Trevogrumab (REGN1033) Australia: What Does the Research Show?
Trevogrumab is an experimental monoclonal antibody that blocks myostatin, one of the body’s natural regulators of skeletal muscle growth. Recent animal and human studies have renewed interest in its potential to preserve and increase muscle mass.
Last updated: August 2026Trevogrumab, also known by its development code REGN1033, is one of the most closely watched experimental drugs in current myostatin research.
It has gained particular attention because it directly blocks myostatin, a protein involved in restricting skeletal muscle growth.
Research in animals has shown that inhibiting myostatin can increase muscle mass. More recently, trevogrumab has entered large human studies exploring whether the same biology can help preserve muscle during substantial weight loss.
Its combination with semaglutide has become especially interesting as researchers investigate ways to improve body composition during GLP-1 based weight loss.
Trevogrumab attempts to remove part of the biological “brake” that myostatin places on muscle growth.
What is trevogrumab?
Trevogrumab is a fully human monoclonal antibody developed to inhibit myostatin, also known as growth differentiation factor 8 or GDF-8.
Myostatin is naturally produced by the body and plays an important role in regulating skeletal muscle mass.
One of its main functions is to prevent excessive muscle growth.
This makes myostatin an attractive pharmaceutical target.
If researchers can safely reduce the signal that limits muscle growth, they may be able to preserve or increase skeletal muscle in people who would otherwise lose it.
Trevogrumab does not directly stimulate muscle in the same way an anabolic androgen does. It works by reducing a biological signal that normally restricts muscle growth.
What does REGN1033 mean?
REGN1033 is the development code used for trevogrumab by Regeneron Pharmaceuticals.
Scientific publications and older clinical trial records may therefore refer to the same drug as either:
- Trevogrumab
- REGN1033
- REGN-1033
These names refer to the same monoclonal antibody.
How does trevogrumab work?
Trevogrumab binds specifically to myostatin.
Normally, myostatin interacts with activin type II receptors and triggers signalling that limits skeletal muscle growth.
By binding myostatin, trevogrumab prevents part of this signalling process.
GDF-8
signalling
restricted
myostatin
reduced
on muscle
Importantly, trevogrumab is relatively selective.
Published research describes it as specific for GDF-8 without cross-reactivity to the closely related protein GDF-11.
Greater selectivity is attractive because broader blockade of the activin receptor system can interfere with numerous signalling proteins throughout the body.
Is trevogrumab a peptide?
No. Trevogrumab is not a conventional peptide.
It is a fully human IgG4 monoclonal antibody.
This is an important distinction because trevogrumab is sometimes discussed online alongside experimental peptides.
Monoclonal antibodies are much larger and more complex biological molecules.
Typically consists of a relatively short chain of amino acids and is much smaller than an antibody.
A large biological protein manufactured using sophisticated pharmaceutical biotechnology.
A product marketed online as a “myostatin peptide” or “myostatin blocker” should not be assumed to be equivalent to trevogrumab.
What did trevogrumab do in animal studies?
Preclinical research into trevogrumab helped establish the biological potential of pharmacological myostatin inhibition.
Myostatin blockade in mice
Published research using REGN1033 demonstrated that myostatin blockade could cause skeletal muscle hypertrophy in both young and aged mice.
The antibody also reversed experimentally induced muscle atrophy in animal models.
The research supported a broader principle that has become central to the myostatin field:
even after an animal has fully developed, pharmacological myostatin inhibition can still increase muscle mass.
That helped distinguish drug treatment from the dramatic muscularity seen in animals genetically lacking functioning myostatin from birth.
The 2025 obese mouse and monkey research
Trevogrumab gained renewed attention after research published in Nature Communications in 2025.
Researchers investigated myostatin blockade alongside another antibody called garetosmab, which targets activin A.
These treatments were combined with GLP-1 receptor agonist treatment in obese animal models.
What happened in the mice?
The combination of myostatin and activin A blockade protected lean mass while the animals lost weight.
It also increased fat loss compared with GLP-1 treatment alone.
Under some experimental conditions, lean mass actually increased while total body weight decreased.
What happened in monkeys?
Researchers then conducted a 20 week experiment in obese male cynomolgus monkeys.
The combination again preserved or increased lean mass while increasing fat loss during semaglutide treatment.
The animals were losing overall body weight while researchers were able to protect, and in some settings increase, lean tissue. This raised the possibility of producing a more favourable form of pharmaceutical weight loss.
Has trevogrumab been tested in humans?
Yes.
Trevogrumab has undergone human clinical research both alone and in combination with other experimental drugs.
Earlier Phase 1 research investigated trevogrumab and garetosmab in healthy postmenopausal women.
Researchers found that blocking both myostatin and activin A together produced greater increases in muscle mass than either pathway alone.
The combination also reduced fat mass.
This was an important result because it demonstrated that the muscle effects seen in animal models were not limited entirely to rodents or monkeys.
Pharmacologically manipulating the myostatin and activin A pathways can meaningfully alter human body composition. The remaining question is how to achieve the best balance between effectiveness, selectivity and safety.
