Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Head-to-head comparison of Follistatin 344 and MK-677 — mechanism, side effects, legal status, and pricing.
Follistatin 344 is a recombinant form of the naturally-occurring glycoprotein (344-residue splice variant) that inhibits activin and myostatin signaling. Clinical validation exists ONLY through small AAV gene-therapy phase 1/2 trials in Becker muscular dystrophy; recombinant injectable protein sold on the grey market has no clinical evidence. NOT FDA-approved. WADA-prohibited (myostatin inhibitor) and banned in competitive sport.
MK-677 (ibutamoren, MK-0677, L-163,191) is an orally active, non-peptide small-molecule growth hormone secretagogue developed by Merck in the 1990s. It is a spiropiperidine ghrelin-receptor (GHSR-1a) agonist — not a peptide and not a SARM, though it is commonly misclassified as both in grey-market retail. Merck discontinued development after mixed efficacy and adverse metabolic / cardiovascular findings; it is not FDA-approved.
Follistatin 344
MK-677
Category
Legal Status
Mechanism
Half-life
Side Effects
COA-verified vendors · trust score ≥70 required · single-vial price — bulk/bundle deals may be lower
Follistatin 344
MK-677
No pricing data yet.
Check MK-677 prices →COA corpus from Disclosed Labs — independently tested batches only.
Follistatin 344
2
COAs
99.5%
Avg purity
2
Labs
MK-677
5
COAs
98.3%
Avg purity
3
Labs
AAV1-FS344 intramuscular gene therapy Phase 1/2a in Becker muscular dystrophy (n=6) reported improved 6-minute walk test and quadriceps volume changes (Mendell et al., Molecular Therapy, 2015). Preclinical mdx mouse and cynomolgus primate studies showed durable muscle mass and strength increases (Kota et al., Science Translational Medicine, 2009). Recombinant Follistatin-344 protein sold as an injectable research chemical has NO validated human clinical data — all positive human evidence is from AAV gene therapy, not peripheral protein injection. Not FDA-approved. WADA-prohibited at all times.
MK-677 has meaningful human data from Merck-sponsored Phase I/II trials. Murphy et al. (JCEM 1998, PMID 9467534) showed 25 mg MK-677 reversed nitrogen wasting during caloric restriction in healthy adults. Svensson et al. (JCEM 1998, PMID 9467542) reported ~40% IGF-1 elevation, increased fat-free mass, and higher energy expenditure over 8 weeks in obese men. Copinschi et al. (Neuroendocrinology 1997, PMID 9349662) documented improved slow-wave and REM sleep in young and older adults. Nass et al. (Ann Intern Med 2008, PMID 18981485) — the pivotal 2-year randomized trial in 65 healthy older adults — restored GH and IGF-1 to young-adult levels and increased fat-free mass, but produced modest fasting glucose elevation and insulin resistance. The Adunsky et al. Phase IIb hip-fracture trial (Arch Gerontol Geriatr 2011, PMID 21067829) was stopped early after a congestive-heart-failure safety signal (4/62 ibutamoren vs 1/60 placebo). Merck discontinued development. MK-677 is commonly mislabeled as a 'SARM' in grey-market retail — it is not; it is a ghrelin-receptor agonist and oral GH secretagogue. It has never been FDA-approved.
Follistatin 344 and MK-677 are both in the Performance category and may have overlapping mechanisms. Researchers should review both profiles carefully, understand the mechanisms of action, and monitor the relevant biomarkers when combining compounds in the same class. As always, consult a licensed healthcare provider before making any decisions about combining research compounds.
This platform provides informational tools only, not medical advice. This comparison is for educational purposes only. Consult a licensed provider.
Contraindications
Lab Testing
Disclosed Labs