ACE-031 Peptide: The Complete Guide - Uses, Mechanism, Dosing, Safety & Research

Quick Facts

ACE-031 Peptide TL;DR - The Short Version

Top Effects Documented in Research

• Significant lean body mass increase within 29 days of a single dose (Strong - human Phase 1 - Attie et al., 2013)
• Thigh muscle volume increase of 5.1% within 29 days of a single injection (Strong - human Phase 1 - Attie et al., 2013)
• Lumbar spine bone mineral density increase of 3.4% versus a 1.5% decrease in placebo (Moderate - human Phase 1 - Attie et al., 2013)
• Functional contractile force improvements alongside mass gains in non-human primate research (Moderate - marmoset study)
• Directional trends toward lean mass maintenance and ambulatory function preservation in DMD patients (Moderate - incomplete Phase 2 - Campbell et al., 2017)
• Glucocorticoid-induced muscle wasting counteracted in preclinical models (Preliminary - animal data - Cadena et al., 2010)

Documented Adverse Effects

• Injection site erythema (skin redness) - typically mild, most common event in Phase 1
• Telangiectasias (small visible blood vessel abnormalities) - observed with multiple dosing in Phase 2; caused by BMP-9/BMP-10 off-target inhibition
• Epistaxis (nosebleeds) - observed in Phase 2; resolved upon drug discontinuation
• Gum bleeding - observed in Phase 2; resolved upon drug discontinuation
• FSH suppression of 43% - endocrine signal documented in pediatric DMD patients; mechanism is activin A capture

Broad Dosing Spectrum: 0.02 mg/kg to 3.0 mg/kg per subcutaneous injection - range from Phase 1 ascending-dose clinical research; not a dosing recommendation

Typical Frequency in Clinical Research: Single dose (Phase 1) to every 2-4 weeks (Phase 2 protocol before termination)

What ACE-031 Does & How It Works

What It Does - Functional Outcomes

• Captures inhibitory proteins that limit muscle growth, allowing skeletal muscle fiber hypertrophy and satellite cell activation to proceed without restriction
• Increases lean body mass and muscle volume - a 3.3% lean mass increase and 5.1% thigh volume increase within 29 days of a single dose were documented in human research
• Increases bone mineral density by shifting the balance from bone resorption toward bone formation
• Reduces fat mass concurrently with lean mass increases, producing net body composition changes
• Improves functional contractile force proportionally to mass increases - not just structural hypertrophy - as confirmed in non-human primate research
• Counteracts muscle wasting in disease contexts, including models of glucocorticoid-induced myopathy and ALS (preclinical)

How It Works - ACE-031 Peptide Mechanism of Action

Decoy Receptor Strategy - Competitive Ligand Sequestration (Evidence: Human clinical)

ACE-031 is built around a two-part design. The first part is the extracellular domain of the human activin receptor type IIB (ActRIIB) - the same structural component that muscle cells use to receive myostatin signals. The second part is the Fc region of human IgG1, which dramatically extends how long the compound stays active in the body. Together, they form a soluble decoy that circulates in the bloodstream and captures muscle-inhibitory proteins before those proteins can reach actual muscle cells. The compound does not need to penetrate tissue - it intercepts its targets upstream in the bloodstream.

Multi-Ligand Capture - Myostatin, Activin A, GDF-11, and BMPs (Evidence: Human clinical + Animal)

ACE-031 binds multiple members of the TGF-beta superfamily: myostatin (GDF-8), activin A, GDF-11, BMP-2, BMP-7, BMP-9, and BMP-10. Myostatin is the primary target - it is the canonical negative regulator of skeletal muscle mass. Activin A operates through the same receptor pathway to suppress muscle growth. GDF-11, BMP-2, and BMP-7 contribute additional inhibitory input through ActRIIB. This broad multi-ligand capture is what makes ACE-031 more potent than approaches targeting myostatin alone. It is also what creates the vascular safety problem discussed below - BMP-9 and BMP-10 are not muscle-inhibitory ligands. They are endothelial stability signals, and capturing them is an off-target consequence of the broad binding profile.

Pathway Disinhibition in Muscle Cells (Evidence: Animal + In vitro)

When myostatin and activin A are captured before reaching cell-surface receptors, the entire downstream signaling cascade is disrupted. Normally, myostatin binds to ActRIIB and recruits a second receptor (ALK4 or ALK5 - types of cell-surface co-receptors). That combined receptor complex then activates internal messenger proteins called SMADs, which carry the inhibitory signal into the cell nucleus. Once inside the nucleus, these SMAD messenger proteins (specifically a complex of SMAD2, SMAD3, and SMAD4) switch off the gene programs that drive muscle fiber growth, satellite cell activation, and protein synthesis. With ACE-031 blocking ligand arrival at the receptor, the SMAD messengers never get activated. The nuclear off-switch stays open, and muscle-building gene programs run without inhibition.

