ACE-031 vs MK-2866
Emerging vs Moderate Research
monitor Mechanism-based · 46% Both ACE-031 and MK-2866 suppress the HPTA axis. Combined suppression deepens shutdown and extends recovery time. Plan PCT accordingly and monitor LH/FSH/testosterone.
Molecular Data
ACE-031 MK-2866
Weight — 389.33 Da
Half-life 12-15 days ~24 hours
Type Soluble activin receptor type IIB-Fc fusion protein Non-steroidal selective androgen receptor modulator (C19H14F3N3O3)
Key Benefits
ACE-031
01 Significant lean mass increases (up to 1.7% in 29 days) observed in Phase 1 trials
02 Simultaneous reduction in fat mass alongside muscle gains
03 Long half-life (12-15 days) allows infrequent dosing
04 Broad TGF-beta ligand neutralization for robust anti-catabolic effects
05 Dose-dependent increases in thigh muscle volume confirmed by MRI
MK-2866
01 Increases lean body mass in a dose-dependent manner with clinical trial support
02 Preserves muscle mass during caloric deficit or catabolic conditions
03 Selective tissue activity reduces androgenic side effects compared to anabolic steroids
04 Oral bioavailability eliminates the need for injections
05 Does not aromatize to estrogen, avoiding gynecomastia and water retention
06 Improves physical function and stair-climbing power in clinical populations
07 Long 24-hour half-life allows convenient once-daily dosing
08 Mild side effect profile at commonly studied doses
Dosing Protocols
ACE-031
0.5-3 mg/kg IV every 2 weeks (clinical research doses only) / Every 2 weeks
Phase 1 Research Protocol (Healthy Volunteers) 0.1-3 mg/kg Single IV dose
Phase 2 Research Protocol (DMD) 0.5-2.5 mg/kg Every 2 weeks
MK-2866
10-25 mg/day oral / Once daily
Side Effects
ACE-031
Nosebleeds (epistaxis) - most frequently reported adverse event
Gum bleeding
Telangiectasia (dilated small blood vessels visible on skin)
Skin erythema (redness)
Minor injection site reactions
MK-2866
Mild testosterone suppression (dose-dependent, typically 10-30% reduction at 25 mg)
HDL cholesterol reduction (10-20% suppression observed in clinical trials)
Headaches, particularly during the first 1-2 weeks
Mild back pain or muscle cramps
Transient fatigue toward the end of longer cycles
Slight reduction in libido at higher doses or extended cycle lengths
Contraindications
NEVER approved for human use - clinical development discontinued
History of bleeding disorders or vascular malformations
Concurrent anticoagulant or antiplatelet therapy
Known hypersensitivity to Fc fusion proteins
Pregnancy or breastfeeding
Active liver disease or significantly elevated liver enzymes
Hormone-sensitive cancers (breast, prostate) without oncologist clearance
Pregnancy or breastfeeding (potential endocrine disruption to fetus/infant)
Individuals under 21 years of age (risk of premature HPTA disruption during development)
Concurrent use of hepatotoxic medications without liver function monitoring
Known hypersensitivity to MK-2866 or any formulation excipients
Competitive athletes subject to WADA or USADA anti-doping testing
Research Evidence
ACE-031 MK-2866
Status Emerging Moderate Research
References 4 studies 5 studies
FDA Approved No No
This comparison is for educational and research purposes only. Consult a healthcare professional before use.