Ibutamoren
updated
Ibutamoren raises growth hormone, IGF-1, and fat-free mass. In the main older-adult trial, it did not improve strength or physical function and increased body weight and glucose measures. A separate hip-fracture trial stopped early after a congestive-heart-failure signal.
Oral small-molecule ghrelin-receptor agonist
- Investigational small molecule, not a peptide
- Also studied as MK-677, MK-0677, and LUM-201
- Free base and mesylate are distinct substance records
Are ibutamoren, ibutamoren mesylate, MK-677, MK-0677, and LUM-201 interchangeable?
The names point to the same active-moiety development family, but they do not define the same material. FDA substance records distinguish ibutamoren free base from its mesylate salt, and a gray-market label does not establish which form, purity, formulation, or exposure it contains.
| Record | Formula | Molecular weight | CAS | UNII |
|---|---|---|---|---|
| Ibutamoren free base | C27H36N4O5S | 528.67 | 159634-47-6 | GJ0EGN38UL |
| Ibutamoren mesylate | C27H36N4O5S·CH4O3S | 624.77 | 159752-10-0 | R90JB6QJ2B |
A UNII identifies a substance; it does not mean the substance or a finished product is approved.
Is the often-quoted human half-life established?
The cited human evidence does not include a qualifying concentration-time dataset. FDA's 2024 literature review found only statements that MK-677 had high oral bioavailability, a long duration of action, or 24-hour activity, without supporting pharmacokinetic detail, and found no additional clinical pharmacokinetic data. A duration-of-action statement is not a measured elimination half-life.
FDA 2024 briefing · evidence, PK, and safety review
Official regulatory evidence review
FDA Pharmacy Compounding Advisory Committee briefing document, October 29, 2024
FDA found insufficient evidence of effectiveness for the nominated uses, serious safety concerns including hyperglycemia, liver-enzyme elevation, edema, fluid overload, and CHF in older hip-fracture patients, and no detailed public clinical pharmacokinetic dataset beyond unsupported general statements.
- FDA proposed not adding ibutamoren mesylate to the 503A Bulks List.
- The review separately analyzed older-adult, hip-fracture, obesity, Alzheimer disease, osteoporosis, and pediatric growth-hormone-deficiency evidence.
- Participants / model
- Published clinical programs and compounding nomination evidence
- Treatment
- Ibutamoren mesylate across investigated uses
- Follow-up
- Literature and safety review current to the 2024 meeting
- Study design
- FDA regulatory review, not a clinical trial
The FDA review found no detailed public clinical pharmacokinetic dataset beyond unsupported general statements.
Read the original sourceFDA substance record · free base
Official substance identity record
U.S. Food and Drug Administration, Global Substance Registration System
The record classifies ibutamoren as a chemical and gives formula C27H36N4O5S, molecular weight 528.67, CAS 159634-47-6, and UNII GJ0EGN38UL.
- Participants / model
- Not applicable
- Treatment
- Not applicable
- Study design
- Official chemical-substance registry
A UNII does not imply product approval.
Read the original sourceFDA substance record · mesylate salt
Official substance identity record
U.S. Food and Drug Administration, Global Substance Registration System
The record gives formula C27H36N4O5S·CH4O3S, molecular weight 624.77, CAS 159752-10-0, UNII R90JB6QJ2B, and links the salt to ibutamoren as its active moiety.
- Synonyms include MK-0677 and MK-677.
- Participants / model
- Not applicable
- Treatment
- Not applicable
- Study design
- Official chemical-substance registry
A substance identity record does not establish a finished product's formulation, quality, or approval.
Read the original sourceIs ibutamoren an FDA-approved drug or dietary supplement?
No. FDA stated in September 2025 that ibutamoren is not an approved active ingredient and that its safety and efficacy have not been established. FDA also lists ibutamoren mesylate in Category 2 for both 503A and 503B compounding because of potential significant safety risks.
FDA laboratory testing found undeclared ibutamoren in a children's growth product in 2025. A separate December 2025 warning letter said ibutamoren is excluded from the dietary-supplement definition because substantial publicly known new-drug investigations preceded any shown food or supplement marketing. Both actions concern the U.S. market; ibutamoren remains unapproved.
