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Background And Regulatory History — Deep Dive

By Editorial Desk · published 2026-04-04 · last reviewed 2026-04-24 · Data

The short version of PPARδ agonist fits in a sentence. The long version — which is the one that helps — is below.

Reviewed 2026-04-24. Anything still debated is marked as such rather than presented as settled.

Background and Regulatory History

GW501516 acts on PPARδ, a nuclear receptor that helps regulate fatty acid oxidation and energy homeostasis. In animal studies, activation of this receptor was associated with increased endurance and changes in lipid metabolism. Human trials examined effects on blood lipids and other metabolic markers, but the compound did not advance to approval. Rodent studies later reported tumors in multiple tissues at doses used in those experiments. Whether those findings translate to human risk remains uncertain, and the clinical relevance of the animal data is still debated.

Regulatory bodies treat GW501516 as a prohibited substance in competitive sport. The World Anti-Doping Agency added it to the prohibited list, and it falls under classes covering metabolic modulators and hormone-related agents. It is not approved by drug regulators for human use, and it is not a lawful dietary supplement. Products sold under the cardarine name may contain unlisted ingredients or different compounds. Because no approved product exists, quality and identity are not guaranteed by pharmaceutical manufacturing standards.

Detection, Regulation, and Quality Context

Cardarine can be detected in biological samples and product materials using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). The method separates compounds by chromatography and identifies them by mass-to-charge transitions, allowing low-level detection in urine or blood. Sample preparation often involves enzymatic hydrolysis, solid-phase extraction, or protein precipitation. Certified reference materials and isotope-labeled internal standards improve quantification. Detection windows depend on metabolism, matrix, and assay sensitivity, so no single universal window applies.

Regulatory treatment of cardarine differs by context and jurisdiction. In competitive sport, the World Anti-Doping Agency lists PPARδ agonists, including GW501516, as prohibited at all times. Outside sport, it lacks approval as a prescription medicine in major drug markets, and products sold for human consumption may be treated as unapproved drugs. Some countries also restrict importation or sale through general consumer protection and medicines laws. These classifications affect availability, testing, and legal risk without establishing therapeutic value.

Because cardarine is not an approved medicine, no pharmacopeial monograph defines its identity, purity, or storage requirements. Laboratories typically rely on in-house methods and reference standards when testing materials labeled as GW501516. Certificates of analysis may report purity and identity for a specific batch, but their scope varies and they do not guarantee safety or legal status. Independent verification can include high-performance liquid chromatography, mass spectrometry, nuclear magnetic resonance, and elemental analysis. The distinction between research chemical labeling and human use is significant because quality standards and oversight differ.

Cardarine at a glance

PropertyValueNotes
Common nameCardarineCommon internet and media name.
Research codeGW501516Also written GW-1516.
Drug classPPARδ agonistNot a selective androgen receptor modulator.
Development statusDiscontinuedClinical development halted after rodent cancer findings.
Regulatory statusProhibited in sportListed by WADA; not approved as medicine.

Mechanism and Detection

GW501516 acts as a ligand for PPAR delta, a nuclear receptor that regulates transcription of genes involved in fatty acid oxidation and energy use. Activation of this receptor in skeletal muscle shifts metabolism toward fat burning in animal models. The compound does not burn fat directly; it changes gene expression over hours to days. Researchers study it to understand metabolic flexibility and exercise adaptation. Effects observed in rodents are not automatically expected in humans.

Preclinical research reported that GW501516 increased running endurance in mice and improved lipid profiles in some animal species. Early human trials explored effects on high-density lipoprotein cholesterol, triglycerides, and glucose handling, but the program was discontinued. Published human data are sparse and do not establish efficacy for any condition. Studies also examined PPAR delta in cancer biology, with conflicting findings across models. The relationship between receptor activation, tissue context, and disease risk remains an active area of investigation.

