Phase 1 Clinical Trials

Phase I Early clinical stage Phase I studies are designed to examine the safety of a new medication and understand how it will work in humans by gathering extensive data on how it is absorbed, distributed, metabolized and eliminated from the human body; other data include assessment of how quickly therapeutic concentrations is achieved, how long the drug remains in the body, and what, if any, the effect drug metabolite by-products may have; with step-by-step increases in dose, the optimal dosage is determined where minimum side effects are coupled with maximum therapeutic effect, termed the toxic-therapeutic window; a trial to determine the best way to give a new treatment and what doses can be safely given; phase 1's involve 20-80 subjects and generate data on toxicity and maximum safe dose, to later allow a properly controlled trial; A Regulatory Authority (e.g. FDA, TGA) review at this point ensures that subjects are not exposed to unreasonable risks.

Phase I studies generally enrol only healthy persons to evaluate how a new drug behaves in humans, but may enrol Pts with the disease that the new drug seeks to treat; candidates are enrolled in a study only after a review of their medical history and physical confirms eligibility and informed consent for treatment is given; the number of Pts enrolled in a phase I trial will vary depending on the step-wise progression established for achieving optimal dosing as well as prior clinical experience with similar compounds and approaches; follow-up time periods may range from just a few days to 6+ months; further trials may continue only if phase 1 results indicate that the new therapy is reasonably safe in humans, and the Regulatory Authority approves further work; the ultimate goal of phase 1 trials is to obtain sufficient information about the drug's pharmacokinetics and pharmacological effects to permit the design of well-controlled, sufficiently valid phase 2 studies; other examples of phase 1 studies include studies of drug metabolism, structure-activity relationships, and mechanisms of actions in humans, as well as studies in which investigational drugs are used as research tools to explore biological phenomena or disease processes
 

Source: McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.