Development is active under the name LUM-201. ClinicalTrials.gov listed a sponsor-run Phase 3 pediatric growth-hormone-deficiency trial as recruiting, with no posted results, in a record updated September 4, 2026. The pediatric protocol reports no bodybuilding or anti-aging outcomes.
FDA 2025 alert · unapproved hidden ibutamoren
Official FDA laboratory and safety notification
U.S. Food and Drug Administration, September 23, 2025
FDA laboratory analysis found undeclared ibutamoren in a product promoted for children and stated that ibutamoren is not FDA approved. FDA named increased appetite, water retention, fatigue, muscle pain, glucose and insulin-sensitivity changes, possible congestive-heart-failure risk, unknown long-term effects, and possible harmful interactions.
- Participants / model
- Product promoted for children aged five and older; risk statements draw on broader evidence
- Treatment
- A named product containing undeclared ibutamoren
- Study design
- FDA product testing and public-health notification
The laboratory finding applies to the named product; the approval and ibutamoren safety statements are FDA's broader regulatory assessment.
Read the original sourceFDA current list · potential CHF risk
Current official compounding-risk page
U.S. Food and Drug Administration, Category 2 bulk substances
FDA lists ibutamoren mesylate in Category 2 under both the 503A and 503B interim policies because of potential significant safety risk, specifically the congestive-heart-failure signal in the terminated hip-fracture trial.
- Participants / model
- Compounding nominations and human safety evidence
- Treatment
- Ibutamoren mesylate bulk substance
- Study design
- FDA regulatory risk listing
Category 2 is an interim compounding-policy status, not a clinical-trial result or product approval.
Read the original sourceFDA 2025 letter · excluded from supplement definition
Official enforcement letter
U.S. Food and Drug Administration, December 12, 2025
FDA said the named GE Labs MK 677 product contained ibutamoren and that ibutamoren is excluded from the dietary-supplement definition because substantial public new-drug investigations preceded any shown food or supplement marketing.
- Participants / model
- The named company, product, and U.S. dietary-supplement claims
- Treatment
- GE Labs MK 677
- Follow-up
- Letter issued December 12, 2025
- Study design
- FDA enforcement document
The product findings are seller-specific; the statutory conclusion concerns ibutamoren's dietary-supplement status.
Read the original sourceNCT06948214 · recruiting, no results posted
Current clinical-trial registry record
ClinicalTrials.gov, NCT06948214, record updated September 4, 2026
The sponsor record lists a Phase 3, randomized, placebo-controlled pediatric growth-hormone-deficiency trial as recruiting, with an estimated enrollment of 150 and no posted results.
- Participants / model
- Treatment-naive children with pediatric growth hormone deficiency selected under trial criteria
- Treatment
- Once-daily oral LUM-201 versus matched placebo
- Follow-up
- Active Phase 3 registry record
- Study design
- Randomized parallel Phase 3 trial; registry-only, no results posted
- Funding
- Lumos Pharma
The recruiting record had no posted efficacy results and enrolled children with growth-hormone deficiency, not adults seeking bodybuilding or anti-aging effects.
Read the original sourceWhat do the human trials establish about mechanism and biomarkers?
Oral MK-677 increases pulsatile endogenous growth-hormone secretion and circulating IGF-1. In the cited trials, those biomarker changes did not produce consistent gains in strength, mobility, or recovery, and longevity was not measured.
Ibutamoren is a ghrelin or growth-hormone-secretagogue receptor agonist. In the 12-month older-adult comparison, 24-hour mean growth hormone rose about 1.8-fold and IGF-1 about 1.5-fold from baseline in the active group. In the later hip-fracture trial, the between-group IGF-1 difference was 51.4 ng/mL at 24 weeks.
The drug stimulates release of the participant's own growth hormone; it is not injected growth hormone or IGF-1. In the older-adult and hip-fracture trials, higher IGF-1 did not produce consistent strength or recovery gains.
71-person RCT · fat-free mass without function
Randomized double-blind placebo-controlled trial
Nass R, et al. Annals of Internal Medicine. 2008;149(9):601-611
At 12 months, MK-677 increased fat-free mass and body weight but did not improve strength or function. Fasting glucose and HbA1c increased, insulin sensitivity declined, and increased appetite, edema, and muscle pain were reported more often numerically than with placebo.
- Fat-free mass: +1.1 kg with MK-677 versus -0.5 kg with placebo; P<0.001 for the between-group comparison.
