Tesamorelin: the GHRH analog that did clear the FDA

A GH-axis peptide with marketing approval

Tesamorelin is a stabilized analog of human growth hormone-releasing hormone, GHRH(1-44), given subcutaneously once a day³⁷. It does not supply GH from outside: it stimulates the pituitary to release its own, and IGF-1 rises with it⁸. The FDA approved it in November 2010⁹¹⁵, and the current label indicates it for "the reduction of excess abdominal fat in HIV-infected adult patients with lipodystrophy"⁸.

That approval sets it apart from the secretagogues sold without approval, such as CJC-1295, ipamorelin or MK-677, whose balance is discussed in CJC-1295, ipamorelin and MK-677: the GH and IGF-1 debate. Tesamorelin offers something those compounds lack: large, placebo-controlled trials reviewed by a regulator³⁹.

The phase 3 trials

The first trial, published in NEJM in 2007, randomized 412 patients with HIV and abdominal fat accumulation to tesamorelin 2 mg daily or placebo for 26 weeks. Visceral fat measured by CT fell 15.2% with tesamorelin and rose 5.0% with placebo; triglycerides fell 50 mg/dL vs a 9 mg/dL rise, and IGF-1 rose 81.0% vs a 5.0% fall (P < 0.001 for all comparisons). There were no significant differences in glycemic measures or in adverse events, although more patients in the active arm withdrew because of an adverse event¹.

The pooled analysis of the two phase 3 trials included 806 patients randomized 2:1. At 26 weeks, the effect on visceral fat was −15.4% vs placebo, with no significant change in abdominal subcutaneous fat (P = 0.08). Triglycerides fell with a −12.3% treatment effect, body image improved, and mean IGF-1 rose 108 ng/mL vs −7 ng/mL with placebo³. In a post hoc analysis, patients with at least an 8% visceral reduction had, compared with those who did not reach it, greater improvement in triglycerides and adiponectin and smaller changes in glucose⁴; among those with elevated transaminases, responders also had larger declines in ALT and AST¹³. Two 2026 meta-analyses of the controlled trials confirmed the reduction in visceral and trunk fat¹¹¹²; one found no significant change in subcutaneous fat¹¹, and the other cautioned that long-term safety data remain limited¹².

Liver fat: the most promising finding

In a 50-patient HIV trial published in JAMA in 2014, six months of tesamorelin were associated with reductions in visceral fat (effect −42 cm²; P = 0.005) and in liver fat, with a net effect of −2.9% in lipid-to-water percentage (P = 0.003). The authors described it as a preliminary study, with modest reductions in liver fat⁵.

The multicenter Lancet HIV trial (2019) was designed specifically for non-alcoholic fatty liver disease in 61 people with HIV. At 12 months, hepatic fat fraction fell 4.1 points more than with placebo, a 37% relative reduction (p = 0.016). Of treated patients, 35% ended below 5% liver fat, vs 4% with placebo. Fasting glucose and HbA1c did not differ between groups at 12 months⁶. A later analysis of participants on integrase inhibitors, the backbone of current antiretroviral therapy, also found declines in visceral and liver fat vs placebo¹⁴.

Beyond HIV: the cognition trial

The main trial outside the approved indication is a randomized study of 152 adults aged 55 to 87, healthy or with mild cognitive impairment, who received tesamorelin 1 mg/day or placebo for 20 weeks. It was associated with a favorable effect on cognition (P = 0.03), mainly on executive function (P = 0.005), with a 117% rise in IGF-1 that stayed within the physiological range and a 7.4% reduction in percent body fat⁷.

It is a single 20-week trial, and the authors themselves called for longer studies. Mild adverse events were reported by 68% of the active group vs 36% with placebo, and fasting insulin rose 35% in participants with cognitive impairment⁷. Pharmacology reviews agree that the data supporting off-label uses are limited¹⁵.

Glucose and IGF-1: what to monitor

In the phase 3 trials, glucose changes were not clinically meaningful at 26 or 52 weeks³. But the detail matters: in the JAMA trial, fasting glucose rose 7 mg/dL more than with placebo at 2 weeks, a difference that was no longer significant at 6 months⁵. The label reports HbA1c ≥ 6.5% in 5% of treated patients vs 1% with placebo at week 26, with a diabetes hazard odds ratio of 3.3, and asks for glucose evaluation before and during treatment⁸.

IGF-1 follows a similar pattern. At 26 weeks, 47% of patients had IGF-1 above 2 standard deviation scores and 36% above 3. The label warns that the effects of prolonged elevation are unknown and recommends considering discontinuation if IGF-1 stays high (for example, above 3 standard deviation scores), particularly if the response is not robust⁸.

What happens on discontinuation

In the extension phase of the first trial, the visceral fat reduction was sustained at −18% at 52 weeks while patients stayed on treatment. Those switched to placebo regained it: "Upon discontinuation of tesamorelin, VAT reaccumulated". The authors concluded that the effects do not last beyond treatment². In the pooled analysis, the group that continued tesamorelin maintained its reductions in visceral fat, waist and triglycerides at 52 weeks³.

Limits physicians should know

• Narrow indication. Approval covers excess abdominal fat in HIV with lipodystrophy. The label states it is not indicated for weight loss, because its effect on weight is neutral, and that long-term cardiovascular safety has not been established⁸.
• Contraindications. Active malignancy, disruption of the hypothalamic-pituitary axis, pregnancy and known hypersensitivity⁸.
• Local reactions and fluid retention. Injection-site reactions occurred in 25% of treated patients vs 14% with placebo in the first 26 weeks; edema, arthralgia and carpal tunnel syndrome may also occur⁸.
• Europe did not approve it. The EMA application was withdrawn in 2012. The committee had provisionally concluded it could not be approved: it doubted that the fat reduction translated into clinical benefit and was concerned about the IGF-1 rise in a considerable number of patients¹⁰.