The verdict
Our read at a glance.
Whether the endurance and fat-oxidation effects reported for a PPARdelta agonist can be separated from the tumor findings that ended its development.
- The signal
- GW501516 is a selective PPARdelta agonist developed by GlaxoSmithKline and Ligand as a metabolic and cardiovascular candidate. The 2008 Cell paper that established the exercise-mimetic idea used it alongside AICAR in mice. Development was discontinued after long-term rodent carcinogenicity findings, and it has never been approved for any use in any country.
- The unknown
- Whether any dose or duration is free of the cancer signal in humans, which is unresolved because the work that would answer it was stopped rather than completed. Long-term human safety data does not exist and, given the reason development ended, is unlikely to be generated.
- Our read
- The clearest cautionary tale in the exercise-mimetic category, and the reason the newer ERR agonists deserve patience rather than enthusiasm. A drug company with every commercial incentive to continue walked away from this one, and the compound outlived the program only because it is easy to synthesise and sell.
The mechanism
How it works.
Safety & regulatory boundary
The consequential part.
This is the memo where the safety finding is the headline. In a mouse mammary carcinogenesis model, GW501516 accelerated tumor formation and shifted tumor histology toward adenosquamous and squamous carcinoma. The developer discontinued the program on long-term rodent carcinogenicity across multiple organ systems. WADA issued a public alert stating that clinical approval has not been and will not be given for this substance, and it is prohibited at all times under S4.5 metabolic modulators. It is routinely mis-sold as a SARM; it is not one, it is a nuclear-receptor agonist.
What's next
What we're watching.
Nothing is pending. No sponsor is developing it, no trial is registered, and the anti-doping status is settled. What changes is enforcement and black-market supply, not evidence.
Context
Why this is discussed.
It is still sold and still discussed as endurance in a bottle, often described as a SARM, and the endurance story circulates far more widely than the reason the drug was abandoned.
The evidence base
5 cited references.
Regulatory & labels3
World Anti-Doping Agency · 2013
United States Anti-Doping Agency · Accessed 2026
World Anti-Doping Agency · Effective 2026-01-01
Indexed literature (PubMed)2
Narkar VA, Downes M, Yu RT, Embler E, Wang YX, Banayo E, Mihaylova MM, Nelson MC, Zou Y, Juguilon H, Kang H, Shaw RJ, Evans RM (Cell) · 2008
Yin Y, Russell RG, Dettin LE, Bai R, Wei ZL, Kozikowski AP, Kopelovich L, Glazer RI (Cancer Research) · 2005
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