MK-677

Fat LossOral ghrelin-mimetic small moleculeExperimental

Also known as: Ibutamoren, Nutrobal, MK677

MK-677 (also called Ibutamoren or Nutrobal) is an oral ghrelin-mimetic small molecule in the Growth Hormone Secretagogue class. MK-677, also called ibutamoren, is an orally bioavailable non-peptide agonist at growth hormone secretagogue receptor 1a.

Calculate Dose

For research use only.

Key Facts

CAS
159752-10-0
Molecular Weight (MW)
624.8 g/mol
Half-life
Not reported in an indexed human study; the trials dosed once daily
FDA status
Not Approved
Evidence level
Clinical Trial Evidence
Human dose established
Yes
Administration Route
Oral
Frequency
Once daily in every trial reviewed here; two sleep and hormone studies gave it at bedtime
Last updated
Oct 5, 2026
Reviewed
Aug 30, 2026
Targets
GHSR

Vendor price snapshot

Each vendor counts once, at the median price per mg of its own listings; the typical range is the middle half of vendors. From public vendor listings collected between Dec 2025 and Oct 2026, so confirm the live price on the vendor site. Peptide Library does not sell peptides.

Vendors listing this peptide
10
Listed offers
21
Median price per mg
$3.22/mg
Typical $0.128–$11.81/mg

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Research summary

Oral non-peptide GH secretagogue (ibutamoren) that raises GH and IGF-1. Not FDA-approved. WADA S2 names ibutamoren (MK-677).

Peptide Library's MK-677 profile summarises 5 cited studies listed in the Science section, the compound's regulatory status, and research-protocol parameters reported for it. It is a research reference, not medical advice.

MK-677 dosage chart

MK-677 (ibutamoren mesylate) has no approved dosage, but it has been studied in randomised human trials. The year-long trials gave 25 mg by mouth once daily, in Alzheimer's disease, postmenopausal osteoporosis and healthy older adults (the last for up to 2 years); shorter studies used 2–50 mg. It reliably raised growth hormone and IGF-1 and increased fat-free mass, but it did not slow Alzheimer's disease, did not improve most functional measures after hip fracture or strength and function in healthy older adults, and it raised fasting glucose and reduced insulin sensitivity. A hip-fracture trial was stopped early over a heart failure safety signal. MK-677 is not a peptide: it is an orally active small-molecule agonist of the ghrelin receptor.

Clinical Trial Evidence
Dosage evidence summary for MK-677
Human dosing establishedYes
Studied dose range2–50 mg once daily studied in adults; 25 mg once daily in the year-long trials
RouteOral
FrequencyOnce daily in every trial reviewed here; two sleep and hormone studies gave it at bedtime
Duration studied4 days to 2 years; 12 months in the Alzheimer's and osteoporosis trials, up to 2 years in healthy older adults
TitrationThe year-long trials gave 25 mg daily without escalation. In the 2-year trial the dose was reduced, blinded, to 10 mg daily in 4 participants because of raised fasting glucose or joint pain.
Half-lifeNot reported in an indexed human study; the trials dosed once daily
Evidence levelClinical Trial Evidence
Last reviewed2026-10-05

Research-reported dosing

Doses as studied, one row per regimen. Different trials used different regimens; they are listed separately rather than averaged.