BMP-9/BMP-10 Inhibition and Vascular Effects (Evidence: Human clinical)

BMP-9 and BMP-10 are TGF-beta superfamily members that operate through the ALK1 receptor (a vascular cell-surface receptor) in combination with ActRIIB on endothelial cells - the cells lining blood vessel walls. Their normal function is maintaining endothelial stability and vascular tone. ACE-031's extracellular ActRIIB binding domain captures these ligands along with its muscle targets. When BMP-9 and BMP-10 are removed from circulation, endothelial cells lose a stabilizing signal. The result observed in the Phase 2 DMD trial was telangiectasias (abnormal small vessel formation visible under the skin), epistaxis, and gum bleeding. All events resolved after stopping the drug. This mechanism is the direct cause of ACE-031's clinical development being terminated.

ACE-031 Molecular Profile

Structure reference: View ACE-031 / ActRIIB compound data on PubChem - Publishing team: search for CAS 1621169-52-5 to retrieve 2D structure data.

Note on classification: ACE-031 is a recombinant fusion protein biologic, not a conventional peptide. It is substantially larger (~57,320 g/mol) than any short synthetic peptide and is produced through cell-based biological expression systems rather than chemical peptide synthesis. This distinction affects its pharmacokinetics, stability, storage requirements, and manufacturing quality considerations.

ACE-031 Uses & Benefits

Muscle Mass and Lean Tissue Research

The most extensively documented research application for ACE-031 is its effect on skeletal muscle mass. The compound was designed specifically to remove inhibitory brakes on muscle growth, and the Phase 1 human clinical study delivered the clearest evidence: a single subcutaneous injection produced statistically significant increases in lean body mass and thigh muscle volume within 29 days. This is not an animal model finding extrapolated to humans - it is direct human data. Research applications in this area span both disease contexts (where muscle wasting is a primary pathology) and general muscle physiology investigation, where ACE-031 serves as a tool for understanding how TGF-beta superfamily inhibition affects muscle tissue at the fiber level. (Evidence: Strong - Attie et al., 2013)

Duchenne Muscular Dystrophy

DMD was ACE-031's primary therapeutic development indication and received FDA Orphan Drug and Fast Track designations in 2010. The rationale is direct: DMD patients experience progressive skeletal muscle degeneration, and maintaining functional muscle mass is a primary therapeutic goal. ACE-031's mechanism targets the inhibitory pathways that limit muscle repair and growth - relevant whether the patient is dealing with progressive disease or with steroid-induced myopathy from the glucocorticoids that form the standard of care. The Phase 2 clinical trial showed directional efficacy trends before termination, but the program was discontinued before efficacy could be formally established. DMD efficacy for ACE-031 must be considered directional, not proven. (Evidence: Moderate - Campbell et al., 2017)

Bone Mineral Density and Osteoporosis Research

ACE-031's effects on bone mineral density are mechanistically independent of its muscle effects - both are consequences of TGF-beta superfamily inhibition, but through different tissue pathways. In the Phase 1 study, treated subjects showed a 3.4% lumbar spine BMD increase while placebo controls showed a 1.5% decrease - a roughly five-percentage-point differential from a single dose. Bone formation markers increased and bone resorption markers decreased simultaneously, confirming the mechanism. This simultaneous anabolic effect on both muscle and bone from a single compound is pharmacologically unusual - most compounds in either space affect one tissue preferentially. (Evidence: Moderate - Attie et al., 2013)

Muscle Wasting Conditions - Sarcopenia, Cachexia, and Glucocorticoid Myopathy

Beyond DMD, ACE-031 has been studied preclinically in several muscle wasting contexts where maintaining functional muscle mass has direct therapeutic relevance. In ALS animal models, it prevented muscle wasting and improved motor function metrics. In obesity and cancer cachexia models, it preserved lean mass alongside fat changes. The glucocorticoid interaction finding is particularly notable: co-administration with dexamethasone produced an 11% net lean mass increase despite active steroid-induced wasting in the animal model. Given how widely glucocorticoids are used in medicine - from DMD to asthma to transplant care - the preclinical demonstration that ACE-031 can overcome corticosteroid myopathy represents a meaningful research signal. (Evidence: Preliminary - Cadena et al., 2010)

Metabolic Research - Body Composition and Fat Tissue

Preclinical research documents ACE-031's effects on fat tissue alongside its muscle effects. These include reduced adipogenesis (the process by which new fat cells are formed), proposed white-to-brown adipose tissue conversion, potential improvements in insulin sensitivity, and elevated basal oxygen consumption. These metabolic effects reflect TGF-beta superfamily signaling's role in regulating adipose tissue biology. The Phase 1 human study documented fat mass changes alongside lean mass gains, supporting the direction of preclinical metabolic findings. None of the metabolic applications have been studied in dedicated human trials. (Evidence: Preliminary - preclinical only)

Where This Guide Comes From

ACE-031 Results & Timelines

ACE-031's outcome timeline data is unusual compared to most research peptides because the primary human evidence comes from a single-dose Phase 1 clinical study with carefully measured endpoints. The timelines below reflect published clinical research findings and documented observations from that study record.

