Non-peptide
Bimagrumab
Also known as
BYM338 · bima
Community talk. May contain inaccuracies. Not medical advice. Not a protocol. Not for human or animal use.
What it is
| Identity | An investigational antibody that blocks activin type II receptors, discussed for fat loss with preserved or increased lean mass. |
|---|---|
| Large protein biologic | It is an antibody rather than a small peptide. IV infusions and separate under-the-skin research formulations are different preparations. |
Notes
Bimagrumab is an investigational antibody discussed for fat loss while preserving or increasing lean mass, especially alongside GLP-1 drugs. Modern forum accounts here describe expectations rather than confirmed self-use; increased lean mass does not guarantee increased strength.
An antibody, rather than a small peptide. Bimagrumab, also called BYM338 or bima, blocks activin type II receptors: receiving points for signals that restrain muscle growth. Bodybuilding discussion calls it a myostatin inhibitor, but receptor blockade affects more than myostatin alone. It is a manufactured antibody, a large protein biologic. Heymsfield et al. — BELIEVE randomized phase 2 trial (Official context · Accessed 2026-09-30)
IV and under-the-skin research are different. IV means infusion into a vein. Subcutaneous means delivery beneath the skin. Forums emphasize IV logistics, while separate trials also studied subcutaneous formulations. r/ResearchCompounds — Bimagrumab plus semaglutide discussion (Community discussion · Accessed 2026-09-30) · Petricoul et al. — IV and SC bimagrumab pharmacokinetics and pharmacodynamics (Official context · Accessed 2026-09-30)
Source context — Heymsfield et al. — BELIEVE randomized phase 2 trial: 507 adults with obesity, excluding diabetes; controlled IV bimagrumab and SC semaglutide, not a retatrutide stack or bodybuilding trial. Lean mass is not an isolated muscle/strength measurement. Publisher redirected with a cookie-error query while returning readable article body.
Source context — r/ResearchCompounds — Bimagrumab plus semaglutide discussion: Expectation-focused anonymous discussion. Statements about insurance or professional bodybuilders are guesses, not verified prices or use reports.
Source context — Petricoul et al. — IV and SC bimagrumab pharmacokinetics and pharmacodynamics: Abstract only; full article requires subscription and was not inspected. Fixed-dose research formulations are not equivalent to mg/kg IV doses or consumer vials. Older original misattributes this paper to Garito; actual first author is Petricoul.
What people notice
| Modern forum expectations | People hope to lose fat without losing muscle, especially alongside GLP-1 drugs. The modern threads describe predictions rather than confirmed personal use. |
|---|---|
| One trial participant | An inclusion body myositis participant reported easier typing and opening cans, little walking improvement, and persistent diarrhea. This is one disease-specific account. |
| Lean mass versus strength | An older single-dose study found body-composition changes without increased strength. More lean mass on a scan does not guarantee stronger lifts or easier walking. |
Notes
Bimagrumab is an investigational antibody discussed for fat loss while preserving or increasing lean mass, especially alongside GLP-1 drugs. Modern forum accounts here describe expectations rather than confirmed self-use; increased lean mass does not guarantee increased strength.
A leaner body without losing as much lean tissue. The Retatrutide discussion imagines combining fat loss with muscle preservation; some replies expect muscle gain, while others question the cost and usefulness alongside training. These are predictions. Semaglutide combination results do not establish the same outcome with retatrutide. r/Retatrutide — Reta + Bimagrumab? (Community discussion · Accessed 2026-09-30)
Daily tasks may matter more than a scan. A participant blogging as stephhicks described easier typing and opening cans during an inclusion body myositis trial. That is a disease-specific perceived benefit, not evidence of a bodybuilding effect or a cure. A Guinea Pig's Tale — That's all folks! (Personal report · Accessed 2026-09-30)
Noticing benefits does not settle causation. In May 2016, stephhicks reported little walking improvement and questioned whether exercise explained other changes. A commenter reported continued weakness but guessed placebo assignment; that cannot establish active-drug nonresponse. A Guinea Pig's Tale — BYM338: no answers yet (Personal report · Accessed 2026-09-30)
Everyday improvement came with a burden. Stephhicks's later account paired practical gains with diarrhea and exhausting infusion journeys. Both posts describe one participant, not two successful users. Disease progression, exercise and treatment exposure complicate the story. A Guinea Pig's Tale — That's all folks! (Personal report · Accessed 2026-09-30)
Lean mass and strength can separate. The older single-dose study found body-composition changes without increased strength. A larger number on a body-composition scan does not automatically mean easier walking or heavier lifts. Rooks et al. — Single-dose safety and pharmacokinetics in older and obese adults (Official context · Accessed 2026-09-30)
Source context — r/Retatrutide — Reta + Bimagrumab?: Anonymous expectations and secondhand trial numbers, not administration diaries. The author's linked GLP1.Guide article and this opening post are the same author's narrative, not independent evidence. Hidden/deleted replies not inspected.