Research-reported dosing for MK-677, one row per studied regimen
Study / contextPopulationDoseRouteFrequencyDurationOutcome studiedSource
Two-year trial in healthy older adults (Nass et al., 2008)Clinical trial · Double-blind randomised placebo-controlled modified-crossover trial65 healthy adults aged 60–81: men, and women on or off hormone replacement therapy25 mg (reduced, blinded, to 10 mg daily in 4 participants)OralOnce daily12 months for the primary endpoints; 2 years in total, modified crossoverGrowth hormone and IGF-1 rose to young-adult levels. Fat-free mass increased 1.1 kg against a mean 0.5 kg fall on placebo; abdominal visceral fat and total fat mass did not differ from placebo, and strength and function did not change. Body weight rose 2.7 kg, fasting glucose rose 0.3 mmol/L and insulin sensitivity fell.Nass R et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial. Ann Intern Med. 2008.
Alzheimer's disease, 12 months (Sevigny et al., 2008; NCT00074529)Clinical trial · Multicentre double-blind randomised placebo-controlled trial563 patients with mild to moderate Alzheimer's disease randomised; 416 completed 12 months25 mgOralOnce daily12 monthsSerum IGF-1 rose 60.1% at 6 weeks and 72.9% at 12 months, but there was no difference from placebo on CIBIC-plus, ADAS-Cog, ADCS-ADL or CDR sum of boxes. The authors concluded it was ineffective at slowing progression.Sevigny JJ et al. Growth hormone secretagogue MK-677: no clinical effect on AD progression in a randomized trial. Neurology. 2008.
Hip fracture, phase IIb, terminated early (Adunsky et al., 2011; NCT00128115)Clinical trial · Phase IIb multicentre double-blind randomised placebo-controlled trial123 elderly patients recovering from hip fracture (62 on MK-0677, 61 on placebo)25 mgOralDaily24 weeks planned; the trial was terminated earlyIGF-1 rose 51.4 ng/mL versus placebo and gait speed improved, but stair-climbing power and most other functional measures did not. The trial was terminated early because of a safety signal of congestive heart failure in a limited number of patients, and the authors concluded MK-0677 has an unfavourable safety profile in this population.Adunsky A et al. MK-0677 (ibutamoren mesylate) for the treatment of patients recovering from hip fracture: a multicenter, randomized, placebo-controlled phase IIb study. Arch Gerontol Geriatr. 2011.
Postmenopausal osteoporosis, with and without alendronate (Murphy et al., 2001)Clinical trial · Multicentre double-blind randomised placebo-controlled trial292 women aged 64–85 with low femoral neck bone mineral density25 mg, alone or with alendronate 10 mgOralOnce daily12 months, with bone mineral density followed to 18 monthsIGF-1 rose 39–45% and bone turnover markers increased. Combined with alendronate it raised femoral neck bone mineral density more than alendronate alone (4.2% vs 2.5%), but not lumbar spine, total hip or total body density. Growth hormone-mediated side effects were reported in the MK-677 groups.Murphy MG et al. Effect of alendronate and MK-677 (a growth hormone secretagogue), individually and in combination, on markers of bone turnover and bone mineral density in postmenopausal osteoporotic women. J Clin Endocrinol Metab. 2001.
Obese men, 8 weeks (Svensson et al., 1998)Clinical trial · Double-blind randomised placebo-controlled parallel-group trial24 otherwise healthy obese men aged 18–50 (12 on MK-677, 12 on placebo)25 mgOralDaily8 weeksIGF-1 rose about 40% and fat-free mass increased; total and visceral fat did not change significantly. Basal metabolic rate rose at 2 weeks but not at 8 weeks. Oral glucose tolerance tests showed impaired glucose homeostasis at 2 and 8 weeks.Svensson J et al. Two-month treatment of obese subjects with the oral growth hormone (GH) secretagogue MK-677 increases GH secretion, fat-free mass, and energy expenditure. J Clin Endocrinol Metab. 1998.
Dose-ranging study in healthy older adults (Chapman et al., 1996)Clinical trial · Double-blind randomised placebo-controlled dose-ranging trial32 healthy adults aged 64–812, 10 or 25 mg, or placeboOralOnce dailyTwo study periods of 14 and 28 daysGrowth hormone rose in a dose-dependent manner; 25 mg raised mean 24-hour growth hormone by 97% and restored IGF-1 to young-adult levels. Fasting glucose rose from 5.4 to 6.8 mmol/L at 4 weeks.Chapman IM et al. Stimulation of the growth hormone (GH)-insulin-like growth factor I axis by daily oral administration of a GH secretogogue (MK-677) in healthy elderly subjects. J Clin Endocrinol Metab. 1996.
