Does it build muscle, or just stop you losing it?

What this archive is for. Trials of the compound come first, ranked by how many people were actually given it. Studies that only observed people are below them and labelled.

1. 01RetatrutidePeptideStrong. At least two finished studies in people, and at least 1,000 people who took it. 5 completed trials, 1,345 people given it.8 reported

   189 people given it1 trial

   • Most of the weight lost was fat, on scans from a small slice of a larger trial. 189 people joined the scan study and only 103 had usable scans at both the start and week 36. Fat mass fell 26.1% and 23.2% at the two higher doses, against 4.5% on the dummy shot. The share of the loss that was muscle looked like what other obesity drugs produce. 103 people is a thin basis for reassurance about muscle.

     The numbers 189 enrolled in the DXA substudy, 103 with both baseline and week 36 scans: total fat mass fell 26.1% on pooled 8 mg and 23.2% on 12 mg versus 4.5% on placebo. The lean mass proportion of total loss was similar to other obesity treatments.

     The Lancet Diabetes & Endocrinology, 2025· 189 people

2. 02TeduglutidePeptideLimited. People have taken it in a published study, but fewer than 100 of them. 2 completed trials, 83 people given it.4 reported

   83 people given it1 trial

   • It worked, and the doses came out backwards. People with short bowel syndrome cannot absorb enough from food, so they are fed through a vein, often for hours every night. 83 of them got one of two doses of teduglutide or a dummy injection for about six months. The lower dose beat the dummy. The higher dose did not, which the researchers think came down to those patients starting out needing more feeding. Three people came off vein feeding altogether. Serious side effects were about the same across all groups.

     The numbers 83 adults with short bowel syndrome and intestinal failure randomised to teduglutide 0.10 mg/kg/day (n = 32), 0.05 mg/kg/day (n = 35) or placebo (n = 16) for 24 weeks. On the graded response score the higher dose did NOT separate from placebo (8 of 32 against 1 of 16, p = 0.16) while the lower dose did (16 of 35, p = 0.007); the authors attribute the inversion to a higher baseline parenteral volume in the 0.10 group. Parenteral volume reductions were equal between doses at about 353 and 354 mL/day. Three patients came off parenteral support entirely. Villus height, plasma citrulline and lean body mass all rose against placebo. Serious adverse events were distributed similarly.

     Gut, 2011· 83 people

3. 03MecaserminPeptideLimited. People have taken it in a published study, but fewer than 100 of them. 1 completed trial, 76 people given it.6 reported

   76 people given it1 trial

   • Children who cannot make their own IGF-1 grew much faster on the replacement, and kept growing for years. 76 children were treated for up to twelve years with shots under the skin twice a day. Growth went from under three centimetres a year to eight in the first year, and stayed above where it started for up to eight years. Low blood sugar was the commonest problem, in about half the children. Almost everybody knew they were on the drug and there was no comparison group.

     The numbers The long-term efficacy and safety experience behind the approval. 76 children with IGF-1 deficiency due to growth hormone insensitivity treated with recombinant human IGF-1 for up to 12 years under a predominantly open-label design, at 60 to 120 micrograms per kilogram subcutaneously twice daily. Height velocity rose from a mean of 2.8 cm per year at baseline to 8.0 cm per year in the first year (p less than 0.0001) and was dose dependent; velocities were lower in subsequent years but stayed above baseline for up to 8 years. The most common adverse event was hypoglycaemia, reported by 49 percent of treated subjects and observed both before and during therapy, followed by injection site lipohypertrophy (32 percent) and tonsillar or adenoidal hypertrophy (22 percent). Note the design: predominantly open label, not randomised against placebo.

     Journal of Clinical Endocrinology and Metabolism, 2007· 76 people

4. 04MK-677 with ipamorelinBlendModerate. At least one finished study in people, and at least 100 people who took it. 2 completed trials, 182 people given it.7 reported

   65 people given it1 trial

   • MK-677 worked in the longest study any of these drugs has had, and the gains were modest. 65 healthy adults aged 60 to 81 took a 25 mg pill or a dummy pill every day for two years. Nobody knew which they had. Growth hormone and IGF-1 climbed back into the range of a healthy young adult, with no serious harms. Lean weight rose about 1.1 kg on the drug and fell 0.5 kg on the dummy pill. That is roughly two pounds gained against one pound lost.

     The numbers 65 healthy adults aged 60 to 81 took MK-677 25 mg orally once daily or placebo for two years in a double-blind randomised modified-crossover trial. Growth hormone and IGF-1 rose into the healthy young adult range without serious adverse events. Fat-free mass increased 1.1 kg on MK-677 against a 0.5 kg fall on placebo, and body cell mass measured as intracellular water rose 0.8 kg against a 1.0 kg fall. This is the longest randomised trial of any secretagogue in this database.