The COURAGE Phase 2 trial
The most important current trevogrumab research is Regeneron’s COURAGE trial.
COURAGE is a Phase 2 study investigating trevogrumab with or without garetosmab alongside semaglutide in adults with obesity.
The study was designed to examine whether these treatments could improve fat loss and preserve lean mass during GLP-1 based weight loss.
Trevogrumab is still being investigated and is not an established obesity medicine.
ClinicalTrials.gov lists actual enrolment of 1,005 participants.
The COURAGE trial began in March 2024.
As of the ClinicalTrials.gov update posted in May 2026, the study was listed as active, not recruiting.
The trial includes both healthy volunteers and participants with obesity across different parts of the study.
Trevogrumab and semaglutide
The combination of trevogrumab and semaglutide is currently one of the most interesting areas of myostatin research.
GLP-1 medicines can cause large reductions in body weight.
However, weight loss is not purely body fat.
Some lean tissue can also be lost.
Regeneron’s researchers therefore investigated whether blocking myostatin could change the composition of that weight loss.
What did the completed 26 week results show?
Regeneron reported that approximately 33% of the weight lost with semaglutide alone came from lean mass.
When trevogrumab was added, approximately half of that lean mass loss was prevented.
Fat mass loss was also increased.
The current obesity trial provides evidence of meaningful lean mass preservation in humans. It should not be interpreted as evidence that trevogrumab causes the extreme muscle growth seen in genetically myostatin deficient animals.
Trevogrumab and garetosmab
Trevogrumab is frequently discussed alongside another Regeneron antibody called garetosmab.
The two drugs target different proteins.
Targets GDF-8 or myostatin, one of the main proteins responsible for restricting skeletal muscle growth.
Targets activin A, another important negative regulator acting through overlapping activin receptor pathways.
Research suggests that simultaneously blocking both proteins can produce a greater effect on muscle mass than blocking either individually.
In animal experiments, dual blockade produced muscle growth comparable with much broader activin receptor blockade.
Human Phase 1 research also reported greater than additive increases in muscle mass when the two antibodies were combined.
However, stronger inhibition can also introduce additional safety and tolerability concerns.
A useful way to understand the combination is that trevogrumab removes the myostatin brake while garetosmab reduces another brake created by activin A.
Can trevogrumab actually build muscle?
The biological evidence indicates that blocking myostatin can increase muscle mass.
Trevogrumab has produced muscle hypertrophy in preclinical models, and human research confirms that manipulating the same pathway can alter muscle mass and body composition.
The more difficult question is how large the effect of trevogrumab alone will be in healthy humans.
This is where some online discussion gets ahead of the evidence.
There is a major difference between:
- an animal genetically lacking myostatin from birth
- powerful dual pathway inhibition in an experimental study
- trevogrumab alone in a human clinical setting
These should not be treated as equivalent.
Trevogrumab is clearly biologically active in humans. The strongest current clinical application is muscle preservation during weight loss rather than proven extreme muscle gain in healthy people.
Could trevogrumab replace anabolic steroids?
There is currently no evidence supporting trevogrumab as a direct replacement for anabolic steroids.
The mechanisms are fundamentally different.
| Feature | Trevogrumab | Anabolic steroids |
|---|---|---|
| Primary pathway | Myostatin / GDF-8 inhibition | Androgen receptor signalling |
| Drug type | Monoclonal antibody | Steroid hormones or derivatives |
| Main research goal | Muscle preservation and medical applications | Varies by approved medical indication |
| Established physique use | No | Non-medical use is well documented |
| Long term evidence in healthy users | Very limited | Much larger evidence base, including known risks |
Myostatin inhibition may eventually become relevant to performance and physique enhancement, but current pharmaceutical research is not designed to answer that question.
What do we know about trevogrumab safety?
Trevogrumab remains investigational, which means its complete long term safety profile has not yet been established.
This is especially important when discussing use outside a medical setting.
The current research needs to answer several questions.
Why is trevogrumab becoming relevant now?
Trevogrumab itself is not brand new.
Myostatin antibodies have been researched for many years.
What has changed is the potential commercial use.
The rapid growth of GLP-1 and GIP based obesity medicines has created a new problem for pharmaceutical companies to solve.
Patients can now lose large amounts of total body weight, but researchers would ideally like to maximise fat loss while minimising muscle loss.
This has transformed myostatin inhibition from a relatively specialised muscle wasting concept into a potentially major obesity treatment strategy.
One medicine reduces appetite and body weight. A second medicine helps protect skeletal muscle so that a larger proportion of the weight lost comes from body fat.
Is trevogrumab available in Australia?
Trevogrumab should currently be considered an investigational pharmaceutical compound, not an established myostatin treatment available to healthy Australian consumers.
The main current obesity program remains in Phase 2 clinical research.
Australia’s Therapeutic Goods Administration generally requires therapeutic medicines to be included in the Australian Register of Therapeutic Goods before they can be routinely supplied in Australia.
Unapproved therapeutic goods can sometimes be accessed through specific clinical trial, Special Access Scheme or Authorised Prescriber pathways, but these are controlled medical pathways rather than normal consumer availability.