Source context — A Guinea Pig's Tale — That's all folks!: One self-described inclusion body myositis participant. Allocation/dose and records not independently verified; perceived benefit does not prove causation or healthy-user benefit. Dose shorthand and monkey-heart hearsay in comments lack interpretable units/primary support and are not adopted.
Source context — A Guinea Pig's Tale — BYM338: no answers yet: Same participant as June post, not independent corroboration. Gary's blinded allocation unknown, so his deterioration is not established active-drug nonresponse. Participant's recounting of trial arms is secondhand protocol information.
Source context — Rooks et al. — Single-dose safety and pharmacokinetics in older and obese adults: 24 participants, single IV administration; not community onset/duration. Initial reCAPTCHA result, subsequent open returned full readable text. Pregnant/nursing participants were excluded.
Doses people talk about
| Trial figures repeated online | 10 or 30 mg/kg per IV administration appears in forum discussion. These are weight-based trial figures, not a verified self-use band or a daily total. |
|---|---|
| Separate IV trial schedules | One study used 10 mg/kg every four weeks, capped at 1200 mg. BELIEVE used 10 or 30 mg/kg at entry/week four, then weeks 16, 28, 40, 52 and 64. |
| Separate SC trial | Adults aged 70 or older received 52.5, 150 or 300 mg per weekly subcutaneous bolus for twelve doses. These fixed amounts are not interchangeable with IV mg/kg. |
Notes
10 or 30 mg/kg IV: trial figures repeated online. A Retatrutide commenter cites these weight-based study amounts while discussing cost. Milligrams per kilogram refers to the amount per administration based on body weight; it is not 10–30 mg total or a daily amount. No verified self-use dose band emerges from that thread. r/Retatrutide — Reta + Bimagrumab? (Community discussion · Accessed 2026-09-30)
IV dose and visit intervals varied. The 2021 diabetes/obesity study used 10 mg/kg per IV infusion every four weeks, capped at 1200 mg. BELIEVE gave 10 or 30 mg/kg at randomization and week four, then weeks 16, 28, 40, 52 and 64. These are separate trial schedules. Heymsfield et al. — Bimagrumab in adults with type 2 diabetes and obesity (Official context · Accessed 2026-09-30) · Heymsfield et al. — BELIEVE randomized phase 2 trial (Official context · Accessed 2026-09-30)
SC trials used fixed amounts. In adults aged at least 70, one phase 1 study used 52.5, 150 or 300 mg per weekly subcutaneous bolus for twelve doses, with separate SC infusion arms. Fixed milligrams and weight-based IV amounts are not interchangeable. Petricoul et al. — IV and SC bimagrumab pharmacokinetics and pharmacodynamics (Official context · Accessed 2026-09-30)
Source context — r/Retatrutide — Reta + Bimagrumab?: Anonymous expectations and secondhand trial numbers, not administration diaries. The author's linked GLP1.Guide article and this opening post are the same author's narrative, not independent evidence. Hidden/deleted replies not inspected.
Source context — Heymsfield et al. — Bimagrumab in adults with type 2 diabetes and obesity: Small controlled disease-population trial; effects and adverse-event occurrence do not establish gray-market safety or causality for every event.
