Trevogrumab

Trevogrumab is an investigational antibody from Regeneron that blocks myostatin, a signal that holds muscle growth back. It is not a peptide. In the phase 2 COURAGE trial, added to semaglutide, the lower-dose portion cut lean-mass loss by roughly 20 to 50 percent depending on dose and time point, according to company-reported results. Doses studied were 25 to 400 mg alongside semaglutide 2.4 mg. A phase 2 study in older adults is planned, and the drug is not approved anywhere.

Research snapshot

Peptide category	Fully human monoclonal antibody against myostatin (GDF8). Not a peptide.
Primary research interest	Preserving lean mass and muscle during GLP-1 weight loss; earlier work in sarcopenia (age-related muscle loss)
Highest available evidence	Company-reported phase 2 results (COURAGE); full paper described as in press at The Lancet
Human research available	Yes. COURAGE (975 adults with obesity across two portions, plus a healthy-volunteer part in the registry) and an earlier 253-person phase 2 sarcopenia trial with no posted results
Development status	Phase 2 complete; a new phase 2 study in older adults with obesity and low muscle mass or strength is planned
Regulatory status	Not approved anywhere

Technical identity

Primary name	Trevogrumab (INN)
Alternative names	REGN1033, SAR391786 (during the Regeneron and Sanofi sarcopenia trial)
Peptide sequence	Not reliably established. A complete antibody sequence was not found in the sources reviewed.
Amino-acid length	Not reliably established
Molecular formula	C6374H9884N1696O2018S46 (single source: Wikipedia; not confirmed in a second database)
Molecular weight	144,037.80 g/mol (single source: Wikipedia; not confirmed in a second database)
CAS Registry Number	1429201-24-0 (single source: Wikipedia)
PubChem CID	Not reliably established
UNII	87T4327873 (single source: Wikipedia)
DrugBank ID	Not reliably established
Chemical modifications	Fully human monoclonal antibody; Regeneron’s 2015 mouse paper describes REGN1033 as an IgG4
Peptide class	Monoclonal antibody (a protein therapeutic, not a peptide)
Primary biological target	Myostatin (GDF8), blocking its interaction with activin type II receptors
Developer or originator	Regeneron Pharmaceuticals (with Sanofi in the 2013 to 2015 sarcopenia phase 2 trial)
Development status	Phase 2 complete in obesity; new phase 2 in older adults planned

Not a peptide: why it is on this site

Trevogrumab is an antibody, a protein far larger than a peptide such as semaglutide. It appears here because it is tested as an add-on to peptide weight-loss drugs. The wider field is mapped in our guide to GLP-1 muscle loss and the drugs aimed at it.

What is trevogrumab?

Trevogrumab, also known as REGN1033, is a lab-made human antibody designed to bind myostatin and keep it from signaling. Myostatin is a protein that restrains muscle growth, so blocking it should in theory help muscle hold on. Regeneron first tested the idea in older adults with sarcopenia. A 253-person phase 2 trial run with Sanofi (NCT01963598) gave subcutaneous REGN1033 for three months in people aged 70 and older, with change in lean body mass as the main outcome. The registry shows it completed in 2015 and posted no results.

The drug returned with the rise of GLP-1 medicines. Drugs like semaglutide cause large weight loss, but a meaningful share of what is lost is lean mass. Regeneron launched COURAGE (NCT06299098) to test whether trevogrumab, with or without garetosmab, an antibody that blocks activin A, could reduce that loss when added to semaglutide.

COURAGE enrolled adults with obesity in two portions that Regeneron describes as higher-dose (599 adults) and lower-dose (376 adults), 975 in total. The registry lists a larger enrollment of 1,005 because it also counts a healthy-volunteer safety part, and it labels the parts differently from the press releases. Results were shown at European Association for the Study of Diabetes meetings in 2025 and 2026. They are company-reported, with a Lancet paper described as in press.

The headline: lower trevogrumab doses kept more lean mass without meaningfully changing weight loss. Adding garetosmab preserved still more, but two participants in that combination group died within 26 weeks, and Regeneron says it will not advance the combination.

How does it work?

