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Classes

Myostatin inhibitors

Compounds that remove the myostatin brake on skeletal muscle growth.

3 compounds in this class. 0 approved by the FDA for at least one indication. 1 have no published human trial data.

All 3 myostatin inhibitors compared

CompoundEvidenceReported rangeHalf-lifeStatus
ACE-031
A soluble activin receptor decoy that increased muscle mass in trials before being discontinued over vascular side effects.
 Clinical trials 500 mcg - 3 mg ~10-15 days Research only
Follistatin-344
A natural myostatin-binding glycoprotein, of interest for muscle growth but with a very short circulating half-life.
 Animal models only 100-300 mcg ~30 minutes Research only
YK-11
A steroidal compound marketed as a SARM and a myostatin inhibitor. It is neither a peptide nor, strictly, a SARM.
 In vitro only 5-10 mg ~6-10 hours Research only

Head-to-head comparisons

ACE-031 vs Follistatin-344ACE-031 vs YK-11Follistatin-344 vs YK-11Follistatin-344 vs IGF-1 LR3

Myostatin inhibitors: common questions

What are myostatin inhibitors?

Compounds that remove the myostatin brake on skeletal muscle growth. This class has 3 compounds in our directory.

Which myostatin inhibitors are FDA approved?

None of the 3 compounds in this class is FDA approved for any indication.

Which myostatin inhibitors have the strongest evidence?

By evidence level and number of human studies: ACE-031 (clinical trials, ~4 human studies); Follistatin-344 (animal models only, ~1 human studies); YK-11 (in vitro only, ~0 human studies).

Can compounding pharmacies make these?

ACE-031, Follistatin-344, YK-11 are not FDA approved and not on the 503A bulks list, so there is no routine legal path to compound them. Material sold online is labelled for research use only. Status checked against FDA lists in October 2026.

References

Regulatory and primary sources

  1. FDA: Bulk drug substances that may present significant safety risks (Category 2 and withdrawn nominations) ↗ · content current as of April 22, 2026; checked October 18, 2026
  2. FDA: Bulk drug substances used in compounding under section 503A ↗ · how the 503A categories work
  3. FDA: Unapproved drugs ↗ · status of products sold "for research use only"
  4. WADA Prohibited List ↗ · peptide hormones and growth factors, class S2
  5. PubMed (National Library of Medicine) ↗ · source of every literature reference on this site

Published literature

  1. Campbell C, McMillan HJ, Mah JK, et al.. Myostatin inhibitor ACE-031 treatment of ambulatory boys with Duchenne muscular dystrophy: Results of a randomized, placebo-controlled clinical trial.Muscle Nerve 2017.PubMed 27462804 · doi:10.1002/mus.25268
  2. Tsuchida K. Clinical Applications of Ligand Traps Targeting Activin Type II Receptors.Antiinflamm Antiallergy Agents Med Chem 2026.PubMed 41487000 · doi:10.2174/0118715230416604251029062751
  3. Attie KM, Borgstein NG, Yang Y, et al.. A single ascending-dose study of muscle regulator ACE-031 in healthy volunteers.Muscle Nerve 2013.PubMed 23169607 · doi:10.1002/mus.23539
  4. Angelidi AM, Stefanakis K, Chou SH, et al.. Relative Energy Deficiency in Sport (REDs): Endocrine Manifestations, Pathophysiology and Treatments.Endocr Rev 2024.PubMed 38488566 · doi:10.1210/endrev/bnae011
  5. Seo MW, Jung SW, Kim SW, et al.. Effects of 16 Weeks of Resistance Training on Muscle Quality and Muscle Growth Factors in Older Adult Women with Sarcopenia: A Randomized Controlled Trial.Int J Environ Res Public Health 2021.PubMed 34201810 · doi:10.3390/ijerph18136762
  6. Zhang M, Song Y, Zhu J, et al.. Effectiveness of low-load resistance training with blood flow restriction vs. conventional high-intensity resistance training in older people diagnosed with sarcopenia: a randomized controlled trial.Sci Rep 2024.PubMed 39558011 · doi:10.1038/s41598-024-79506-9
  7. Ren Y, Zhao H, Yin C, et al.. Adipokines, Hepatokines and Myokines: Focus on Their Role and Molecular Mechanisms in Adipose Tissue Inflammation.Front Endocrinol (Lausanne) 2022.PubMed 35909571 · doi:10.3389/fendo.2022.873699
  8. Vannuccini S, Clemenza S, Rossi M, et al.. Hormonal treatments for endometriosis: The endocrine background.Rev Endocr Metab Disord 2022.PubMed 34405378 · doi:10.1007/s11154-021-09666-w
  9. Bolanle IO, de Liedekerke Beaufort GC, Weinberg PD. Transcytosis of LDL Across Arterial Endothelium: Mechanisms and Therapeutic Targets.Arterioscler Thromb Vasc Biol 2025.PubMed 40013359 · doi:10.1161/ATVBAHA.124.321549
  10. Stefanakis K, Kokkorakis M, Mantzoros CS. The impact of weight loss on fat-free mass, muscle, bone and hematopoiesis health: Implications for emerging pharmacotherapies aiming at fat reduction and lean mass preservation.Metabolism 2024.PubMed 39481534 · doi:10.1016/j.metabol.2024.156057
  11. Zhuang M, Gu Y, Wang Z, et al.. Effects of 12-week whole-body vibration training versus resistance training in older people with sarcopenia.Sci Rep 2025.PubMed 40011687 · doi:10.1038/s41598-025-91644-2
  12. Thevis M, Schänzer W. Detection of SARMs in doping control analysis.Mol Cell Endocrinol 2018.PubMed 28137616 · doi:10.1016/j.mce.2017.01.040
  13. Harding C, Viljanto M, Habershon-Butcher J, et al.. Equine metabolism of the selective androgen receptor modulator YK-11 in urine and plasma following oral administration.Drug Test Anal 2023.PubMed 36519889 · doi:10.1002/dta.3425
  14. Sobolevsky T, Kucherova Y, Ahrens B. Detection of selective androgen receptor modulator YK-11 in a doping control sample.Drug Test Anal 2024.PubMed 37946705 · doi:10.1002/dta.3604

Literature retrieved from PubMed on October 16, 2026, favouring human studies and reviews. Numbered markers in the text show which paper supports which statement; uncited entries are background reading.