87, 66 of them with mild cognitive impairment, tesamorelin had a favourable effect on a cognitive composite (intention-to-treat P=.03), driven mainly by executive function. IGF-1 rose by 117% and percent body fat fell by 7.4%. Adverse events, all mild, were reported by 68% of the tesamorelin group and 36% of the placebo group [15]. This is a single trial and has not led to an approved use.

Safety findings reported in studies and the label

The US label summarises safety from 740 HIV-infected patients treated in clinical trials, 543 of them during the 26-week placebo-controlled phase [1]. Its main points:

• Most common adverse reactions (above 5%): arthralgia, administration-site erythema, administration-site pruritus, pain in extremity, peripheral oedema and myalgia [1].
• IGF-1: among patients treated for 26 weeks, 47% had IGF-1 above 2 standard deviation scores and 36% above 3, seen as early as week 13; the label says the effects of prolonged IGF-1 elevation are unknown [1].
• Other warnings: fluid retention (oedema, arthralgia, carpal tunnel syndrome), glucose intolerance or diabetes, hypersensitivity reactions, and increased risk of neoplasms; contraindicated in active malignancy and pregnancy [1].
• Limitations of use: long-term cardiovascular safety not established; not indicated for weight loss management [1].

In non-clinical studies, dogs given repeated daily subcutaneous TH9507 for up to 4 months showed reversible liver and kidney findings, anaemia and clinical chemistry changes, which the authors attributed to sustained supraphysiological growth hormone and IGF-1 [2]. The European regulator’s concerns in 2012 were along the same lines: the CHMP considered rising IGF-1 a major concern, noted the absence of long-term safety data, and found that the fat reduction had not been shown to be clinically meaningful in terms of actual health benefits to patients [10].

Tesamorelin regulatory status by region

Jurisdiction	Status	Ref
United States	Approved 10 November 2010; now BLA 022505, prescription status	[3]
European Union	Marketing authorisation application withdrawn on 21 June 2012; CHMP’s provisional view was that it could not have been approved	[10]
Sport (all WADA signatories)	Prohibited at all times under S2.2.4 (named GHRH analogue)	[20]
UK, India, China	We did not identify a marketed authorisation in the sources reviewed; check national registers	n/a

Tesamorelin in laboratory research

Tesamorelin is used as a stable GHRH receptor agonist in endocrine and metabolic research, and as a reference standard in analytical and anti-doping work. Validated methods detect tesamorelin, sermorelin and CJC-1295 in urine by nano-LC quadrupole/Orbitrap MS [21]. Relevant study designs from the literature include plasma stability assays against dipeptidyl aminopeptidase-IV [2], growth hormone and IGF-1 response models in rodents, pigs and dogs [2], CT- and MR-based body composition endpoints [14] [12], and hepatic transcriptomics [18].

For identity and purity, a 44-mer with an acylated N-terminus needs more than a single HPLC purity number. LC-MS confirms the intact mass and the presence of the hexenoyl group; peptide mapping or MS/MS sequencing confirms the backbone; and acetate and water content are required to calculate peptide content, since the approved salt carries about seven acetates per molecule [1].

Synthesis, purity and impurities

Tesamorelin is produced synthetically [1]. A 44-residue N-acylated peptide of this kind is typically assembled by solid-phase peptide synthesis, acylated at the N-terminal tyrosine, purified by preparative reversed-phase HPLC and lyophilized. At this length the expected impurity classes are deletion and truncated sequences, plus des-hexenoyl peptide (incomplete acylation), the Met27 sulfoxide, deamidation at the Asn and Gln residues, and aspartimide-derived variants. Geometric isomerism of the hexenoyl double bond (trans versus cis) is a tesamorelin-specific identity point. See SPPS versus LPPS for route choice at this length and peptide API impurities and specifications for how related-substance limits are set.

Storage and stability of lyophilized tesamorelin

The approved product is a sterile lyophilized powder formulated with histidine, mannitol, polysorbate 20 and sucrose [1], which shows the type of excipient system used to stabilise this peptide. Research material is usually supplied as a lyophilized acetate salt without excipients and should be kept sealed, dry, cold and protected from light, with containers brought to room temperature before opening. Our guide to lyophilised peptide stability and storage explains why moisture and temperature drive degradation. This applies to laboratory material only.

Tesamorelin vs sermorelin vs CJC-1295

Feature	Tesamorelin	Sermorelin	CJC-1295 (with DAC)
Backbone	GHRH(1-44)-NH2	GHRH(1-29)-NH2 [22]	GHRH(1-29) with four substitutions plus Lys30 [23]
Stabilising strategy	N-terminal trans-3-hexenoyl (DPP-4 resistance) [2]	None	D-Ala2 plus covalent albumin binding [23] [24]
Molecular weight	5135.9 Da [1]	3357.9 g/mol [22]	3647.2 g/mol [24]
Human half-life	8 minutes [1]	Minutes (native GHRH data) [5]	5.8–8.1 days [25]
US status	Approved 2010, marketed [3]	Approved 1990 and 1997; later discontinued, not for safety or effectiveness reasons [26]	Not approved
WADA	S2.2.4 [20]	S2.2.4 [20]	S2.2.4 [20]

The comparison shows three different answers to the same problem: GHRH’s minute-scale half-life [5]. Tesamorelin keeps the native sequence and blocks the enzyme; CJC-1295 changes the sequence and borrows albumin’s half-life. More detail is in our sermorelin and CJC-1295 overviews.

How Winhycare Pharma supplies tesamorelin

Winhycare Pharma supplies tesamorelin as research-use-only material for laboratory work, at a purity of ≥99% as stated in our product brochure, with batch QC documentation. Custom synthesis of GHRH analogues, including acylated variants, is available on request. Specifications are on the tesamorelin product page, or contact us about research peptides. Research material is not the approved medicinal product.

For laboratory research use only. Not for human or veterinary use.