Bimagrumab_Dosage, benefits & legal status
Also known as BYM338
An experimental shot that strips fat while adding muscle.
Common vial size is what vendors typically sell, not a recommendation. Enter your own vial in the calculator.
What is Bimagrumab?
Plain language first. The technical label stays, but it never stands alone.Overview
By releasing that brake it builds muscle while the body sheds fat, an unusual combination being studied with GLP-1 drugs. It is still experimental.
Bimagrumab is a monoclonal antibody that blocks the activin type II receptor, a signal that normally limits muscle.
What it's used for
An unusual experimental shot that strips fat while adding muscle, by blocking a signal that limits muscle. It is being studied alongside GLP-1 drugs.
How does Bimagrumab work?
What it does in the body, and where.Bimagrumab is not a weight-loss drug in the usual sense. It changes what you lose rather than how much.
- 01It blocks the activin type II receptorThat receptor carries the signal that normally limits how much muscle you build. Blocking it releases the brake.
- 02Muscle grows while fat is lostAn unusual combination. Most weight loss, including from GLP-1 drugs, takes muscle along with fat.
- 03It is being tested alongside GLP-1 drugs, not instead of themThe interest is in pairing it with semaglutide so the weight lost is fat rather than lean tissue.
- 04Dosed by body weight, into a vein10 to 30 mg per kilogram by infusion, which is a very different proposition from a weekly self-injection.
- 05Phase 2 only.
What else is it used for?
Each use below carries its own evidence level. Approved means regulators have cleared it for that purpose. Investigational means it is in trials. Early research means it is being studied and is not established.
- Losing fat while gaining muscle, an unusual combination being studied alongside the GLP-1 drugsInvestigational
- Muscle-wasting conditions, where an earlier trial failed to show functional benefitInvestigational
The published record
Papers and trials about Bimagrumab
Searched: Bimagrumab, BYM338.
73 papers tagged human · 32 not reviews or lab · 17 clinical trial publications
17 registered trials · 10 with posted results
Furthest stage reached: Phase 3, results posted
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Prohibited at all times, in and out of competition. S4.3 Anti-activin receptor IIB antibodies (e.g. bimagrumab). Non-Specified.RegulatorsCounted from Europe PMC indexing, not read by a person; a human tag can land on reviews, commentary or lab papers; clinical trial publications is the narrower count.
At a glance
Four things to know about Bimagrumab
Evidence
Investigational
Category
Muscle building
Common vial
Varies
Half-life
5 to 19 days, depending on concentration
How much, and do you cycle it?
The range, and whether you take breaks.10 up to 30 mg/kg per month (trial doses), monthly. Not cycled. Infused every 12 weeks in the trials Trial dose
The dosing interval is long because the antibody lasts a long time, not because anyone is cycling it. The phase 2b trial ran 48 weeks blinded with a further 24 weeks open label.
5 to 19 days, depending on concentrationTrial protocol
The half-life is not fixed. It runs about 19 days when blood levels are high and falls to about 5 days when clearance is at its fastest, because the antibody is consumed by the target it binds.
Source: Petricoul O, et al. Clin Pharmacokinet 2023;62:141-155, DOI 10.1007/s40262-022-01189-0
You can compare this against the whole library to see where it sits.
How is it given?
Dosing context and source notes.Dosed by body weight, into a vein, not as a flat amount. Phase 2 used 10 or 30 mg per kg. Dosed by body weight and given into a vein, so no vial draw can be shown. Phase 2 used 10 or 30 mg per kg.
How do you store it?
Before mixing, and after.Dry powder in the freezer or fridge. Once mixed, fridge, and use within about a month.
Unmixed lyophilized Bimagrumab keeps for a long time cold. Once you add water the clock starts: most reconstituted vials hold up for roughly 28 to 30 days at fridge temperature. Keep it out of light, and do not freeze it after mixing.
What are the side effects and cautions?
Known cautions and warnings for this compound.This compound is in clinical trials and is not sold in a standard vial, so there is no common vial size to show. Trial doses are given as prepared by the study, and the reconstitution calculator does not apply. Dosed by body weight and given by infusion in trials, so no vial size applies.
Who should avoid it
- No formal contraindications established
- Pregnancy
Stop and get help
- Severe upper stomach pain, which can signal pancreas inflammation
- Signs of an allergic reaction such as face or throat swelling, hives, or trouble breathing
Common effects
- Muscle spasms, in roughly half to two thirds of people at higher doses
- Diarrhea in about four in ten
- Acne or skin eruptions
- Falls, in older trial participants
Where this page says nothing is established, that means nobody has studied it, not that a compound is safe.
Is Bimagrumab approved?
And where the numbers on this page come from.No. Bimagrumab is not approved anywhere and is currently in company-run clinical trials. There is no legal route to obtain it outside a trial.
- Approval statusInvestigational
- RouteInto a vein or under the skin
- Checked22 September 2026
- DoseFrom published clinical trials. Not approved by a regulator for this dose.
- Vial sizeFrom what vendors typically list; not a recommendation.
- SourcesNone traced yet.
What has happened recently
We have not yet written a full regulatory note for this compound. The status above is current as of the date shown.
What regulators say
From official documentsProhibited at all times, in and out of competition. S4.3 Anti-activin receptor IIB antibodies (e.g. bimagrumab). Non-Specified.
Checked 12 September 2026WADA: The 2026 Prohibited List (in force 1 January 2026)
You can compare this against the whole library, or read how to check a seller.
What else is like Bimagrumab?
Others in Muscle building, side by side.If you're weighing Bimagrumab, it's worth reading Mecasermin (Increlex), Mifomelatide, and Tesamorelin in the same class.
An experimental shot that strips fat while adding muscle.
- Dose
- 10 up to 30 mg/kg per month (trial doses)
- How often
- Monthly
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- 0.04 to 0.08 mg/kg twice daily to start, up to 0.12 mg/kg twice daily (label)
- How often
- Twice a day, with a meal or snack
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- Dose
- 12.5 to 50 mg daily (phase 2 doses)
- How often
- Daily
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- Dose
- 1.28 up to 2 mg per day, depending on which product you have
- How often
- Daily
Guides for this compound
- How to Reconstitute a Peptide
Mix peptide powder with bacteriostatic water, step by step.
- How to Read an Insulin Syringe
Read the units, convert to millilitres, and draw the exact dose.
- mcg vs mg: The Peptide Dosing Mistake to Avoid
Your vial says mg and your protocol says mcg. Here is the conversion and how to check it.
- Why Does My Peptide Injection Itch or Welt
Injection-site irritation, a histamine reaction, or a true allergy, and how to tell them apart.
- How to Read a Peptide COA
What the purity number does and does not tell you, and how to spot an edited report.
Sources
No primary source has been traced for this compound yet. Treat everything on this page as unverified until one is. How we grade evidence
Beyond these, 97 records are indexed. Browse the records