Which is better, Follistatin-344 or ACE-031 (ramatercept)?
On evidence grade ACE-031 wins: two randomized placebo controlled trials (48 healthy postmenopausal women and 24 boys with Duchenne muscular dystrophy) documented real lean mass gains, while injected follistatin-344 is graded animal only. That same evidence documents ACE-031's harm, since the Duchenne trial stopped early for bleeding and telangiectasia and the program was discontinued. Neither is approved, neither can be compounded, and products sold under either name are unverified, so the win is about what is known, not a recommendation to use it. [1] [2] [3] [4] [5]
How do Follistatin-344 and ACE-031 (ramatercept) compare?
| Dimension | Follistatin-344 | ACE-031 (ramatercept)Favored |
|---|---|---|
| What it is [1] [6] | Recombinant form of the 344 amino acid precursor of follistatin, a natural glycoprotein that binds myostatin, activins, and related ligands. | Recombinant fusion protein of the activin receptor type IIB extracellular domain and an IgG1 Fc fragment, acting as a ligand trap. |
| Mechanism [1] [2] [6] | Binds myostatin and activin A and B directly and keeps them off activin type II receptors; also binds some bone morphogenetic proteins. | A soluble decoy receptor that soaks up myostatin, activin A, GDF-11, and other ActRIIB ligands, including ligands that act on blood vessels and red cell production. |
| Human evidence [1] [2] [3] [7] | No trial of the injected peptide. Two open label gene therapy trials (AAV1-FS344, 6 patients each) in Becker muscular dystrophy and inclusion body myositis reported better 6 minute walk distance without a placebo group. | Two randomized placebo controlled trials: a single dose raised lean mass by about 1 kg and thigh muscle volume by about 5% at 29 days in 48 women; in 24 boys with Duchenne muscular dystrophy lean mass rose but walking distance did not improve significantly. |
| Animal evidence [1] [4] [6] | Transgenic mice gained 194% to 327% in muscle weight; a single gene therapy injection in macaques increased quadriceps size and strength for 15 months. | Soluble ActRIIB decoys produced rapid large muscle gains in mice across dystrophy, cachexia, and disuse models, with more bone mass. |
| Key safety findings [1] [2] [4] | No human safety data for the injected peptide. Fertility hormone suppression is a theoretical concern because follistatin binds activins that regulate FSH; it was not seen in the macaque study. | Nosebleeds, telangiectasia, gum bleeding, and erythema halted the Duchenne trial; FSH fell in the single dose study. |
| Development and regulatory status [2] [5] | Never submitted to FDA and not on any 503A category list; as a biologic sized protein it has no lawful compounding path. | Investigational biologic whose sponsor ended development in 2011; never nominated for compounding and not a 503A candidate. |
| Doses in the literature [1] [2] [3] | None for the peptide. Gene therapy used a single intramuscular series of 6 x 10^11 to 1.2 x 10^12 vector genomes per kg, which does not translate to a peptide dose. | Single subcutaneous doses of 0.02 to 3 mg/kg in healthy women; 0.5 or 1 mg/kg every 2 to 4 weeks for 12 weeks in boys with Duchenne muscular dystrophy. |
| WADA status [8] | Prohibited at all times under S4; follistatin is named as a myostatin binding protein. | Prohibited at all times under S4 as a myostatin inhibitor. |
Evidence grade and regulatory status
Pulled from each peptide’s own record, so it stays in step with the peptide pages.
| Attribute | Follistatin-344 | ACE-031 (ramatercept) |
|---|---|---|
| Class | Recombinant form of the 344 amino acid precursor isoform of human follistatin, a secreted glycoprotein that binds and neutralizes myostatin, activins, and related TGF-beta family ligands | Recombinant fusion protein (extracellular domain of activin receptor type IIB fused to human IgG1 Fc), a myostatin and activin ligand trap |
| What it is | Protein that blocks myostatin, the body's muscle growth brake: big gains in mice and monkeys; human data only from gene therapy, not injections; WADA banned. | A myostatin blocking fusion protein that grew lean mass in a small human trial but was abandoned after bleeding side effects in boys with DMD. |
| Evidence | Evidence: Animal-only evidence | Evidence: Human RCT evidence |
| FDA status | Regulatory: Unscheduled | Regulatory: Unscheduled |
| Compounding | Follistatin-344 has never been submitted to or reviewed by FDA as a drug and does not appear on the 503A bulk drug substance Category 1, 2, or 3 lists or the 503B bulks list as of the last verification date. It is a biologic sized protein rather than a small peptide, so even a nomination would face the biologics compounding limits. There is no approved product and no lawful compounding pathway; products sold online are labeled for research use only. | ACE-031 is an investigational biologic that was never submitted for FDA approval; its sponsor ended development in 2011 after the Duchenne trial was halted. It is not on the FDA 503A bulks list, has not been nominated or reviewed by the Pharmacy Compounding Advisory Committee, and as a recombinant fusion protein it is not a candidate for 503A compounding. Products sold under this name are not lawful for human use and their identity cannot be verified. |
| WADA | WADA: WADA prohibited | WADA: WADA prohibited |
| Routes | Subcutaneous or intramuscular injection (as sold, no human data), Intramuscular AAV1 gene therapy (clinical trials only), Transgenic overexpression and intramuscular viral vector (animal studies) | Subcutaneous injection (clinical trials) |
| Typical cost | Not available through licensed channels. Research chemical listings for 1 mg vials are not lawful for human use and are not verified for identity or purity. | Not available through licensed channels. Research chemical listings for material labeled ACE-031 exist, but the products are unverified and are not lawful for human use. |
| Last verified |
Has Follistatin-344 been tested directly against ACE-031 (ramatercept)?
