MK-677 plus alendronate boosted femoral neck BMD 4.2% vs 2.5% with alendronate alone in postmenopausal women
Background
Postmenopausal osteoporosis is driven by an imbalance between osteoblast-mediated bone formation and osteoclast-mediated bone resorption, leaving women at elevated fracture risk. Alendronate, a bisphosphonate and standard-of-care agent, potently suppresses bone resorption but indirectly dampens bone formation as well — a coupling effect that limits net anabolic benefit. Growth hormone (GH) stimulates osteoblast activity and elevates IGF-1, suggesting that activating the GH axis alongside antiresorptive therapy could preserve or amplify the bone-building signal. MK-677, an orally active small-molecule GH secretagogue, was investigated as a way to harness GH-driven anabolism without injectable peptides, with the hypothesis that the combination would outperform alendronate monotherapy on BMD gains.
Study Design
A multicenter, randomized, double-blind, placebo-controlled trial enrolled 292 postmenopausal women aged 64–85 yr with low femoral neck BMD. Participants were assigned in a 3:3:1:1 ratio to four daily oral regimens for 12 months: MK-677 25 mg plus alendronate 10 mg; alendronate 10 mg alone; MK-677 25 mg alone; or double-dummy placebo. Patients on MK-677 alone or placebo crossed to the combination arm from months 12–18; all others continued assigned therapy. All participants received 500 mg/day calcium. Primary endpoints through month 12 included serum IGF-1, osteocalcin, bone-specific alkaline phosphatase, and urinary NTx; BMD was tracked to 18 months.
Results
MK-677, with or without alendronate, raised IGF-1 by 39% and 45% from baseline respectively (both P < 0.05 vs. placebo), confirming robust GH axis activation. MK-677 monotherapy increased osteocalcin by 22% and urinary NTx by 41% (both P < 0.05 vs. placebo), indicating simultaneous stimulation of both bone formation and resorption markers. When combined with alendronate, MK-677 attenuated the drug's suppression of bone formation: mean relative change in osteocalcin was -40% for the combination vs. -54% for alendronate alone (P < 0.05), and NTx resorption suppression was -52% vs. -61% (P < 0.05).
MK-677 plus alendronate increased femoral neck BMD by 4.2% versus 2.5% for alendronate alone (P < 0.05) — the only skeletal site showing a significant combination advantage.
No significant enhancement over alendronate alone was observed at the lumbar spine, total hip, or total body. GH-mediated side effects were noted in MK-677-receiving groups, though adverse events leading to discontinuation were described as relatively infrequent.
Key Findings
- MK-677 + alendronate increased femoral neck BMD by 4.2% vs 2.5% for alendronate alone (P < 0.05)
- MK-677 raised IGF-1 by 39–45% from baseline (P < 0.05 vs placebo) regardless of alendronate co-administration
- Combination mitigated alendronate-induced osteocalcin suppression: -40% vs -54% (P < 0.05)
- NTx resorption suppression was -52% (combination) vs -61% (alendronate alone) (P < 0.05)
- No significant BMD benefit over alendronate alone at lumbar spine, total hip, or total body
Why It Matters
Femoral neck fracture is among the most clinically consequential osteoporotic injuries, making even a modest site-specific BMD advantage potentially meaningful for fracture prevention — the combination's +1.7 percentage-point femoral neck benefit is therefore not trivial. However, the absence of whole-skeleton benefit tempers enthusiasm for routine combination use: clinicians and patients must weigh a targeted gain against the tolerability burden of chronic GH pathway activation. For anyone considering MK-677 alongside bisphosphonate therapy, the data suggest a real but anatomically narrow anabolic rescue effect rather than a global skeletal upgrade. The 18-month design also hints at a longer-term protocol direction, but the lack of fracture endpoint data means BMD surrogates are the entire evidence base for now.
TitrateLab articles covering MK-677
Written by TitrateLab, separately from the study summarized above.
