Tesamorelin: from discovery to FDA approval

Tesamorelin is a synthetic analogue of growth hormone-releasing hormone (GHRH), the hypothalamic peptide that signals the pituitary to release growth hormone. It has one approved clinical use: reducing excess abdominal fat in adults living with HIV, a condition that can develop as a consequence of long-term antiretroviral therapy. Getting from a laboratory concept to a licensed medicine took roughly two decades, and the path outside the United States remained blocked. This article traces the key moments.

Origins: the GHRH problem and TH9507

Natural GHRH is a 44-amino-acid peptide, but the full-length molecule is fragile in the bloodstream. Its half-life is measured in minutes once injected because enzymes, particularly dipeptidyl peptidase IV, cleave the N-terminal end rapidly. Researchers at Theratechnologies, a Montreal-based biopharmaceutical company, addressed this by attaching a trans-3-hexenoic acid group to the first amino acid. The resulting compound, called TH9507, retained full GHRH-like activity while resisting the enzymatic attack that limits the parent molecule.

The rationale for targeting HIV-associated lipodystrophy was partly scientific and partly commercial. By the early 2000s, lipodystrophy had become a recognised complication of antiretroviral regimens, particularly older protease inhibitors. Patients often experienced visceral fat accumulation, peripheral fat wasting, or both. Visceral fat excess in this population is associated with metabolic dysfunction, and no approved pharmacological option existed at the time. If TH9507 could drive a measurable reduction in visceral adipose tissue through the GHRH-GH-IGF-1 axis, it filled an unmet clinical need.

Early clinical evidence: dose-ranging to phase 3

Phase 2 dose-ranging work, published in AIDS in 2005, showed that TH9507 produced dose-related increases in IGF-1 and meaningful reductions in truncal fat at the 2 mg daily dose, with improvements in triglyceride and cholesterol-to-HDL ratios in the highest-dose group^[1]. The 2 mg subcutaneous injection once daily became the dose carried into phase 3.

Two pivotal phase 3 trials, conducted at centres across North America and Europe, enrolled patients with HIV who were on stable antiretroviral therapy and had documented excess visceral fat. Results from the pooled analysis of both trials, published in the Journal of Clinical Endocrinology and Metabolism in 2010, covered 806 patients (543 on tesamorelin, 263 on placebo)^[1]. Over 26 weeks, visceral adipose tissue fell by a mean of 24 cm² in the tesamorelin group versus an increase of 2 cm² in the placebo group. Triglycerides also declined more in the treatment arm. Glucose parameters did not differ in a clinically meaningful way between groups, though IGF-1 levels rose substantially, an observation that would attract regulatory scrutiny in Europe.

A parallel trial with a 52-week safety extension phase confirmed that the visceral fat reduction was maintained with continued treatment and that discontinuation led to reversal of the effect, indicating that ongoing administration was needed to sustain the benefit^[2]. The 18% VAT reduction observed at 52 weeks and the 51 mg/dL drop in triglycerides from that study supported Theratechnologies' regulatory dossier.

FDA approval, November 2010

The US Food and Drug Administration approved tesamorelin for injection, under the brand name Egrifta, in November 2010, making it the first GHRH analogue to reach the market for any indication^[4]. The approved indication was reduction of excess abdominal fat in HIV-infected patients with lipodystrophy. Theratechnologies held the New Drug Application. The approval was notable partly for what it was not: the FDA did not extend the indication to obesity in the general population, and the labelling was explicit that Egrifta is not indicated for weight loss management.

Europe: application withdrawn, June 2012

Theratechnologies filed a marketing authorisation application with the European Medicines Agency, listing Ferrer Internacional S.A. as the European applicant. The Committee for Medicinal Products for Human Use reviewed the evidence and raised several concerns. The CHMP concluded that the reduction in abdominal fat had not been shown to be clinically meaningful in terms of actual health benefits to patients, partly because the study populations were not representative of European HIV patients, who generally had lower body mass index and smaller abdominal fat deposits than the trial participants^[3].

Safety concerns also featured in the CHMP's assessment. The marked elevation in IGF-1 levels observed in many treated patients raised questions about potential long-term risks, including an association with cancer and complications of diabetic eye disease. The committee also identified difficulties in clinical practice: distinguishing lipodystrophy-related abdominal fat from ordinary obesity using the proposed visceral fat cutoff of 130 cm² lacked sufficient evidentiary support. On 21 June 2012, the applicant withdrew the application before the CHMP issued a formal opinion. The EMA's published withdrawal assessment reached the conclusion that benefits did not outweigh risks under the proposed conditions of use^[3].

Since 2012: reformulation and continued US use

Egrifta remained on the US market after the European withdrawal. Theratechnologies later developed a higher-concentration formulation, Egrifta SV (2 mg/0.36 mL), which the FDA approved in 2019. The SV version uses a smaller injection volume and eliminates some of the excipients in the original formulation, addressing practical tolerability concerns raised by prescribers and patients. The underlying active ingredient and indication are unchanged from the 2010 approval. For a full overview of tesamorelin's current regulatory status across markets, see the peptide page.

There is no current marketing authorisation for tesamorelin in the European Union, United Kingdom, or European Economic Area. As of mid-2026, no new application has been publicly filed with the EMA, MHRA, or any comparable authority outside the United States. The drug has no approved status in Canada through a publicly listed marketing authorisation, though Theratechnologies is a Canadian company and has historically supplied the Canadian market through mechanisms separate from standard new drug submissions.

What we do not know

The long-term effects of sustained IGF-1 elevation from tesamorelin remain an open question. The 52-week extension data provided reassurance on short-term glucose parameters, but no randomised trial has tracked cancer incidence or other outcomes over many years of continuous use^[1]. The reversal of fat reduction after treatment stops also leaves a gap: no controlled data defines the optimal duration of therapy or the best strategy for maintaining benefit with the least possible exposure.

Research in GHRH analogues has not stopped. Whether newer chemical modifications can produce a profile with a lower IGF-1 signature, or whether tesamorelin's effects on metabolic markers have implications beyond HIV-associated lipodystrophy, remain active research questions. Nothing in the published pipeline as of mid-2026 suggests an imminent regulatory filing in Europe.

This article covers the regulatory and scientific history of tesamorelin for general educational purposes. It is not medical advice. If you are considering any treatment involving tesamorelin or any other prescription medicine, consult a licensed clinician who can assess your individual situation.