Phase I studies are the first phase of human testing that determine the pharmacovigilance (drug safety), tolerability (safe dosage range), pharmacokinetics (the movement of drug into, through, out, and the absorption rate in the body), and pharmacodynamics (biochemical and physiological effects of a specific drug on the body). This initial phase of testing normally includes a small group of patients, typically 20-100. Patients are typically compensated for the time they spend in the trial, which can last several months. Phase I clinical trials are typically performed in a clinical trial clinic where patients are observed full time. This phase of trials are run by contract research organizations (CRO’s) on behalf of pharmaceutical companies or research investigators. Patients that participate in the study are more often healthy volunteers, but occasionally there are test performed with terminal patients. Approximately 70% of experimental drugs pass this phase.
Phase II studies test the the ability to produce a desired or intended result of a drug or device. After a range of doses is determined, it’s determined if the drug has any biological activity or effect. Phase II of testing can last from several months to two years, and typically involves a larger group, from 100-300 patients. Most phase II studies are random trials where group “A” receives the experimental drug, while group “B” receives the “control” or placebo. These are what you call “blind test” which means that neither group “A”, group “B” or the researchers know who has received the drug or the placebo. This allows investigators to provide the pharmaceutical company, sponsors, and the FDA with comparative data concerning safety and effectiveness of the drug. About 20% of experimental drugs successfully make it to phase III. If the clinical research of a new drug fails, it typically occurs during Phase II trials because the drug is discovered to not perform as planned, or become toxic.
Phase III studies are designed to determine the effectiveness, monitor side effects, and compare commonly used treatments to the new drug or treatment. Phase III trials are randomized and “blind tested” in very large groups, typically 100’s to 1,000’s of patients which can last several years. These trials provide pharmaceutical companies sponsors, and the FDA with a more thorough understanding of the effectiveness of the drug or device, the benefits, and the range of possible adverse reactions. Phase III trials are typically the most costly, time-consuming, and difficult to run. It is common that certain Phase III trials continue while the regulatory submission is pending at the FDA or other regulatory agency, allowing patients to continue to receive what may be considered life saving treatment. It is also common for each new drug or treatment to be required to perform a phase III trial more than once demonstrating safety and efficacy. This is one of the reasons that it’s common to see phase III drugs on the market. Only between 10% and 30% of drugs that are in phase III fail.
Phase IV studies are often called “Post Marketing Surveillance Trials” and are conducted after a drug or device has been approved for the consumer market. The goals in phase IV is to compare new drugs with existing drugs, monitor long-term effectiveness on quality of life, and to determine the cost-effectiveness. During a phase IV study, a new drug can become restricted within a certain patient demographic or even removed from the market if determined to be harmful.