Cardarine (GW-501516)
GW-501516 · GW501516
Cardarine (GW-501516, also known as Endurobol or GSK-516) is a non-hormonal peroxisome proliferator-activated receptor delta (PPAR-delta) agonist originally developed by GlaxoSmithKline and Ligand Pharmaceuticals in the 1990s for dyslipidemia and metabolic syndrome. It is commonly grouped with SARMs in the research-chemical market but is NOT a SARM - it does not bind the androgen receptor, does not suppress testosterone, and does not produce androgen-related effects. Instead it activates PPAR-delta signaling in muscle and liver, which upregulates fatty acid oxidation, glucose utilization, and mitochondrial biogenesis.
Once daily. 2.5 mg is the LOWEST of the three doses studied in the Phase 2 (2.5 / 5 / 10 mg for 12 weeks). A separate 10 mg arm was studied for 2 weeks. DEVELOPMENT WAS HALTED after long-term rodent studies found tumours across multiple organ systems; no human study ran beyond 12 weeks so that question was never answered in people.
Start here. Every protocol below is ordered lowest-first. Begin at the smallest effective dose, hold about a week to assess tolerance, and step up only if needed.
How it works
Cardarine is a selective PPAR-delta agonist. PPAR-delta (peroxisome proliferator-activated receptor delta) is a nuclear receptor expressed heavily in skeletal muscle, heart, adipose, and liver tissue. Activation drives a transcriptional program that upregulates fatty acid transport and beta-oxidation (making fat a preferred fuel source during exercise), increases mitochondrial biogenesis, improves skeletal muscle oxidative capacity, and shifts glucose utilization toward more efficient pathways.
Because it does not bind the androgen receptor, it does not produce any of the classic SARM or AAS side effects - no HPT-axis suppression, no estrogen or DHT conversion, no aromatization, no gynecomastia risk, no virilization risk in women. It does not require post-cycle therapy. This is why it is commonly stacked with SARMs - it provides endurance and fat-oxidation benefits without adding AR load.
The primary safety question is the rodent carcinogenicity data from the discontinued GSK development program. At high doses administered for two years (essentially a lifetime for a rat), Cardarine produced dose-dependent tumors in multiple organ systems. The relevance of those doses to human off-label use (short cycles, lower exposure) is debated. No human tumor signals have been reported in the short-term clinical trials conducted before program discontinuation, but lifetime human safety data does not exist.
What to expect
First 1-2 weeks: endurance shift noticeable within the first week on cardio days. Steady-state reached around day 5.
Weeks 3-5: peak endurance benefit, visible fat oxidation acceleration during a deficit, possible lipid improvement.
Weeks 6-10: continued body composition benefit. Consider cycle-off at 10-12 weeks given the unresolved lifetime safety question from rodent data.
Evidence
References for this compound are being re-checked against their source records. We are not showing them until each one is confirmed to support the claim it sits under.
Side effects & safety
Commonly reported
- No hormonal side effects (does not bind the androgen receptor)
- Mild headache in some users early in cycle
- Mild GI upset possible
Less common & notes
- Mild sleep disturbance, mild fatigue (paradoxical - usually energy-enhancing), transient blood sugar shifts in some users.
- Notable concern: two-year lifetime rodent carcinogenicity data at high doses showed dose-dependent tumors in multiple organ systems.
- Clinical relevance to short-course human use is debated but the data is the defining regulatory fact for this compound.
- No human tumor signals were reported in the short-term Phase I/II trials before GSK discontinued the program, but lifetime human data does not exist and likely never will.
Pharmacokinetics
High oral bioavailability
Per dose - supports once daily dosing
Hepatic metabolism. Renal and biliary excretion of metabolites.
Storage. Store at controlled room temperature (20-25°C / 68-77°F). Protect from moisture and light. Keep capsules in original container with desiccant when available. Liquid suspensions should be kept sealed and used within 12 months of opening. Shelf life typically 2-3 years from manufacture date for capsules, 1-2 years for liquid. Keep out of reach of children.
Regulatory status
Cardarine (GW-501516) is NOT FDA-approved for any indication. GSK and Ligand discontinued development in 2007 after lifetime rodent carcinogenicity studies. Classified as a research chemical in the United States - not a controlled substance federally as of this writing, but banned by WADA (specifically flagged as a substance of concern due to the preclinical cancer data), USADA, the NCAA, and most professional sports leagues. Use falls outside regulated medical practice.
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The guide & community
The complete Cardarine (GW-501516) walkthrough, real protocol discussion and coaching live inside the BlessUp community on Skool.
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