Lean Mass and Muscle Volume

• Day 1-7: No measurable body composition changes expected - the compound is still being absorbed from the subcutaneous depot and reaching peak serum concentrations
• Week 2-3: Early pharmacodynamic activity during this window, though measurable lean mass changes are not yet documented at this stage in the published data
• Week 4 (Day 29): Statistically significant lean body mass increase of 3.3% and thigh muscle volume increase of 5.1% documented in Phase 1 human subjects - this is the primary outcome timepoint in the Attie et al. study
• Weeks 2-14 (marmoset model): Sustained lean mass differences measurable throughout the full 14-week observation window in non-human primate research, with early divergence from vehicle controls as soon as week 2

Bone Density Markers

• Week 2-4: Biomarker changes documented within the Phase 1 observation period. Specifically, osteocalcin and P1NP (proteins that indicate new bone is being formed) rose, while CTX and NTX (proteins that indicate bone is being broken down) fell.
• Week 4 (Day 29): Lumbar spine BMD differential of approximately 4.9 percentage points versus placebo documented at this timepoint

Adverse Effects Timeline

• Single dose (Phase 1): Injection site erythema was the primary adverse event; no vascular events documented with single administration
• Multiple doses (Phase 2): Vascular adverse events - telangiectasias, epistaxis, gum bleeding - emerged after the second dosing cohort's exposure; this is the multi-dose pattern that terminated the program
• After discontinuation: All vascular adverse events documented in Phase 2 resolved upon stopping the drug

How to Administer ACE-031

Subcutaneous Injection (SubQ)

Subcutaneous injection is the exclusive administration route studied in all published human clinical research for ACE-031. This is consistent with how all IgG1-Fc fusion protein biologics are administered - subcutaneous injection provides a depot that allows gradual systemic absorption over hours to days, which suits the compound's long pharmacodynamic profile. The Phase 1 study documented effective systemic exposure with linear pharmacokinetics across all dose cohorts via this route. All safety and efficacy data for ACE-031 in humans derives from subcutaneous administration.

Intramuscular Injection (IM)

IM injection has not been studied for ACE-031 in published research. The subcutaneous route produces adequate systemic exposure given the compound's size and absorption characteristics. IM administration is not the standard approach for IgG1-Fc fusion biologics and is not supported by the ACE-031 research record.

Oral

Oral administration is not viable for ACE-031. As a recombinant fusion protein with a molecular weight of approximately 57,320 g/mol, the compound would be completely degraded by gastric acid and digestive proteases before any meaningful absorption could occur. The gastrointestinal tract has no mechanism to absorb an intact protein of this size into systemic circulation. This is a fundamental characteristic of all biologic drugs in this class - every therapeutic antibody and Fc-fusion protein on the market requires injection for this reason.

Topical

Topical administration is not applicable and has not been studied. A recombinant fusion protein of this molecular weight cannot penetrate intact skin to any meaningful degree.

ACE-031 Dosage & Cycle Length

ACE-031 is not approved for human use and is not available through any legal prescribing or compounding channel. The dosing information below comes exclusively from published clinical trial records and serves as research context only - it documents what clinical investigators actually used, not what any individual should use.

Dosing range studied in human clinical trials: 0.02 mg/kg to 3.0 mg/kg per single subcutaneous injection

How the dose relates to outcomes:

• Low end of range (0.02-0.1 mg/kg): Used in Phase 1 safety and pharmacokinetic cohorts; pharmacodynamic effects on body composition were minimal or not measurable at these doses
• Mid range (0.3-1.0 mg/kg): Intermediate pharmacodynamic effects on lean mass and bone markers documented across ascending-dose cohorts
• High end of range (3.0 mg/kg): The primary efficacy dose in Phase 1; this is where the 3.3% lean body mass increase and 5.1% thigh muscle volume increase within 29 days were documented - the most striking data point in the human research record

Frequency in clinical research:

• Phase 1: Single subcutaneous dose (the full efficacy dataset from Attie et al. 2013 comes from one injection)
• Phase 2 DMD trial: Every 2-4 weeks (multiple-dose schedule, which is what triggered the vascular adverse event signal)

Cycle length in clinical protocols: The Phase 1 study was a single-dose observation study. The Phase 2 DMD study was designed as a multi-dose chronic treatment protocol but was terminated after the second dosing cohort due to vascular adverse events. No long-term cycle data beyond 14 weeks (marmoset model) exists.

Pharmacokinetic context for dosing: The 10-15 day plasma half-life is the primary driver of the once-monthly or less frequent dosing schedule in research protocols. This is not an arbitrary timing choice - it reflects genuine pharmacological duration. Drug accumulates with repeated dosing, which means each subsequent injection adds to circulating concentrations from the previous dose. This accumulation dynamic is directly relevant to the adverse event profile: the vascular effects emerged with multiple doses, not with a single administration.

ACE-031 Vial Sizes, Costs & Quality

ACE-031 occupies a different market position from conventional research peptides. It is a recombinant fusion protein - a biologic compound - which means it is manufactured through a fundamentally different and considerably more expensive process than chemically synthesized peptides. The following reflects general market context.

Common vial sizes: Typically available in 1 mg vials from research suppliers offering this compound, occasionally in 2 mg configurations. Given the extremely high per-milligram cost relative to conventional peptides, small vial sizes are the norm.

Typical cost range: $200-$500 per milligram is a reasonable baseline expectation for U.S.-manufactured research-grade ACE-031, with prices varying significantly based on supplier, purity specifications, and documented manufacturing provenance. Because ACE-031 is a biologic requiring cell-based expression systems for synthesis - not a standard chemical synthesis process - production costs are substantially higher than for short peptides.

