Classification explainer
Cardarine (GW501516): not a SARM, and the carcinogenicity data
Short answer
The classification: GW501516, sold as cardarine, is a peroxisome proliferator-activated receptor delta agonist. It is not a selective androgen receptor modulator and it has no androgen receptor activity.
Where it came from: a pharmaceutical discovery programme, published in 2001, built around reverse cholesterol transport in cells and in monkeys rather than around endurance in people.
Why development ended: the anti-doping agency's 2013 alert says the drug was withdrawn from research and terminated when serious toxicities were discovered in pre-clinical studies.
What the cancer claim rests on: a peer-reviewed 2019 letter reports that the compound causes cancer in rats and in mice after 104 weeks of dosing, citing two 2009 toxicology meeting abstracts. Those abstracts are the primary record.
Where it sits now: the 2026 WADA Prohibited List names GW1516 at S4.4.1, metabolic modulators, prohibited at all times, and no approved medicine anywhere contains it.
On this page
What is GW501516?
The molecule: a synthetic agonist selective for the delta subtype of the peroxisome proliferator-activated receptor family, built with combinatorial chemistry and structure-based design and first described in 2001 (Oliver, 2001).
What that receptor family does: the three subtypes are lipid sensors that regulate fatty acid and carbohydrate metabolism. Fibrates work through the alpha subtype and glitazones through the gamma subtype; the delta subtype had no selective ligand until this compound.
The original target: reverse cholesterol transport. In cells the compound raised expression of the cholesterol transporter ABCA1, and in insulin-resistant middle-aged obese rhesus monkeys it produced a dose-dependent rise in HDL cholesterol while lowering small dense LDL, fasting triglycerides and fasting insulin.
What it is not: anything to do with the androgen receptor. The retail category it is sold in has no bearing on where it binds.
Where the endurance claim starts
The paper everyone quotes: a 2008 mouse study testing pathway-specific drugs on treadmill running (Narkar, 2008). It reported that a PPAR-beta/delta agonist together with exercise training raised oxidative muscle fibres and running endurance in adult mice, and that the two acted together rather than the drug acting alone.
The number that gets misattributed: the headline 44 percent endurance increase in sedentary mice came from four weeks of AICAR, an AMPK agonist, not from GW501516. Two different compounds, one paper, one figure that travels under the wrong name.
What the paper did not do: it did not run in humans, and it did not measure endurance in humans. Every endurance claim aimed at a person is an extrapolation from mice on a treadmill.
The published human record
What happened when it reached people
How to read this: two short published human studies, each with the amount it administered and the endpoint it measured. Both were metabolic studies, not performance studies.
| Source | Population | What the study gave | Reported result |
|---|---|---|---|
| Sprecher, 2007 | 24 healthy volunteers, hospitalised and sedentary | 2.5mg or 10mg by mouth once daily, 2 weeks | HDL cholesterol rose in both arms while it fell 11.5 percent on placebo; serum triglycerides trended down at the higher arm; clearance of triglyceride after a fat meal improved |
| Risérus, 2008 | moderately obese men | oral, short duration | reversal of several metabolic abnormalities, reduced oxidative stress, increased fatty acid oxidation |
The scale of the human record: two short studies in fewer than a hundred people, running two weeks and a few weeks. Nothing longer reached publication, because the programme stopped.
The carcinogenicity record, and what it is made of
Why this section is careful: the cancer claim is the load-bearing fact about this compound, and it circulates without anyone naming the document. Here is the document trail as we found it.