- Body weight: +2.7 kg versus +0.8 kg; fasting glucose: +5 mg/dL versus no increase.
- Participants / model
- 71 healthy adults aged 60 to 81; 65 completed year one
- Treatment
- MK-677 25 mg once daily versus placebo, randomized 2:1
- Follow-up
- 12-month pivotal comparison with exploratory modified-crossover follow-up through 24 months
- Study design
- Randomized double-blind placebo-controlled modified-crossover trial
- Funding
- NIH-funded investigator-initiated study; Merck Research Laboratories supplied blinded tablets
The small selected cohort excluded diabetes and several common comorbidities and was not powered for clinical function or uncommon safety events.
Read the original source123-person Phase 2b · mixed function, CHF stop
Randomized double-blind placebo-controlled Phase 2b trial
Adunsky A, et al. Archives of Gerontology and Geriatrics. 2011;53(2):183-189
The trial randomized 123 older hip-fracture patients. Gait ranking favored MK-0677, stair-climbing power and several other functional measures did not, and the trial stopped early after CHF occurred in four active recipients versus one placebo recipient.
- MK-0677 25 mg/day: 62 randomized; placebo: 61 randomized; 83 completed treatment.
- Any adverse event: 77% versus 55%; serious adverse event: 24% versus 13%.
- Participants / model
- Selected adults aged 60 or older after recent unilateral hip-fracture repair
- Treatment
- MK-0677 25 mg once daily versus placebo
- Follow-up
- Up to 24 weeks; terminated early
- Study design
- Multicenter randomized double-blind placebo-controlled Phase 2b trial
- Funding
- Merck Research Laboratories; all authors except Abraham Adunsky were Merck employees and could hold company equity
Small sample, selected mostly white population, heterogeneous rehabilitation settings, early termination, and no single primary functional endpoint limit efficacy and safety estimates.
Read the original sourceFDA 2024 briefing · evidence, PK, and safety review
Official regulatory evidence review
FDA Pharmacy Compounding Advisory Committee briefing document, October 29, 2024
FDA found insufficient evidence of effectiveness for the nominated uses, serious safety concerns including hyperglycemia, liver-enzyme elevation, edema, fluid overload, and CHF in older hip-fracture patients, and no detailed public clinical pharmacokinetic dataset beyond unsupported general statements.
- FDA proposed not adding ibutamoren mesylate to the 503A Bulks List.
- The review separately analyzed older-adult, hip-fracture, obesity, Alzheimer disease, osteoporosis, and pediatric growth-hormone-deficiency evidence.
- Participants / model
- Published clinical programs and compounding nomination evidence
- Treatment
- Ibutamoren mesylate across investigated uses
- Follow-up
- Literature and safety review current to the 2024 meeting
- Study design
- FDA regulatory review, not a clinical trial
The FDA review found no detailed public clinical pharmacokinetic dataset beyond unsupported general statements.
Read the original sourceDid the healthy older-adult trial show more muscle or better function?
It showed more fat-free mass, not better strength or physical function. Seventy-one healthy adults aged 60 to 81 were randomized 2:1 to MK-677 or placebo; 65 completed the first year.
At 12 months, mean fat-free mass changed by +1.1 kg with MK-677 and -0.5 kg with placebo, a 1.6 kg between-group difference. Total body water increased by 1.7 kg with MK-677 and 0.1 kg with placebo. The paper also found no significant increase in thigh-muscle cross-sectional area and no significant change in any tested strength or function measure.
Fat-free mass includes water, organs, bone, and lean tissue; DXA does not measure contractile muscle quality. The authors interpreted the accompanying intracellular-water and appendicular-lean changes as body-cell and anabolic effects, but strength, walking, chair-rise, and stair measures did not improve significantly.
The participants were selected healthy older adults. The trial excluded diabetes, smoking, BMI of 35 or higher, untreated hypertension, most malignancy histories, and medications affecting growth-hormone secretion. It was not a sarcopenia trial or an athletic-performance trial.
71-person RCT · fat-free mass without function
Randomized double-blind placebo-controlled trial
Nass R, et al. Annals of Internal Medicine. 2008;149(9):601-611
At 12 months, MK-677 increased fat-free mass and body weight but did not improve strength or function. Fasting glucose and HbA1c increased, insulin sensitivity declined, and increased appetite, edema, and muscle pain were reported more often numerically than with placebo.