Storage - lyophilized (dry powder):

• Temperature: Refrigerate at 2-8 degrees C; freezing at -20 degrees C is recommended for long-term storage beyond a few months
• Shelf life: Approximately 12-24 months from manufacture when stored frozen and dry; shorter at refrigerator temperatures
• Light sensitivity: Protect from light; store in original vial packaging

Normal appearance after reconstitution: ACE-031 should dissolve into a clear, colorless to slightly pale solution. Some minor opalescence may be normal given the protein nature of the compound. The solution should not contain visible particulates or chunks.

Signs of degradation: Heavy cloudiness, visible particulate matter, discoloration (yellowing or browning), or unusual odor. Protein-based compounds are more susceptible to degradation from freeze-thaw cycling, heat exposure, and mechanical shaking than conventional peptides. A degraded protein should not be used.

Quality Considerations

Synthesis purity is easier to fake with ACE-031 than with most research peptides, and that is worth understanding before buying. Standard peptide synthesis is a chemical process - purity can be independently verified by HPLC and sequence confirmed by mass spectrometry. Recombinant protein production is a biological process that depends on cell expression systems and a purification chain that is considerably harder to verify and easier to cut corners on. What gets compromised at suspiciously low price points is almost never obvious from the vial - it shows up as lower protein concentration than labeled, inactive misfolded protein, or host cell protein contamination from the expression system. Third-party mass spectrometry and activity assays are the meaningful quality signals for a compound like ACE-031, not just HPLC purity. U.S.-manufactured research biologics come with documented expression system records, purification process verification, and endotoxin testing that overseas sources typically cannot provide and often do not attempt.

ACE-031 Side Effects & Safety

ACE-031's safety profile is defined largely by a single, well-documented mechanism - off-target BMP-9/BMP-10 inhibition - rather than a diffuse set of unrelated adverse effects. This makes the safety picture scientifically cleaner than many research compounds, but it does not make it less serious.

Side Effect Spectrum

Contraindications

• Pregnancy and breastfeeding: Insufficient safety data; the compound's effects on TGF-beta superfamily signaling - which is essential for fetal development, placentation, and reproductive biology - make use during pregnancy or breastfeeding inappropriate without specific medical supervision
• Pre-existing vascular conditions: Given documented BMP-9/BMP-10 inhibition and resultant vascular effects, individuals with hereditary hemorrhagic telangiectasia, vascular malformations, or other endothelial stability conditions have elevated theoretical risk
• Active malignancy: Myostatin and activin signaling play roles in tumor biology; the effects of broad TGF-beta superfamily inhibition in active cancer are unstudied and theoretically complex
• Pediatric populations: The FSH suppression documented in the Phase 2 DMD trial (43% reduction in pediatric male patients) represents an endocrine signal with potential implications for reproductive development - insufficient data to confirm safety in this context without medical supervision

Populations Where Caution Is Warranted

• Pregnancy and breastfeeding: Insufficient safety data; use is not recommended without medical supervision
• Pediatric use: Studied in DMD boys under clinical supervision, but the FSH suppression finding warrants caution; not appropriate outside formal medical supervision
• Cardiovascular or vascular disease history: Elevated theoretical risk from BMP-9/BMP-10 inhibition affecting endothelial stability
• Individuals on anticoagulants or with bleeding disorders: The epistaxis and gum bleeding documented in Phase 2 suggest compounding bleeding risk in already-vulnerable individuals

Red Flags - Stop Use and Seek Medical Attention If:

• Any appearance of telangiectasias (small, spider-like blood vessel patterns becoming visible under the skin)
• Epistaxis (nosebleeds) that occur or increase after administration
• Gum bleeding or other unexplained mucosal bleeding
• Unusual skin vascular changes or expanding erythema beyond the injection site
• Any unexpected bleeding from sites that were not previously problematic

Drug and Compound Interactions

No formal drug interaction studies for ACE-031 have been published. The documented glucocorticoid interaction is relevant in the functional direction - ACE-031 counteracted dexamethasone-induced muscle wasting in preclinical research, suggesting antagonism of glucocorticoid myopathic effects rather than a dangerous combined adverse reaction. Theoretical caution is warranted with anticoagulants and antiplatelet agents given the vascular bleeding events documented in Phase 2. Combining ACE-031 with other TGF-beta superfamily inhibitors, follistatin-class compounds, or myostatin-targeting agents would produce mechanistically overlapping effects with unpredictable compounding interactions - no data exists on this.

ACE-031 Research & Studies

Pharmacokinetics & Metabolism

Absorption & Bioavailability

ACE-031 was studied exclusively via subcutaneous injection in human trials. Like all IgG1-Fc fusion proteins, absorption from the subcutaneous depot is gradual. The compound enters systemic circulation over hours to days rather than immediately. No specific bioavailability percentage has been published for ACE-031. The pharmacokinetic profile confirmed effective systemic exposure at all studied doses from 0.02 mg/kg to 3.0 mg/kg. Both Cmax (peak concentration in blood) and AUC (total drug exposure over time) scaled proportionally to dose across the full range, confirming linear pharmacokinetics - meaning the dose-response relationship is clean and predictable.