No published trial has compared Follistatin-344 and ACE-031 (ramatercept) directly. The dimensions above come from separate studies and labels, and cross-trial comparisons are less reliable than a direct trial.
What do Follistatin-344 and ACE-031 (ramatercept) cost?
| Dimension | Follistatin-344 | ACE-031 (ramatercept) |
|---|---|---|
| Typical cost | Not available through licensed channels. Research chemical listings for 1 mg vials are not lawful for human use and are not verified for identity or purity. | Not available through licensed channels. Research chemical listings for material labeled ACE-031 exist, but the products are unverified and are not lawful for human use. |
| Price detail | Price index in progress | Price index in progress |
Where a price index exists, the range is the cash price per month across branded, compounded, and telehealth channels, without insurance. The cost pages give each channel separately with its sources. Otherwise the typical cost from the peptide record is shown. Legal access depends on your state: see peptide legality by state.
Frequently asked questions
Which builds more muscle, follistatin-344 or ACE-031?
Only ACE-031 has been measured in a randomized human trial: a single dose raised lean mass by about 1 kg and thigh muscle volume by about 5% at 29 days. Injected follistatin-344 has no human data; the muscle gains come from transgenic mice, macaque gene therapy, and small open label human gene therapy trials. [1] [3] [4] [6]
Why was ACE-031 discontinued?
Its trial in boys with Duchenne muscular dystrophy was stopped early after participants developed nosebleeds, dilated small blood vessels (telangiectasia), and gum bleeding. The ligand trap also blocks signals that maintain blood vessels, and the sponsor ended development in 2011. [2]
Is the follistatin gene therapy the same as follistatin-344 injections?
No. The human trials delivered the follistatin gene (AAV1-FS344) into the thigh muscle with a viral vector, so the muscle made its own follistatin. They say nothing about the dose, stability, or safety of injected follistatin-344 peptide sold online. [3] [7]
Can either be prescribed or compounded?
No. Neither is FDA approved, neither is on the 503A bulks list or any 503A category list, and both are large recombinant proteins rather than small peptides. Products sold under either name are research chemicals that are not lawful for human use. [5]
Are they banned in sport?
Yes. Myostatin inhibitors, including follistatin and ActRIIB ligand traps, are prohibited at all times under S4 of the WADA Prohibited List. [8]
Conditions studied
From the blog
- Peptides for muscle growth, ranked by human evidence
MK-677, sermorelin, tesamorelin, CJC-1295, IGF-1 LR3, and more ranked by human evidence. None is approved for muscle growth, and all ten are banned in tested sport.
Sources
Numbered citations above point to these primary sources. PubMed entries link to the indexed abstract.
- [1]Attie KM et al. A single ascending-dose study of muscle regulator ACE-031 in healthy volunteers. Muscle Nerve 2013PubMed 23169607, 2013
- [2]Campbell C et al. Myostatin inhibitor ACE-031 treatment of ambulatory boys with Duchenne muscular dystrophy: results of a randomized, placebo-controlled clinical trial. Muscle Nerve 2017PubMed 27462804, 2017
- [3]Mendell JR et al. A phase 1/2a follistatin gene therapy trial for Becker muscular dystrophy. Mol Ther 2015PubMed 25322757, 2015
- [4]Kota J et al. Follistatin gene delivery enhances muscle growth and strength in nonhuman primates. Sci Transl Med 2009PubMed 20368179, 2009
- [5]FDA: Bulk drug substances used in compounding under section 503A of the FD&C Act (links to the Category 1, 2, and 3 lists and the bulks list)FDA, 2026
- [6]Lee SJ, McPherron AC. Regulation of myostatin activity and muscle growth. Proc Natl Acad Sci USA 2001PubMed 11459935, 2001
- [7]Mendell JR et al. Follistatin gene therapy for sporadic inclusion body myositis improves functional outcomes. Mol Ther 2017PubMed 28279643, 2017
- [8]WADA Prohibited List, section S4 hormone and metabolic modulators (names follistatin as a myostatin binding protein)WADA, 2026
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