Tesamorelin

Tesamorelin is a synthetic analog of growth-hormone-releasing hormone (GHRH). It is a 44-amino-acid peptide stabilized at the N-terminus with a trans-3-hexenoic acid group, which extends its half-life enough to support once-daily subcutaneous dosing. Developed by Theratechnologies in Montreal, it is sold as Egrifta SV and Egrifta WR for HIV-associated lipodystrophy.

The molecule was originally designated TH9507 during development. The N-terminal modification protects the peptide from dipeptidyl peptidase IV (DPP-IV) cleavage, which inactivates native GHRH within minutes of release. Native GHRH has a circulating half-life of around seven minutes. Tesamorelin has a half-life closer to 30 minutes in plasma, which is long enough to produce a clinically meaningful GH pulse from a single daily injection.

The Phase 3 Trials in HIV Lipodystrophy

Two pivotal Phase 3 trials supported the 2010 FDA approval.

Trial 1 (NCT00123253, LIPO-010), n = 412. HIV-infected patients on stable antiretroviral therapy with central fat accumulation. Patients were randomized 2:1 to tesamorelin 2 mg daily or placebo for 26 weeks.

Trial 2 (NCT00435136, CTR-1011), n = 404. Same design and patient population.

At week 26, the tesamorelin arms showed an average 15.4 percent reduction in VAT versus a 5.1 percent increase in placebo in the pooled analysis (Falutz et al., JCEM 2010). Subcutaneous adipose tissue was largely unchanged, confirming the selective visceral effect.

The continuation arms maintained the VAT reduction at 52 weeks. The switch-to-placebo arms regained visceral fat toward baseline within six months. Stop the drug, lose the benefit.

Tesamorelin in NAFLD: The Stanley Studies

The most important off-indication trial was conducted at Massachusetts General Hospital. The pivotal study (Stanley et al., Lancet HIV, 2019) was a 12-month randomized, double-blind, placebo-controlled trial of tesamorelin 2 mg daily in 61 adults with HIV and nonalcoholic fatty liver disease. Tesamorelin reduced liver fat by an absolute 4.1 percentage points versus placebo at one year. Fibrosis progression occurred in 10.5 percent of tesamorelin patients versus 37.5 percent on placebo.

A follow-up transcriptomic analysis (Stanley et al., JCI Insight, 2020) reported that tesamorelin upregulated hepatic oxidative phosphorylation gene sets and downregulated inflammation gene sets.

A Phase 3 trial of tesamorelin for general MASLD independent of HIV status has not been announced.

Tesamorelin acts upstream of the pituitary. It binds the GHRH receptor on pituitary somatotrophs and triggers endogenous growth-hormone release. The pulse pattern that follows is similar to physiological GH secretion, with peaks lasting roughly two to three hours after injection.

Increased GH then drives hepatic IGF-1 synthesis. Serum IGF-1 typically rises 30 to 50 percent above baseline within six to eight weeks of treatment. The downstream fat-loss effect appears to come from two pathways. First, GH directly stimulates lipolysis in adipose tissue, with stronger effects on visceral fat than on subcutaneous fat. Second, IGF-1 modifies adipose tissue metabolism in ways that favor lipid mobilization. The result is a preferential reduction in visceral adipose tissue (VAT).

A key point about the mechanism. Tesamorelin restores GH secretion to the upper end of the physiological range. It does not bypass the negative feedback loop that controls pituitary GH release. This is the difference between a GHRH analog and exogenous recombinant human GH, and explains why tesamorelin has a different safety profile from rhGH.

Approximately 15.4 percent visceral adipose tissue reduction at six months in the pooled Phase 3 trials of 816 HIV-infected patients with lipodystrophy (Falutz et al., 2010). Waist circumference decreased by an average of 2.3 cm. Subcutaneous adipose tissue was largely unchanged.

In the Stanley NAFLD trial, 12 months of tesamorelin reduced hepatic fat fraction by 4.1 percentage points versus placebo in 61 adults with HIV and NAFLD, and reduced fibrosis progression from 37.5 percent on placebo to 10.5 percent on active.

Serum IGF-1 typically rises 30 to 50 percent above baseline within six to eight weeks. Visceral fat returns toward baseline within six months of stopping.

Labeled dose is 2 mg subcutaneously, once daily, typically administered into the abdomen. Tesamorelin is supplied as a lyophilized powder reconstituted with sterile water. The Egrifta WR formulation introduced in 2024 is a multi-dose vial that provides seven daily doses from a single reconstitution.

Off-label use exists in three contexts: non-HIV visceral fat reduction (no FDA approval, no Phase 3 data in this population); NAFLD/MASLD treatment (off-label, supported by the Stanley studies in HIV populations only); and anti-aging or bodybuilding use in healthy adults seeking GH/IGF-1 elevation, which sits entirely outside the approved indication and any published trial evidence.

The most common adverse events in Phase 3 were injection-site reactions in approximately 25 percent of tesamorelin-treated patients. Joint pain (arthralgia) occurred in 13 percent versus 6 percent on placebo. Peripheral edema occurred in approximately 6 percent versus 3 percent.

Glucose intolerance is the clinically meaningful metabolic signal. Tesamorelin increased fasting glucose by approximately 4 mg/dL on average. A subset of patients with baseline insulin resistance developed treatment-emergent diabetes during the trial period. Labeling recommends periodic monitoring of fasting glucose and HbA1c.

IGF-1 elevation above the age-adjusted upper limit of normal occurred in 10 to 15 percent of patients. Sustained IGF-1 elevation is theoretically associated with cancer risk for breast, prostate, and colorectal cancers based on epidemiologic associations. No excess cancer signal has been observed in the trial dataset, but the trials were not powered to detect that endpoint. Active malignancy is a contraindication.

Carpal tunnel syndrome and fluid retention are class effects of GH/IGF-1 elevation and have been reported at low rates. Discontinuation due to adverse events was approximately 11 percent in active-treatment arms versus 8 percent in placebo arms.

Tesamorelin is the only stabilized GHRH analog with a Phase 3 evidence base and an FDA approval. Sermorelin (GRF 1-29) was the first GHRH analog approved (pediatric GH deficiency, 1997), but has a seven-minute half-life and was discontinued from the US market in 2008. It is available again through compounding pharmacies for off-label adult use.

CJC-1295 with DAC is a research-grade GHRH analog with an albumin-binding modification producing a half-life of six to eight days. It has no FDA approval, no Phase 3 program, and limited published human safety data. It is on the FDA Category 2 bulks list and the WADA Prohibited List.

For visceral fat specifically, tesamorelin remains the only molecule with prospective controlled-trial evidence. Tesamorelin is on the WADA Prohibited List under section S2.