Distribution

As a large recombinant protein (~57,320 g/mol), ACE-031 does not cross the blood-brain barrier. It circulates as a soluble fusion protein in the systemic bloodstream, where it encounters and binds target ligands - myostatin, activin A, GDF-11, and multiple BMPs - in the extracellular space. Tissue-specific distribution data beyond systemic circulation is not available in published research. The compound operates upstream in the circulation rather than requiring tissue penetration to exert its primary effects.

Half-Life

Plasma half-life was confirmed at 10-15 days in human subjects in the Phase 1 study, measured directly from serum samples across the ascending-dose cohorts. This is among the longest half-lives documented for any research compound in the muscle-modulating space. The extended duration is entirely attributable to the IgG1-Fc engineering. The Fc component works via a natural antibody recycling process (called FcRn recycling) that prevents the compound from being broken down as quickly as unmodified proteins would be. The half-life was consistent across the full dose range studied.

Metabolism & Elimination

ACE-031 is eliminated through protein catabolism pathways, not hepatic metabolism or renal filtration. The molecular weight (~57,320 g/mol) exceeds the renal filtration threshold by a substantial margin. The compound is broken down into constituent amino acids and peptide fragments through normal protein degradation. Zero urinary excretion was found at any tested timepoint. No published data identifies specific metabolic enzymes or elimination sites.

Note on data gaps: No published bioavailability percentage exists for ACE-031 via subcutaneous injection. Tissue distribution data beyond systemic circulation has not been published. The 10-15 day half-life is confirmed in humans; all other pharmacokinetic parameters are inferred from linear PK modeling.

Mechanistic Research

Competitive Ligand Sequestration - Decoy Receptor Confirmation (Evidence: Human clinical + Animal - Attie et al., 2013)

The decoy receptor mechanism was confirmed across multiple research models. ACE-031's extracellular ActRIIB domain binds myostatin, activin A, GDF-11, BMP-2, BMP-7, BMP-9, and BMP-10 with high affinity in the circulation. This prevents these ligands from reaching cell-surface receptors. The breadth of binding distinguishes ACE-031 from myostatin-selective antibodies and accounts for its superior potency in head-to-head preclinical comparisons. Confirming this mechanism in human subjects required pharmacodynamic markers - most directly, the FSH suppression observed via activin A capture, which provided an endocrine readout of how completely the compound was sequestering its targets in real human biology.

SMAD Pathway Disinhibition in Muscle (Evidence: Animal + In vitro - Cadena et al., 2010)

When myostatin and activin A are sequestered extracellularly, their downstream intracellular signaling is prevented. Normally, myostatin binding triggers a chain reaction inside the muscle cell: internal messenger proteins called SMADs get activated and travel to the nucleus, where they switch off the gene programs that drive muscle growth. With ACE-031 blocking the upstream signal, those messenger proteins (the SMAD complex) never get activated. The nuclear off-switch stays open, allowing muscle fiber hypertrophy, satellite cell activation, myoblast differentiation, and muscle protein synthesis to proceed unchecked. This mechanism was characterized in murine models where ACE-031 produced dose-dependent increases in muscle mass alongside measurable reductions in SMAD activation markers in treated muscle tissue.

BMP-9/BMP-10 Off-Target Inhibition and Endothelial Effects (Evidence: Human clinical - Campbell et al., 2017)

The Phase 2 DMD trial provided clinical confirmation of a mechanism that was mechanistically anticipated. ACE-031's binding affinity extends to BMP-9 and BMP-10, which are critical stability signals for blood vessel walls. They operate through the ALK1 receptor on endothelial cells. With these ligands removed from circulation by ACE-031, endothelial cells lost a stabilizing signal, producing telangiectasias, epistaxis, and gum bleeding in multiple patients. These events resolved fully upon drug discontinuation. The direct clinical observation, combined with the established biology of BMP-9/BMP-10 in vascular homeostasis, provides the definitive mechanistic explanation for ACE-031's clinical failure.

Bone Remodeling Through TGF-beta Superfamily Modulation (Evidence: Human clinical - Attie et al., 2013)

TGF-beta superfamily signaling governs the balance between bone-building cells (osteoblasts) and bone-breaking cells (osteoclasts) that determines net bone density. ACE-031's inhibition of multiple family members shifted this balance toward bone formation in human subjects. Osteocalcin and P1NP - proteins that signal active bone formation - increased significantly. CTX and NTX - proteins that signal active bone breakdown - decreased. The net result was a 3.4% lumbar spine BMD increase in treated subjects versus a 1.5% decrease in placebo controls within the Phase 1 observation window, roughly a five-percentage-point differential from a single dose.