- Fat-free mass: +1.1 kg with MK-677 versus -0.5 kg with placebo; P<0.001 for the between-group comparison.
- Body weight: +2.7 kg versus +0.8 kg; fasting glucose: +5 mg/dL versus no increase.
- Participants / model
- 71 healthy adults aged 60 to 81; 65 completed year one
- Treatment
- MK-677 25 mg once daily versus placebo, randomized 2:1
- Follow-up
- 12-month pivotal comparison with exploratory modified-crossover follow-up through 24 months
- Study design
- Randomized double-blind placebo-controlled modified-crossover trial
- Funding
- NIH-funded investigator-initiated study; Merck Research Laboratories supplied blinded tablets
The small selected cohort excluded diabetes and several common comorbidities and was not powered for clinical function or uncommon safety events.
Read the original sourceWhat did the older-adult trial show about glucose, appetite, weight, edema, and pain?
MK-677 increased fasting glucose, HbA1c, body weight, and appetite, and it reduced estimated insulin sensitivity. Edema and muscle pain were also more common numerically than with placebo.
At one year, fasting glucose increased by 5 mg/dL with MK-677 and did not increase with placebo; HbA1c changed by +0.2 percentage points versus -0.1, and the QUICKI estimate of insulin sensitivity declined. Two active recipients required blinded dose reduction for increased fasting glucose during their initial active exposure; one withdrew after three months.
| Effect | MK-677 | Placebo | Between-group P value |
|---|---|---|---|
| Increased appetite | 29/43 (67%) | 8/22 (36%) | 0.02 |
| Mild transient edema | 19/43 (44%) | 6/22 (27%) | 0.3 |
| Transient muscle pain | 14/43 (33%) | 2/22 (9%) | 0.1 |
Only the appetite difference met the paper's conventional significance threshold. The small trial was not powered to rule out less common serious harms.
Mean body weight increased 2.7 kg with MK-677 and 0.8 kg with placebo. Abdominal visceral fat and total fat mass did not differ significantly, although limb fat increased more with MK-677. The fat-free-mass change also included a 1.7 kg increase in total body water.
71-person RCT · fat-free mass without function
Randomized double-blind placebo-controlled trial
Nass R, et al. Annals of Internal Medicine. 2008;149(9):601-611
At 12 months, MK-677 increased fat-free mass and body weight but did not improve strength or function. Fasting glucose and HbA1c increased, insulin sensitivity declined, and increased appetite, edema, and muscle pain were reported more often numerically than with placebo.
- Fat-free mass: +1.1 kg with MK-677 versus -0.5 kg with placebo; P<0.001 for the between-group comparison.
- Body weight: +2.7 kg versus +0.8 kg; fasting glucose: +5 mg/dL versus no increase.
- Participants / model
- 71 healthy adults aged 60 to 81; 65 completed year one
- Treatment
- MK-677 25 mg once daily versus placebo, randomized 2:1
- Follow-up
- 12-month pivotal comparison with exploratory modified-crossover follow-up through 24 months
- Study design
- Randomized double-blind placebo-controlled modified-crossover trial
- Funding
- NIH-funded investigator-initiated study; Merck Research Laboratories supplied blinded tablets
The small selected cohort excluded diabetes and several common comorbidities and was not powered for clinical function or uncommon safety events.
Read the original sourceFDA 2025 alert · unapproved hidden ibutamoren
Official FDA laboratory and safety notification
U.S. Food and Drug Administration, September 23, 2025
FDA laboratory analysis found undeclared ibutamoren in a product promoted for children and stated that ibutamoren is not FDA approved. FDA named increased appetite, water retention, fatigue, muscle pain, glucose and insulin-sensitivity changes, possible congestive-heart-failure risk, unknown long-term effects, and possible harmful interactions.
- Participants / model
- Product promoted for children aged five and older; risk statements draw on broader evidence
- Treatment
- A named product containing undeclared ibutamoren
- Study design
- FDA product testing and public-health notification
The laboratory finding applies to the named product; the approval and ibutamoren safety statements are FDA's broader regulatory assessment.
