GW501516 and ATX-304 are each a small molecule rather than a peptide.
Same target, different schedules: GW501516 not established; ATX-304 daily in the trial.
| Comparison | GW501516 (Cardarine) Cardarine · GW-501516 | ATX-304 (O-304) O-304 · ATX304 |
|---|---|---|
| How it works | How it works This is the compound in this library with the clearest reason not to take it. | How it works AMPK is the low-energy alarm. Most things that activate it do so by making the cell short of energy. |
| What it is | A discontinued drug whose development stopped over cancer in multiple organs. | An exercise mimetic that got through a phase 2a trial and then went quiet. |
| Status | Research only | Research only |
| Typical dose | — | — |
| How often | Not established | Daily in the trial |
| Stays active | Nothing published | Long in rodents, unverified in humans |
| Dose comes from | No established range | No established range |
| Cycled? | Not established No established range | Continuous in the one human trial Clinical trial protocol |
| What it does | ||
| Drug class | PPAR-delta agonist (small molecule) | Pan-AMPK activator (oral, not a peptide) |
| Used for | Sold for endurance and fat loss. Development was discontinued after animal carcinogenicity findings. | An oral AMPK activator sold as an exercise mimetic, with one real human trial behind it and nothing since. |
| Receptors hit | — | — |
| Numbers | ||
| Full dose line | Research only | No established dose outside the trial |
| Why that cycle | No schedule has been studied for this compound in people. | The phase 2a trial ran it daily for 28 days alongside metformin, with no break. Nothing longer has been published, so there is no evidence either way about extended use. |
| Weight / effect | Not measured in a trial | Not measured in a trial |
| Chain length | Not disclosed | Not disclosed |
| Common vial | — | — |
| Before you start | ||
| Route | By mouth (oral) | By mouth (oral) |
| Do not use if | Anyone, on the basis of the carcinogenicity findings that stopped its development Pregnancy or breastfeeding Any history of cancer Anyone competing in drug-tested sport Anyone who wants established safety data, because none exists for this compound in humans | Pregnancy and breastfeeding Taking metformin or other glucose-lowering drugs, without medical supervision, since the trial combined them deliberately Any condition affecting blood sugar control Banned in drug-tested sport |
What separates them
Proof behind the dose. Every dose here comes from community practice. Not one is backed by a published human study, which is worth knowing before you read the numbers as if they were equivalent.
What doesn't differ: They are both taken the same way (by mouth) and aimed at the same thing (endurance & fat loss). Neither has a measured effect size from a published trial, so there is no number to rank them on.
What people actually report
GW501516 (Cardarine)
- High risk: animal carcinogenicity findings ended its pharmaceutical development.
- Banned in drug-tested sport, and the subject of an unusual public warning from anti-doping authorities.
- Signs of an allergic reaction, including spreading hives, facial or throat swelling, or trouble breathing
- Anything unusual, since there is no known safety profile to compare it against
ATX-304 (O-304)
- One published human trial exists, it was small, and it was a proof-of-concept study in people already taking metformin.
- AMPK activators are banned in drug-tested sport as metabolic modulators, the same class as AICAR.
- Vendor CAS numbers and salt forms are inconsistent between sellers, so identity is not something to take on trust.
- Signs of low blood sugar such as shakiness, sweating, confusion or a pounding heartbeat
- Persistent vomiting or severe stomach pain
Side effects are what users and trials report most often, not a complete list. Anything sudden, spreading, or breathing-related is an emergency regardless of which compound caused it.
People also compare
This comparison does not cover cost, long-term safety, or how you personally will respond. Effect figures come from separate trials in different populations and are not always directly comparable to each other. Nothing here is medical advice or a recommendation to use any of these. Talk to a clinician about your own situation.