Anti-doping laboratories identify GW501516 and its metabolites using liquid chromatography-tandem mass spectrometry. Urine is the usual matrix, and detection can occur after the parent compound has cleared from blood. The exact detection window depends on dose, formulation, individual metabolism, and assay sensitivity. Because the compound is prohibited at all times, athletes are subject to testing in and out of competition. Analytical methods continue to improve as new metabolites and designer analogs are characterized.

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Mechanism and Safety Research

Early clinical research explored GW501516 for lipid disorders, obesity, and diabetes. Some short-term human studies reported changes in HDL cholesterol, LDL cholesterol, and triglycerides. The development program was discontinued after rodent studies showed dose-dependent tumor formation in multiple tissues, including liver, bladder, stomach, and skin. These findings raised concerns about long-term cancer risk in humans. Because human exposure data are limited, the clinical significance of the rodent tumors remains uncertain.

Literature on cardarine often separates receptor pharmacology from toxicology. Mechanistic papers describe PPARδ activation and gene expression changes, while safety assessments focus on carcinogenicity and species differences. Questions remain about whether rodent tumors arise through PPARδ-dependent or off-target mechanisms. Another open area is how human metabolism and exposure compare with those in animal studies. Analytical methods such as liquid chromatography–mass spectrometry are used to confirm identity in biological and product samples.

Supporting material

== Clinical correlation == Nerve entrapment is a complex lesion involving the multiple tissue types in a fascicle. There may be mixed lesions where individual tissue lesions contribute to the whole of the symptoms. Tissue injury may contribute to positive and/or negative symptoms, which can be attributed to the loss of nerve function and the hyperexcitability of nerve tissue. Additionally, nerve fibers may be differently affected by compression/ischema depending on their size, location and topography. Studies on human tissues have no found a clear correlation between the amount of structural damage to a nerve and the degree of symptoms. Patients can have significant symptoms without nerve fiber changes.

An anaerobic organism or anaerobe is an organism that does not require molecular oxygen for growth or energy metabolism. Anaerobes produce adenosine triphosphate (ATP) by fermentation, anaerobic respiration, or both. During anaerobic respiration, substances other than oxygen serve as the terminal electron acceptor. Anaerobes are commonly classified according to their relationship with oxygen. Obligate anaerobes are harmed by it. Aerotolerant organisms do not use oxygen but can tolerate it, whereas facultative anaerobes can grow without oxygen but use it when available. Most anaerobes are microorganisms, including bacteria, archaea, protozoa, and fungi, although a small number of anaerobic multicellular animals are known. Anaerobes occur in oxygen-depleted environments and in symbiotic associations with other organisms. Culturing anaerobes often requires oxygen-free techniques.

San Juan Bautista was built in 1613 by Date Masamune, the daimyō of Sendai in northern Japan, in Tsuki-No-Ura harbour (Ishinomaki, Miyagi Prefecture). The project had been approved by the Bakufu, the shōgun's government in Edo. The shōgun already had two smaller ships (80 and 120 tons) built for him by the English pilot William Adams. The larger, the San Buena Ventura, was given to Spanish shipwrecked sailors to return to New Spain in 1610. The shōgun also issued numerous permits for Red seal ships, destined for Asian trade and incorporating many elements of Western ship design. San Juan Bautista is reported to have required 45 days' work, with the participation of technical experts from the Bakufu, 800 shipwrights, 700 smiths, and 3000 carpenters. Two Spanish men also participated to the endeavour: the friar Luis Sotelo, and the Spanish captain Sebastián Vizcaíno. These efforts were seen with disapproval by the Spanish government in Manila, and Los Rios Coronel suggested that Luis Sotelo should not be allowed into Japan any further (C. R. Boxer).

