Cardarine
GW501516 (cardarine)
Also known as: GW501516, GW-501516, Endurobol
A PPAR-delta agonist GSK stopped developing, reportedly after long-term rodent studies produced cancers in multiple organs; still sold widely for endurance and fat loss despite that report and a WADA ban.
Overview
Cardarine shifts muscle toward fat oxidation and in the 2008 Cell paper combined with training to raise mouse endurance. Human testing did happen: GSK ran a 268-person, 12-week lipid trial in which HDL cholesterol rose up to 16.9% and triglycerides fell 16.9%. Development then stopped, and the reason given in anti-doping and regulatory communications is that two-year rodent studies produced tumours across multiple organs. Those carcinogenicity studies were never published as a primary paper, so the specific finding cannot be read first-hand. No human efficacy trial for endurance or fat loss exists, WADA prohibits it, and health regulators including Health Canada have seized products as recently as 2025.
Mechanism of action
PPAR-delta agonism that upregulates fatty-acid oxidation genes in skeletal muscle.
Key studies & citations
- Animal2008
AMPK and PPARdelta agonists are exercise mimetics
GW501516 plus training improved endurance in mice.
Cell - Human2012
Lipid effects of peroxisome proliferator-activated receptor-delta agonist GW501516 in subjects with low high-density lipoprotein cholesterol: characteristics of metabolic syndrome
The largest published human trial, run by GSK: 268 people with low HDL took 2.5, 5 or 10 mg or placebo for 12 weeks. HDL cholesterol rose up to 16.9%, triglycerides fell 16.9% and apoB fell 14.9%. Twelve weeks is the longest published human exposure; the rodent carcinogenicity findings that ended development were never published as a primary paper.
Arteriosclerosis, Thrombosis, and Vascular Biology
Frequently asked questions
How real is the cancer risk?
Serious enough that the manufacturer stopped development. The rodent carcinogenicity data are described in anti-doping and regulatory communications rather than in a published study, so the detail cannot be checked directly. The longest published human exposure is 12 weeks, which tells you nothing about cancer risk either way.