Source context — Heymsfield et al. — BELIEVE randomized phase 2 trial: 507 adults with obesity, excluding diabetes; controlled IV bimagrumab and SC semaglutide, not a retatrutide stack or bodybuilding trial. Lean mass is not an isolated muscle/strength measurement. Publisher redirected with a cookie-error query while returning readable article body.
Source context — Petricoul et al. — IV and SC bimagrumab pharmacokinetics and pharmacodynamics: Abstract only; full article requires subscription and was not inspected. Fixed-dose research formulations are not equivalent to mg/kg IV doses or consumer vials. Older original misattributes this paper to Garito; actual first author is Petricoul.
Half-life, onset & duration
| Felt onset | Modern threads provide no dependable first-dose timeline for noticeable fat loss, easier movement or a feeling. |
|---|---|
| Felt duration | No reliable single-dose felt window. One participant's decline during a three-month break cannot measure an infusion's duration or prove withdrawal. |
| Half-life | Sponsor human IV estimates are about 19 days at high concentrations and 5 days when removal is fastest. These depend on concentration and do not establish SC timing or felt duration. |
Notes
No dependable self-use onset window. Modern discussions provide no first-dose timeline for fat loss, easier movement or a noticeable feeling. r/PeptideForum — Bimagrumab (Community discussion · Accessed 2026-09-30) · r/ResearchCompounds — Bimagrumab plus semaglutide discussion (Community discussion · Accessed 2026-09-30)
No reliable single-dose felt duration. No healthy-user duration diary is available here. A participant's decline during a three-month treatment break cannot measure one infusion's benefit or establish withdrawal as its cause. A Guinea Pig's Tale — BYM338: no answers yet (Personal report · Accessed 2026-09-30) · r/PeptideForum — Bimagrumab (Community discussion · Accessed 2026-09-30)
19 days and 5 days describe different concentrations. Sponsor documentation gives about 19 days at high blood concentrations and about 5 days when removal is fastest. These human IV estimates do not describe SC kinetics or felt duration. Novartis amended protocol — JAMA Supplement 2, human half-life (Official context · Accessed 2026-09-30)
Source context — r/PeptideForum — Bimagrumab: No visible firsthand use account; no source establishes an absolute inability to manufacture a copy or current global availability. Regulatory/development assertions not adopted as facts.
Source context — r/ResearchCompounds — Bimagrumab plus semaglutide discussion: Expectation-focused anonymous discussion. Statements about insurance or professional bodybuilders are guesses, not verified prices or use reports.
Source context — A Guinea Pig's Tale — BYM338: no answers yet: Same participant as June post, not independent corroboration. Gary's blinded allocation unknown, so his deterioration is not established active-drug nonresponse. Participant's recounting of trial arms is secondhand protocol information.
Source context — Novartis amended protocol — JAMA Supplement 2, human half-life: Sponsor synthesis of prior human IV data; exact estimation cohort/derivation not specified. Concentration-dependent 19 and 5 days do not give SC kinetics or felt duration. Direct unsigned CDN URL failed; linked PDF opened through publisher's generated delivery URL.
Cycles people discuss
| Personal on/off use | Older weeks-on/weeks-off discussion mentions cost and caution, with no verified self-use calendar or tolerance-reset interval. |
|---|---|
| Research visits | Study infusion intervals are protocol schedules, not evidence of a community cycle or of how long benefits feel present. |
Notes
Weeks on and off remain unverified. Older discussion links weeks-on/off breaks to cost and caution without a verified personal calendar. It establishes no cycle length or tolerance-reset interval.
No community-measured half-life established. These discussions provide no participant measurement. Weeks between infusion visits describe a schedule, not the antibody's half-life; human-study estimates appear separately below. r/PeptideForum — Bimagrumab (Community discussion · Accessed 2026-09-30)
IV dose and visit intervals varied. The 2021 diabetes/obesity study used 10 mg/kg per IV infusion every four weeks, capped at 1200 mg. BELIEVE gave 10 or 30 mg/kg at randomization and week four, then weeks 16, 28, 40, 52 and 64. These are separate trial schedules. Heymsfield et al. — Bimagrumab in adults with type 2 diabetes and obesity (Official context · Accessed 2026-09-30) · Heymsfield et al. — BELIEVE randomized phase 2 trial (Official context · Accessed 2026-09-30)
Source context — r/PeptideForum — Bimagrumab: No visible firsthand use account; no source establishes an absolute inability to manufacture a copy or current global availability. Regulatory/development assertions not adopted as facts.
