Ibutamoren (MK-677)

Ibutamoren (MK-677) is a real, decades-old growth hormone secretagogue with genuine randomized-trial history on both ends of its story: a serious cardiac safety signal that ended Merck's own elderly/hip-fracture development in 2011, and a currently-recruiting Phase 3 trial — under a different name and sponsor — testing the same molecule in a genetically-selected pediatric population instead. It has never been approved for any indication, and despite being sold and marketed alongside this site's other growth-hormone-secretagogue peptides, it isn't actually a peptide.

A non-peptide growth hormone secretagogue

Ibutamoren (MK-677, originally MK-0677) is an orally-bioavailable small molecule — not a peptide, unlike every other growth-hormone secretagogue this site covers — that activates the ghrelin receptor (GHS-R1a) in the pituitary and hypothalamus, stimulating the body's own release of growth hormone and, downstream, IGF-1. Merck began developing it in the 1990s as a potential oral alternative to injected growth hormone and to injectable GH-secretagogue peptides like sermorelin, CJC-1295 and ipamorelin — all covered elsewhere on this site, and all real peptides, which ibutamoren chemically is not, whatever online marketing implies by lumping them together.

Merck's own 2008 trial: real gains, real metabolic costs

The best-known ibutamoren trial is Merck-sponsored and genuinely rigorous: Nass et al. (Ann Intern Med 2008;149(9):601-611, PMID 18981485), a 2-year, randomized, double-blind, placebo-controlled, modified-crossover trial in 65 healthy adults aged 60-81, taking 25mg of oral MK-677 or placebo daily. Fat-free mass rose about 1.1kg relative to a roughly 0.5kg decline on placebo, and IGF-1 rose into the young-adult range — but that fat-free-mass gain did not translate into measurable improvements in strength or physical function, and it came with a real metabolic cost: fasting glucose rose about 0.3mmol/L (5mg/dL) on average and insulin sensitivity declined, consistent with growth hormone's known diabetogenic effect. The most common side effects were increased appetite and mild, self-limited lower-leg edema and muscle pain.

The 2011 hip-fracture trial that ended adult development

Merck did not advance ibutamoren into Phase 3 for any adult indication after this result, and its original patents have since expired — leaving no company with the exclusivity incentive to fund the further trials an FDA approval for an adult indication would require, and none has.

A second life: a genetically-selected pediatric trial

The same molecule has resurfaced under a different name, a different sponsor, and a deliberately different patient population: it has been licensed and renamed LUM-201, and is now in development as a once-daily oral treatment for pediatric growth hormone deficiency (PGHD) — a population with essentially none of the cardiovascular risk factors present in the elderly hip-fracture patients who developed heart failure in 2011. The current development strategy centers on a "Predictive Enrichment Marker" (PEM) test — a baseline IGF-1 above 30ng/mL plus a peak growth-hormone response of at least 5ng/mL after a single test dose — intended to select children likely to respond, rather than treating all comers. Phase 2 trials (registered on ClinicalTrials.gov as OraGrowtH210 and OraGrowtH212) reported topline results in November 2023 meeting their primary and secondary endpoints, including validation of the PEM strategy and annualized height velocities of 8.2cm/year at 6 months and 8.0cm/year at 12 months on the 1.6mg/kg dose — real measured results, though from an open-label Phase 2 stage rather than a placebo-controlled comparison. A randomized, double-blind, placebo-controlled Phase 3 trial (ClinicalTrials.gov NCT06948214), assigning roughly 150 treatment-naive children 2:1 to the drug or placebo over 12 months, was listed as actively recruiting as of this review — a real, current, ongoing program, not yet approved and not yet complete.

Grey-market sale today, and the FDA's response

None of that pediatric program changes ibutamoren's legal status as sold online today: no FDA-approved product exists for any use, at any age, and the DEA has not scheduled it. It's prohibited at all times — in and out of competition — under the World Anti-Doping Agency's 2026 Prohibited List, category S2.2 ("Growth Hormone Releasing Factors"), listed by name in that category's growth-hormone-secretagogues-and-mimetics subgroup — the same broad S2.2 category, via its separate GH-releasing-peptide subgroup, that covers hexarelin and the other GH-secretagogue peptides this site tracks. In December 2025, the FDA sent a wave of warning letters to online sellers marketing products under names including "MK-677" and "Ibutamoren" alongside actual SARMs (ostarine, LGD-4033, RAD-140 and similar compounds), citing all of them as unapproved new drugs under section 505(a) of the Food, Drug and Cosmetic Act and flagging safety concerns — including liver toxicity and elevated cardiovascular risk — associated with that broader product category. Worth noting: ibutamoren isn't actually a SARM — it doesn't touch the androgen receptor at all — but it's routinely sold, and evidently regulated, alongside them anyway.