Phase I

Phase I clinical trials represent the first evaluation of an investigational drug in humans, primarily focused on assessing safety, tolerability, and pharmacokinetics in a small group of participants typically involving 20-100 healthy volunteers or, in oncology, patients with advanced disease, marking the critical transition from preclinical research to human testing.

During Phase I trials, researchers employ dose-escalation designs to identify the maximum tolerated dose and characterise dose-limiting toxicities. Investigators collect intensive pharmacokinetic samples to understand drug absorption, distribution, metabolism, and elimination in humans. These early studies also explore preliminary pharmacodynamic effects, providing initial evidence of biological activity guiding subsequent development phases. Approximately 70% of therapies advance beyond Phase I, with novel modalities demonstrating higher progression rates than traditional small molecules. These early-stage investigations demand meticulous protocol design, ethical oversight, and transparent communication with participants, establishing the safety foundation necessary for broader clinical development programmes that ultimately deliver innovative therapeutics to patients in need.