Source context — Heymsfield et al. — Bimagrumab in adults with type 2 diabetes and obesity: Small controlled disease-population trial; effects and adverse-event occurrence do not establish gray-market safety or causality for every event.
Source context — Heymsfield et al. — BELIEVE randomized phase 2 trial: 507 adults with obesity, excluding diabetes; controlled IV bimagrumab and SC semaglutide, not a retatrutide stack or bodybuilding trial. Lean mass is not an isolated muscle/strength measurement. Publisher redirected with a cookie-error query while returning readable article body.
Stacks
| Retatrutide ideas | Forum contributors imagine combining bimagrumab with retatrutide, protein and resistance training; they do not report having tried that stack. |
|---|---|
| Semaglutide research | Semaglutide was studied in combination with bimagrumab. Those trial results do not establish the same outcome with retatrutide. |
Notes
A leaner body without losing as much lean tissue. The Retatrutide discussion imagines combining fat loss with muscle preservation; some replies expect muscle gain, while others question the cost and usefulness alongside training. These are predictions. Semaglutide combination results do not establish the same outcome with retatrutide. r/Retatrutide — Reta + Bimagrumab? (Community discussion · Accessed 2026-09-30)
Excitement meets practical skepticism. In the Retatrutide thread, enthusiasts imagine adding resistance training and protein to a drug combination; others prefer lifting to the complexity of antibody administration. They disagree about the value of the idea, without reporting that they tried the stack. r/Retatrutide — Reta + Bimagrumab? (Community discussion · Accessed 2026-09-30)
Abstract; Main; Results/body composition; Safety; Discussion on lean-mass measurement; dosing Procedures and loading-dose discussion. Heymsfield et al. — BELIEVE randomized phase 2 trial (Official context · Accessed 2026-09-30)
Source context — r/Retatrutide — Reta + Bimagrumab?: Anonymous expectations and secondhand trial numbers, not administration diaries. The author's linked GLP1.Guide article and this opening post are the same author's narrative, not independent evidence. Hidden/deleted replies not inspected.
Source context — Heymsfield et al. — BELIEVE randomized phase 2 trial: 507 adults with obesity, excluding diabetes; controlled IV bimagrumab and SC semaglutide, not a retatrutide stack or bodybuilding trial. Lean mass is not an isolated muscle/strength measurement. Publisher redirected with a cookie-error query while returning readable article body.
Watch for
| Reported adverse events | Trials report muscle spasms, diarrhea, rash/acne and respiratory infections. One participant described persistent diarrhea and exhausting infusion journeys. |
|---|---|
| Laboratory monitoring | The diabetes/obesity study recorded muscle- and pancreatic-enzyme changes and a serious pancreatitis event. An event during treatment does not prove causation. |
| Unverified products | A listing does not establish antibody identity, combination safety or long-term safety. Trials excluding pregnancy/nursing cannot establish safety there. |
Notes
Cramps, diarrhea and skin effects. Trials report muscle spasms, diarrhea, rash or acne, and respiratory infections. Persistent diarrhea appears in stephhicks's account. An event occurring during treatment does not prove the drug caused it. Heymsfield et al. — Bimagrumab in adults with type 2 diabetes and obesity (Official context · Accessed 2026-09-30) · A Guinea Pig's Tale — That's all folks! (Personal report · Accessed 2026-09-30)
Everyday improvement came with a burden. Stephhicks's later account paired practical gains with diarrhea and exhausting infusion journeys. Both posts describe one participant, not two successful users. Disease progression, exercise and treatment exposure complicate the story. A Guinea Pig's Tale — That's all folks! (Personal report · Accessed 2026-09-30)
Monitoring involves more than body weight. The diabetes/obesity trial recorded muscle-enzyme increases, pancreatic-enzyme changes and a serious pancreatitis event. Trial supervision and laboratory monitoring do not transfer to an unidentified product. Heymsfield et al. — Bimagrumab in adults with type 2 diabetes and obesity (Official context · Accessed 2026-09-30)
Product identity and combinations remain uncertain. Community cautions question vial identity and long-term use. Older generic notes also list redness, itching, lumps or bruising without verified antibody-user events. A listing or hypothetical stack does not establish identity, compatibility or safety; multiple agents would complicate attribution.
