ABSTRACT
In this chapter we discuss the use of group sequential methods in evaluating drug efficacy. The therapy against which the new drug ( experimental therapy) will be compared will be referred to as the standard therapy, with the recognition that in some instances standard therapy may consist of no intervention and be implemented using a placebo. Typically, the evaluation of a new drug in human subjects is performed in three phases. Phase I is a dose-seeking pilot study that evaluates pharmacokinetics and toxicity. When safe dose levels have been established, the drug is administered to a relatively small series of patients (phase II) to determine if there is sufficient preliminary evidence of efficacy (relative to historical data) to warrant further study. Ideally, in phase III, patients are randomly assigned to experimental or standard therapy in such a manner that neither the patient nor the physician is aware of the therapy used.
