Evidence Grade C — Moderate human evidence. 38 published studies, 28 human. 8 registered clinical trials.
Medically reviewed by a licensed medical professional
MK-677 (ibutamoren) is an orally active small molecule — not a peptide — that stimulates growth hormone release by activating the ghrelin receptor. Developed by Merck, it was never approved after clinical trials showed that the growth hormone and IGF-1 increases it produced did not translate into meaningful functional improvements. It is widely available through unregulated sources.
MK-677 (Ibutamoren) is also known by these brand and alternate names:
38 published studies: 28 human, 6 animal, 5 in-vitro, 3 reviews
MK-677 has no marketing authorisation from any regulatory agency. Multiple clinical trials were conducted by Merck: a 2-year study in elderly subjects showed increased IGF-1 and modest body composition changes but no functional improvement. A Phase II trial in hip fracture recovery did not meet its primary endpoints. Clinical development was discontinued.
MK-677 is not a peptide but a small-molecule peptidomimetic. Despite generating pharmacological effects on growth hormone and IGF-1 levels, these effects did not translate into clinically meaningful outcomes in the trials conducted. Products available through unregulated channels lack pharmaceutical quality assurance.
Research suggests MK-677 activates the ghrelin receptor orally, producing sustained growth hormone elevation and IGF-1 increases over 24 hours. It also stimulates appetite (consistent with ghrelin receptor activation). Unlike injectable growth hormone secretagogue peptides, its oral bioavailability allows sustained daily dosing without injection. These pharmacological observations are from clinical studies that did not demonstrate functional clinical benefit.
Research suggests a two-year study in elderly subjects showed increased IGF-1 levels and modest body composition changes but no functional improvement — the growth hormone elevation did not make people stronger or more mobile. A Phase II hip fracture recovery trial also failed to meet its primary endpoints. Clinical development was discontinued. Side effects include appetite and weight gain, increased fasting glucose (HbA1c rose from 5.5% to 5.8% over two years), and oedema. The unknown long-term cancer risk of sustained IGF-1 elevation is a theoretical concern. It is prohibited by WADA. Products from unregulated channels lack pharmaceutical quality assurance.
PeptideTrace tracks 8 registered clinical trials for MK-677 (Ibutamoren) sourced from ClinicalTrials.gov.
Phase 3 Study of LUM-201 in Children With Growth Hormone Deficiency
The Impact of Ibutamoren on Nonalcoholic Fatty Liver Disease
Growth Hormone Secretagogue MK-0677's Effect on Lean Body Mass in Chronic Kidney Disease Stage 4/5 Subjects
Growth Hormone Secretagogue MK-0677 Effect on IGF-1 Levels in ESRD Patients
Treatment of Sarcopenia in Post-Hip Fracture Patients (0677-032)
MK-677 (ibutamoren) is a non-peptide spiropiperidine GH secretagogue, MW 528.67 Da (free base). Not a peptide but a small-molecule peptidomimetic. Developed by Merck. Orally bioavailable (~70%). Produces sustained 24-hour GH/IGF-1 elevation. Half-life ~4-6 hours (pharmacodynamic effect ~24h). Not approved. WADA-prohibited.
Research suggests oral non-peptide GHS-R1a agonism, binding same orthosteric site as ghrelin. Produces pulsatile GH, increases IGF-1 40-80% chronically. Increases appetite (ghrelin mimicry), modestly elevates cortisol initially (normalizes), improves sleep quality by increasing Stage IV slow-wave sleep ~50%.
No marketing authorization. 2-year RCT in elderly (Nass, JCEM 2008; N=65): IGF-1 to youthful levels, +1.6 kg fat-free mass (P<0.01), no functional improvement. Murphy et al. (1998; N=32 obese): GH AUC +55%, IGF-1 +40%, FFM +3 kg. Hip fracture Phase II (N=161): improved gait speed, primary endpoints NS. Slow-wave sleep +50%.
The information on this page is provided for educational and research reference purposes only. This is not medical advice. Always consult a qualified healthcare professional before making any health-related decisions.
Somatrogon is marketed as Ngenla (approved June 2023) for paediatric growth hormone deficiency in children aged 3 years and older. In the pivotal trial, once-weekly somatrogon produced growth rates equivalent to daily somatropin injections (10.1 cm/year versus 9.8 cm/year), confirming that reducing injection frequency does not compromise growth outcomes. Ngenla represents a meaningful advance for paediatric patients and their families, reducing injections from 365 to 52 per year. Treatment adherence has been a persistent challenge with daily growth hormone, and weekly dosing is expected to improve long-term outcomes through better compliance. Somatrogon competes directly with somapacitan (Sogroya), the other approved weekly growth hormone, creating a new generation of less burdensome treatment options.
Somapacitan is marketed as Sogroya (approved August 2020 for adult growth hormone deficiency; expanded April 2023 to paediatric growth hormone deficiency in children aged 2.5 years and older). It is the first once-weekly growth hormone approved for both adult and paediatric patients. In adults, clinical trials showed improvements in body composition including reduced truncal fat. In children, growth rates were comparable to daily somatropin. The albumin-binding approach provides predictable drug levels with lower peak-to-trough variation than some other long-acting growth hormone technologies. Sogroya competes with somatrogon (Ngenla) in the growing once-weekly growth hormone market, with both products expected to gradually replace daily injections as the standard of care.
ACE-031 has no marketing authorisation. A Phase I trial in healthy women showed increased lean mass and decreased fat mass. A Phase II trial in DMD (24 patients) showed lean body mass increases but was discontinued due to bleeding-related safety concerns (epistaxis, telangiectasias, and gum bleeding), likely caused by inhibition of BMP-9/10 vascular signalling. ACE-031 is a large fusion protein (~90 kDa), not a peptide. Its clinical development was halted. The non-selective ligand-trapping profile — capturing beneficial vascular signalling molecules alongside the intended muscle-growth targets — illustrates the challenge of targeting the TGF-beta superfamily. Acceleron subsequently developed more selective agents.
This content is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before making decisions about your health.