Sources: en.wikipedia.org

Notes from published material

==== MeSH D12.776.167.200.067 – cdc2-cdc28 kinases ==== MeSH D12.776.167.200.067.249 – cdc2 protein kinase MeSH D12.776.167.200.067.500 – cdc28 protein kinase, s cerevisiae MeSH D12.776.167.200.067.875 – cyclin-dependent kinase 5 MeSH D12.776.167.200.067.900 – cyclin-dependent kinase 9

== Veterinary use == Ivermectin is routinely used to control parasitic worms in the gastrointestinal tract of ruminant animals. These parasites normally enter the animal when it is grazing, pass the bowel, and set and mature in the intestines, after which they produce eggs that leave the animal via its droppings and can infest new pastures. Ivermectin is only effective in killing some of these parasites, because of an increase in anthelmintic resistance. This resistance has arisen from the persistent use of the same anthelmintic drugs for the past 40 years. Resistance to ivermectin has also been reported in cattle tick (Rhipicephalus microplus) populations from the Brazilian Amazon, including resistant populations identified in western Pará. Additionally, the use of Ivermectin for livestock has a profound impact on dung beetles, such as T. lusitanicus, as it can lead to acute toxicity within these insects. In dogs, ivermectin is routinely used as prophylaxis against heartworm. Dogs with defects in the P-glycoprotein gene (MDR1), often collie-like herding dogs, can be severely poisoned by ivermectin. The mnemonic "white feet, don't treat" refers to Scotch collies that are vulnerable to ivermectin. Some other dog breeds (especially the Rough Collie, the Smooth Collie, the Shetland Sheepdog, and the Australian Shepherd), also have a high incidence of mutation within the MDR1 gene (coding for P-glycoprotein) and are sensitive to the toxic effects of ivermectin. For dogs, the insecticide spinosad may have the effect of increasing the toxicity of ivermectin.

The first five stations, covering the approaches to London, were installed by 1937 and began full-time operation in 1938. Over the next two years, additional stations were built while the problem of disseminating the information to the fighter aircraft led to the first integrated ground-controlled interception network, the Dowding system. By the time the war started, most of the east and south coasts had radar coverage. Chain Home proved important during the Battle of Britain in 1940. CH systems could detect enemy aircraft while they were forming over France, giving RAF commanders ample time to marshal their aircraft in the path of the raid. This had the effect of multiplying the effectiveness of the RAF to the point that it was as if they had three times as many fighters, allowing them to defeat frequently larger German forces. The Chain Home network was continually expanded, with over 40 stations operational by the war's end, including mobile versions for use overseas. Late in the war, when the threat of Luftwaffe bombing had ended, the CH systems were used to detect V2 missile launches. UK radar systems were wound down after the war but the start of the Cold War led to the Chain Home radars being pressed into service in the new ROTOR system until replaced by newer systems in the 1950s. Only a few of the original sites remain.

Sources: en.wikipedia.org

Background from the literature

Deuterium is most commonly used in hydrogen nuclear magnetic resonance spectroscopy (proton NMR) in the following way. NMR ordinarily requires compounds of interest to be analyzed as dissolved in solution. Because of deuterium's nuclear spin properties which differ from the light hydrogen usually present in organic molecules, NMR spectra of hydrogen/protium are highly differentiable from that of deuterium, and in practice deuterium is not "seen" by an NMR instrument tuned for 1H. Deuterated solvents (including heavy water, but also compounds like deuterated chloroform, CDCl3 or C2HCl3, are therefore routinely used in NMR spectroscopy, in order to allow only the light-hydrogen spectra of the compound of interest to be measured, without solvent-signal interference. Nuclear magnetic resonance spectroscopy can also be used to obtain information about the deuteron's environment in isotopically labelled samples (deuterium NMR). For example, the configuration of hydrocarbon chains in lipid bilayers can be quantified using solid state deuterium NMR with deuterium-labelled lipid molecules. Deuterium NMR spectra are especially informative in the solid state because of its relatively small quadrupole moment in comparison with those of bigger quadrupolar nuclei such as chlorine-35, for example.