     Annals of Internal Medicine, 2008· 65 people

5. 05SermorelinPeptideModerate. At least one finished study in people, and at least 100 people who took it. 3 completed trials, 139 people given it.8 reported

   19 people given it1 trial1 found nothing

   • found nothingThe hormone response faded while the injections carried on. Nineteen adults aged 55 to 71 injected salt water nightly for a month, then a sermorelin-like peptide for four more months. Growth hormone and its main blood marker rose within two weeks, stayed up for three months, then drifted back to where they started even though dosing never stopped. Muscle, insulin response, mood and libido improved in the men and not the women. Bone density and sleep did not change in anyone.

     The numbers 19 adults aged 55 to 71 on 4 weeks of placebo then 16 weeks of the Nle27 analogue at 10 micrograms/kg nightly: IGF-1 and IGFBP-3 rose within 2 weeks and returned toward baseline by week 16 while dosing continued. Lean mass, insulin sensitivity, well-being and libido improved in men only; bone mineral density and sleep quality did not change.

     Journal of Clinical Endocrinology and Metabolism, 1997· 19 people

Vitamins, minerals, amino acids and botanicals sold over the counter, held to the same standard.

1. 01EcdysteroneSupplementModerate. At least one finished study in people, and at least 100 people who took it. 3 completed trials, 233 people given it.5 reported

   233 people given it2 trials1 found nothing

   • found nothingThe drug version of this molecule was tested in 233 older adults losing muscle with age. It missed its main target. Across everyone who took part, walking speed over a 400 metre course barely changed compared with a dummy pill. A smaller group who stuck to the plan walked a little faster. Counting only those people is not the fair test. Full detail is on the BIO101 page.

     The numbers The pharmaceutical-grade version of this molecule in 233 older adults with sarcopenia. The primary endpoint, gait speed on a 400-metre walk, improved 0.07 m/s against placebo in the full analysis set and was not significant, and improved 0.09 m/s in the per-protocol population at p = 0.008. Detail on the BIO101 page.

     Journal of Cachexia, Sarcopenia and Muscle, 2025· 233 people

   • In a study in people, those taking ecdysterone gained more muscle than the comparison group and lifted more on the bench press. Blood tests for liver and kidney damage did not rise. The researchers checked everyone for banned drugs and tested the supplement for hidden steroids first. They said it should go on the banned list in sport. That is how strong they judged the effect. In a dish, the same growth showed up in muscle cells.

     The numbers A controlled clinical trial in humans. Significantly higher increases in muscle mass in participants dosed with ecdysterone, and significantly more pronounced increases in one-repetition bench press performance. The same hypertrophic effect appeared in C2C12 myotubes in vitro. No increase in liver or kidney toxicity biomarkers. Participants were screened for prohibited performance-enhancing substances and the supplement was tested for anabolic steroid contamination before administration. The authors conclude their results strongly suggest including ecdysterone on the prohibited list in class S1.2, other anabolic agents.

     Archives of Toxicology, 2019· number of people not given

2. 02ForskolinSupplementLimited. People have taken it in a published study, but fewer than 100 of them. 2 completed trials, 53 people given it.5 reported

   53 people given it2 trials1 found nothing

   • Body fat fell and testosterone rose, in thirty overweight men. The men all had a body mass index of 26 or above and took 250 mg of a 10 percent forskolin extract twice a day, or a dummy, decided by chance, for 12 weeks. Scans showed body fat percentage and fat mass dropped against the dummy group. Bone mass changed and free testosterone rose. Muscle gain leaned upward but was too small to separate from chance. That is fifteen men per group, and the companion study in women found nothing.

     The numbers 30 men with BMI at or above 26, randomised double-blind to 250 mg of a 10 percent forskolin extract twice daily or placebo for 12 weeks. Body fat percentage and fat mass on DXA fell significantly against placebo, bone mass changed significantly, serum free testosterone rose significantly, and lean body mass showed a non-significant trend upward (p equals 0.097). Fifteen participants per arm.

     Obesity Research, 2005· 30 people

   • found nothingThe same supplement was tested in women and it did not work. 23 mildly overweight women took a 10 percent Coleus forskohlii extract twice a day or a dummy for 12 weeks, seven on the extract. Fat mass, lean mass and body fat percentage came out the same in both groups. Slight leanings toward less weight gain were too weak to call. Blood fats, liver enzymes, thyroid, insulin, heart rate and blood pressure were unchanged. Seven people is too few to spot anything but a huge effect.

