MEDICAL DISCLAIMER: Educational research guidelines only. Lyophilized peptides are investigational chemical compounds and are NOT approved for human consumption, diagnosis, or therapy. Consult a licensed physician before any research application.
Bimagrumab Dosage Chart, Schedule & Reconstitution Protocol
Quickstart Highlights
Bimagrumab (BYM338) is a fully human anti-ActRII (ActRIIA/ActRIIB) IgG1 monoclonal antibody that blocks myostatin, activin A, and GDF11 to build skeletal muscle and, notably, strip body fat. Originally developed by Novartis for muscle-wasting disorders such as sporadic inclusion body myositis, it missed its functional endpoint in the phase 2b RESILIENT trial but showed a powerful metabolic signal — large fat-mass loss with preserved lean mass — that has redirected it toward obesity and type 2 diabetes (PMID 33264516, 41772149). The clinically studied regimen is 10 mg/kg by intravenous infusion once every 4 weeks, capped at 1200 mg. Because it is a large protein given IV, the subcutaneous reconstitution figures on this page are an educational measurement reference only, not the real route. Bimagrumab is investigational and not approved by the FDA or EMA; everything here is educational, not medical advice.
Reconstitute: Add 2 mL bacteriostatic water → 100 mg/mL concentration.
Typical dose: 10 mg/kg IV every 4 weeks (max 1200 mg)
Easy measuring: At 100 mg/mL, 1 unit = 0.01 mL = 1 mg (1000 mcg) on a U-100 insulin syringe.
Storage: Lyophilized antibody stored refrigerated at 2-8 °C, protected from light; do NOT freeze. Once reconstituted and diluted (clinically in 5% dextrose), the solution is used promptly or kept refrigerated and infused within hours per the clinical protocol rather than stored long-term.
Half-life: Concentration-dependent (target-mediated): about 5 days at maximal clearance up to ~19 days when ActRII is saturated; supports monthly dosing.
Route: Intravenous infusion over ~30 minutes every 4 weeks; not oral or subcutaneous (the subq model here is educational only).
Status: Investigational; not FDA/EMA approved. Failed RESILIENT (inclusion body myositis); now in obesity development (Versanis/Eli Lilly).
About Bimagrumab
Bimagrumab (BYM338) is a fully human anti-activin type II receptor (anti-ActRII) IgG1 monoclonal antibody developed by Novartis and later advanced for obesity by Versanis Bio (acquired by Eli Lilly). It competitively blocks ActRIIA and ActRIIB, neutralizing myostatin, activin A, and GDF11 signaling to drive skeletal-muscle hypertrophy and, notably, marked loss of body fat [1][4]. Clinically it is administered as an intravenous (IV) infusion, not by injection: the established Bimagrumab dosage in trials is 10 mg/kg given over roughly 30 minutes once every 4 weeks, capped at 1200 mg per dose [3][4].\n\nBecause the real route is IV and the per-dose amounts are in the hundreds of milligrams, the subcutaneous reconstitution figures below are an educational measurement reference only. They mirror this site's standard vial-and-bacteriostatic-water convention and are not a clinically validated delivery method. This guide models a 200 mg vial reconstituted with 2 mL of bacteriostatic water (100 mg/mL) so the math maps onto a U-100 insulin syringe: 1 mg ≈ 1 unit, so an 80 mg modeled dose ≈ 80 units (0.8 mL), while a full 800 mg therapeutic dose ≈ 800 units (8 mL) and would be delivered as a single IV infusion rather than injections.\n\nFrequency: Once every 4 weeks. Bimagrumab is investigational and is NOT approved by the FDA or EMA for any indication; the dosing, half-life, and protocol figures here are educational and not medical advice.
Quick Protocol Navigation
Reconstitution Instruction & Mixing Step-by-Step
Lyophilized powder must be reconstituted carefully. Agitating peptide chains can shear disulfide bonds and render the peptide biologically inert.
Draw 2 mL of bacteriostatic water into a sterile syringe (clinically, the supplied sterile diluent and then 5% dextrose are used; bacteriostatic water mirrors this site's standard reconstitution convention).