Pregnancy and serious symptoms are separate concerns. Pregnant or nursing people were excluded from the older study, leaving its findings unable to establish safety there. Severe allergy, chest pain, sudden neurological changes or uncontrolled blood pressure/glucose require medical care. Rooks et al. — Single-dose safety and pharmacokinetics in older and obese adults (Official context · Accessed 2026-09-30)
Source context — Heymsfield et al. — Bimagrumab in adults with type 2 diabetes and obesity: Small controlled disease-population trial; effects and adverse-event occurrence do not establish gray-market safety or causality for every event.
Source context — A Guinea Pig's Tale — That's all folks!: One self-described inclusion body myositis participant. Allocation/dose and records not independently verified; perceived benefit does not prove causation or healthy-user benefit. Dose shorthand and monkey-heart hearsay in comments lack interpretable units/primary support and are not adopted.
Source context — Rooks et al. — Single-dose safety and pharmacokinetics in older and obese adults: 24 participants, single IV administration; not community onset/duration. Initial reCAPTCHA result, subsequent open returned full readable text. Pregnant/nursing participants were excluded.
Full notes
Bimagrumab is an investigational antibody discussed for fat loss while preserving or increasing lean mass, especially alongside GLP-1 drugs. Modern forum accounts here describe expectations rather than confirmed self-use; increased lean mass does not guarantee increased strength.
What Bimagrumab is
- An antibody, rather than a small peptide. Bimagrumab, also called BYM338 or bima, blocks activin type II receptors: receiving points for signals that restrain muscle growth. Bodybuilding discussion calls it a myostatin inhibitor, but receptor blockade affects more than myostatin alone. It is a manufactured antibody, a large protein biologic. Official context
- The appeal is changing what weight is lost. GLP-1 communities want fat loss with less loss of muscle and strength. The GLP1.Guide introduction frames it as a possible muscle-preserving addition. That describes the hope behind combination talk, not someone reporting a successful personal stack. Community guide
- IV and under-the-skin research are different. IV means infusion into a vein. Subcutaneous means delivery beneath the skin. Forums emphasize IV logistics, while separate trials also studied subcutaneous formulations. Reddit Official context
Benefits people seek
- A leaner body without losing as much lean tissue. The Retatrutide discussion imagines combining fat loss with muscle preservation; some replies expect muscle gain, while others question the cost and usefulness alongside training. These are predictions. Semaglutide combination results do not establish the same outcome with retatrutide. Reddit
- Daily tasks may matter more than a scan. A participant blogging as stephhicks described easier typing and opening cans during an inclusion body myositis trial. That is a disease-specific perceived benefit, not evidence of a bodybuilding effect or a cure. Personal report
- Lean mass and strength can separate. The older single-dose study found body-composition changes without increased strength. A larger number on a body-composition scan does not automatically mean easier walking or heavier lifts. Official context
Doses people discuss
- 10 or 30 mg/kg IV: trial figures repeated online. A Retatrutide commenter cites these weight-based study amounts while discussing cost. Milligrams per kilogram refers to the amount per administration based on body weight; it is not 10–30 mg total or a daily amount. No verified self-use dose band emerges from that thread. Reddit
- Other numbers belong to other drugs. The same thread mentions 3 or 6 mg daily for enobosarm, a different compound. Those numbers are not Bimagrumab doses, and the suggested multi-drug combinations are hypothetical. Reddit
Half-life in community discussion
- No community-measured half-life established. These discussions provide no participant measurement. Weeks between infusion visits describe a schedule, not the antibody's half-life; human-study estimates appear separately below. Reddit
When people notice a change
- No dependable self-use onset window. Modern discussions provide no first-dose timeline for fat loss, easier movement or a noticeable feeling. Reddit Reddit
How long changes seem to last
- No reliable single-dose felt duration. No healthy-user duration diary is available here. A participant's decline during a three-month treatment break cannot measure one infusion's benefit or establish withdrawal as its cause. Personal report Reddit
Courses and breaks discussed