Read the original sourceFDA 2024 briefing · evidence, PK, and safety review
Official regulatory evidence review
FDA Pharmacy Compounding Advisory Committee briefing document, October 29, 2024
FDA found insufficient evidence of effectiveness for the nominated uses, serious safety concerns including hyperglycemia, liver-enzyme elevation, edema, fluid overload, and CHF in older hip-fracture patients, and no detailed public clinical pharmacokinetic dataset beyond unsupported general statements.
- FDA proposed not adding ibutamoren mesylate to the 503A Bulks List.
- The review separately analyzed older-adult, hip-fracture, obesity, Alzheimer disease, osteoporosis, and pediatric growth-hormone-deficiency evidence.
- Participants / model
- Published clinical programs and compounding nomination evidence
- Treatment
- Ibutamoren mesylate across investigated uses
- Follow-up
- Literature and safety review current to the 2024 meeting
- Study design
- FDA regulatory review, not a clinical trial
The FDA review found no detailed public clinical pharmacokinetic dataset beyond unsupported general statements.
Read the original sourceWhat did the hip-fracture trials show, and why did the later trial stop?
Two randomized placebo-controlled hip-fracture trials raised IGF-1 without a reliable overall recovery benefit. The later 123-person trial found one gait signal among mostly negative functional outcomes and stopped early after more congestive-heart-failure cases with MK-0677.
What happened in the earlier 161-person trial?
Adults aged 65 or older who had recently undergone hip-fracture repair were randomized to daily MK-0677 or placebo for six months and followed for six more months. IGF-1 rose 84% with MK-0677 and 17% with placebo, but the groups did not differ significantly on the functional-performance panel, overall Sickness Impact Profile for Nursing Homes score, or independent-living outcome. The trial excluded congestive heart failure and diabetes.
161-person RCT · IGF-1 rose, function uncertain
Randomized double-blind placebo-controlled trial
Bach MA, et al. Journal of the American Geriatrics Society. 2004;52(4):516-523
Among 161 previously mobile adults aged at least 65 after hip fracture, six months of MK-0677 increased IGF-1 but produced no statistically significant between-group differences in the functional-performance panel, overall nursing-home Sickness Impact Profile score, or independent-living outcome.
- IGF-1 increased 84% with MK-0677 and 17% with placebo.
- Participants / model
- 161 medically stable, mentally competent, previously ambulatory adults aged 65 or older after hip-fracture repair
- Treatment
- Daily MK-0677 versus placebo
- Follow-up
- Six months of treatment and six months of follow-up
- Study design
- Multicenter randomized double-blind placebo-controlled trial
- Funding
- Merck clinical development program
The trial excluded diabetes and congestive heart failure; favorable directions on several individual measures were not statistically significant.
Read the original sourceWhat happened in the later 123-person trial?
Participants aged 60 or older were randomized to MK-0677 25 mg daily, 62 people, or placebo, 61 people, for up to 24 weeks. Stair-climbing power differed by 12.5 W, with a 95% confidence interval from -10.95 to 35.88 and P=0.292. A gait-speed ranking favored MK-0677 by 0.7 score units, 95% CI 0.17 to 1.28, P=0.011, while several other functional measures did not improve and the fewer-falls comparison was not statistically significant at P=0.096.
Congestive heart failure occurred in 4 of 62 active recipients, 6.5%, and 1 of 61 placebo recipients, 1.7%. One or more adverse events occurred in 77% versus 55%, serious adverse events in 24% versus 13%, and adverse-event discontinuations in 11.3% versus 6.6%. The trial stopped early for the heart-failure signal. The authors described the safety profile as unfavorable in this selected post-fracture population.
123-person Phase 2b · mixed function, CHF stop
Randomized double-blind placebo-controlled Phase 2b trial
Adunsky A, et al. Archives of Gerontology and Geriatrics. 2011;53(2):183-189
The trial randomized 123 older hip-fracture patients. Gait ranking favored MK-0677, stair-climbing power and several other functional measures did not, and the trial stopped early after CHF occurred in four active recipients versus one placebo recipient.
- MK-0677 25 mg/day: 62 randomized; placebo: 61 randomized; 83 completed treatment.
- Any adverse event: 77% versus 55%; serious adverse event: 24% versus 13%.