The existence of trevogrumab listings on research or grey market websites does not establish that the product is genuine REGN1033 or equivalent to pharmaceutical material used in Regeneron’s clinical trials.
Trevogrumab research status
| Question | Current position |
|---|---|
| What is it? | Fully human monoclonal antibody |
| Other name | REGN1033 |
| Target | Myostatin / GDF-8 |
| Developer | Regeneron Pharmaceuticals |
| Main current research | Preserving lean mass during obesity treatment |
| Major current study | COURAGE Phase 2 |
| Human evidence? | Yes |
| Animal muscle growth evidence? | Yes |
| Approved bodybuilding treatment? | No |
| Established Australian consumer medicine? | No |
Trevogrumab vs other myostatin inhibitors
Trevogrumab is only one approach to targeting myostatin.
| Compound | Target | Approach |
|---|---|---|
| Trevogrumab | Active myostatin / GDF-8 | Direct anti-myostatin antibody |
| Apitegromab | Pro and latent myostatin | Prevents myostatin activation |
| SRK-439 | Pro and latent myostatin | Selective precursor targeting |
| Bimagrumab | Activin type II receptors | Broader receptor blockade |
| Garetosmab | Activin A | Related pathway, often combined with myostatin blockade |
The major difference is selectivity.
Some drugs directly target myostatin while others interfere with a broader section of the biological pathway.
The bottom line
Trevogrumab is one of the most important current drugs in myostatin research.
It directly targets myostatin, the protein also known as GDF-8 that helps limit skeletal muscle growth.
Animal research has demonstrated that myostatin blockade with REGN1033 can produce muscle hypertrophy.
More recent mouse and monkey research has shown that targeting myostatin alongside activin A can preserve or increase lean mass during substantial weight loss.
Human research has now provided an important additional signal.
In Regeneron’s 26 week COURAGE results, adding trevogrumab to semaglutide prevented approximately half of the lean mass loss associated with semaglutide treatment alone.
This does not yet make trevogrumab an effortless muscle building drug for healthy humans.
It does, however, provide strong evidence that pharmacologically targeting myostatin can meaningfully change human body composition.
The question is no longer whether trevogrumab affects muscle biology. The more important questions are how large the effect can become in humans, how well it translates into strength and function, and whether long term myostatin inhibition can be used safely.
Frequently asked questions
What is trevogrumab?
Trevogrumab is an investigational fully human monoclonal antibody that binds to and inhibits myostatin, also known as GDF-8.
Is REGN1033 the same as trevogrumab?
Yes. REGN1033 is the development code for trevogrumab.
Is trevogrumab a peptide?
No. Trevogrumab is a monoclonal antibody rather than a conventional research peptide.
Does trevogrumab block myostatin?
Yes. Trevogrumab is designed to bind myostatin or GDF-8 and reduce its biological activity.
Can trevogrumab increase muscle?
Myostatin blockade with trevogrumab has produced muscle hypertrophy in animal research. Human research confirms that the pathway can alter lean mass, although extreme muscle gains in healthy humans have not been established.
Why is trevogrumab being combined with semaglutide?
Researchers are investigating whether trevogrumab can preserve skeletal muscle while semaglutide causes substantial weight loss, allowing a greater proportion of total weight loss to come from body fat.
What did the COURAGE study find?
Regeneron’s completed 26 week results reported that adding trevogrumab prevented approximately half of the lean mass loss associated with semaglutide alone while also increasing fat mass loss.
What is the difference between trevogrumab and garetosmab?
Trevogrumab targets myostatin or GDF-8. Garetosmab targets activin A. Research suggests that simultaneously blocking both signals can produce a stronger effect on muscle mass.
Is trevogrumab available in Australia?
Trevogrumab remains an investigational drug and should not be considered an established consumer treatment in Australia. Its major obesity program remains in clinical development.
Explore myostatin research
Research hub Myostatin Inhibitors AustraliaLearn how myostatin controls muscle growth and compare the main experimental drugs currently targeting the pathway.
Read the complete myostatin guide →Research sources
- Mastaitis JW, Gomez D, Raya JG, et al. GDF8 and activin A blockade protects against GLP-1 induced muscle loss while enhancing fat loss in obese male mice and non-human primates. Nature Communications. 2025.
- Gonzalez Trotter D, et al. GDF8 and activin A are key negative regulators of muscle mass in postmenopausal females: a randomized Phase I trial. Nature Communications. 2025.
- Regeneron Pharmaceuticals. Complete 26 week results from the Phase 2 COURAGE trial investigating trevogrumab with semaglutide. September 2025.
- ClinicalTrials.gov. NCT06299098. COURAGE: A randomized double blind study of trevogrumab, with or without garetosmab, in addition to semaglutide in patients with obesity.
- Latres E, Pangilinan J, Miloscio L, et al. Myostatin blockade with a fully human monoclonal antibody induces muscle hypertrophy and reverses muscle atrophy in young and aged mice. Skeletal Muscle. 2015.