Peptide education
ACE-031
ACE-031, generic name ramatercept, is a decoy receptor: the outer portion of the activin type IIB receptor fused to an antibody Fc region, built to soak up myostatin and related ligands before they can restrain muscle growth. It is the one myostatin-pathway product on the gray market that reached randomized human testing, and that history cuts both ways. Early studies did show lean-mass signals, and then the Duchenne program was stopped over bleeding-type side effects. Development ended, but the name lives on in vendor catalogs, where tested vials have come back as the wrong receptor material entirely.
ACE-031 moved lean mass in early human studies, then had its Duchenne program stopped over nosebleeds and telangiectasias, the signature of a ligand trap catching more than myostatin. What is sold under the name today has failed identity testing.
Overview
Quick answer
Clinical ACE-031 was not a routine retail peptide vial. It was a larger activin receptor type IIB extracellular-domain and IgG1-Fc fusion protein. Some online listings use the ACE-031 name for much smaller "myostatin inhibitory peptide" products, so the label on a vendor page may not mean the same molecule studied in clinical trials.
What is ACE-031?
A soluble ActRIIB-IgG1 Fc fusion protein: the extracellular part of the activin IIB receptor grafted onto an antibody fragment, circulating as a trap for myostatin and related ligands. It is a large engineered biologic, not a peptide in the usual vendor-vial sense.
What do people use it for or talk about?
In the literature, an investigational drug tested in healthy postmenopausal women and in boys with Duchenne muscular dystrophy. In the market, muscle growth, bodybuilding, bone, fat loss, and performance, usually beside a research-use disclaimer and a 1 mg vial.
What route and dose patterns appear in the sources?
Human studies used weight-based subcutaneous dosing: single doses up to about 3 mg/kg in healthy volunteers, and every-2-to-4-week schedules around 0.5 to 1.0 mg/kg in the DMD trial. Fixed 1 mg vendor vials do not map onto any of that arithmetic.
What limits practical confidence in ACE-031?
Three problems, each sufficient alone. The efficacy record is early and small, the safety record includes a program-stopping vascular signal, and independent testing of black-market vials found missing or wrong protein. ACE-031 carries all three at once.
Reported practice
Commonly reported protocol
No established community protocol. Community-reported patterns, not verified by controlled human trials and not a use recommendation. Full use-pattern detail
Evidence
Evidence snapshot
Clinical and database sources describe ACE-031 as a soluble ActRIIB-IgG1 Fc fusion protein, also called ramatercept, developed to block myostatin and related ligands.
A single-ascending-dose healthy-volunteer study reported increased muscle mass, and the DMD trial reported lean-mass and body-composition signals. The public DMD abstract did not show a statistically clean 6-minute walk benefit.
ACE-031 received orphan and Fast Track designations for Duchenne muscular dystrophy, but those designations were development tools. The program did not become an approved marketed drug.
The DMD study was stopped after the second dosing regimen because of potential safety concerns including epistaxis and telangiectasias, even though the published report did not describe serious or severe adverse events.
Black-market ACE-031 testing found that some products lacked the expected immunoreactive protein, many contained additional proteins, and deeper analysis indicated full-length human activin receptor IIB rather than the clinical ACE-031 fusion protein.
