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Antibodies have been a major focus in biopharmaceutical research and development for the last two decades, ever since the first development of a process for the isolation of monoclonal antibodies (mAbs) in the 1970s. Following the FDA approval of the first therapeutic mAb in 1986 (1), and as a result of significant technological advances in the 1990s, mAbs and antibody fragments are now an increasingly important class of drugs. Reports from 2008 indicate that there are currently over 200 mAb candidates in clinical development (2), with 24 mAbs having been approved for therapeutic use (1).
Therapeutic antibodies in clinical use today cover a broad range of indications, including cancer, chronic inflammatory diseases, transplant rejection, infectious diseases and cardiovascular disease. The majority of antibody drugs are full-sized IgG forms, although there is increased interest in the use of antibody fragments, with three fragment-based drugs being approved for therapeutic use in the US.
ANTIBODY CLASSES, STRUCTURE AND FUNCTION
Human antibodies are grouped into five different isotypes (IgG, IgE, IgD, IgM and IgA) and then split further into sub-classes (IgG1, IgG2, IgG3, IgG4, IgA1 and IgA2) (see Figure 1). The different isotypes have distinct functions within the body.
Antibodies are relatively large globular proteins, consisting of two heavy chains (which define the isotype and subclass) and two light chains. |