| Source | What kind of record | What it states |
|---|---|---|
| Geiger, 2009 | meeting abstract, Society of Toxicology, abstract PS895 | rat carcinogenicity study with GW501516 |
| Newsholme, 2009 | meeting abstract, Society of Toxicology, abstract PS896 | mouse carcinogenicity study with GW501516 |
| Mitchell and Bishop-Bailey, 2019 | peer-reviewed letter, Pulmonary Circulation | states the compound causes cancer in rats after 104 weeks of dosing and in mice after 104 weeks of dosing, citing the two abstracts above |
| Pollock, 2010 | peer-reviewed full paper, PPAR Research | in mice given a carcinogen first, the compound drove metastatic squamous cell carcinoma of the forestomach within two months |
| WADA alert, 22 March 2013 | anti-doping agency alert | the drug was withdrawn from research and terminated when serious toxicities were discovered in pre-clinical studies |
What that trail supports: two-year rodent carcinogenicity studies were run and reported tumours, and the peer-reviewed literature repeats that finding by citation. That is a real and serious record.
What it does not support: a specific organ list, a specific dose threshold, or a quantified human risk. Anyone quoting those numbers is quoting something they did not read either.
The one full paper's limit: the 2010 mouse model gave a carcinogen first and the compound afterwards, so it describes tumour promotion in a sensitised animal. It is strong evidence of a mechanism and it is not a two-year carcinogenicity study.
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Is cardarine a SARM?
No. A SARM binds the androgen receptor. This compound binds a nuclear receptor in the lipid-sensing family, which is why the 2026 WADA Prohibited List files it at S4.4.1 under metabolic modulators, next to AMPK activators and Rev-erb agonists, while the SARMs sit at S1.2 under anabolic agents. Two sections apart, on purpose.
Where the mislabel comes from: retail listings, not chemistry. In a 2017 analysis of products sold online as SARMs, GW501516 was one of the unapproved drugs found inside products in that category (Van Wagoner, 2017).
Does cardarine cause cancer?
In rodents, on the published record, tumours were reported after two years of dosing, and the developer stopped the programme. The precise wording in the peer-reviewed literature is that the compound causes cancer in rats and in mice after 104 weeks of dosing, sourced to two 2009 toxicology meeting abstracts rather than to full papers.
In humans: there is no carcinogenicity data, because the human exposure was two short metabolic studies and then nothing. Absence of human data is not reassurance, it is absence.
The honest summary: a rodent carcinogenicity signal strong enough to end a pharmaceutical programme, documented mainly in conference abstracts, with no human evidence in either direction.
Why was GW501516 abandoned?
Because pre-clinical toxicity ended it. The World Anti-Doping Agency issued an alert on 22 March 2013 stating that the compound was withdrawn from research by the pharmaceutical company and terminated when serious toxicities were discovered in pre-clinical studies, and that clinical approval has not and will not be given for it.
Why an anti-doping agency issued a drug-safety alert: athletes were testing positive for it, the compound was circulating on a grey market, and the agency judged the health risk serious enough to warn people it was trying to catch.
Is cardarine legal?
There is no approved medicine containing it anywhere. The United States Anti-Doping Agency states plainly that GW1516 is not legally permitted in any medications, supplements, or foods, and is not available anywhere as an approved medication. In sport it is prohibited at all times, in and out of competition, under S4.4.1 of the 2026 list, where the entry names it by its full chemical name and both code names.
What sellers rely on: the phrase "research use only", which describes an intention rather than a legal category. Regulators have said in writing that such labelling does not change what a product is when the marketing sells it for human effects.
Where the evidence runs out
Four things nobody can source:
- The tumour detail. The two carcinogenicity studies are conference abstracts. Organs, incidence and dose response are not in the retrievable peer-reviewed record.
- Any human risk figure. No human carcinogenicity study exists and none will be run.
- Duration in people. The longest published human exposure we found is 2 weeks.
- Endurance in people. The endurance literature is rodent. No human performance trial was published before the programme closed.
No approved product contains GW501516, in any jurisdiction we could check.
How this page is sourced
Where each claim comes from: the pharmacology and the human data come from the four papers below, the carcinogenicity statement from a peer-reviewed letter and the two abstracts it cites, and the development history from the anti-doping alert of March 2013.
Eight sources: six papers with DOIs and PubMed IDs, one international standard, and two agency documents. The two 2009 abstracts are named as abstracts, not as papers, because that is what they are.