Adults with childhood-onset growth hormone deficiency, rising dose (Chapman et al., 1997)Clinical trial · Double-blind rising-dose study with a placebo crossover arm9 severely growth hormone-deficient men aged 17–34, treated with growth hormone in childhood10 mg, then 50 mg in 5 participants; the other 4 received placebo and 10 mg in crossoverOralOnce daily4 days per treatment period, two periods at least 28 days apartIGF-1 rose 52% on 10 mg and 79% on 50 mg, and 24-hour mean growth hormone rose 79–82%. Fasting and postprandial insulin and postprandial glucose increased.Chapman IM et al. Oral administration of growth hormone (GH) releasing peptide-mimetic MK-677 stimulates the GH/insulin-like growth factor-I axis in selected GH-deficient adults. J Clin Endocrinol Metab. 1997.
Sleep study in young and older adults (Copinschi et al., 1997)Clinical trial · Double-blind placebo-controlled crossover in young adults; sequential dosing without placebo in older adults8 healthy young adults aged 18–30 and 6 older adults aged 65–71Young adults: 5 mg, 25 mg and placebo in crossover. Older adults: 2 mg, then 25 mgOral, at bedtimeOnce daily at bedtime7-day periods in young adults; 14-day periods in older adultsIn young adults 25 mg increased stage IV sleep by about 50% and REM sleep by more than 20% versus placebo. In older adults REM sleep rose by nearly 50% and REM latency fell; the older group had no placebo period.Copinschi G et al. Prolonged oral treatment with MK-677, a novel growth hormone secretagogue, improves sleep quality in man. Neuroendocrinology. 1997.
NCT00395291 — haemodialysis patients, crossover, results postedClinical trial · Randomised blinded placebo-controlled crossover pilot study with posted resultsAdults with end-stage renal disease on haemodialysis (26 started treatment, 22 completed both periods)25 mgOralOnce dailyAbout 30 days per period, crossed over with placebo after a 30-day washoutIGF-1 rose by a mean 92.7 ng/mL after MK-0677 versus 6.7 ng/mL after placebo (p < 0.001). The posted serious adverse events for the MK-0677 period include one case of congestive heart failure; the published report (Campbell et al., 2018) found no serious adverse effects attributable to MK-0677.NCT00395291 — Growth Hormone Secretagogue MK-0677 Effect on IGF-1 Levels in ESRD Patients
NCT05364684 — non-alcoholic fatty liver disease pilot, results postedClinical trial · Single-arm open-label phase 2 pilot study with posted results12 adults aged 21–60 with a BMI of 25 or more and non-alcoholic fatty liver disease; 7 completed25 mg, given as LUM-201 (ibutamoren mesylate)OralOnce daily6 monthsLiver fat measured by MR spectroscopy did not fall: the mean change was +3.9 percentage points (SD 6.7; p = 0.4) in the 7 who completed. 7 of 12 reported increased appetite and 4 of 12 hyperglycaemia; there were no serious adverse events.NCT05364684 — The Impact of Ibutamoren on Nonalcoholic Fatty Liver Disease
NCT04614337 — OraGrowtH210, LUM-201 in children with growth hormone deficiency, results postedClinical trial · Phase 2 randomised open-label active-controlled trial with posted resultsPrepubertal children aged 3–12 with idiopathic growth hormone deficiency, not previously treated (18, 22 and 22 on the three LUM-201 doses; 20 on injected growth hormone)0.8, 1.6 or 3.2 mg/kg per day, given as LUM-201 (ibutamoren mesylate)OralOnce daily6-month primary analysis within a 24-month studySix-month annualised height velocity was 6.8, 8.2 and 7.7 cm per year on the three LUM-201 doses, against 10.6 cm per year on daily injected growth hormone at 34 mcg/kg.NCT04614337 — Phase 2 Study of LUM-201 in Children With Growth Hormone Deficiency (OraGrowtH210 Trial)
NCT06948214 — phase 3, LUM-201 in children with growth hormone deficiency, recruitingClinical trial · Phase 3 randomised placebo-controlled trial, recruitingPrepubertal children aged 3–11 with growth hormone deficiency, not previously treated (150 planned)1.6 mg/kg per day, given as LUM-201 (ibutamoren mesylate)OralOnce daily12 monthsAnnualised height velocity at 12 months versus placebo. No results have been posted.NCT06948214 — Phase 3 Study of LUM-201 in Children With Growth Hormone Deficiency