Claims
Common claims vs evidence
| Claim | Human evidence | Mechanistic evidence | Anecdotal evidence | Verdict |
|---|---|---|---|---|
| ACE-031 is an established muscle-growth peptide. | Early human work supports an anabolic-looking signal. The healthy postmenopausal single-dose study reported increased muscle mass, and the DMD trial reported lean-mass and body-composition trends. | Myostatin and related ActRIIB ligands restrain muscle growth, and soluble ActRIIB decoy receptors produced large anabolic effects in animal models. | Vendor and gray-market pages commonly frame ACE-031 around muscle growth, bodybuilding, performance, and body composition, often while selling 1 mg research-use vials. | Too broad. The human evidence shows an early lean-mass signal, not a healthy-user muscle-growth or performance benefit. |
| ACE-031 improves Duchenne muscular dystrophy function. | The randomized DMD trial reported a trend toward preserved 6-minute walk distance versus placebo decline, plus trends in lean mass, bone mineral density, and reduced fat mass. The available abstract did not present the walk result as statistically significant. | DMD is a plausible setting for muscle-growth pathway research because loss of muscle strength and progressive muscle damage are core features. | Advocacy and disease-community interest followed the trial program, but the program was halted after safety concerns rather than moving to an approved treatment. | The DMD signal is worth knowing about, but the program stopped before it became an approved treatment or a settled functional-benefit claim. |
| ACE-031 is safe because serious adverse events were not reported. | The DMD paper reported no serious or severe adverse events, but the same program stopped after the second regimen because of potential safety concerns including epistaxis and telangiectasias. | ActRIIB-Fc can bind more than myostatin. Reviews and vascular-biology sources connect broad ligand trapping with concern around BMP9 and BMP10, ligands involved in vascular homeostasis. | Vendor pages often emphasize research-use purity and omit the clinical development halt or reduce it to a vague caution. | Misleading if stated broadly. "No serious adverse events in a short early trial" does not mean the safety profile is settled. |
| ACE-031 is available as a standard research peptide. | The clinical molecule was a biologic fusion protein, not a conventional small peptide. Human trial sources describe that fusion protein; they do not confirm that current vendor vials contain the same construct. | A correct ActRIIB-Fc construct requires the right receptor-domain and Fc architecture. A small "myostatin inhibitory peptide" listing is a different material, not a harmless naming variant. | Vendor pages and catalogs use the ACE-031 name inconsistently, with some describing an ActRIIB-Fc fusion and others describing a much smaller peptide-like material. | Insufficient. A seller would need construct identity, protein-impurity, aggregation, sterility, endotoxin, and lot-traceability evidence before the vial could be compared with clinical ACE-031. |
| A COA proves a gray-market ACE-031 vial matches clinical ACE-031. | No clinical study can vouch for a vial sold today. Trial outcomes and product-quality tests cover different facts. | For a fusion protein, identity needs more than a simple purity percentage: construct identity, expected architecture, protein impurities, aggregation, endotoxin, sterility, and handling all matter. | Vendor pages advertise HPLC, mass spectrometry, purity percentages, and certificates of analysis, but independent testing found major identity and impurity failures in black-market products. | For ACE-031, no. The best current gray-market evidence says the name on the vial is not reliable. |
Bottom line
Main takeaway
ACE-031 is an unapproved muscle-pathway drug that produced a real early signal and a real safety problem, and the gray-market versions have tested as the wrong material.
Read the story in order: phase 1 lean-mass signal, phase 2 halt on epistaxis and telangiectasias, no approval, then black-market identity failures. The vendor pages skip the middle chapter.
Attie 2013 for the healthy-volunteer signal, Campbell 2017 for the DMD trial and the halt, the ActRIIB-Fc binding literature for the BMP9 and BMP10 vascular hypothesis, and the 2025 black-market paper for what the market actually contains.
Identity
What it is
ACE-031 is a soluble fusion of the activin receptor type IIB with an IgG1 Fc region. It floats outside cells and intercepts myostatin and related ligands before they can signal through the pathway that restrains muscle growth, which is why it is called a ligand trap rather than a blocker in the narrow sense.
The excitement was earned at first. Soluble ActRIIB decoys produced large muscle, force, and bone effects across animal models, and a phase 1 study in healthy postmenopausal women reported increased muscle mass with general tolerability.
The ending matters more than the setup. In the randomized DMD trial, body-composition and lean-mass trends came without a statistically clean six-minute-walk benefit, and the study was stopped after the second dosing regimen over potential safety concerns including nosebleeds and telangiectasias. Because ActRIIB-Fc traps more than myostatin, including BMP9 and BMP10 ligands tied to vascular homeostasis, the side effects looked like the mechanism rather than bad luck, and later drug programs moved toward more selective designs.
