Which statement about Phase 1 is correct?

• A. Phase 1 uses healthy volunteers to determine tolerance and toxicity after IND.
• B. Phase 1 uses patient volunteers with the target condition.
• C. Phase 1 does not involve any human subjects.
• D. Phase 1 is conducted after Phase 3.

Answer: (A)

Phase I trials are the first studies in humans after an IND approval, and the primary goal is safety. They test how the drug is absorbed, distributed, metabolized, and excreted (pharmacokinetics) and how it affects the body (pharmacodynamics), while focusing on tolerability and identifying dose-limiting toxicities. Using healthy volunteers is standard because it allows researchers to assess safety and basic PK without the confounding factors of a disease state. This helps establish a safe starting dose and the maximum tolerated dose before any larger studies in patients.

The other common approach—testing in patients with the target condition in Phase I—occurs in specific situations (such as when a drug would be too unsafe for healthy volunteers). But the typical, correct description is that Phase I uses healthy volunteers to determine tolerance and toxicity after IND, before moving on to later-phase trials that evaluate efficacy in patients.