Plain-English explanation

Think of myostatin as a brake pedal on muscle growth. Trevogrumab grabs the myostatin before it can press the pedal. When someone is losing weight quickly on a GLP-1 drug, the body also sheds muscle, and a drug that releases the brake might reduce that loss. COURAGE is the first large human test of the idea with this drug, and the results look promising but come from the company, not from a peer-reviewed paper.

Technical explanation

Trevogrumab neutralizes myostatin (GDF8), preventing its binding to activin type II receptors (ActRIIA and ActRIIB) on muscle cells. Its sister drug in COURAGE, garetosmab, neutralizes activin A, a related ligand, which is why the two were combined. In Regeneron’s 2015 mouse study, REGN1033 given subcutaneously at 10 mg/kg raised muscle mass by about 19 to 21 percent over three to four weeks and protected against muscle loss from casting and steroid exposure. Human pharmacokinetics such as half-life were not found in the sources reviewed, and COURAGE measures drug concentrations and anti-drug antibodies as secondary outcomes.

Potential benefits and research applications

Preserving lean mass during GLP-1 weight loss

What is being investigated: whether adding trevogrumab to semaglutide reduces the lean mass lost along with fat.

Evidence (Tier 2, company-reported human trial): in the lower-dose portion, DXA-measured lean mass fell 7.3 percent at 52 weeks with semaglutide plus placebo, versus 5.8 percent with trevogrumab 25 mg and 4.2 percent with 75 mg. At 26 weeks the figures were 6.7, 4.7 and 3.3 percent. In the higher-dose portion, Regeneron reported lean-mass loss of about 6.5 to 6.6 percent with semaglutide alone versus about 3.3 to 3.9 percent with trevogrumab. After semaglutide was stopped and participants stayed on trevogrumab, lean mass was 0.4 percent above baseline versus 2.4 percent below on placebo.

Limits: lean mass is not the same as muscle, strength or function. No functional result has been released. The lower trevogrumab doses did not meaningfully change weight loss.

Muscle volume on MRI

Evidence: in an MRI substudy of 76 participants, which the meeting abstract calls exploratory, fat-free thigh muscle volume loss at 52 weeks was avoided by about 72 percent (25 mg) and 69 percent (75 mg), relative to semaglutide alone, by Regeneron’s calculation. Units and the number of evaluable participants per arm were not stated in the release. This moves the claim toward muscle but rests on a small, exploratory sample.

Sarcopenia and other settings

Evidence: the 2013 to 2015 sarcopenia trial posted no results. A phase 2 study of trevogrumab with GLP-1 therapy in older adults with obesity and reduced muscle mass or strength is planned, with no design, dose or timeline given. Benefit in older adults has not been shown.

What dosage information circulates?

Figures in this section summarize amounts and schedules reported in published research or circulating online. Their inclusion documents what is reported and does not establish that a regimen is verified, safe, effective, or appropriate. Trevogrumab is available only in clinical trials, and Regeneron’s releases do not state the route or the dosing interval for COURAGE.

Reported use or research objective	Route reported	Amount reported	Frequency reported	Reported duration	Evidence or source category
Lean-mass preservation with semaglutide, lower-dose portion of COURAGE	Not stated by the sponsor; a community site says subcutaneous	25 mg or 75 mg of trevogrumab, with semaglutide 2.4 mg	Not consistently reported	52 weeks	Company-reported human trial results (Regeneron); registered trial without posted results
Lean-mass preservation with semaglutide, higher-dose portion of COURAGE	Not stated by the sponsor; a community site says subcutaneous	200 mg or 400 mg of trevogrumab, with semaglutide 2.4 mg	Not consistently reported	26 weeks with semaglutide, then 26 weeks trevogrumab or placebo alone	Company-reported human trial results (Regeneron); registered trial without posted results
Trevogrumab plus garetosmab plus semaglutide (higher-dose portion)	Not stated by the sponsor	Trevogrumab 400 mg reported by a community site; garetosmab amount not confirmed	Not consistently reported	26 weeks	Company-reported; community figures origin unclear. Not being advanced
Sarcopenia in adults aged 70 and older (NCT01963598)	Subcutaneous	Not disclosed in the registry	Not consistently reported	3 months (12 weeks)	Registered human trial without posted results
Muscle mass and atrophy models in mice	Subcutaneous	0.1 to 30 mg/kg; 10 mg/kg standard	Not consistently reported	3 to 4 weeks	Published animal research (Skeletal Muscle, 2015)
Use outside registered trials	Not consistently reported	No established or reliably sourced dosing information was identified.	Not consistently reported	Not consistently reported	None identified