The market afterlife is the last chapter. The same name now appears on small "myostatin inhibitory peptide" listings that are not the clinical construct, and 2025 black-market testing found products lacking the expected protein or carrying full-length activin receptor IIB instead of the fusion. A vial label that says ACE-031 currently proves very little.
How people talk about it online
Forum memory keeps the animal data and the lean-mass headline: muscle growth, bone density, fat loss, and whether ACE-031 can reproduce the dramatic broad-blockade effects seen in mice. The halt tends to get a sentence at most.
Vendor pages sell 1 mg lyophilized vials with HPLC and mass-spectrometry language, purity percentages, and research-use disclaimers. Some catalogs appear to mix the clinical fusion protein with a much smaller "myostatin inhibitory peptide 7" identity under the same name.
This is one of the few cases where the product problem is measured rather than suspected. Independent black-market testing found products that did not behave like authentic ACE-031, so dose talk built on those listings starts from an unverified vial.
Use context
Routes, doses, and cycle patterns
ACE-031 route and schedule information comes from early clinical studies, registry or conference-linked summaries, and vendor listings. Human sources describe subcutaneous study dosing in mg/kg, including every-2-to-4-week schedules in DMD material. Gray-market pages more often sell fixed-size lyophilized vials and purity claims without clinical product validation.
Human studies and product labels
Healthy-volunteer single ascending-dose study
- Purpose
- Muscle-mass and early safety signal
- Context
- Phase 1 clinical study
- Route
- Subcutaneous
- Amount
- Single ascending-dose design; secondary summaries place studied levels around 0.02 to 3 mg/kg
- Frequency
- Single dose
- Duration
- Short early study; exact follow-up window is not clear from the available abstract
The study in healthy postmenopausal women reported that ACE-031 was generally well tolerated and increased muscle mass. It was not a healthy-adult performance trial or a long-term-use study.
Healthy-volunteer multiple-dose study
- Purpose
- Multiple-dose safety and dose escalation
- Context
- ClinicalTrials.gov registry and conference-level reporting
- Route
- Subcutaneous
- Amount
- Multiple-dose escalation; conference reporting described levels up to 3 mg/kg
- Frequency
- Not clear from the available public sources
- Duration
- Not clear from the available public sources
Multiple-dose clinical testing occurred, but the public schedule is incomplete; dose timing should not be inferred from the available summaries.
Duchenne muscular dystrophy randomized trial
- Purpose
- DMD muscle function, body composition, and safety
- Context
- Randomized double-blind placebo-controlled phase 2 trial
- Route
- Subcutaneous
- Amount
- Registry-linked summaries describe 0.5 mg/kg and 1.0 mg/kg regimens among exposed cohorts
- Frequency
- Every 2 to 4 weeks
- Duration
- Stopped after the second dosing regimen
The trial reported body-composition signals and a non-significant trend toward preserved 6-minute walk distance, but it was halted because of potential safety concerns including epistaxis and telangiectasias.
Real-world discussion
No established community protocol
- Purpose
- Muscle growth discussion
- Context
- Historical trial coverage and niche vendor listings
- Route
- Trial work used subcutaneous injection every two to four weeks
- Amount
- No consistent community range exists; trial doses were weight-based, around 0.5 to 1.0 mg/kg in the DMD trial and up to about 3 mg/kg in healthy-volunteer escalation
- Frequency
- Trial context was every two to four weeks
- Duration
- Trial context was multi-dose
ACE-031 development stopped after vascular adverse events in trials, which is the dominant fact for anyone encountering it today. There is no responsible community protocol to report, and products sold under this name are unverified.
What varies
- Identity: clinical ACE-031 was an ActRIIB-Fc fusion protein; some online ACE-031 listings appear to refer to a different small peptide-like material.
- Goal: lean-mass signals in early trials do not answer healthy-user strength, performance, or bodybuilding questions.
- Amount: study sources use mg/kg exposure, while vendor pages often sell fixed 1 mg vials; those numbers do not translate cleanly.
