Which phase of clinical trials primarily focuses on safety?

Phase I clinical trials are primarily focused on assessing the safety of a drug or treatment in humans. These trials typically involve a small group of healthy volunteers or patients and are designed to evaluate the drug's pharmacokinetics, pharmacodynamics, and any potential side effects. The primary goal is to determine a safe dosage range and identify any adverse effects associated with the drug.

During Phase I, researchers gather crucial data regarding how the drug is metabolized and whether it poses any risks, thereby establishing a foundational understanding of the safety profile before moving on to subsequent phases. These later phases build upon this safety data by assessing the drug's efficacy and further evaluating its safety in larger and more diverse populations.