     The numbers 23 women randomised double-blind to 250 mg of a 10 percent Coleus forskohlii extract twice daily (n equals 7) or placebo (n equals 12) for 12 weeks. No significant differences in fat mass, fat-free mass or body fat percentage. Non-significant trends toward mitigating gains in body mass (p equals 0.10) and scanned mass (p equals 0.08). Treated participants reported less hunger and fullness. No clinically significant changes in blood lipids, liver or muscle enzymes, thyroid hormones, insulin, heart rate or blood pressure. The authors concluded it does not appear to promote weight loss but may help mitigate weight gain.

     Journal of the International Society of Sports Nutrition, 2005· 23 people

3. 03L-leucineSupplementLimited. People have taken it in a published study, but fewer than 100 of them. 1 completed trial, 30 people given it.3 reported

   30 people given it1 trial1 found nothing

   • found nothingThree months of leucine did nothing at all for muscle in healthy older men. 30 men averaging 71 took 2.5 g of leucine with each main meal, 7.5 g a day, or a dummy, decided by chance. Scans of muscle size showed no change in either group. Strength on a one-lift maximum did not change either. Insulin sensitivity, long-run blood sugar and blood fats were all unmoved. These men were healthy to begin with, not frail and not already losing muscle.

     The numbers 30 healthy men, mean age 71, randomised to 2.5 g leucine or placebo with each main meal, 7.5 g daily for three months. No change in skeletal muscle mass measured by computed tomography and DXA, and no change in one-repetition-maximum strength, in either group. No improvement in whole-body insulin sensitivity, HbA1c or plasma lipids.

     American Journal of Clinical Nutrition, 2009· 30 people

4. 04Ursolic acidSupplementLimited. People have taken it in a published study, but fewer than 100 of them. 1 completed trial, 16 people given it.6 reported

   16 people given it1 trial1 found nothing

   • found nothingThe entire human record for ursolic acid is sixteen men. 16 healthy men averaging 29 did eight weeks of weight training, seven on training alone and nine also taking ursolic acid capsules three times a day. Body fat percentage fell in the supplemented group. Body weight, body mass index, muscle mass, blood sugar and insulin did not change. Two hormones rose from their own starting points, as did several leg strength measures. Nine people on a supplement cannot settle anything, and nobody has repeated it.

     The numbers 16 healthy men, mean age 29, randomised to eight weeks of resistance training alone (n equals 7) or with ursolic acid (n equals 9), one capsule three times daily. Body fat percentage fell significantly in the supplemented group (p less than 0.001) while body weight, body mass index, lean body mass, glucose and insulin were unchanged. IGF-1 and irisin rose from baseline in the supplemented group, as did several maximal extension and flexion measures.

     Korean Journal of Physiology and Pharmacology, 2014· 16 people

5. 05Collagen peptidesSupplementLimited. People have taken it in a published study, but fewer than 100 of them. 2 completed trials, 69 people given it.4 reported

   nobody was given it1 watch-only study

   • Put side by side with whey, collagen did not build muscle. Healthy older women were given the same amount of protein as either whey or collagen, with and without a workout. Whey switched muscle building on, both straight after the dose and over the longer run. Collagen did not, even when the researchers matched leucine, the amino acid that sets the response off. This is the head to head comparison the collagen literature almost never runs.

     The numbers The head to head the skin literature never runs. Against an equal protein dose, collagen did not stimulate muscle protein synthesis where whey did, including when leucine was matched.

     American Journal of Clinical Nutrition, 2020· number of people not givenobserved only, nobody was given it

Approved drugs, biologics and hormones that have been measured for this. They are here because leaving them out would misrepresent the evidence, and they are below the peptides because that is not what most people come here to read.

1. 01LandogrozumabBiologicModerate. At least one finished study in people, and at least 100 people who took it. 3 completed trials, 726 people given it.

   601 people given it2 trials1 found nothing

   • The same antibody was tested around hip replacement surgery, and again it built muscle. Four hundred adults having a planned hip replacement were split by chance between three doses and a dummy injection. Twelve weeks later, arm and leg muscle had risen at every dose, and it rose more the higher the dose. The dummy group gained a little too. These results sit on the registry. Nothing here shows that the extra muscle helped anyone walk, recover or leave hospital sooner.

     The numbers 400 participants undergoing hip replacement, randomised to LY2495655 at 35, 105 or 315 mg or placebo (NCT01369511, results posted 2018). Appendicular lean body mass rose dose dependently at week 12: 0.297 kg on placebo against 0.741, 1.018 and 1.357 kg across the three doses. A setting where rapid muscle loss around surgery is predictable and measurable, and one of three populations the programme tested.