- Frequency: DMD sources describe every-2-to-4-week subcutaneous dosing, not daily peptide-style routines.
- Product quality: COA, HPLC, or purity language cannot confirm correct fusion-protein identity, sterile injectable quality, endotoxin control, or chain of custody.
Human data
Human evidence
Small, early, and it ends with a stop sign. A single-ascending-dose study in healthy postmenopausal women reported increased muscle mass, and the randomized DMD trial reported lean-mass and body-composition trends alongside a six-minute-walk trend that did not reach significance. That trial was stopped after the second dosing regimen because of potential safety concerns including epistaxis and telangiectasias, and the program never became an approved product. No published study has tested anything currently sold as ACE-031.
Evidence maturity
ACE-031 reached randomized human testing with an early lean-mass signal, then development halted on vascular-type safety concerns and no approved product ever followed.
Soluble ActRIIB decoy-receptor blockade produced large muscle, force, and bone effects across animal models.
Single- and multiple-dose studies in healthy postmenopausal women reported the drug was generally tolerated and increased muscle mass.
A randomized trial in boys with Duchenne muscular dystrophy reported lean-mass and body-composition trends but no statistically clean 6-minute-walk benefit.
The program stopped after the second dosing regimen because of potential safety concerns including epistaxis and telangiectasias, and it was never approved.
Current gray-market listings are unverified, and independent testing found products lacking authentic ACE-031 or containing the wrong receptor material.
| Study / evidence area | Population | Design | Product context | Main outcome | Limitations | Weight |
|---|---|---|---|---|---|---|
| Healthy postmenopausal women single-dose study | Healthy postmenopausal women | Phase 1 single ascending-dose study | Investigational product | The study reported that ACE-031 was generally well tolerated and increased muscle mass. | Early, short, narrow population; not a healthy-adult, bodybuilding, long-term safety, or functional-performance study. | weak |
| Healthy postmenopausal women multiple-dose study | Healthy postmenopausal women | Phase 1 multiple ascending-dose registry and conference context | Investigational product | The registry and conference-level sources show that multiple-dose testing was planned or reported, with dose levels up to 3 mg/kg described in secondary conference reporting. | The available primary documents do not give the exact schedule or full outcome table. | weak |
| Duchenne muscular dystrophy randomized trial | Ambulatory boys with Duchenne muscular dystrophy | Randomized double-blind placebo-controlled ascending-dose phase 2 trial | Investigational product | The study reported trends toward maintained 6-minute walk distance, increased lean mass and bone mineral density, and reduced fat mass, but the available abstract does not make a statistically clean walk-test efficacy claim. | The study was stopped after the second dosing regimen because of potential safety concerns, limiting interpretation and preventing approval-level conclusions. | weak |
| DMD conference safety reporting | Steroid-treated boys with Duchenne muscular dystrophy | Conference abstract from phase 2 program | Investigational product | Conference reporting described reversible telangiectasias and mild epistaxis at higher dose levels. | Abstract reporting is useful safety context but not a full clinical study report. | weak |
| Preclinical ActRIIB and ACE-031 animal work | Mouse, rodent, mdx-model, and marmoset studies | Preclinical | Research material | Soluble ActRIIB pathway blockade produced muscle-growth, force, bone, and lean-mass signals across animal models. | Animal anabolic effects explain why the pathway drew attention, but they do not answer whether a broad ligand trap is safe or useful for human performance. | preclinical |
Cautions
Safety and unknowns
- Nosebleeds, gum bleeding, and telangiectasias matter because they point to effects involving blood vessels, not just ordinary injection-site nuisance.
- The DMD program halt means long-term safety, dose durability, and later-cohort tolerability were never resolved in a marketed-product program.
- Broad ActRIIB ligand trapping may affect ligands beyond myostatin, including pathways relevant to vascular homeostasis; that is a plausible explanation for why more selective myostatin approaches became attractive later.
- The human studies were not conducted in healthy bodybuilders, athletes, or gray-market users, so real-world risk in those settings remains outside the clinical trial record.
