Clinical research is the final stage before FDA review. This is the first time the drug is tested on humans. You’ve probably heard of clinical trials, which roll out in four phases and are overseen by the FDA. For a brief refresher, Phase 1 is small, with just 20 to 100 human test subjects. It measures safety and dosage—like in animal models, but more accurately. This stage only lasts a few months. About 70 percent of drugs that enter Phase 1 move onto the second round of testing. Phase 2, which includes up to several hundred participants, can last up to two years. The trials measure side effects and the drug’s efficiency, meaning whether it actually treats the condition or ailment it’s meant to treat. Finally, Phase 3 is when things get really serious. The trials last up to four years and include as many as 3,000 voluntary participants who hope the new drug will be able to treat a disease or condition they’re fighting. The trials include more efficiency monitoring and look out for adverse effects.