Egrifta (Tesamorelin) + MK-677 (Ibutamoren): When to Pick One Over the Stack

What each drug is

Tesamorelin is a synthetic analog of human growth hormone-releasing factor: the 44-amino-acid human sequence with a hexenoyl group on the N-terminal tyrosine, molecular weight about 5,135.9 Da [2]. It binds pituitary GRF receptors with potency similar to the body's own GRF and causes the pituitary to release its own growth hormone, which raises IGF-1 and IGFBP-3 [2]. Egrifta was first approved on November 10, 2010 [5]. The current versions are Egrifta SV (2 mg vial, 1.4 mg dose) and Egrifta WR (11.6 mg vial, 1.28 mg dose), both once-daily subcutaneous injections into the abdomen, and the two are not substitutable [2][9].

MK-677 (ibutamoren mesylate) is not a peptide. It is an oral, non-peptide small molecule that stimulates growth hormone release by acting on the ghrelin receptor [3]. Merck first synthesized it in 1995 and development was discontinued in 1999; it has no USP or National Formulary monograph and is not a component of any FDA-approved drug [3]. It is also not a SARM, although it is often sold alongside them [3].

What tesamorelin is approved for, and what the trials showed

The only approved use is reduction of excess abdominal fat in HIV-infected adults with lipodystrophy [2]. The label adds limits: long-term cardiovascular safety has not been established, the risk/benefit of continuing should be considered in patients who have not had a reduction in visceral adipose tissue, and it is not indicated for weight loss because its effect on weight is neutral [2].

The main trial enrolled 412 HIV-infected adults with excess abdominal fat on antiretrovirals and gave tesamorelin 2 mg or placebo subcutaneously daily for 26 weeks (the 2 mg dose of the original 1 mg/vial product) [1][2]. Visceral adipose tissue fell 15.2% on tesamorelin and rose 5.0% on placebo; triglycerides fell 50 mg/dL versus a 9 mg/dL rise, and IGF-1 rose 81.0% versus a 5.0% fall [1]. A pooled analysis of the two phase 3 trials, 806 patients in total, found visceral fat change of -24 versus +2 cm2 at week 26 [10].

The effect did not last without treatment. In the extension data, people who continued tesamorelin held visceral fat at roughly 0% to -5% from week 26 to week 52, while those switched to placebo regained it, +16% to +22% [2][11].

The label also sets out what to watch. Among patients treated 26 weeks, 47% had IGF-1 above 2 SDS and 36% above 3 SDS, and the label asks prescribers to monitor IGF-1 and consider stopping for persistent elevations, particularly when the fat-loss response is not robust [2]. HbA1c of 6.5% or higher developed in 5% on tesamorelin versus 1% on placebo by week 26, a hazard ratio of about 3.3 [2]. Egrifta is contraindicated in people with disruption of the hypothalamic-pituitary axis, active malignancy, known hypersensitivity, and pregnancy [2].

Use outside HIV lipodystrophy is not covered by the label. A 2019 trial of 61 people with HIV and fatty liver found liver fat fell by 4.1 percentage points more than placebo over 12 months, a 37% relative reduction, but FDA has not approved tesamorelin for fatty liver and liver histology effects remain unproven [12].

What the MK-677 trials actually measured

There is no approved dose. Trials used fixed oral doses from 2 mg to 50 mg per day, 25 mg once daily in most adult trials, for up to 2 years [3].

A 2-year crossover trial in 65 healthy adults aged 60 to 81 gave 25 mg daily [6]. At 12 months, fat-free mass rose 1.1 kg versus a 0.5 kg fall on placebo and body weight rose 2.7 kg versus 0.8 kg, but strength and function did not improve. Fasting blood glucose rose about 5 mg/dL and insulin sensitivity fell [6].

A hip-fracture trial of 123 older adults receiving 25 mg of MK-677 daily was terminated early because of a congestive-heart-failure safety signal; FDA's summary counts 4 patients on MK-677 versus 1 on placebo [13][3]. The study found no improvement in most functional measures and concluded that MK-0677 had an unfavorable safety profile in this population [13].