     ClinicalTrials.gov, 2014· 400 people

   • found nothingA myostatin antibody added muscle to older people who fall, and barely moved how they function. Two hundred older adults were split by chance between the drug and a dummy injection. After six months the drug group had gained about four hundred grams of arm and leg muscle, while the dummy group had lost a little. Climbing twelve stairs got slightly faster. Most other movement tests did not separate. Injection site reactions were far more common on the drug. Eli Lilly paid for it.

     The numbers 201 older adults randomised, 99 to placebo and 102 to the antibody, from 365 screened. At 24 weeks appendicular lean body mass changed by minus 0.123 kg on placebo and plus 0.303 kg on drug, a difference of 0.43 kg (95% CI 0.192 to 0.660, p < 0.0001). On function: twelve-step stair climb minus 1.28 s (p = 0.011), four-step stair climb minus 0.46 s (p = 0.093), chair rise with arms minus 4.15 s (p = 0.054), fast gait speed plus 0.05 m/s (p = 0.088), tested against a prespecified two-sided alpha of 0.1 for performance tests. No effect on other performance measures. Injection site reactions in 30% on drug against 9% on placebo (p < 0.0001). Funded by Eli Lilly.

     Lancet Diabetes and Endocrinology, 2015· 201 people

2. 02BIO101Small moleculeModerate. At least one finished study in people, and at least 100 people who took it. 1 completed trial, 233 people given it.3 reported

   233 people given it1 trial, 1 watch-only1 found nothing

   • found nothingIt missed the target it was built to hit. 233 older adults losing muscle with age, average age 75, took BIO101 at one of two doses or a dummy pill for six months. The measure was walking speed over 400 metres. Counting everyone, the drug made almost no difference. Covid wiped out more than half the final in-person check-ups, which made any effect harder to spot. Many authors work for or advise the company that makes it.

     The numbers SARA-INT. 233 randomised, mean age 75.5, 54.3% female, three arms at 175 mg twice daily, 350 mg twice daily or placebo, planned six months and up to nine in 50 subjects. Eligibility required meeting FNIH sarcopenia criteria and a Short Physical Performance Battery score of 8 or less out of 12. Primary endpoint was change in gait speed on the 400-metre walk test. At 350 mg twice daily, gait speed improved 0.07 m/s against placebo in the full analysis set, not significant, and 0.09 m/s in the per-protocol population, p = 0.008. COVID-19 cost 55% of on-site end-of-treatment efficacy assessments, reducing power. Predefined higher-risk subpopulations showed effects of 0.047 to 0.066 m/s with a trend toward dose response. Safety was good, with related treatment-emergent adverse events in 16.0%, 13.3% and 13.5% of the placebo, 175 mg and 350 mg groups. Many authors are employees, former employees, advisory board members or consultants of the sponsor, Biophytis.

     Journal of Cachexia, Sarcopenia and Muscle, 2025· 233 people

   • The same molecule worked in young people who train and fell short in frail older people. In a sports study, ecdysterone added muscle and bench press strength. In older adults losing muscle with age, the drug version did not clearly improve walking speed. A gain in the gym in young healthy bodies does not mean an older person can walk further.

     The numbers The same molecule in a sports context, where a controlled human trial found increased muscle mass and bench press performance. Included because the contrast between a positive strength result in trained young people and a missed functional endpoint in sarcopenic older adults is the central fact about this compound.

     Archives of Toxicology, 2019· number of people not givenobserved only, nobody was given it

3. 03EnobosarmSmall moleculeModerate. At least one finished study in people, and at least 100 people who took it. 1 completed trial, 159 people given it.5 reported

   159 people given it1 trial1 found nothing

   • found nothingMuscle did grow, in people who were losing it to cancer. 159 patients who had already lost weight took one of two doses of enobosarm or a dummy pill for up to about four months. Muscle mass rose on both doses, by roughly 1 to 1.5 kg, while the dummy group did not change. Here is the limit. Growing muscle is not the same as being able to do more, and the larger studies that followed did not succeed.

     The numbers 159 patients with cancer and at least 2% weight loss, randomised to enobosarm 1 mg, 3 mg or placebo for up to 113 days. Total lean body mass rose significantly on both doses (median 1.5 kg on 1 mg, 1.0 kg on 3 mg) while placebo did not change. This is the Phase 2 trial that preceded the POWER Phase 3 program.

