Abandoned therapies and unpublished trials in rheumatoid arthritis.

The capability of selectively targeting pathogenic elements of disease with biologic therapies has created a new therapeutic repertoire. Although a substantial number of biologic agents have been developed for treatment of rheumatoid arthritis, few have been approved for use. Most of the agents have failed to reach the approval stage because of inadequate clinical benefit. Despite this, studies of these agents have provided extremely valuable lessons in study design, immunobiology, pharmacodynamic evaluation, and the utility of animal models in the development of biologic agents. These insights have laid the groundwork for future development of other novel therapeutic agents in the treatment of rheumatoid arthritis.