Inject the water slowly down the inner wall of the 200 mg bimagrumab vial; antibodies foam easily, so do not aim the stream at the powder and never shake the vial.
Swirl gently until the solution is completely dissolved and clear to slightly opalescent (~100 mg/mL, i.e. 1 mg per U-100 unit); inspect for particulates and discard if cloudy or discolored.
Educational syringe math: an 80 mg modeled dose ≈ 80 units (0.8 mL), 240 mg ≈ 240 units (≈2.4 mL), and a full 800 mg therapeutic dose ≈ 800 units (≈8 mL) — note that any dose above ~100 units exceeds a single 1 mL syringe.
Honest route note: clinically bimagrumab is given as a 30-minute IV infusion diluted in 5% dextrose once every 4 weeks, NOT subcutaneously and NOT orally; these reconstitution figures are an educational measurement reference only.
Interactive Bimagrumab Syringe Calculator
Currently visualizing the 200 mg vial reconstituted with 2 mL bacteriostatic water. Adjust the target dose to dynamically render syringe units.
Reconstitution Calculation: 200mg dry powder in 2mL water yields 100.00 mg/mL. To evaluate a 250mcg dose, pull to 0.3 units (0 syringe ticks).
U-100 Syringe Representation
Educational reference visual. Assumes standard U-100 insulin syringe where 1.0 mL volume = 100 units.
Titration & Dose Escalation Schedules
| Phase | Dose per injection | Units (per injection) |
|---|---|---|
| Low dose tier — 1 mg/kg (RESILIENT dose-finding, ~80 kg reference) | 80000 mcg (80 mg) | 80 units (0.80 mL) |
| Mid dose tier — 3 mg/kg (RESILIENT dose-finding, ~80 kg reference) | 240000 mcg (240 mg) | 240 units (2.40 mL) |
| Therapeutic dose — 10 mg/kg IV every 4 weeks (~80 kg reference) | 800000 mcg (800 mg) | 800 units (8.00 mL) |
| Weight cap — 1200 mg maximum per dose (patients ≥120 kg) | 1200000 mcg (1200 mg) | 1200 units (12.00 mL) |
Administration guidelines: Refer to guidelines | 2 mL Reconstitution
Research Supplies Quantity Planner
Scientific mathematical planning of syringes, bacteriostatic water and dry vials needed for extended research blocks using the 200 mg vial.
Peptide Vials (Bimagrumab, 200 mg each):
- check8-week course (2 infusions at ~800 mg) ≈ 8 vials (1,600 mg total)
- check12-week course (3 infusions) ≈ 12 vials (2,400 mg total)
- check16-week course (4 infusions) ≈ 16 vials (3,200 mg total) — the high vial count reflects gram-level antibody dosing given by IV infusion, not injection
Insulin Syringes (U-100):
- checkEach modeled 800 mg dose ≈ 800 units ≈ 8 mL, i.e. ~8 full 1 mL syringe-equivalents — clinically this is a single IV infusion bag, not subcutaneous injections
- check8-week course ≈ 16 syringe-equivalents; 12-week ≈ 24; 16-week ≈ 32
- checkIn real practice an infusion set and a 5% dextrose bag replace syringes entirely
Bacteriostatic Water (30 mL bottles): Use 2 mL per 200 mg vial for reconstitution.