     The Lancet Oncology, 2013· 159 people

4. 04MetforminSmall moleculeModerate. At least one finished study in people, and at least 100 people who took it. 3 completed trials, 489 people given it.6 reported

   94 people given it1 trial

   • Metformin got in the way of the muscle that lifting weights is meant to build. 94 adults aged 65 and over trained with weights for 14 weeks under supervision. Half took metformin every day, half took a dummy pill. The dummy group put on more lean weight and more thigh muscle, and their thigh muscle came out denser. Strength gains leaned the same way without being clear cut. So the drug did not block the training, it took the edge off it.

     The numbers 94 adults aged 65 and over did 14 weeks of supervised resistance training on 1,700 mg/day metformin or placebo. Placebo gained more lean body mass (p = .003) and thigh muscle mass (p < .001), with greater gains in thigh muscle area (p = .005) and density (p = .020), plus a trend toward blunted strength gains.

     Aging Cell, 2019· 94 people

5. 05MK-677Small moleculeLimited. People have taken it in a published study, but fewer than 100 of them. 2 completed trials, 65 people given it.11 reported

   65 people given it1 trial1 found nothing

   • found nothingIt shifted muscle and fat, and it did not make anyone stronger or more able. 65 adults aged 60 to 81 took MK-677 or a dummy pill daily for up to two years. Growth hormone and IGF-1 climbed back to young-adult levels. Lean tissue rose about 1.1 kg while the dummy group lost about half a kilo. Strength and everyday function did not improve at all. Fasting blood sugar rose and the body handled insulin worse. That last sentence is the part people skip.

     The numbers 65 adults aged 60 to 81 on MK-677 25 mg daily for up to 2 years: GH and IGF-1 rose to young-adult levels and fat-free mass increased 1.1 kg vs a 0.5 kg loss on placebo, but strength and function did not improve and fasting glucose and insulin resistance rose.

     Annals of Internal Medicine, 2008· 65 people

6. 06SupaglutideBiologicModerate. At least one finished study in people, and at least 100 people who took it. 3 completed trials, 190 people given it.

   50 people given it1 trial

   • The entire published obesity record for this drug is fifty people. They were spread across five doses and a dummy, starting at an average weight of 92.9 kg. Weight fell 7.16 percent against 0.86 percent on the dummy, and 82.5 percent of treated people lost at least a twentieth of their body weight, against nobody on the dummy. Fat mass fell 4.47 kg. Muscle fell too, by 2.00 kg. This was a dose-ranging study, not an obesity trial, and the drug is not approved for weight management.

     The numbers The entire published obesity efficacy record: 50 participants across five dose cohorts and placebo, mean baseline weight 92.9 kg. Mean weight reduction was 7.16 percent against 0.86 percent on placebo, and 82.5 percent of treated participants lost at least 5 percent against none on placebo. Fat mass fell 4.47 kg and lean mass also fell 2.00 kg. This is a 50 person dose-ranging study, not an obesity efficacy trial, and the compound is not approved for weight management.

     Diabetes, Obesity and Metabolism, 2026· 50 people

7. 07ACE-031BiologicLimited. People have taken it in a published study, but fewer than 100 of them. 1 completed trial, 48 people given it.5 reported

   48 people given it1 trial, 1 watch-only

   • One dose of ACE-031 added measurable muscle to healthy women within a month. Forty-eight women past menopause each received a single injection at one of several dose levels. At the highest dose, total muscle rose 3.3% and thigh muscle volume 5.1% by day 29. The drug lingers, taking ten to fifteen days for the body to clear half of it. This was a safety and dosing study in healthy people. Nobody was tested on whether they got stronger or functioned better.

     The numbers One dose in 48 postmenopausal women: half-life 10 to 15 days; at 3 mg/kg total lean mass rose 3.3% and thigh muscle volume 5.1% by day 29.

     Muscle and Nerve, 2013· 48 people

   • The trial was stopped early for safety, and it never showed a benefit. Boys with Duchenne muscular dystrophy were given ACE-031 or a dummy injection. After the second dose level, the study was halted because boys were getting nosebleeds and small spidery blood vessels in the skin. Walking distance and muscle mass leaned in the drug's favour, but not by enough to call it a real effect. Treat this as a harm signal with no proven upside.

     The numbers The trial was stopped after the second dose level because of epistaxis and telangiectasias; only non-significant trends toward preserved six-minute walk and higher lean mass were seen.