This is mathematically incorrect (if the rule was precisely accurate the required temperature increase would be about 15.8 °C (28.4 °F)), and in any case the rule is only a rough approximation and cannot always be relied on. Chemists often use the more comprehensive Arrhenius equation for better estimations. The same is true, up to a point, of the chemical reactions of living things. They are usually catalyzed by enzymes which change reaction rates, but with no variation in catalytic action, the rule of thumb is still mostly applicable. In the case of bacteria and fungi, the reactions needed to feed and reproduce speed up at higher temperatures, up to the point that the proteins and other compounds in their cells themselves begin to break down, or denature, so quickly that they cannot be replaced. This is why high temperatures kill bacteria and other micro-organisms: 'tissue' breakdown reactions reach such rates that they cannot be compensated for and the cell dies. On the other hand, 'elevated' temperatures short of these result in increased growth and reproduction; if the organism is harmful, perhaps to dangerous levels. Just as temperature increases speed up reactions, temperature decreases reduce them. Therefore, to make explosives stable for longer periods, or to keep rubber bands springy, or to force bacteria to slow down their growth, they can be cooled. That is why shelf life is generally extended by temperature control: (refrigeration, insulated shipping containers, controlled cold chain, etc.) and why some medicines and foods must be refrigerated.

In March 2019, two FDA specialists publicly demanded that the FDA suspend new opioid approvals, alleging that the FDA's oversight of opioid approvals had been dangerously deficient. In July 2017, a 400-page report by the National Academy of Sciences presented plans to reduce the addiction crisis, which it said was killing 91 people each day. The Substance Abuse and Mental Health Services Administration administers the Opioid State Targeted Response grants, a two-year program authorized by the 21st Century Cures Act which provided $485 million to states and US territories in the fiscal year 2017 for the purpose of preventing and combatting opioid misuse and addiction. Thomas Frieden, former director of the Centers for Disease Control and Prevention, said that "America is awash in opioids; urgent action is critical." The crisis has changed moral, social, and cultural resistance to street drug alternatives such as heroin. Many state governors have declared a "state of emergency" to combat the opioid epidemic or undertaken other major efforts against it. In July 2017, opioid addiction was cited as the "FDA's biggest crisis". In October 2017, President Donald Trump concurred with his Commission's report and declared the country's opioid crisis a "public health emergency". Federal and state interventions are working on employing health information technology in order to expand the impact of existing drug monitoring programs.

Split-thickness A split-thickness skin graft (STSG) includes the epidermis and part of the dermis. Its thickness depends on the donor site and the needs of the person receiving the graft. It can be processed through a skin mesher which makes apertures onto the graft, allowing it to expand up to four times its size. For larger expansions the modified MEEK technique can be used, allowing it to expand up to nine times its size. Split-thickness grafts are frequently used as they can cover large areas and the rate of autorejection is low. The same site can be harvested again after six weeks. The donor site heals by re-epithelialisation from the dermis and surrounding skin and requires dressings. Full-thickness A full-thickness skin graft consists of the epidermis and the entire thickness of the dermis. The donor site is either sutured closed directly or covered by a split-thickness skin graft. Composite graft A composite graft is a small graft containing skin and underlying cartilage or other tissue. Donor sites include, for example, ear skin and cartilage to reconstruct nasal alar rim defects.

Sources: en.wikipedia.org

Frequently asked questions

Is cardarine a selective androgen receptor modulator?

No. Cardarine is a PPARδ agonist, while selective androgen receptor modulators act on androgen receptors. The two classes differ in receptor target and downstream effects.

Why did clinical development stop?

Preclinical rodent studies reported cancers, including liver and bladder tumors, at tested doses. The human relevance of those findings is uncertain, but development was discontinued. No approved human product resulted.

Is cardarine approved for medical use?

No. It remains an investigational compound without approved therapeutic labeling. Sports regulators prohibit its use, and health agencies have warned against consuming it.

How is cardarine detected in anti-doping tests?

Anti-doping laboratories typically use LC-MS/MS to detect GW501516 and its metabolites in urine. The method is sensitive and can identify the compound at low concentrations. Detection depends on sample timing, metabolism, and the specific assay.

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