Biologic therapies: what and when?

Over the past two decades, major advances have been made in the understanding of the immune system and disease pathogenesis. This has coincided with the development of biologic therapies--monoclonal antibodies and fusion proteins. The decision of when to use such treatment in the clinic is not always straightforward. In addition to immune biology, the focus of this review will be on the application of these treatments to immune-mediated diseases and the molecular targets involved in pathogenesis, specifically those that have US Food and Drug Administration/European Medicines Agency approval. Brief comments will be made on biologics that have approval for non-immune disorders.