Condition-Focused Research

Musculoskeletal and Lean Mass Research {#research-muscle}

In the Phase 1 single ascending-dose study, healthy postmenopausal women received a single subcutaneous injection of ACE-031 at doses from 0.02 to 3.0 mg/kg. At the 3.0 mg/kg dose, total lean body mass increased by 3.3% (P = 0.03) and thigh muscle volume increased by 5.1% (P = 0.03) within 29 days, measured by DXA and MRI respectively. These changes from a single injection within four weeks represent some of the most striking acute lean mass data documented in any human muscle pharmacology study to date. (Evidence: Strong - human Phase 1 clinical trial - Attie et al., 2013)

Duchenne Muscular Dystrophy {#research-dmd}

The Phase 2 trial in ambulatory boys with DMD (NCT01099761) showed directional trends toward lean mass maintenance and preservation of ambulatory function on the 6-minute walk test in treated patients compared to placebo before the trial was terminated. The study was stopped following vascular adverse events in the second dosing cohort. The most meaningful pharmacodynamic safety finding from this study - beyond the vascular events - was the 43% reduction in FSH in the pediatric patients. This systemic endocrine effect, secondary to activin A capture, raised additional concerns about broad ActRIIB inhibition in a developing pediatric population. (Evidence: Moderate - incomplete Phase 2 human trial - Campbell et al., 2017)

Preclinical Fiber-Type and Contractile Force Research {#research-fiber}

A 14-week study in common marmosets documented lean body mass increases measurable from weeks 2 through 14 of treatment. Type I muscle fiber cross-sectional area increased by 34%, and Type II fiber cross-sectional area increased by 20%. Crucially, both absolute and specific twitch and tetanic forces improved significantly in the extensor digitorum longus muscle. This demonstrated that muscle mass increases translated to proportional functional force improvements - distinguishing ACE-031 from myostatin-knockout genetic models, which in mice produce visibly larger muscles that are often weaker per unit of size.

Preclinical Muscle Wasting and Glucocorticoid Interaction {#research-wasting}

In murine models, ACE-031 at 10 mg/kg produced maximum force generation increases of 50% and total contractile force increases of 25%. Co-administration with dexamethasone produced an 11% net increase in lean mass despite the glucocorticoid's muscle-wasting effects. This demonstrated that ACE-031's anabolic mechanism was sufficient to overcome iatrogenic (treatment-caused) corticosteroid myopathy in preclinical models. ALS model animals showed prevention of muscle wasting and improved motor function metrics. (Evidence: Preliminary - animal models - Cadena et al., 2010)

Bone Density Research {#research-bone}

Phase 1 human data documented a 3.4% lumbar spine BMD increase in treated subjects versus a 1.5% decrease in placebo controls. Concurrent increases in bone formation markers (osteocalcin and P1NP) and decreases in bone resorption markers (CTX and NTX) confirmed the mechanism. Preclinical osteoporosis models confirmed femoral and vertebral BMD improvements. The simultaneous anabolic effects on both muscle and bone from a single compound represents a pharmacologically unusual finding - most compounds in the osteoporosis space do not simultaneously build muscle, and vice versa. (Evidence: Moderate - human Phase 1 plus preclinical - Attie et al., 2013)

Safety & Tolerability Research

The Phase 1 single-dose study in healthy postmenopausal women found ACE-031 generally well-tolerated across all dose cohorts, with injection site erythema as the primary adverse event. No serious adverse events were reported in Phase 1. The critical safety findings emerged in Phase 2 with multiple-dose administration in DMD patients: telangiectasias, epistaxis, and gum bleeding caused by BMP-9/BMP-10 off-target inhibition, all resolving on drug discontinuation. The 43% FSH suppression in the pediatric DMD population represents a secondary systemic safety signal. No irreversible harm, hospitalizations, or severe adverse events were documented in the published clinical record. The Phase 1b multiple ascending-dose study in healthy volunteers also showed general tolerability - the vascular adverse events were specific to the Phase 2 patient population with repeated dosing in a disease context, not observed in healthy volunteer multiple-dose studies.

Research Limitations

The ACE-031 research record carries several specific and significant limitations. The Phase 2 DMD trial was terminated before reaching its primary efficacy endpoints - the efficacy data is directional but not statistically confirmed, and DMD efficacy in humans must be considered formally unproven. All condition-specific applications beyond muscle mass and bone density in healthy postmenopausal women lack completed human trial data. Long-term safety with sustained exposure is entirely unknown - the longest human exposure comes from the incomplete Phase 2, which extended to only a small number of multi-dose cycles. The FSH suppression finding in pediatric patients was documented but not fully characterized before the program was discontinued. All metabolic and fat composition findings are preclinical only. No detection window has been formally established in human subjects for anti-doping purposes; the available data comes from rodent models only.

Is ACE-031 Legal? Regulatory & Sports Status

FDA status: ACE-031 is not approved for any human use. During active clinical development, it held FDA Orphan Drug Designation for Duchenne muscular dystrophy (granted 2010) and FDA Fast Track designation for DMD (granted 2010). Both designations became moot following discontinuation of the clinical program in 2011-2013. It is not available through licensed compounding pharmacies for any indication - recombinant protein biologics are outside the scope of traditional compounding practice.

Research Use Only (RUO): In all jurisdictions, ACE-031 is classified as a research compound with no approved human use indication. It is not available through any legal prescribing channel. The compound exists in research supplier markets under research-use-only designation.

WADA / USADA status: ACE-031 is banned under the WADA prohibited list, classified under S2 - Peptide Hormones, Growth Factors, Related Substances and Mimetics, which covers myostatin inhibitors specifically. Myostatin inhibitors as a class are explicitly banned in-competition and out-of-competition. This prohibition extends to all competitive sports under the World Anti-Doping Code.

