Phase 1 clinical trials primarily assess safety in a small number of subjects. Which phase is this?

• A. Phase 0
• B. Phase 1
• C. Phase 2
• D. Phase 3

Answer: (B)

The main concept here is how early human testing is designed to protect participants while establishing a safe starting point for further study. Phase 1 trials are the first step in human testing after preclinical work. Their primary goal is safety and tolerability in a small group of participants, which may be healthy volunteers or patients depending on the drug. These studies look at how the drug is absorbed, distributed, metabolized, and excreted (pharmacokinetics) and identify any immediate or dose-related adverse effects. The dose is typically escalated carefully to determine the maximum tolerated dose and to establish safe dosing ranges for later trials. In contrast, later phases shift focus toward whether the drug actually works (efficacy) and how it performs in larger, more diverse populations, while continuing to monitor safety. Phase 0 is a preliminary exploratory step with very limited exposure for PK data, phase 2 tests efficacy and safety in more people, and phase 3 confirms efficacy and safety in large populations before potential approval.