With advances in modern pharmaceutical sciences, the processes of discovery and development of new therapeutic drugs have changed dramatically, resulted in an extraordinary improvement in potential prophylactic and therapeutic interventions. Patents for biologic agents first marketed in the early 1980s are now beginning to expire, paving the way for non-proprietary agents to enter the market. However, there are fundamental differences between biologics and traditional pharmaceuticals that

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... de the extrapolation of existing regulatory processes for traditional generic agents to these new biologic products. Atpresent, many new classes of vaccines are being developed to prevent infection and to treat cancers and chronic diseases. The benefits for disease treatment and prevention will result from a better understanding of disease pathogenesis and expandedknowledge of immune mechanisms, the molecular structures of drugs, biologics, and biotechnology. This review provides both a conceptual approach and specific information about each phase of clinical development before licensure of a drug. Italso describes the design of post-marketing studies and examines how recent advances in pharmaceutical sciences increased demand for safer and more effective drugs have changed the processes, in which drugs are developed and approved.