In a randomized trial of 161 older adults recovering from hip fracture, MK-0677 increased IGF-1 by 84% versus 17% with placebo, but did not produce a significant functional benefit [14]. In a 12-month randomized trial of 563 patients with mild to moderate Alzheimer's disease, MK-677 raised IGF-1 by 72.9% but did not slow disease progression [15].

The fat-loss rationale is the weakest part. In 24 obese men given 25 mg daily for 8 weeks, IGF-1 rose about 40% and fat-free mass increased, but total and visceral fat did not change and an oral glucose tolerance test showed impaired glucose handling [16].

Is there any evidence for stacking them?

Tesamorelin and MK-677 act on different targets, a pituitary GRF receptor for tesamorelin and the ghrelin receptor for MK-677, and both raise GH and IGF-1 [2][3].

The pieces that would matter are known separately. Tesamorelin labeling calls for monitoring IGF-1 and glucose; in the trials, 36% of patients were above 3 SDS for IGF-1 at 26 weeks and HbA1c of 6.5% or higher developed in 5% versus 1% on placebo [2]. MK-677 trials also reported rises in IGF-1 and in blood glucose; in healthy older adults given 25 mg daily, fasting glucose rose about 5 mg/dL with lower insulin sensitivity [6]. The combined effect of the two on either measure is unknown.

Interaction data are thin in both directions. FDA's review of MK-677 reports no formal drug-interaction studies [3]. The Egrifta label covers glucocorticoid replacement, where patients on cortisone acetate or prednisone may need higher maintenance or stress doses, and drugs cleared by CYP450 enzymes, and it does not name MK-677 [2].

Regulatory status, which is very different for the two

Tesamorelin is a prescription drug approved under application BLA 022505 [5]. It is not on FDA's list of bulk substances that may present significant safety risks when compounded, and it appears in no category of FDA's lists for state-licensed pharmacies and physicians or for outsourcing facilities, so FDA has made no category-based statement about compounding it; it is already a component of an FDA-approved drug [7][17][18]. It is also not one of the six peptides in HHS's draft enforcement-discretion policy for compounding [19].

MK-677 is in a different position. In a December 12, 2025 warning letter, FDA stated that ibutamoren is excluded from the dietary supplement definition because it was authorized for investigation as a new drug and was not marketed as a supplement or food before that, and that products marketed with drug claims are unapproved new drugs [4]. FDA lists ibutamoren mesylate among bulk substances that raise significant safety risks for compounding (category 2), added December 29, 2022 for outsourcing facilities and September 29, 2023 for state-licensed pharmacies and physicians, citing the potential for congestive heart failure and the hip-fracture trial terminated early for that signal [7][17][18][13]. The category 1 policy, under which FDA generally does not act against compounders, does not apply to category 2 substances [20]. On October 29, 2024, FDA's Pharmacy Compounding Advisory Committee voted 1 yes to 13 no against adding ibutamoren mesylate to the pharmacy bulks list [21]. Compounded drugs are not FDA-approved, and FDA does not review their safety, effectiveness or quality before marketing [22].

WADA names both drugs in section S2.2.4 of its Prohibited List, tesamorelin as a growth hormone-releasing factor and ibutamoren as a growth hormone secretagogue; both are prohibited at all times, in and out of competition, on the 2026 List and the 2027 List [8][23].

When one is the better fit than the other

For HIV-associated lipodystrophy with excess abdominal fat, tesamorelin is the only one of the two with an approval and phase 3 data in that exact population, and it is the only setting where either drug has a labeled dose and a labeled monitoring plan [2][1].

Outside that population, neither has an approval to point to. Tesamorelin's label does not cover use in people without HIV, and MK-677 has no approved use anywhere [2][4].

If the route matters, MK-677 is the only oral option of the two, but the trade is an unapproved drug that had one trial stopped early for a congestive heart failure signal and that did not change visceral fat in an 8-week study of obese men [13][16].