- Current market products add risks beyond the trial record: wrong molecule, extra proteins, aggregation, endotoxin, sterility failure, degradation, concentration error, and misleading COA interpretation.
Product quality
A vial label is only a starting point
ACE-031 has more product-identity uncertainty than many peptide products because the clinical molecule was a fusion protein and some current listings use the same name for a smaller peptide-like material.
A 2025 black-market testing paper reported that tested products often did not behave like authentic ACE-031 and could contain full-length human activin receptor IIB plus other proteins.
Vendor purity percentages and COAs are weak evidence unless they document the correct construct, representative lot testing, protein impurities, aggregation, endotoxin, sterility, storage, and chain of custody.
Identity
The material may be the clinical ActRIIB-Fc construct, a full-length receptor contaminant, a small peptide-like substitute, or something else entirely; the identity must be established.
Protein impurities and aggregation
A fusion protein can carry impurity and aggregation concerns that a simple peptide purity percentage may not capture.
Sterility and endotoxin
Injectable research-use material needs sterility and endotoxin controls; HPLC purity alone leaves both unverified.
Storage and handling
Protein biologics can be sensitive to handling, temperature, and reconstitution conditions, so shipping and storage claims matter.
Dose math
Trial sources use mg/kg exposure, while vendor pages often sell fixed vial sizes. Converting one into the other would require body weight, vial identity, concentration, and administration assumptions that the listing usually lacks.
Mechanism
How it is proposed to work
ACE-031 acts like a decoy receptor. It floats outside cells and binds myostatin-related ligands before they can signal through activin receptor pathways that restrain muscle growth.
Myostatin is a negative regulator of skeletal muscle growth. Blocking that signaling neighborhood can increase muscle mass in animals, which explains why ACE-031 attracted attention.
ACE-031 is broader than a myostatin-only blocker. ActRIIB-Fc can bind multiple ligands, and that broader binding may help explain both anabolic potency and off-target vascular concern.
Later myostatin-drug development has often tried to become more selective, because broad ligand trapping can make the tradeoff between muscle gain and tolerability harder to manage.
The same broad ligand-trapping that made it potent is the likely source of the vascular adverse events that ended its development.
FAQ
Common questions
Why was ACE-031 discontinued?
Human trials for muscular dystrophy stopped after vascular adverse events — nosebleeds, gum bleeding, and dilated skin vessels — which is the dominant safety fact for anyone encountering it today.
Is ACE-031 still being developed?
The original development program ended years ago. Products sold under the name now are unverified research-market material with no program behind them.
Is there a safe community protocol?
There is no responsible protocol to report. Trial doses were weight-based and medically monitored, and the safety signal that ended development applies to any use.
Details
Technical details
Sources
References
- 1.
Attie single-dose study. Attie 2013, healthy-volunteer single-dose clinical study
- 2.
DMD phase 2 study. Campbell 2017, DMD randomized clinical study
- 3.
Single-dose registry. Single-dose trial registration
- 4.
Multiple-dose registry. Multiple-dose trial registration
- 5.
DMD safety abstract. DMD conference abstract
- 6.
ActRIIB biology. Foundational broad ActRIIB decoy biology
- 7.
ActRIIB-Fc binding. Ligand-binding specificity of ActRIIB-Fc
- 8.
Muscle animal study. Preclinical muscle-growth paper
- 9.
Force and bone study. Rodent force and bone-density paper
- 10.
mdx bone study. mdx bone-mass paper
- 11.
Marmoset ACE-031. Recent marmoset ACE-031 paper
- 12.
FDA designations. FDA development designations context
- 13.
Program halt context. Program halt or suspension context after the DMD trial's second dosing regimen
- 14.
Black-market testing. 2025 black-market testing paper on ACE-031 identity and detection
- 15.
Vendor examples. Vendor sales, research-use language, COA language
- 16.
Identity mismatch. Sources behind vendor-listing identity mismatches between the clinical fusion protein and smaller peptide listings