- check8-week course (8 vials) ≈ 16 mL ≈ 1 bottle
- check12-week course (12 vials) ≈ 24 mL ≈ 1 bottle
- check16-week course (16 vials) ≈ 32 mL ≈ 2 bottles — note that clinically the drug is diluted in 5% dextrose, not bacteriostatic water
Alcohol Swabs:
- check1-2 swabs per vial top plus infusion-site prep
- check8-week course ≈ 20-30 swabs; 12-week ≈ 30-45 swabs
- check16-week course ≈ 40-60 swabs; keep extras for multi-vial reconstitution
Mechanism of Action (MOA)
Bimagrumab is a fully human IgG1 monoclonal antibody that targets the activin type II receptors (ActRIIA and ActRIIB) on the surface of skeletal-muscle cells. It binds ActRIIB with extraordinarily high affinity (KD ≈ 1.7 pM) and ActRIIA with lower affinity (KD ≈ 434 pM), occupying the receptor competitively so that its natural ligands — myostatin (GDF8), activin A, and GDF11 — can no longer dock and signal [1]. Normally these ligands activate the receptor's serine/threonine kinase, phosphorylating the intracellular transcription factors Smad2 and Smad3 to restrain muscle growth. By blocking the receptor itself rather than a single ligand, bimagrumab simultaneously neutralizes multiple negative regulators, inhibits Smad2/3 phosphorylation, and tips the balance toward muscle-fiber hypertrophy. In preclinical work this dual blockade produced larger gains in muscle mass (25-50% in mouse muscles) than inhibiting myostatin alone, and it both built new muscle and protected against atrophy [1].\n\nBeyond muscle, ActRII blockade has a striking metabolic effect: it drives a large reduction in total body fat mass while lean mass is preserved or increased, accompanied by improved insulin sensitivity and lower HbA1c — effects attributed partly to increased energy expenditure and brown-adipose activity [4]. This fat-lowering action is what redirected bimagrumab's development from muscle-wasting diseases toward obesity and type 2 diabetes [8].\n\nPharmacokinetics: bimagrumab is given by intravenous infusion (about 30 minutes) and displays clearly nonlinear pharmacokinetics consistent with target-mediated drug disposition — the abundant ActRII target binds and clears antibody until it is saturated [5]. As a result, both clearance and half-life are concentration-dependent: the terminal half-life is short (around 5 days) when target-mediated clearance is maximal at low concentrations and lengthens toward roughly 2-3 weeks (up to about 19 days) in the linear, high-concentration range once the receptor is saturated [5][6]. This long effective half-life, together with sustained target engagement and muscle-mass gains, supports the once-every-4-weeks 10 mg/kg dosing used across the clinical program [3][6]. Doses are weight-based and capped at 1200 mg for heavier patients.\n\nAs a large protein antibody, bimagrumab is not absorbed orally and would be degraded in the gut, which is why it is delivered parenterally; the subcutaneous reconstitution model on this page is an educational measurement convention and not the clinical route. Like other therapeutic antibodies it can elicit anti-drug antibodies, and broad ActRII inhibition can affect other tissues where activin signaling operates, including reproductive and endocrine axes [8]. Bimagrumab remains investigational and is not approved by any regulator.
Clinical Trial Efficacy Highlights
- starIn the foundational preclinical study (Lach-Trifilieff et al., Molecular and Cellular Biology, 2014), the dual anti-ActRIIA/IIB antibody that became bimagrumab bound human ActRIIB at KD ≈ 1.7 pM, enhanced human myoblast differentiation, blocked myostatin- and activin-A-induced atrophy via reduced Smad2/3 phosphorylation, and increased mouse skeletal-muscle mass by 25-50% — more than inhibiting myostatin alone [1].
- starAmato and colleagues (Neurology, 2014) ran a randomized, double-blind, placebo-controlled proof-of-concept trial in 14 patients with sporadic inclusion body myositis; a single 30 mg/kg IV dose increased thigh muscle volume by 6.5-7.6% at 8 weeks (p<0.025) and improved 6-minute walking distance by 14.6% versus placebo at 16 weeks (p=0.008) [2].
- starThe phase 2b RESILIENT trial (Hanna et al., Lancet Neurology, 2019) randomized 251 sporadic inclusion body myositis patients to monthly IV bimagrumab 1, 3, or 10 mg/kg or placebo for 52 weeks; bimagrumab increased lean body mass but did NOT meet its primary endpoint of improving the 6-minute walk distance, so development in this indication was halted — a reminder that muscle-mass gains need not translate into function [3].
- starHeymsfield and colleagues (JAMA Network Open, 2021) treated 75 adults with type 2 diabetes and obesity using 10 mg/kg IV every 4 weeks (cap 1200 mg) for 48 weeks; bimagrumab reduced total body fat mass by 20.5% (−7.5 kg) versus −0.5% with placebo, increased lean mass by 3.6%, lowered body weight 6.5%, and reduced HbA1c by 0.76 percentage points (all significant) [4].