Country-specific notes: As a recombinant fusion protein biologic with no approved indication anywhere in the world, ACE-031 has no legal prescription pathway in any major jurisdiction. Some countries regulate it more specifically under general biologic or unapproved therapeutic frameworks, but no country has an approved human use pathway for this compound.

Detection: ACE-031 cannot be detected in urine - its molecular weight (~57,320 g/mol) far exceeds the renal filtration threshold, making blood-based testing the only viable detection method. In rodent models, detection was confirmed for at least 48 hours post-dose but not detected by 7 days. Given ACE-031's 10-15 day plasma half-life in humans, the serum detection window in human subjects is likely substantially longer - potentially weeks - though the exact duration has not been formally established in published research. (Regulatory status as of July 2026)

ACE-031 vs. Alternatives

Commonly Paired With - Synergistic Stacks

Given ACE-031's discontinued clinical status and the absence of widespread approved use, formal stacking documentation is limited. The research literature provides one directly relevant combination.

• ACE-031 + Glucocorticoids (research context only): The preclinical dexamethasone interaction study is the only documented combination, showing an 11% net lean mass gain despite concurrent corticosteroid-induced wasting. This combination was studied specifically because DMD standard of care includes glucocorticoids - the research question was whether ACE-031 could overcome steroid myopathy in the target patient population.

• ACE-031 + Other myostatin pathway inhibitors (theoretical - no data): Combining ACE-031 with follistatin-class compounds or myostatin-specific antibodies would produce mechanistically overlapping TGF-beta superfamily inhibition. No human or animal data exists on this combination and the compounding effects are unpredictable.

Alternatives - When Another Compound May Be Considered

Follistatin (FST-344) Follistatin is a naturally occurring binding protein that sequesters myostatin and activin A through a different mechanism than ACE-031 - it binds these ligands directly rather than acting as a soluble receptor fragment. Follistatin-344 is the most studied isoform in research contexts and produces lean mass increases in animal and limited human data. Compared to ACE-031, follistatin has a narrower binding profile that may reduce the risk of BMP-9/BMP-10 off-target effects, though its own selectivity profile is not fully characterized.

Myostatin-Specific Antibody Approaches (Apitegromab, Trevogrumab - Research Stage) Multiple pharmaceutical programs have pursued myostatin-specific monoclonal antibodies to avoid the multi-ligand inhibition problems that terminated ACE-031. These represent the lesson learned from ACE-031 translated into next-generation compounds - targeting myostatin specifically without BMP-9/BMP-10 cross-reactivity. None are currently approved or available outside active clinical trials.

IGF-1 LR3 (Insulin-Like Growth Factor-1 Long R3) IGF-1 works through a completely different pathway - direct anabolic signaling via the IGF-1 receptor rather than removal of inhibitory signals. ACE-031 and IGF-1 act through complementary mechanisms: one removes the brakes on muscle growth, the other presses the accelerator. Preclinical research suggests the combination may be additive in muscle mass effects. IGF-1 LR3 is a longer-acting research variant with substantially more community data on use patterns and tolerability than ACE-031.

Comparison table:

Build Your ACE-031 Protocol

ACE-031 Peptide FAQs

What is ACE-031?

ACE-031 is a recombinant fusion protein developed by Acceleron Pharma that blocks multiple muscle-inhibitory proteins in the TGF-beta superfamily by acting as a circulating molecular trap in the bloodstream. It consists of the extracellular binding domain of the human activin receptor type IIB fused to the Fc region of human IgG1, giving it an active duration of 10-15 days per dose. ACE-031 reached Phase 2 clinical trials for Duchenne muscular dystrophy before being discontinued in 2013 due to vascular side effects.

What does ACE-031 do?

ACE-031 captures inhibitory proteins that normally prevent muscle growth, allowing muscle fiber hypertrophy and satellite cell activation to proceed without restriction. In human clinical research, a single dose produced a 3.3% lean body mass increase and a 5.1% thigh muscle volume increase within 29 days, alongside a 3.4% increase in lumbar spine bone mineral density. Non-human primate studies also confirmed functional improvements in contractile force - not just increased muscle size.

How long does ACE-031 take to work?

Based on the Phase 1 human clinical study, measurable changes in lean body mass and thigh muscle volume were documented within 29 days of a single subcutaneous injection at the 3.0 mg/kg dose. Bone formation and resorption biomarkers shifted within the same observation window. The compound's 10-15 day plasma half-life means pharmacodynamic effects are active and accumulating throughout that period.

What is the typical dose of ACE-031?

Human clinical trial doses ranged from 0.02 mg/kg to 3.0 mg/kg per single subcutaneous injection. The 3.0 mg/kg dose was the primary efficacy dose in Phase 1, producing the lean mass and bone density findings most cited in the literature. ACE-031 is not approved for any use and is not available through any legal prescribing channel - these figures are research context from published clinical trial records only.

Is ACE-031 legal?

ACE-031 has no approved human use indication in any country and is classified as a research compound in all jurisdictions. It is not available through any legal prescribing or compounding channel. For competitive athletes, it is explicitly banned under WADA's S2 category both in-competition and out-of-competition.