- Participants / model
- Selected adults aged 60 or older after recent unilateral hip-fracture repair
- Treatment
- MK-0677 25 mg once daily versus placebo
- Follow-up
- Up to 24 weeks; terminated early
- Study design
- Multicenter randomized double-blind placebo-controlled Phase 2b trial
- Funding
- Merck Research Laboratories; all authors except Abraham Adunsky were Merck employees and could hold company equity
Small sample, selected mostly white population, heterogeneous rehabilitation settings, early termination, and no single primary functional endpoint limit efficacy and safety estimates.
Read the original sourceFDA 2024 briefing · evidence, PK, and safety review
Official regulatory evidence review
FDA Pharmacy Compounding Advisory Committee briefing document, October 29, 2024
FDA found insufficient evidence of effectiveness for the nominated uses, serious safety concerns including hyperglycemia, liver-enzyme elevation, edema, fluid overload, and CHF in older hip-fracture patients, and no detailed public clinical pharmacokinetic dataset beyond unsupported general statements.
- FDA proposed not adding ibutamoren mesylate to the 503A Bulks List.
- The review separately analyzed older-adult, hip-fracture, obesity, Alzheimer disease, osteoporosis, and pediatric growth-hormone-deficiency evidence.
- Participants / model
- Published clinical programs and compounding nomination evidence
- Treatment
- Ibutamoren mesylate across investigated uses
- Follow-up
- Literature and safety review current to the 2024 meeting
- Study design
- FDA regulatory review, not a clinical trial
The FDA review found no detailed public clinical pharmacokinetic dataset beyond unsupported general statements.
Read the original sourceThese patients were medically vulnerable and recently injured, so the 6.5% versus 1.7% heart-failure rates cannot be transferred numerically to healthy adults. The trial nevertheless stopped early because of that imbalance.
Can the 123-person publication and 83-person registry counts be reconciled?
Partly. The paper says 123 were randomized and 83 completed treatment. ClinicalTrials.gov lists actual enrollment as 83. Because both sources identify the same protocol, 0677-032 and NCT00128115, the matching number strongly suggests the registry field reflects completers, but the registry does not explain why it labels that number enrollment.
The publication reports 62 active and 61 placebo assignments, then 39 active and 44 placebo completers. Those completion counts total 83. The current registry, last updated in 2016, has no posted results and gives 83 as actual enrollment. Its late history shows the 83 field appeared with the corrected sponsor protocol number, but no public note resolves the field-definition mismatch.
The publication's 123 randomized participants provide the treatment and safety denominators. Its 83 completers match the registry's stated enrollment, but the registry does not explain that field.
123-person Phase 2b · mixed function, CHF stop
Randomized double-blind placebo-controlled Phase 2b trial
Adunsky A, et al. Archives of Gerontology and Geriatrics. 2011;53(2):183-189
The trial randomized 123 older hip-fracture patients. Gait ranking favored MK-0677, stair-climbing power and several other functional measures did not, and the trial stopped early after CHF occurred in four active recipients versus one placebo recipient.
- MK-0677 25 mg/day: 62 randomized; placebo: 61 randomized; 83 completed treatment.
- Any adverse event: 77% versus 55%; serious adverse event: 24% versus 13%.
- Participants / model
- Selected adults aged 60 or older after recent unilateral hip-fracture repair
- Treatment
- MK-0677 25 mg once daily versus placebo
- Follow-up
- Up to 24 weeks; terminated early
- Study design
- Multicenter randomized double-blind placebo-controlled Phase 2b trial
- Funding
- Merck Research Laboratories; all authors except Abraham Adunsky were Merck employees and could hold company equity
Small sample, selected mostly white population, heterogeneous rehabilitation settings, early termination, and no single primary functional endpoint limit efficacy and safety estimates.
Read the original sourceNCT00128115 · 83 registry count, no results
Clinical-trial registry record and history
ClinicalTrials.gov, NCT00128115, last update posted January 20, 2016
The registry identifies terminated protocol 0677-032, gives actual enrollment as 83, and posts no results. The linked publication identifies 123 randomized and 83 completers.
- Current registry count: 83 actual enrollment.
- The 83 field appeared in a late record update; the public history gives no reason for using the completion count as enrollment.
- Participants / model
- Patients recovering from hip fracture
- Treatment
- MK-0677 versus placebo
- Follow-up
- Trial completed in 2007; registry last updated in 2016
- Study design
- Randomized parallel double-blind Phase 2 registry record; no results posted
- Funding
- Merck Sharp & Dohme LLC
The registry's enrollment field conflicts with the publication. The numerical match to completers is strong but does not reveal why the field was entered that way.
