MK-0677 raises IGF-1 but fails functional recovery and signals heart failure risk in hip fracture patients
Background
Hip fracture in elderly patients is a major cause of functional decline, loss of independence, and increased mortality, yet pharmacological tools to accelerate functional recovery remain limited. The GH/IGF-1 axis declines with age and is believed to contribute to muscle loss and impaired rehabilitation. MK-0677 (ibutamoren mesylate) is a small-molecule GHSR agonist that stimulates growth hormone secretion and raises circulating IGF-1, making it a candidate to counteract sarcopenia and speed recovery. Earlier phase II work in hip fracture patients hinted at possible functional benefits, motivating this larger confirmatory phase IIb trial.
Study Design
A multicenter, randomized, double-blind, placebo-controlled phase IIb trial enrolled 123 elderly hip fracture patients. Participants were assigned 25 mg/day MK-0677 orally (n = 62) or matched placebo (n = 61) for up to 24 weeks. Co-primary endpoints were a rank analysis of change in objective functional performance measures (including stair climbing power and gait speed) and change in plasma IGF-1 levels measured by immunoassay. The trial was terminated early following a safety signal.
Results
Plasma IGF-1 in the MK-0677 group rose by 51.4 ng/ml above placebo (95% CI = 34.42–68.44; p < 0.001), confirming robust pharmacodynamic target engagement. Despite this biochemical effect, most functional performance measures did not improve significantly in the treated group. Stair climbing power increased by 12.5 W in the MK-0677 arm (95% CI = -10.95–35.88; p = 0.292), a non-significant result. Gait speed showed a statistically significant difference of 0.7 score in the means (95% CI = 0.17–1.28; p = 0.011) in favor of MK-0677, but this was not mirrored across other endpoints.
The trial was terminated early due to a safety signal of congestive heart failure in a limited number of MK-0677-treated patients — a critical finding that overshadows the isolated gait speed benefit.
The MK-0677 group experienced fewer falls and a smaller proportion of patients with any falls compared to placebo, but this difference did not reach statistical significance (p = 0.096).
Key Findings
- IGF-1 rose by 51.4 ng/ml vs placebo (95% CI 34.42–68.44; p < 0.001)
- Gait speed improved significantly: 0.7-score mean difference (p = 0.011)
- Stair climbing power gain of 12.5 W was non-significant (p = 0.292)
- Fewer falls in MK-0677 group vs placebo, but not significant (p = 0.096)
- Trial terminated early due to congestive heart failure safety signal
Why It Matters
Elevated IGF-1 alone does not translate to clinically meaningful functional recovery in frail elderly hip fracture patients — a finding that should temper enthusiasm for GHSR agonists in this population. The emergence of a congestive heart failure signal serious enough to terminate the trial is a major safety red flag for anyone considering MK-0677 in elderly or cardiovascularly vulnerable individuals. Clinicians and researchers must weigh that the only significant functional gain (gait speed) was isolated and not corroborated by other performance measures, undermining the case for a clinical protocol. For peptide-adjacent biohackers exploring ibutamoren for recovery or anti-aging stacks, this trial provides the strongest human evidence yet of cardiac risk in a vulnerable population at a standard 25 mg/day dose.
TitrateLab articles covering MK-677
Written by TitrateLab, separately from the study summarized above.
