Tesamorelin in HIV: the trial that showed it trims deep belly fat, and what it cost

In 412 people with HIV who had built up abdominal fat on antiretroviral treatment, a daily 2 mg injection of tesamorelin for 26 weeks reduced visceral fat, the fat packed around the organs, by 15.2%, while it rose 5.0% on placebo [1]. Triglycerides and cholesterol ratios improved and blood sugar didn't worsen. The costs: more people quit because of side effects, and 48.6% of those on the drug developed antibodies to it [1].

Why this study matters

Antiretroviral treatment for HIV often came with a distinctive change in body shape: fat lost from the arms, legs and face, and fat gained deep in the abdomen [1]. That visceral fat is linked to heart disease, and it was hard to shift. Diet, exercise and insulin-sensitising drugs had given inconsistent results, and growth hormone itself worked but pushed IGF-1 to well above normal levels [1].

Tesamorelin takes a different route. It's a modified version of growth hormone-releasing hormone (GHRH), the 44-amino-acid signal from the brain that tells the pituitary to release its own growth hormone. The manufacturer added a chemical group to one end to make it last longer [1]. This NEJM paper reports one of two phase 3 trials, later pooled in a 2010 analysis [2]. The FDA approved tesamorelin as Egrifta in November 2010 [3].

What they did

Recruitment ran from June 2005 to April 2006 [1]. To qualify, people had to have been on antiretroviral therapy for at least eight weeks and meet waist criteria: at least 95 cm with a waist-to-hip ratio of 0.94 or more for men, or at least 94 cm with a ratio of 0.88 or more for women [1]. In total, 275 got tesamorelin and 137 got placebo.

Visceral fat was measured on a single CT slice between the fourth and fifth lumbar vertebrae, read centrally by assessors who didn't know who was on what [1]. Body composition in the limbs and trunk came from DXA scans.

What they found

All of the between-group differences in the first, third, fourth and fifth rows had p below 0.001 [1]. The effect was specific to deep abdominal fat: subcutaneous belly fat and limb fat barely moved, which matters for a population that often has too little fat in the limbs already [1]. People with more visceral fat at the start tended to lose more [1].

The authors estimate the loss at about 1.0 kg of visceral fat in six months [1]. That's modest on a scale, which is part of the point. This drug reshapes where fat sits more than it reduces total weight.

Participants also rated their “belly image distress” and “belly profile” as improving more on tesamorelin (p = 0.03 for each), though their rating of belly size didn't differ between groups [1]. Fasting glucose, two-hour glucose and insulin didn't differ significantly, and neither did CD4 counts or viral load [1]. C-reactive protein didn't change; adiponectin, a hormone released by fat tissue, rose by a relative 10% more on tesamorelin [1].

Side effects

Overall adverse events and serious adverse events didn't differ significantly between groups, but both were common, as you'd expect in a group living with HIV [1]. More people on tesamorelin withdrew because of an adverse event, most often for joint pain, swelling and injection-site reactions [1]. Four serious events were judged possibly related to tesamorelin: peripheral neuropathy, feverish diarrhoea with dehydration, loss of mobility and congestive heart failure [1].

Two findings stand out:

• Antibodies. IgG antibodies against tesamorelin appeared in 48.6% of users, against 2.7% on placebo. They didn't appear to blunt the drug's effect on IGF-1 or visceral fat [1].
• Hives. Six people on tesamorelin (2.2%) developed urticaria beyond the injection site after four to five months; all six stopped the drug and all tested positive for antibodies. One had a brief systemic reaction with nausea, a racing heart and shortness of breath that settled within three minutes [1].

Adjusted for age and sex, the average IGF-1 rise on tesamorelin was 2.69 standard deviations, against −0.39 on placebo [1]. The authors reported fewer growth-hormone-excess symptoms such as joint pain and swelling than in earlier growth hormone trials, but the IGF-1 rise is worth keeping in mind, since it's the lever through which the drug works.

Caveats

• Funding and design. Theratechnologies, the developer, funded and designed the study with two of the academic authors. Three authors were company employees with equity in it, and several others reported grants or fees from the company [1].
• Dropouts. 20.5% dropped out: 22.7% on tesamorelin and 16.1% on placebo (p = 0.12). Missing values were filled by carrying forward the last observation, a method that can distort results when dropout is uneven [1].
• An imbalance at baseline. More tesamorelin users were on non-nucleoside reverse-transcriptase inhibitors, which can affect fat and lipids. The results held after adjusting for this [1].
• Few women. Only 14% were women, though the effect looked similar in both sexes [1].
• Short. The randomised phase lasted six months, and the authors say long-term benefits, including any effect on heart disease, remained unknown [1].

What happened next

A pooled analysis of this trial and a second phase 3 trial, 806 patients in all, found a 15.4% placebo-adjusted fall in visceral fat at 26 weeks [2]. People who stayed on tesamorelin for a full year kept the reduction (17.5% below baseline at week 52), with no clinically meaningful change in glucose measures [2]. In the safety extension of the NEJM trial, two people on tesamorelin died, one from complications of tonsil surgery and one from coronary artery disease; investigators didn't judge either death related to the drug [1].

What it means in practice

For people with HIV-associated abdominal fat, this trial shows tesamorelin does one specific thing well: it selectively shrinks visceral fat and improves blood lipids over six months without worsening blood sugar. Whether that translates into fewer heart attacks is a separate question the trial did not test, and the population was adults with HIV on antiretroviral therapy, not anyone else.

What is still open

• Whether the fat and lipid changes translate into fewer cardiovascular events.
• What anti-tesamorelin antibodies mean over many years of use.
• The long-term consequences of keeping IGF-1 raised above the normal range.
• How the results apply to people on today's antiretroviral regimens, which differ from those in use when the trial ran in 2005–2006.

What this means

Tesamorelin is the uncommon case of a peptide that cleared the bar: an approved medicine, Egrifta, on the strength of this trial and the one pooled with it. We think that deserves stating plainly. In a group of people with HIV who had few good options for the fat antiretroviral therapy put on their abdomen, a daily injection moved visceral fat in the right direction, held it there for a year, and did not worsen blood sugar.

The position we would argue for is narrower than the interest around the drug. The trial that would connect a 15% visceral fat reduction to fewer heart attacks or strokes was never run. That gap is not a patent problem: Egrifta is licensed and marketed, and the developer could have funded an outcomes study. It is a scale problem, because an event-driven trial of that size has never been justified in a market this small and this specific. The benefit therefore stays measured in centimetres of fat and in lipid numbers, not in avoided cardiac events, and we read it that way.

The costs are real and belong in the same sentence as the benefit: about half of users develop antibodies to the drug, and IGF-1 sits above the normal range for as long as it is taken. We would accept that trade inside the HIV indication the trial studied. We would not stretch it, on this evidence, to people without HIV chasing a leaner midsection, who were never tested. And tesamorelin is a prescription injectable, so anything sold as research grade carries risks the trial's pharmacy product did not: unverified purity, sterility, endotoxin and heavy metals.

Educational content only — not medical advice. Many peptides discussed on HPR are not approved for human use. Talk to a qualified clinician before making any decision about your health.