Explanation of the reported figures

The amounts that appear most often, 25, 75, 200 and 400 mg, all trace back to COURAGE as described in Regeneron’s September 2025 and October 2026 releases. Regeneron states the amounts and the semaglutide dose (2.4 mg), but not the route or how often trevogrumab was given. The only place that fills those gaps is a community reference site, Peptide Protocol Wiki, which says subcutaneous, lists the interval as not publicly specified and adds a garetosmab figure we could not confirm. That site cites no paper, so it is not independent evidence. Subcutaneous dosing is supported for the earlier sarcopenia trial, whose registry title says 3-month subcutaneous treatment, and for the mouse work.

No body-weight-based scheme is reported for humans, and we have not converted the mouse amount into a human one. The registry lists no doses. Unknown: the route and interval in COURAGE, whether 25 and 75 mg were fixed or titrated, and what dose a future older-adult study will use.

Amounts studied in human research

Research objective	Amount studied	Frequency	Duration	Route	Study population	Source
Lean mass with semaglutide	25 mg, 75 mg	Not stated	52 weeks	Not stated by sponsor	Adults with obesity (376 in the lower-dose portion)	Regeneron release, October 2026
Lean mass with semaglutide	200 mg, 400 mg	Not stated	26 weeks, then 26 weeks off semaglutide	Not stated by sponsor	Adults with obesity (599 in the higher-dose portion)	Regeneron release, September 2025; EASD summaries
Sarcopenia	Not disclosed	Not stated	3 months	Subcutaneous	253 adults aged 70 and older	ClinicalTrials.gov NCT01963598

Amounts studied in animal research

Research objective	Species or model	Amount studied	Frequency	Duration	Route	Source
Muscle hypertrophy and atrophy protection	Mice (young, aged, casting, steroid and hindlimb suspension models)	0.1 to 30 mg/kg; 10 mg/kg standard	Not consistently reported	3 to 4 weeks	Subcutaneous	Latres et al., Skeletal Muscle 2015

Practitioner and community-reported protocols

Peptide Protocol Wiki repeats the COURAGE amounts and describes subcutaneous use, but says the interval is not publicly specified and states that the drug is available only within clinical trials. Beyond that site, no established or reliably sourced dosing information was identified. The garetosmab 10 mg/kg intravenous figure on that site could not be traced to a primary source.

Conflicts and unanswered questions

Two Regeneron sets of 26-week figures differ by about 0.1 point (for example, semaglutide alone is listed at 6.5 percent in one release and 6.6 percent in later summaries); the reason is not stated. The registry’s part labels (A for healthy volunteers, B for 26 weeks, C for 52 weeks) do not match the press-release language. Route, interval and the exact trevogrumab-to-garetosmab dose pairing are not confirmed from primary sources.

Important published research

COURAGE phase 2 (company-reported, 2025 and 2026). About 975 adults with obesity, semaglutide 2.4 mg with placebo or trevogrumab at 25, 75, 200 or 400 mg, with a garetosmab arm; 26 to 52 weeks. Findings are summarized above. Limits: no peer-reviewed paper yet, per-arm sample sizes and some safety data not released, MRI from 76 participants. Meaning: a consistent lean-mass signal that still lacks a functional readout.

Latres et al., Skeletal Muscle 2015 (animal). Regeneron scientists showed that REGN1033 increased muscle mass and force in young and aged mice and blunted atrophy in disuse and steroid models. Limits: mice only; findings in mice do not guarantee the same effect in people.

Timing, duration, and research variables

Effects were reported at 26 and 52 weeks, with the higher-dose trevogrumab effect tending to persist after semaglutide was stopped. Dose mattered: 75 mg preserved more lean mass than 25 mg. Whether continuous treatment is needed, and whether the benefit holds beyond a year, has not been shown. We do not suggest a schedule.