     Muscle and Nerve, 2017· number of people not givenobserved only, nobody was given it

8. 08SomatropinBiologicLimited. People have taken it in a published study, but fewer than 100 of them. 2 completed trials, 84 people given it.9 reported

   24 people given it1 trial1 found nothing

   • found nothingGrowth hormone changed what the body was made of without changing what the scales said. Twenty four adults whose bodies made too little growth hormone took it for six months, against others given a dummy version. They gained about 5.5 kg of muscle and lost about 5.7 kg of fat. Total weight barely moved, because the two changes cancelled out. These were people with a diagnosed shortage. It does not say what happens in someone whose own levels are normal.

     The numbers Six months of rhGH in 24 GH-deficient adults raised lean mass by 5.5 kg and cut fat mass by 5.7 kg versus placebo, with no change in body weight.

     New England Journal of Medicine, 1989· 24 people

9. 09ClenbuterolSmall moleculeLimited. People have taken it in a published study, but fewer than 100 of them. 2 completed trials, 11 people given it.5 reported

   11 people given it1 trial, 1 watch-only2 found nothing

   • found nothingClenbuterol does build muscle in people, and it wrecks your fitness while it does. 11 healthy young men took the drug for two weeks and a dummy for two weeks, in turn, with three weeks between. Lean mass rose by just under a kilogram. Fat mass did not move at all, which matters because fat loss is why most people buy it. The most oxygen their bodies could use fell 7 percent, and exercise capacity fell 4 percent. The muscle response faded across the two weeks.

     The numbers The first randomised controlled trial. 11 healthy men aged 18 to 40, two 2-week cycles of oral clenbuterol at 80 micrograms a day versus placebo with a 3-week washout. Lean mass +0.91 kg (95% CI 0.02 to 1.81, p < 0.05), no effect on fat mass, maximal oxygen uptake -7% (p < 0.001), exercise capacity -4% (p < 0.001), no change in left ventricular mass, blood volume or haemoglobin mass. Muscle protein content rose while 3-hydroxyacyl CoA dehydrogenase activity and OXPHOS complex V fell. The beta-2 signalling response declined across the 2 weeks.

     The Journal of Physiology, 2025· 11 people

   • found nothingClenbuterol built leg muscle in heart failure patients and did nothing for their hearts. 7 people supported by a mechanical heart pump took rising oral doses for three months, up to a very high daily amount. Body weight and lean mass rose, and thigh strength improved from about 37 to about 46 kilograms of force. The pumping fraction did not improve and the heart chamber got larger. No serious side effects or rhythm problems appeared, though a muscle enzyme rose in four patients.

     The numbers 7 heart failure patients on a left ventricular assist device given oral clenbuterol up-titrated to 720 micrograms a day for 3 months. No serious adverse events or arrhythmias, creatine phosphokinase rose in 4 patients. Ejection fraction did not improve and end-diastolic dimension increased; body weight and lean mass rose and quadriceps maximal voluntary contraction improved from 37.0 to 45.8 kg. Cardiac function did not improve.

     The Journal of Heart and Lung Transplantation, 2006· 7 peopleobserved only, nobody was given it

10. 10MyostatinBiologicModerate. At least one finished study in people, and at least 100 people who took it. 3 completed trials, 188 people given it.

    0 people given it2 trials1 found nothing

    • found nothingA drug that blocked myostatin alone failed in boys with Duchenne muscular dystrophy. Boys got the antibody or a dummy. After 49 weeks, the time to climb four stairs differed by a quarter of a second, which is nothing. No other measure of how the boys were doing separated the two groups. Gains in muscle size did not hold up either. This is the clearest evidence that blocking myostatin alone does not turn into better movement.

      The numbers A pure anti-myostatin antibody against placebo. The difference in four-stair climb time at week 49 was 0.27 seconds, 95% CI minus 7.4 to 7.9, p = 0.94. No secondary clinical endpoint separated and muscle volume gains were not significant.

      Neuromuscular Disorders, 2020· number of people not given

    • Blocking the receptor, not the hormone, caused big changes in body makeup. Adults with type 2 diabetes and obesity took bimagrumab or a dummy for 48 weeks. Fat fell by about a fifth, 7.5 kg, against almost nothing on the dummy. Muscle rose by 1.7 kg, waists shrank 9 cm, and average blood sugar fell by three quarters of a point. Note what this drug blocks. It shuts the receptor down, so it blocks activin A as well as myostatin.

      The numbers Receptor-level blockade rather than myostatin-only blockade, so it neutralises activin A too. At 48 weeks fat mass fell 20.5% (7.5 kg) against 0.5% on placebo, lean mass rose 3.6% (1.7 kg), waist fell 9.0 cm and HbA1c fell 0.76 points, all p < 0.006.