- starA dedicated population-pharmacokinetic analysis (Petricoul et al., Clinical Pharmacokinetics, 2023) confirmed that bimagrumab follows nonlinear, target-mediated pharmacokinetics with concentration-dependent clearance and a terminal half-life ranging from about 5 days at maximal clearance to roughly 19 days in the linear high-concentration range, supporting once-monthly IV dosing [5].
- starRooks and colleagues (Journal of Cachexia, Sarcopenia and Muscle, 2020) characterized bimagrumab's safety and pharmacokinetics across single and multiple IV doses in healthy older and obese adults and observed consistent increases in muscle mass with reductions in fat mass in the older cohort, with generally good tolerability [6].
- starIn the phase 2 BELIEVE trial (Heymsfield et al., Nature Medicine, 2026), combining IV bimagrumab with subcutaneous semaglutide produced up to ~17.8 kg weight loss and roughly 42% fat-mass loss at 48 weeks while limiting lean-mass loss to ~2.9% — versus a 7.4% lean-mass loss with semaglutide 2.4 mg alone — highlighting bimagrumab's potential to preserve muscle during GLP-1-driven weight loss [7].
- starA 2024 review (Kaur and Misra, Journal of Basic and Clinical Physiology and Pharmacology) summarizes bimagrumab as an investigational anti-ActRII antibody whose receptor blockade lowers fat mass while raising lean mass and brown-adipose activity, but cautions that broad ActRII inhibition also affects neurohormonal, pituitary, gonadal, and adrenal axes [8].
Side Effects & Tolerability Profile
Clinical subjects transiently report mild side effects. Slowly escalating the titration dose represents the single most effective intervention to limit side effects.
- warningDiarrhea and muscle spasms or cramps were the two most common adverse events in the type 2 diabetes and obesity trial, each affecting roughly 40% of bimagrumab recipients [4].
- warningTransient, usually early elevations in pancreatic enzymes (lipase and amylase) and liver enzymes were observed, and rare cases of pancreatitis led to discontinuation in clinical trials — warranting enzyme monitoring during use [4].
- warningMild acne and increased appetite have been reported, consistent with the compound's anabolic activity and broad effects on the activin/androgen-adjacent axes.
- warningInfusion-related reactions can occur because bimagrumab is delivered intravenously; as a therapeutic antibody it can also induce anti-drug antibodies that may affect exposure over time.
- warningBecause ActRII blockade is broad, it can affect activin and GDF signaling in non-muscle tissues including reproductive, pituitary, gonadal, and adrenal axes; the long-term endocrine consequences are not fully characterized [8].
- warningIn sporadic inclusion body myositis, despite increasing lean mass, bimagrumab did not improve walking distance or strength, so muscle-mass gains should not be assumed to equal functional or clinical benefit [3].
- warningIt is a large protein administered by IV infusion; it is not orally bioavailable, and the subcutaneous reconstitution model on this page is an educational measurement reference rather than a validated route of administration.
- warningRegulatory/research status: bimagrumab is investigational and NOT approved by the FDA, EMA, or any other regulator; it should be regarded as research and educational only and used solely under qualified clinical-trial supervision.
Subcutaneous Injection Technique
Most research peptides require subcutaneous injection into fatty tissue. Never inject directly into a blood vessel or deep muscle tissue unless clinically detailed.
1. Site Selection
Common locations include the abdomen (2 inches from navel), outer upper arms, or thighs.
2. Sanitization
Thoroughly clean the selected site, stopper and vial top using 70% isopropyl alcohol prep swabs.
3. Angle & Push
Pinch the skin and insert the needle at a 45 to 90-degree angle. Depress plunger smoothly.
4. Site Rotation
Rotate injection sites continuously to avoid lipodystrophy or tissue scarring.