Read the original sourceStudies and sources
FDA substance record · free base
Official substance identity record
U.S. Food and Drug Administration, Global Substance Registration System
The record classifies ibutamoren as a chemical and gives formula C27H36N4O5S, molecular weight 528.67, CAS 159634-47-6, and UNII GJ0EGN38UL.
- Participants / model
- Not applicable
- Treatment
- Not applicable
- Study design
- Official chemical-substance registry
A UNII does not imply product approval.
Read the original sourceFDA substance record · mesylate salt
Official substance identity record
U.S. Food and Drug Administration, Global Substance Registration System
The record gives formula C27H36N4O5S·CH4O3S, molecular weight 624.77, CAS 159752-10-0, UNII R90JB6QJ2B, and links the salt to ibutamoren as its active moiety.
- Synonyms include MK-0677 and MK-677.
- Participants / model
- Not applicable
- Treatment
- Not applicable
- Study design
- Official chemical-substance registry
A substance identity record does not establish a finished product's formulation, quality, or approval.
Read the original sourceFDA current list · potential CHF risk
Current official compounding-risk page
U.S. Food and Drug Administration, Category 2 bulk substances
FDA lists ibutamoren mesylate in Category 2 under both the 503A and 503B interim policies because of potential significant safety risk, specifically the congestive-heart-failure signal in the terminated hip-fracture trial.
- Participants / model
- Compounding nominations and human safety evidence
- Treatment
- Ibutamoren mesylate bulk substance
- Study design
- FDA regulatory risk listing
Category 2 is an interim compounding-policy status, not a clinical-trial result or product approval.
Read the original sourceFDA 2025 letter · excluded from supplement definition
Official enforcement letter
U.S. Food and Drug Administration, December 12, 2025
FDA said the named GE Labs MK 677 product contained ibutamoren and that ibutamoren is excluded from the dietary-supplement definition because substantial public new-drug investigations preceded any shown food or supplement marketing.
- Participants / model
- The named company, product, and U.S. dietary-supplement claims
- Treatment
- GE Labs MK 677
- Follow-up
- Letter issued December 12, 2025
- Study design
- FDA enforcement document
The product findings are seller-specific; the statutory conclusion concerns ibutamoren's dietary-supplement status.
Read the original sourceNCT06948214 · recruiting, no results posted
Current clinical-trial registry record
ClinicalTrials.gov, NCT06948214, record updated September 4, 2026
The sponsor record lists a Phase 3, randomized, placebo-controlled pediatric growth-hormone-deficiency trial as recruiting, with an estimated enrollment of 150 and no posted results.
- Participants / model
- Treatment-naive children with pediatric growth hormone deficiency selected under trial criteria
- Treatment
- Once-daily oral LUM-201 versus matched placebo
- Follow-up
- Active Phase 3 registry record
- Study design
- Randomized parallel Phase 3 trial; registry-only, no results posted
- Funding
- Lumos Pharma
The recruiting record had no posted efficacy results and enrolled children with growth-hormone deficiency, not adults seeking bodybuilding or anti-aging effects.
Read the original sourceFDA 2024 briefing · evidence, PK, and safety review
Official regulatory evidence review
FDA Pharmacy Compounding Advisory Committee briefing document, October 29, 2024
FDA found insufficient evidence of effectiveness for the nominated uses, serious safety concerns including hyperglycemia, liver-enzyme elevation, edema, fluid overload, and CHF in older hip-fracture patients, and no detailed public clinical pharmacokinetic dataset beyond unsupported general statements.
- FDA proposed not adding ibutamoren mesylate to the 503A Bulks List.
- The review separately analyzed older-adult, hip-fracture, obesity, Alzheimer disease, osteoporosis, and pediatric growth-hormone-deficiency evidence.
- Participants / model
- Published clinical programs and compounding nomination evidence
- Treatment
- Ibutamoren mesylate across investigated uses
- Follow-up
- Literature and safety review current to the 2024 meeting
- Study design
- FDA regulatory review, not a clinical trial
The FDA review found no detailed public clinical pharmacokinetic dataset beyond unsupported general statements.