      JAMA Network Open, 2021· number of people not given

11. 11RapamycinSmall moleculeLimited. People have taken it in a published study, but fewer than 100 of them. 2 completed trials, 25 people given it.8 reported

    0 people given it1 trial

    • Nearly a year of low dose rapamycin proved reasonably safe in ordinary ageing adults. Safety was the main thing the trial was built to check, and it checked out. Muscle mass and pain improved in women on the higher dose, which was one finding among many measures and needs repeating before anyone leans on it. Safe to take is not the same as doing something.

      The numbers 48 weeks of low-dose intermittent rapamycin was relatively safe in normative-aging adults; lean mass and pain improved in women on 10 mg.

      Aging, 2025· number of people not given

12. 12DomagrozumabBiologicLimited. People have taken it in a published study, but fewer than 100 of them. 1 completed trial, none stating how many people.

    0 people given it1 trial1 found nothing

    • found nothingA second myostatin blocker was tested properly in boys with Duchenne and it failed. 120 boys aged six to fifteen were split by chance across three doses or a dummy injection, for nearly two years. The thing the trial was built to measure was how fast they climbed four stairs. The two groups came out the same. No other clinical measure separated either. Muscle volume rose a bit, but not enough to call. An error notice was published afterwards correcting part of the paper.

      The numbers 120 ambulatory boys aged 6 to under 16 with Duchenne muscular dystrophy, 80 on domagrozumab at 5, 20 and 40 mg/kg and 40 on placebo, two 48-week periods. Primary endpoints were safety and change in four-stair climb time at week 49. The difference in mean change was 0.27 seconds (95% CI minus 7.4 to 7.9), p = 0.94. There were no significant between-group differences in any secondary clinical endpoint. Non-significant increases in muscle volume were observed. An erratum was published in 2021.

      Neuromuscular Disorders, 2020· number of people not given

13. 13ApitegromabBiologicPreliminary. Studied in people, but no published study has had people take it. 2 human studies where nobody was given it.1 reported

    nobody was given it1 watch-only study

    • Adding this antibody to tirzepatide protected about half the muscle people would otherwise have lost. It also changed what came off: 85% of the lost weight was fat, against about 70% on tirzepatide alone. Muscle loss is the main worry with these weight drugs, so this speaks straight to it. The trial was mid-stage and the figures came from the company, not a journal. Nobody has yet shown that the saved muscle makes people stronger.

      The numbers Preserved 54.9% of lean mass on tirzepatide; weight lost was 85% fat.

      Scholar Rock press release, 2025· number of people not givenobserved only, nobody was given it

14. 14TrevogrumabBiologicLimited. People have taken it in a published study, but fewer than 100 of them. 1 completed trial, none stating how many people.3 reported

    nobody was given it1 watch-only study

    • Blocking two muscle brakes at once protected most of the muscle people lose on semaglutide. With all three drugs, about 81% of the muscle normally lost was kept, and people lost about 27% more fat than on semaglutide alone. Two drugs instead of three kept about half. These are company-reported figures from a mid-stage trial. The three-drug group also had more side effects, which is covered in the entry beside this one.

      The numbers Triple regimen preserved 80.9% of lean mass with 27.3% more fat loss.

      Regeneron press release, 2025· number of people not givenobserved only, nobody was given it

Peptides and blends

1. 01IGF-1 LR3PeptidePreliminary. Studied in people, but no published study has had people take it. 1 human study where nobody was given it.8 reported

   1 animal or lab study

   Measured in animals or in the lab

   • In mice. Mice built to make extra IGF-1 in their muscles kept bigger muscles and kept their ability to repair muscle into old age. This is the main reason people think IGF-1 builds muscle.

     The numbers Muscle-restricted IGF-1 expression in mice produced persistent hypertrophy and preserved regenerative capacity into old age, the mechanistic basis for IGF-1 muscle research.

     Nature Genetics, 2001· animal study

2. 02FOXO4-DRIPeptideLimited. People have taken it in a published study, but fewer than 100 of them. 1 completed trial, 74 people given it.8 reported

   1 animal or lab study

   Measured in animals or in the lab

   • In mice and rats, this is the result that cuts the other way, and it is usually left out. In mice, clearing worn-out cells from lung blood vessels, with FOXO4-DRI among the tools, raised pressure in the lung circulation. It thickened the right side of the heart and stripped out lining cells the lung depends on. In rats, a related cell-clearing drug helped slightly at one week and made things worse by three. The authors warn that clearing these cells may worsen blood flow through the lungs.

     The numbers Senescent cell clearance in mice, including with FOXO4-DRI, raised right ventricular systolic pressure and the hypertrophy index, increased vessel remodelling and markedly reduced lung pulmonary endothelial cells. In monocrotaline rats, ABT263 slightly reduced pulmonary hypertension at one week and aggravated it at three. The authors conclude senolytic interventions may worsen pulmonary haemodynamics.