Where sources disagree

  • MK-677 is not a peptide. Ibutamoren mesylate is an orally active small molecule that activates the ghrelin receptor, and the trials themselves describe it as a nonpeptide growth hormone secretagogue. It is sold alongside peptides but shares neither their structure nor their handling: it is swallowed, not injected, and there is nothing to reconstitute.
  • No regulator has approved ibutamoren for any use. Merck took it through phase 2 trials as MK-0677, none of which led to an approved product, and it is now in development by Lumos Pharma as LUM-201 for children with growth hormone deficiency. DailyMed does carry two listings for ibutamoren mesylate powder from AX Pharmaceutical, but both are bulk-ingredient listings, categorised as a bulk ingredient for animal drug compounding, with no prescribing information or dose. A DailyMed listing is not an FDA approval.
  • Oral doses of 10–25 mg once daily are widely published for MK-677, and unlike most compounds sold alongside peptides those figures do match trial doses: 25 mg once daily is the dose in every year-long trial (Nass 2008, Sevigny 2008, Murphy 2001), and 10 mg appears in short dose-ranging studies. What does not carry over is the population. The trials enrolled older adults and people with obesity, Alzheimer's disease, hip fracture, osteoporosis, kidney failure or growth hormone deficiency; the only studies in healthy young adults that this review found lasted 7 days.
  • The fat-free mass gain is real in the trials but did not translate into function. In healthy older adults fat-free mass rose 1.1 kg over a year while strength and function did not change, abdominal visceral fat and total fat mass did not differ from placebo, and body weight rose 2.7 kg. In obese men over 8 weeks fat-free mass rose while total and visceral fat were unchanged.
  • Both large patient trials missed their goals. In 563 people with Alzheimer's disease, 12 months of 25 mg daily raised IGF-1 by 72.9% but did not slow decline on any of the four cognitive, functional or global measures. After hip fracture, IGF-1 rose but most functional measures did not improve, and the phase IIb trial was terminated early because of a safety signal of congestive heart failure. An earlier 161-patient hip-fracture trial (Bach et al., 2004) also found no significant difference in functional performance, and a 24-week fibromyalgia trial of 25 mg daily (NCT00116129) completed in 2008 without posting results.
  • The trials report consistent metabolic effects. Over a year in healthy older adults fasting glucose rose 0.3 mmol/L on average, HbA1c rose and insulin sensitivity fell, and the dose was cut to 10 mg in two participants because of raised fasting glucose; glucose tolerance was impaired in obese men within 2 weeks. Increased appetite, mild transient leg oedema and muscle pain were the most frequent side effects. In the fatty liver pilot, 7 of 12 participants reported increased appetite and 4 had hyperglycaemia.
  • A half-life of about 24 hours is widely quoted for MK-677. No primary source reviewed here states a human half-life: the Merck assay paper describes mapping the plasma time course after a single 5 mg dose but reports no half-life in its abstract, so none is given here. The trials simply dosed once daily.
  • Current development is paediatric and weight-based. As LUM-201, ibutamoren was given at 0.8–3.2 mg/kg once daily to children with growth hormone deficiency, and no dose matched daily injected growth hormone on 6-month height velocity. Those mg/kg doses do not convert into the fixed adult doses above.
  • Case reports in people taking MK-677 as a performance-enhancing supplement describe liver injury that resolved after stopping, and gynaecomastia with hypogonadism from supplements that also contained RAD-140, cardarine and undisclosed hormones. Single case reports do not establish cause, but they show that what is sold as MK-677 is not necessarily what the trials administered.

Handling & administration

Reconstitution Guide
Oral — no reconstitution
Timing Notes
Educational catalog only — not medical advice

Sequence & molecular data

Sequence and molecular data for MK-677
Molecular formulaC28H40N4O8S2
Molecular weight624.8 g/mol
CAS number159752-10-0
Half-life~24 hours
AppearanceOral capsule / powder
FormulationOral capsule
PubChem CID6450830
FDA UNIIR90JB6QJ2B
ChEMBLCHEMBL2105872

Identifiers link to the public PubChem, FDA Substance Registration (UNII), ChEMBL and DrugBank records for the same entity.

