PhaseI

Phase I is the first stage of clinical testing in humans for a new drug or biologic. Its primary purpose is to evaluate safety, tolerability, pharmacokinetics, and pharmacodynamics in humans, after preclinical studies in animals. Phase I trials seek to establish a safe dosage range, characterize the body's handling of the compound, and identify potential adverse effects for further study.

Typically involve small groups of participants, often healthy volunteers, though patients with the target condition may be enrolled when the drug's safety concerns make healthy volunteers inappropriate (for example in cancer therapies). Trials use dose-escalation or single/multiple-dose designs to determine the maximum tolerated dose and recommended phase II dose.

Study designs may be open-label or blinded. Common approaches include traditional 3+3 dose-escalation, accelerated titration, and model-based methods such as the continual reassessment method. Endpoints focus on safety and pharmacology rather than efficacy, though early signals of activity can be observed in some oncology programs.

Phase I is conducted under regulatory oversight and ethical approvals, with informed consent and closely monitored environments. Data from Phase I inform dose selection for Phase II and plans for larger, efficacy-focused trials, and may define additional safety monitoring requirements.

In oncology and some biologics programs, Phase I can involve expansion cohorts at the RP2D to further characterize safety and preliminary efficacy. The Phase I stage is followed by Phase II and Phase III, culminating in regulatory evaluation for market approval.