     Circulation, 2023· animal studypoints the wrong way

3. 03OsteocalcinPeptidePreliminary. Studied in people, but no published study has had people take it. 2 human studies where nobody was given it.

   1 animal or lab study

   Measured in animals or in the lab

   • In mice. A new strain made without osteocalcin had normal bone amount, blood sugar, testosterone and muscle mass. What was off was the lining up of bone's mineral crystals, and the bones got weaker. The authors conclude osteocalcin does not act as a hormone.

     The numbers A new osteocalcin-deficient mouse made by deleting Bglap and Bglap2. Bone quantity, glucose metabolism, testosterone synthesis and muscle mass were all normal. What was abnormal was the crystallographic orientation of bone apatite, and bone strength fell as a result. The authors conclude osteocalcin does not function as a hormone.

     PLoS Genetics, 2020· animal study

Supplements

1. 01TrigonellineSupplementAnimal or lab only. Only animal or lab studies on this page. No study in people yet. 1 animal study, no human study.2 reported

   1 animal or lab study

   Measured in animals or in the lab

   • Mostly in mice and worms. Old mice had better muscle function, and worms lived 17.9% longer. Separately, people with age-related muscle loss had lower blood levels. Nobody was given it.

     The numbers Better muscle function in old mice; 17.9% lifespan extension in C. elegans; low levels in human sarcopenia.

     Nature Metabolism, 2024· animal study

2. 02Urolithin BSupplementLimited. People have taken it in a published study, but fewer than 100 of them. 1 completed trial, none stating how many people.

   1 animal or lab study

   Measured in animals or in the lab

   • In mouse muscle cells in a dish and in mice. Urolithin B made the cells grow, through more protein building and less protein breakdown, and the androgen receptor was involved. In mice, a nonstop dose from a pump under the skin for 28 days made muscles bigger and cut wasting after nerve injury. Not a dose by mouth, and not in people.

     The numbers C2C12 myotubes treated with 15 micromolar urolithin B for 24 hours grew and differentiated more, through increased protein synthesis and repression of the ubiquitin-proteasome pathway, with the androgen receptor implicated. In mice, 10 micrograms a day delivered continuously by implanted mini-osmotic pump for 28 days induced muscle hypertrophy and reduced atrophy after sciatic nerve section. Cells and mice, by continuous infusion, not an oral human dose.

     Journal of Cachexia, Sarcopenia and Muscle, 2017· animal study

Other compounds

1. 01FollistatinBiologicLimited. People have taken it in a published study, but fewer than 100 of them. 2 completed trials, 12 people given it.

   1 animal or lab study

   Measured in animals or in the lab

   • In mice bred to make extra follistatin in muscle, muscle mass rose a lot. Follistatin stops myostatin from docking on its receptor.

     The numbers Follistatin blocks myostatin binding to ActRIIB; transgenic mice overexpressing follistatin in muscle showed dramatic increases in muscle mass.

     Proceedings of the National Academy of Sciences, 2001· animal study

2. 02GDF11BiologicPreliminary. Studied in people, but no published study has had people take it. 1 human study where nobody was given it.3 reported

   1 animal or lab study

   Measured in animals or in the lab

   • In mice. The original claim: GDF11 falls with age, and putting it back reversed age-related heart enlargement in old mice joined to young ones. The whole young blood story rests on this paper.

     The numbers Mouse, heterochronic parabiosis. The original claim: GDF11 declines with age and restoring it reversed age-related cardiac hypertrophy. This is the paper the young blood narrative rests on.

     Cell, 2013· animal study

3. 03Rapamycin plus acarboseSmall moleculeAnimal or lab only. Only animal or lab studies on this page. No study in people yet. 7 animal studies, no human study.5 reported

   1 animal or lab study

   Measured in animals or in the lab

   • In mice. Each drug alone, started at 4 or 16 months, helped old mice of both sexes balance on a spinning rod and keep going longer, and shrank their enlarged hearts. Acarbose changed the fats in the heart more than rapamycin. Some benefits showed up in males only. These are health measures for each drug alone, not for the pair.

     The numbers Each drug alone, started at 4 or 16 months, improved rotarod and endurance and reduced cardiac hypertrophy in aged UM-HET3 mice of both sexes; acarbose changed the cardiac lipidome more than rapamycin; some benefits male-only. Healthspan measures for the single drugs, not the combination.

     Journals of Gerontology Series A, 2023· animal study