Read the original source71-person RCT · fat-free mass without function
Randomized double-blind placebo-controlled trial
Nass R, et al. Annals of Internal Medicine. 2008;149(9):601-611
At 12 months, MK-677 increased fat-free mass and body weight but did not improve strength or function. Fasting glucose and HbA1c increased, insulin sensitivity declined, and increased appetite, edema, and muscle pain were reported more often numerically than with placebo.
- Fat-free mass: +1.1 kg with MK-677 versus -0.5 kg with placebo; P<0.001 for the between-group comparison.
- Body weight: +2.7 kg versus +0.8 kg; fasting glucose: +5 mg/dL versus no increase.
- Participants / model
- 71 healthy adults aged 60 to 81; 65 completed year one
- Treatment
- MK-677 25 mg once daily versus placebo, randomized 2:1
- Follow-up
- 12-month pivotal comparison with exploratory modified-crossover follow-up through 24 months
- Study design
- Randomized double-blind placebo-controlled modified-crossover trial
- Funding
- NIH-funded investigator-initiated study; Merck Research Laboratories supplied blinded tablets
The small selected cohort excluded diabetes and several common comorbidities and was not powered for clinical function or uncommon safety events.
Read the original source161-person RCT · IGF-1 rose, function uncertain
Randomized double-blind placebo-controlled trial
Bach MA, et al. Journal of the American Geriatrics Society. 2004;52(4):516-523
Among 161 previously mobile adults aged at least 65 after hip fracture, six months of MK-0677 increased IGF-1 but produced no statistically significant between-group differences in the functional-performance panel, overall nursing-home Sickness Impact Profile score, or independent-living outcome.
- IGF-1 increased 84% with MK-0677 and 17% with placebo.
- Participants / model
- 161 medically stable, mentally competent, previously ambulatory adults aged 65 or older after hip-fracture repair
- Treatment
- Daily MK-0677 versus placebo
- Follow-up
- Six months of treatment and six months of follow-up
- Study design
- Multicenter randomized double-blind placebo-controlled trial
- Funding
- Merck clinical development program
The trial excluded diabetes and congestive heart failure; favorable directions on several individual measures were not statistically significant.
Read the original source123-person Phase 2b · mixed function, CHF stop
Randomized double-blind placebo-controlled Phase 2b trial
Adunsky A, et al. Archives of Gerontology and Geriatrics. 2011;53(2):183-189
The trial randomized 123 older hip-fracture patients. Gait ranking favored MK-0677, stair-climbing power and several other functional measures did not, and the trial stopped early after CHF occurred in four active recipients versus one placebo recipient.
- MK-0677 25 mg/day: 62 randomized; placebo: 61 randomized; 83 completed treatment.
- Any adverse event: 77% versus 55%; serious adverse event: 24% versus 13%.
- Participants / model
- Selected adults aged 60 or older after recent unilateral hip-fracture repair
- Treatment
- MK-0677 25 mg once daily versus placebo
- Follow-up
- Up to 24 weeks; terminated early
- Study design
- Multicenter randomized double-blind placebo-controlled Phase 2b trial
- Funding
- Merck Research Laboratories; all authors except Abraham Adunsky were Merck employees and could hold company equity
Small sample, selected mostly white population, heterogeneous rehabilitation settings, early termination, and no single primary functional endpoint limit efficacy and safety estimates.
Read the original sourceNCT00128115 · 83 registry count, no results
Clinical-trial registry record and history
ClinicalTrials.gov, NCT00128115, last update posted January 20, 2016
The registry identifies terminated protocol 0677-032, gives actual enrollment as 83, and posts no results. The linked publication identifies 123 randomized and 83 completers.
- Current registry count: 83 actual enrollment.
- The 83 field appeared in a late record update; the public history gives no reason for using the completion count as enrollment.
- Participants / model
- Patients recovering from hip fracture
- Treatment
- MK-0677 versus placebo
- Follow-up
- Trial completed in 2007; registry last updated in 2016
- Study design
- Randomized parallel double-blind Phase 2 registry record; no results posted
- Funding
- Merck Sharp & Dohme LLC
The registry's enrollment field conflicts with the publication. The numerical match to completers is strong but does not reveal why the field was entered that way.
Read the original sourceWhy is Ibutamoren in D tier?
D tier follows measurable endocrine and body-composition effects without improved strength or function in the best older-adult trial. Glucose changes and the hip-fracture heart-failure signal add material safety concerns, while online MK-677 products remain chemically unverified.