- Weeks on and off remain unverified. Older discussion links weeks-on/off breaks to cost and caution without a verified personal calendar. It establishes no cycle length or tolerance-reset interval. Community
Cautions and tradeoffs
- Cramps, diarrhea and skin effects. Trials report muscle spasms, diarrhea, rash or acne, and respiratory infections. Persistent diarrhea appears in stephhicks's account. An event occurring during treatment does not prove the drug caused it. Official context Personal report
- Monitoring involves more than body weight. The diabetes/obesity trial recorded muscle-enzyme increases, pancreatic-enzyme changes and a serious pancreatitis event. Trial supervision and laboratory monitoring do not transfer to an unidentified product. Official context
- Product identity and combinations remain uncertain. Community cautions question vial identity and long-term use. Older generic notes also list redness, itching, lumps or bruising without verified antibody-user events. A listing or hypothetical stack does not establish identity, compatibility or safety; multiple agents would complicate attribution. Community
- Pregnancy and serious symptoms are separate concerns. Pregnant or nursing people were excluded from the older study, leaving its findings unable to establish safety there. Severe allergy, chest pain, sudden neurological changes or uncontrolled blood pressure/glucose require medical care. Official context Community
What the human studies actually measured
- IV dose and visit intervals varied. The 2021 diabetes/obesity study used 10 mg/kg per IV infusion every four weeks, capped at 1200 mg. BELIEVE gave 10 or 30 mg/kg at randomization and week four, then weeks 16, 28, 40, 52 and 64. These are separate trial schedules. Official context Official context
- SC trials used fixed amounts. In adults aged at least 70, one phase 1 study used 52.5, 150 or 300 mg per weekly subcutaneous bolus for twelve doses, with separate SC infusion arms. Fixed milligrams and weight-based IV amounts are not interchangeable. Official context
- The trials included lifestyle counseling. BELIEVE participants received monthly diet, protein and activity counseling. Forum assumptions about trial participants doing nothing special should not be treated as study facts. Official context
- Blood-sugar improvement was studied separately. The older diabetes/obesity trial reported improved blood-sugar measures. That does not establish an effect in healthy self-users. Official context
- 19 days and 5 days describe different concentrations. Sponsor documentation gives about 19 days at high blood concentrations and about 5 days when removal is fastest. These human IV estimates do not describe SC kinetics or felt duration. Official context
- A small IV study could not calculate a conventional half-life. Changing removal rates prevented that analysis. Its body-composition endpoints did not measure a felt-effect window. Official context
What people discuss and report
- Excitement meets practical skepticism. In the Retatrutide thread, enthusiasts imagine adding resistance training and protein to a drug combination; others prefer lifting to the complexity of antibody administration. They disagree about the value of the idea, without reporting that they tried the stack. Reddit
- Cost claims are predictions, not price checks. ResearchCompounds replies anticipate high expense and restricted access, with speculative professional-bodybuilder use. They provide no verified price, insurance decision or bodybuilder diary. The absolute claim that a copy could never exist goes beyond what these comments establish. Reddit
- Noticing benefits does not settle causation. In May 2016, stephhicks reported little walking improvement and questioned whether exercise explained other changes. A commenter reported continued weakness but guessed placebo assignment; that cannot establish active-drug nonresponse. Personal report
- Everyday improvement came with a burden. Stephhicks's later account paired practical gains with diarrhea and exhausting infusion journeys. Both posts describe one participant, not two successful users. Disease progression, exercise and treatment exposure complicate the story. Personal report
- Muscular-animal images are a different comparison. The Bluelight discussion connected receptor inhibition with interest in unusually muscular animals. Inherited myostatin mutations in animals are not a preview of what an adult human will experience after Bimagrumab. Bluelight
- Trial-news arguments are not treatment reports. PeptideForum replies dispute whether stopping one program means development ended. That historical argument provides no personal dose, timing or outcome, and a cancelled trial alone cannot settle the status of every other study. Reddit