Can ACE-031 be taken orally?

No. As a recombinant fusion protein at approximately 57,320 g/mol, ACE-031 would be completely degraded by gastric acid and digestive enzymes before reaching systemic circulation. The gastrointestinal tract has no mechanism for absorbing an intact protein of this size. This applies to all biologic drugs in this class, which is why every therapeutic antibody and Fc-fusion protein requires injection rather than oral dosing.

Why was ACE-031 discontinued if it showed such strong muscle and bone effects?

ACE-031's broad binding profile captured BMP-9 and BMP-10 alongside its muscle targets. These two proteins are essential for maintaining blood vessel wall stability, and removing them from circulation caused telangiectasias, nosebleeds, and gum bleeding in Phase 2 patients. The vascular adverse events resolved after stopping the drug, but were serious enough to terminate the program. The same receptor binding domain responsible for the anabolic effects could not selectively spare the vascular-protective ligands.

How is ACE-031 different from myostatin antibodies?

Myostatin antibodies like apitegromab are designed to target only myostatin with high selectivity, leaving other TGF-beta superfamily members - including BMP-9 and BMP-10 - untouched. ACE-031, as a soluble receptor fragment, binds all ligands with affinity for the ActRIIB extracellular domain, which includes myostatin, activin A, GDF-11, and multiple BMPs. This produces greater potency for muscle effects but also greater off-target effects - next-generation myostatin antibody programs are the pharmaceutical response to the specific failure mode that ACE-031 revealed.

Can ACE-031 be detected in anti-doping tests?

Yes - but only through blood testing, not urine. ACE-031's molecular weight exceeds the renal filtration threshold, so it is never excreted in urine and standard urine-based doping tests cannot detect it. Blood-based testing is required. Given ACE-031's 10-15 day plasma half-life in humans, the blood detection window is likely substantially longer than the rodent detection window, though the exact duration in human subjects has not been formally established.

Does ACE-031 affect hormones?

Yes. The Phase 2 DMD trial documented a 43% reduction in FSH (follicle-stimulating hormone) in treated pediatric patients. This occurs because activin A - one of ACE-031's captured ligands - normally stimulates FSH release from the pituitary gland. When activin A is sequestered by ACE-031, FSH levels fall. This was considered a significant safety signal in a pediatric male population, where FSH plays a role in reproductive development.

Final Thoughts

ACE-031 represents one of the more scientifically compelling - and instructive - stories in biologic and peptide research. A single subcutaneous injection producing a 3.3% lean body mass increase and a 3.4% lumbar spine BMD increase in human subjects within 29 days is not a marginal finding. It is among the most striking acute body composition data in the human clinical pharmacology literature. The mechanism is well-characterized, the pharmacokinetics are clean and predictable, and the compound's simultaneous effects across muscle, bone, and fat tissue reflect the interconnected biology of TGF-beta superfamily signaling in a way that few other research tools reveal as clearly.

The reason ACE-031 is not in clinical use is equally instructive: the same broad binding affinity that makes it more potent than myostatin-specific approaches also captures BMP-9 and BMP-10, vascular stability ligands that cannot be spared by the same receptor fragment doing the anabolic work. The vascular adverse events that terminated the Phase 2 trial are not a footnote - they are the reason clinical development ended. The FSH suppression finding in pediatric patients added a second systemic concern. ACE-031 is also banned under WADA S2, undetectable in urine (blood testing required), and not available through any legal prescribing pathway. These facts matter and should be understood clearly before going further.

What ACE-031 left behind is a sharper understanding of ActRIIB biology, a clear target profile for next-generation compounds, and a detailed account of what human pharmacological TGF-beta superfamily inhibition actually produces - both the benefits and the failure modes. The research record is genuinely valuable, even without an approved compound at the end of it. For anyone interested in where this science leads next, or in exploring compounds with established legal research pathways, MyPeptidePal can help map out what is known and what an evidence-based protocol actually looks like for the compounds that do have that pathway.

References

1. Attie, K. M., Borgstein, N. G., Yang, Y., Condon, C. H., Wilson, D. M., Pearsall, A. E., Kumar, R., Fitts, D. A., Fairhurst, J. L., & Sherman, M. L. (2013). A single ascending-dose study of muscle regulator ACE-031 in healthy volunteers. Muscle & Nerve, 47(3), 416-423.

2. Campbell, C., McMillan, H. J., Mah, J. K., Tarnopolsky, M., Selby, K., McClure, T., Wilson, D. M., Sherman, M. L., Escolar, D., & Attie, K. M. (2017). Myostatin inhibitor ACE-031 treatment of ambulatory boys with Duchenne muscular dystrophy: Results of a randomized, placebo-controlled clinical trial. Muscle & Nerve, 55(4), 458-464.

3. Cadena, S. M., Tomkinson, K. N., Monnell, T. E., Spaits, M. S., Kumar, R., Underwood, K. W., Pearsall, R. S., & Lachey, J. L. (2010). Administration of a soluble activin type IIB receptor promotes skeletal muscle growth independent of fiber type. Journal of Applied Physiology, 109(3), 635-642.