Frequently Asked Questions
What is the typical Bimagrumab dosage?expand_more
The most studied Bimagrumab dosage is 10 mg/kg given as an intravenous infusion once every 4 weeks, capped at a maximum of 1200 mg per dose (used in the type 2 diabetes/obesity and muscle programs). Earlier dose-finding work tested 1, 3, and 10 mg/kg monthly, and the first inclusion-body-myositis study used a single 30 mg/kg dose. Doses are weight-based rather than titrated, and are delivered by IV infusion over about 30 minutes; the subcutaneous figures on this page are an educational reference only.
Is Bimagrumab FDA approved?expand_more
No. Bimagrumab is investigational and is not approved by the FDA, the EMA, or any other regulator for any indication. It failed its primary functional endpoint in the phase 2b RESILIENT trial for inclusion body myositis and is currently being studied for obesity, including in combination with semaglutide. All dosing described here is educational, not a prescription or medical advice.
What is Bimagrumab's half life?expand_more
Bimagrumab has nonlinear, target-mediated pharmacokinetics, so its half-life is concentration-dependent. The terminal half-life is roughly 5 days when target-mediated clearance is maximal and lengthens to about 2-3 weeks (up to ~19 days) once the ActRII receptor is saturated at higher concentrations. This long effective half-life is why it can be dosed just once every 4 weeks.
How is Bimagrumab reconstituted and administered?expand_more
Clinically, bimagrumab is supplied as a sterile antibody that is reconstituted/diluted in 5% dextrose and infused intravenously over about 30 minutes every 4 weeks — it is not injected subcutaneously and is not taken orally. The vial-and-bacteriostatic-water model on this page (a 200 mg vial in 2 mL, giving 100 mg/mL) is the site's standard educational measurement convention so units map onto a U-100 syringe; it is not the real clinical route.
Can Bimagrumab be stacked with semaglutide or other GLP-1 drugs?expand_more
In the phase 2 BELIEVE trial, bimagrumab was combined with subcutaneous semaglutide and produced greater fat loss while preserving lean (muscle) mass compared with semaglutide alone — the lean-mass loss usually seen with GLP-1 therapy was substantially blunted. This combination is investigational and was studied only under clinical-trial conditions; it is not an approved or self-directed regimen.
Related Guides & Tools
Step-by-step references for reconstituting, measuring, and storing Bimagrumab, plus the universal dosing calculator.
Academic References & Study Citations
Lach-Trifilieff E, Minetti GC, Sheppard K, et al. An antibody blocking activin type II receptors induces strong skeletal muscle hypertrophy and protects from atrophy. Mol Cell Biol. 2014;34(4):606-618. View Scientific Paper →
Amato AA, Sivakumar K, Goyal N, et al. Treatment of sporadic inclusion body myositis with bimagrumab. Neurology. 2014;83(24):2239-2246. View Scientific Paper →
Hanna MG, Badrising UA, Benveniste O, et al. Safety and efficacy of intravenous bimagrumab in inclusion body myositis (RESILIENT): a randomised, double-blind, placebo-controlled phase 2b trial. Lancet Neurol. 2019;18(9):834-844. View Scientific Paper →
Heymsfield SB, Coleman LA, Miller R, et al. Effect of Bimagrumab vs Placebo on Body Fat Mass Among Adults With Type 2 Diabetes and Obesity: A Phase 2 Randomized Clinical Trial. JAMA Netw Open. 2021;4(1):e2033457. View Scientific Paper →
Petricoul O, Nazarian A, Schuehly U, et al. Pharmacokinetics and Pharmacodynamics of Bimagrumab (BYM338). Clin Pharmacokinet. 2023;62(1):141-155. View Scientific Paper →
Rooks D, Praestgaard J, Hariry S, et al. Safety and pharmacokinetics of bimagrumab in healthy older and obese adults with body composition changes in the older cohort. J Cachexia Sarcopenia Muscle. 2020;11(6):1525-1534. View Scientific Paper →
Heymsfield SB, et al. Bimagrumab plus semaglutide alone or in combination for the treatment of obesity: a randomized phase 2 trial (BELIEVE). Nat Med. 2026. View Scientific Paper →
Kaur M, Misra S. Bimagrumab: an investigational human monoclonal antibody against activin type II receptors for treating obesity. J Basic Clin Physiol Pharmacol. 2024;35(6):285-295. View Scientific Paper →