Endurobol (also known as GW501516 or Cardarine) is a PPARD (Peroxisome Proliferator-Activated Receptor Delta) receptor agonist. This receptor plays an important role in human metabolism, as it is involved in the regulation of genes that help manage the transport and oxidation of fatty acids. PPARD agonists are of great interest in medical research at present, as they hold the potential to influence areas such as insulin sensitivity, glucose tolerance, and lipid balance. Further, they may offer therapeutic benefit with conditions such as obesity, type 2 diabetes, and high cholesterol. Endurobol is a research drug, once under development for improving HDL cholesterol in patients with dyslipidemia.
|Dose for men||
10-20mg / day (8-12 weeks)
90 x 5mg capsules
As a PPARD agonist, Endurobol has several effects that are of interest in the sports and fitness community. First, its use may cause a shift in energy metabolism, reducing glucose utilization and increasing the capacity for fatty acid oxidation. It can also favor glycogen storage in muscle tissue, improve ATP energy efficiency, and enhance exercise endurance. In early animal studies, it dramatically increased the running capacity of mice. This drastic shift in the utilization of fat for energy may further improve body composition. To that effect, Endurobol has been associated with a significant reduction in body fat in both animal studies and human anecdotal reports.
Perhaps most interesting, PPARD activation increases mitochondrial biogenesis in the muscles. This can actually remodel the muscle tissue. In studies using both trained and untrained mice, Endurobol caused fast twitch muscle fibers to convert to slow twitch fibers. The latter use oxygen for ATP energy, and are less susceptible to fatigue. Slow twitch fibers are also expressed more abundantly in endurance vs. strength athletes. Again, this effect can substantially improve exercise endurance. Endurobol is often called an exercise mimetic, because it can produce these changes in metabolism and fiber composition, which we normally associate with endurance training.
Endurobol successfully completed preliminary Phase I human safety studies, and then Phase II clinical trials. The Phase II study examined the effects of 2.5, 5, and 10 mg daily for 12 weeks in 268 patients with low HDL levels. During this investigation, the drug was shown to significantly improve serum lipids, with the 10 mg dose most impactful. This increased HDL (good) cholesterol by approximately 17%, and reduced LDL and triglycerides by 7% and 17%, respectively. A further analysis of particle size suggests changes that were cardioprotective. Bodyweight also increased by 1.3 kg. Lean vs. fat mass analysis was not done, however an increase in LBM compartment would be consistent with metabolic changes expected of a PPARD agonist.
In 2009, GSK withdrew its New Drug Application. Endurobol was officially pulled from development. During long-term preclinical safety studies, the drug had produced cancer in animals at all doses tested. Neoplasms appeared in the liver, bladder, thyroid, tongue, stomach, skin, testes, eyes, and uterus. With these findings, the drug will likely progress no further. These studies are often criticized in the athletic community for using high doses and a prolonged duration. While this may be true, this type of testing is also standard for preclinical safety evaluations. Incidentally, the lowest dose used and also determined to be carcinogenic was 5 mg/kg per day. When calculated across species, the rough equivalent is 65 mg for an 80 kg human.
Endurobol Side Effects
During Phase I and II human studies, Endurobol was well tolerated. There were no significant side effects reported. Further, an examination of liver enzymes (AST and ALT), hematology (blood cell counts), and renal function (creatinine) tests found no changes with the daily administration of 10 mg. Again, the potential side effects of this drug have not been fully characterized.
Endurobol is taken orally.
When used for physique- or performance-enhancing purposes, Endurobol is most commonly taken at a dosage of 10-20 mg per day. This is administered in one episode, often before exercise on training days. Cycles of Endurobol usually last 6 to 12 weeks.