ACE-031 vs MK-677 (Ibutamoren)
A neutral, side-by-side comparison of two performance & growth hormone peptides — their mechanisms, dosing ranges, administration routes, side effects, and research evidence. For research and educational purposes only.
ACE-031
Soluble form of activin type IIB receptor (ActRIIB-Fc fusion protein) that acts as a myostatin and activin trap. Blocks the primary signals that limit muscle growth by sequestering myostatin, activin, and related ligands before they reach cell surface receptors. Phase 2 trials in Duchenne muscular dystrophy demonstrated significant lean mass increases.
Full profileMK-677 (Ibutamoren)
Oral non-peptide growth hormone secretagogue that mimics ghrelin to stimulate GH and IGF-1 release without injection. Long half-life (~24 hours) enables once-daily oral dosing. Widely researched for body composition, sleep quality, and IGF-1 elevation.
Full profile| ACE-031 | MK-677 (Ibutamoren) | |
|---|---|---|
| Category | Performance & Growth Hormone | Performance & Growth Hormone |
| Also known as | ACVR2B-Fc, ActRIIB-Fc fusion protein | Ibutamoren, Nutrobal, MK677, L-163,191 |
| Evidence | Investigational (in trials) | Research-stage |
| Dosing range | 0.3mg/kg–3mg/kg mg/kg, every 2–4 weeks (subcutaneous injection) | 10mg–50mg mg, once daily oral |
| Administration | Subcutaneous injection | Oral (capsule/liquid) |
| Key side effects | Nosebleeds (epistaxis — most common reported AE), Telangiectasia (visible small blood vessel dilation), Gum bleeding, Elevated hemoglobin | Water retention, Increased appetite, Elevated fasting glucose (long-term), Fatigue (initial, transient) |
| Cited sources | 2 references | 2 references |
Key differences
- Evidence level differs: ACE-031 is investigational (in trials), while MK-677 (Ibutamoren) is research-stage.
- Administration: ACE-031 — Subcutaneous injection; MK-677 (Ibutamoren) — Oral (capsule/liquid).
- Dosing units differ: ACE-031 is dosed in mg/kg, MK-677 (Ibutamoren) in mg — they operate at different scales.
- Frequency: ACE-031 is typically every 2–4 weeks (subcutaneous injection); MK-677 (Ibutamoren) is once daily oral.
How each works
ACE-031
ACE-031 functions as a decoy receptor, binding myostatin, activin A/B, GDF-11, and BMP-9 in circulation before they can activate cellular ActRIIB receptors. In the Duchenne muscular dystrophy Phase 2 trial, ACE-031 produced meaningful lean body mass increases but was halted due to vascular side effects (epistaxis, telangiectasia) requiring dose and safety optimization.
MK-677 (Ibutamoren)
MK-677 binds the ghrelin receptor (GHS-R1a) to stimulate pulsatile GH release and increase circulating IGF-1. Unlike peptide GHRPs it survives oral administration. Clinical trials demonstrate significant increases in GH pulsatility and IGF-1 without suppression of the endogenous GH axis, though long-term use raises glucose metabolism concerns.
This comparison aggregates public research and structured profile data for informational purposes only. It is not medical advice and does not recommend either compound for human use. Consult a qualified healthcare provider before considering any peptide.