Last reviewed: 27 July 2026.
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1
Oliver WR Jr, Shenk JL, Snaith MR, et al. A selective peroxisome proliferator-activated receptor delta agonist promotes reverse cholesterol transport. Proc Natl Acad Sci U S A. 2001;98(9):5306-5311. doi:10.1073/pnas.091021198. PMID 11309497.
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2
Sprecher DL, Massien C, Pearce G, et al. Triglyceride:high-density lipoprotein cholesterol effects in healthy subjects administered a peroxisome proliferator activated receptor delta agonist. Arterioscler Thromb Vasc Biol. 2007;27(2):359-365. doi:10.1161/01.ATV.0000252790.70572.0c. PMID 17110604.
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3
Risérus U, Sprecher D, Johnson T, et al. Activation of peroxisome proliferator-activated receptor (PPAR)delta promotes reversal of multiple metabolic abnormalities, reduces oxidative stress, and increases fatty acid oxidation in moderately obese men. Diabetes. 2008;57(2):332-339. doi:10.2337/db07-1318. PMID 18024853.
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4
Narkar VA, Downes M, Yu RT, et al. AMPK and PPARdelta agonists are exercise mimetics. Cell. 2008;134(3):405-415. doi:10.1016/j.cell.2008.06.051. PMID 18674809.
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5
Mitchell JA, Bishop-Bailey D. PPAR-beta/delta a potential target in pulmonary hypertension blighted by cancer risk. Pulm Circ. 2019;9(1):2045894018812053. doi:10.1177/2045894018812053. PMID 30351241. This letter is the source of the 104-week statement, and it cites Geiger LE, Dunsford WS, Lewis DJ, et al, "Rat carcinogenicity study with GW501516, a PPAR delta agonist", The Toxicologist 2009, abstract PS895, and Newsholme SJ, Dunsford WS, Brodie T, et al, "Mouse carcinogenicity study with GW501516, a PPAR delta agonist", The Toxicologist 2009, abstract PS896. Both are Society of Toxicology meeting abstracts.
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6
Pollock CB, Rodriguez O, Martin PL, et al. Induction of metastatic gastric cancer by peroxisome proliferator-activated receptor delta activation. PPAR Res. 2010;2010:571783. doi:10.1155/2010/571783. PMID 21318167.
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7
Van Wagoner RM, Eichner A, Bhasin S, Deuster PA, Eichner D. Chemical composition and labeling of substances marketed as selective androgen receptor modulators and sold via the internet. JAMA. 2017;318(20):2004-2010. doi:10.1001/jama.2017.17069. PMID 29183075.
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8
World Anti-Doping Agency. WADA issues alert on GW501516, 22 March 2013; and World Anti-Doping Code International Standard: Prohibited List 2026, section S4.4.1, effective 1 January 2026. Accessed 27 July 2026. wada-ama.org, 2026 Prohibited List.
Related pages
Around this page: five neighbouring pages on what a compound is and on what a test result covers.
- Is MK-677 a SARM: the growth hormone secretagogue that shares this compound's retail shelf and none of its pharmacology.
- Is ostarine a steroid: the androgen receptor side of the same three-way mix-up, with the statutory definition.
- MOTS-c guide: another compound filed in the same S4.4.1 metabolic-modulator entry.
- What an HPLC purity number misses: why a percentage on a certificate does not identify what is in a vial.
- PT-141 and the Vyleesi approval: the opposite case, a compound that did reach approval, and exactly what that approval covers.
Next in the series: one compound gets taken apart each week in The Decadewise briefing.
The disclaimer
Every page is reviewed by medical professionals before it ships, and written with longtime biohackers who were doing this before it was a trend. Reviewed still does not mean prescribed: nothing here is medical advice. It is research, trial data, and reported use, with the numbers intact so you can check them. For decisions about your body, see a doctor who can look at your labs.
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