Combinations and related research

Formally studied combinations

Trevogrumab with semaglutide, and trevogrumab with garetosmab plus semaglutide, were studied in COURAGE. The triplet preserved more lean mass but brought more serious adverse events, discontinuations and muscle spasms, plus two deaths, and Regeneron will not advance it.

Mechanistically plausible combinations

Other muscle-preserving antibodies have also been tested with GLP-1 drugs, including bimagrumab and apitegromab. Biohaven’s taldefgrobep alfa is heading the same way. Results do not transfer between drugs.

Practitioner and community combinations

None with an identifiable source.

Side effects, risks, and limitations

In the lower-dose portion, 77 percent of trevogrumab participants reported an adverse event versus 82 percent on placebo plus semaglutide; the most common were nausea, constipation, diarrhea and vomiting, which are typical of semaglutide itself. Regeneron called the lower doses generally well tolerated. Serious adverse events, discontinuations and higher-dose safety were not given in the October 2026 release.

The garetosmab combination had more serious adverse events, discontinuations and muscle spasms. Two participants in that group died within 26 weeks, one of undetermined cause with several cardiovascular risk factors and one of cardiac arrest with cardiovascular disease; Regeneron reports no causal link identified. Mechanism-based concerns for this drug class include muscle spasms and effects from blocking related signals. Long-term effects, immunogenicity and safety in older adults are unknown. Because trevogrumab is available only in trials, any product offered online under this name cannot be verified for identity, purity, sterility or concentration.

Regulatory and developmental status

Trevogrumab is not approved by the FDA, EMA or any other regulator. COURAGE is listed as active, not recruiting, with a registry completion date of October 21, 2026. Regeneron plans a new phase 2 trial in older adults with obesity and reduced muscle mass or strength. Its companion, garetosmab, was approved by the FDA in August 2026 as Pasatru for fibrodysplasia ossificans progressiva, a rare bone disease; that approval does not apply to trevogrumab or to obesity. Status verified from the sources listed below.

Frequently asked questions

What is trevogrumab?

An investigational human antibody from Regeneron that blocks myostatin, a protein that limits muscle growth. It is being tested to preserve muscle during GLP-1 weight loss.

Is trevogrumab a peptide?

No. It is a monoclonal antibody, a much larger protein. It is covered here because it is tested with peptide weight-loss drugs.

How does trevogrumab work?

It binds myostatin so the signal cannot reach muscle cells. In theory that reduces muscle loss during rapid weight loss.

What dosage of trevogrumab has been studied?

COURAGE used 25 mg, 75 mg, 200 mg and 400 mg with semaglutide 2.4 mg. Regeneron has not stated the route or interval in its releases.

What dosage commonly circulates online?

Mainly the COURAGE amounts, repeated by an educational site that lists the interval as unspecified. No other reliably sourced dosing information was identified, and the drug is not available outside trials.

How much lean mass did trevogrumab preserve?

In the lower-dose portion, lean-mass loss at 52 weeks was 5.8 percent (25 mg) and 4.2 percent (75 mg) versus 7.3 percent with semaglutide alone, per Regeneron.

What side effects have been reported?

Mostly semaglutide-type nausea, constipation, diarrhea and vomiting at the lower doses. The trevogrumab plus garetosmab combination had more serious events and two deaths, with no causal link identified by the company.

Has trevogrumab been studied in humans?

Yes: a 253-person phase 2 sarcopenia trial with no posted results and the COURAGE phase 2 obesity trial with company-reported results.

Is trevogrumab approved?

No. Garetosmab, used with it in one COURAGE arm, is approved for a different rare disease.

What remains unknown?

Route and interval in COURAGE, effects on strength and function, safety over longer periods, benefit in older adults, and the full peer-reviewed data.

Bottom line

Trevogrumab has the most substantial human data of the muscle-preserving antibodies still in development, and the lean-mass signal in COURAGE is consistent across doses and time points. The strongest evidence is company-reported, with a Lancet paper still in press. The published dose figures, 25, 75, 200 and 400 mg with semaglutide 2.4 mg, are real trial amounts, but the route and interval are not confirmed from primary sources. The claims that it improves strength, function or health outcomes remain speculative. The drug is not approved anywhere, and a phase 2 study in older adults is planned. Compare it with bimagrumab, apitegromab and taldefgrobep alfa, or see the clinical trial tracker.