Science

Mechanism of Action

MK-677, also called ibutamoren, is an orally bioavailable non-peptide agonist at growth hormone secretagogue receptor 1a. It mimics ghrelin at the pituitary and hypothalamus, producing a sustained increase in growth hormone and IGF-1 with a half-life supporting once-daily dosing — the property that distinguishes it from injectable peptide secretagogues. Because it activates the ghrelin receptor it also increases appetite. The recognised metabolic consequences follow from sustained GH elevation: reduced insulin sensitivity and increased fasting glucose, together with fluid retention and oedema. It has been studied extensively but is not approved for any indication.

Origin

Synthetic spiropiperidine small molecule.

Targets

GHSR

Regulatory & research status

MK-677 is not an FDA-approved product. It is sold for laboratory research and has no approved medical use.

Regulatory and research status for MK-677
FDA statusNot Approved
AvailabilityResearch-Only
WADA (sport)Banned in Sport
Library classificationResearch-Only

Benefits

Oral GH-axis research tool

MK-677 side effects

The effects below are those reported in MK-677 clinical trials; long-term safety data may still be limited.

Side Effects

  • Hunger
  • Edema
  • Insulin resistance
  • Lethargy

Storage & stability

Lyophilized (freeze-dried) peptide powder is far more stable than the reconstituted solution. Keep sealed vials cold, dry and away from light; long-term storage is typically frozen, with short-term refrigeration for vials in use.

Once reconstituted in bacteriostatic water, keep the solution refrigerated, avoid repeated freeze–thaw cycles and agitation, and label the vial with the reconstitution date and concentration. Discard any solution that turns cloudy or shows particulates.

Degradation rates differ by sequence: peptides containing methionine, cysteine, asparagine or glutamine are more prone to oxidation and deamidation, so shelf life after reconstitution is compound-specific rather than universal.

Read the full guide: how to store peptides before and after reconstitution →

Source: Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Stability of protein pharmaceuticals: an update. Pharm Res. 2010;27(4):544–575. (PMID 20143256). General guidance for research handling; not product-specific instructions.

MK-677: frequently asked questions

What is MK-677?

Oral non-peptide GH secretagogue (ibutamoren) that raises GH and IGF-1. Not FDA-approved. WADA S2 names ibutamoren (MK-677).

What are the side effects of MK-677?

MK-677 has no controlled human safety data, so its side-effect profile is not well established. Effects recorded on this profile include hunger, edema, insulin resistance and lethargy. It is on the WADA Prohibited List for athletes. This is reference information, not medical advice.

How does MK-677 work?

MK-677, also called ibutamoren, is an orally bioavailable non-peptide agonist at growth hormone secretagogue receptor 1a. It mimics ghrelin at the pituitary and hypothalamus, producing a sustained increase in growth hormone and IGF-1 with a half-life supporting once-daily dosing — the property that distinguishes it from injectable peptide secretagogues.

Is MK-677 FDA approved?

No. MK-677 is not approved by the FDA for any indication and is categorised as research-only. It has not been reviewed for safety or efficacy as a medicine, and published research should be read as investigation rather than established use.

What is the half-life of MK-677?

Reported half-life for MK-677 is ~24 hours. Half-life describes how long the compound persists in circulation, not how long any effect lasts, and published figures vary with route of administration, formulation and the population studied.

Is MK-677 banned in sport?

MK-677 is recorded here as prohibited in sport. Athletes subject to anti-doping rules should check the current WADA Prohibited List directly, since it is revised annually and classifications change.

What peptides are similar to MK-677?

Compounds most often compared with MK-677 include Ipamorelin, GHRP-6, GHRP-1 and Pralmorelin (GHRP-2). They are grouped by shared mechanism or research area rather than by equivalence, and their regulatory status and evidence base differ.

References

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Compiled by Peptide Library Editorial · Reviewed Aug 30, 2026 · Updated Oct 5, 2026 · Version 5

This MK-677 profile is compiled from published literature (5 cited studies linked above), public regulatory records and chemical registries. It describes what research reports; it is not medical advice, and nothing here is a dosing recommendation for humans. Peptide Library does not sell peptides. Editorial policy · How profiles are compiled · Report an error

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