Pharmacogenetics of therapies in rheumatoid arthritis

Rheumatoid arthritis (RA) is an inflammatory, aggressive arthritis causing irreversible joint destruction and damage when left untreated. Disease-modifying antirheumatic drugs (DMARDs) are the mainstay of treatment for RA and ameliorate not only the clinical signs and symptoms but also joint damage associated with the disease. In recent years, biological therapies have been introduced for the treatment of RA, and the effectiveness of these agents in slowing the clinical and radiographic progression in RA has been established beyond question. However, there is significant variability in the response of patients with RA to these therapies. Moreover, the biological therapies are expensive, totaling several thousand dollars in yearly patient costs. Pharmacogenomics, the study of genetic variations in drug-metabolizing enzymes and their translation to differential responses to drugs, is a nascent but rapidly evolving field. The application of pharmacogenomics to therapies used in RA, particularly the new expensive biological agents, holds great promise for tailoring therapy with these agents based on a patient's genetics. Published literature on the pharmacogenetics of commonly used DMARDs and the emerging body of literature on the pharmacogenetics of the new biological therapies in RA are the focus of this review. As evident from the contents of this review, pharmacogenomics is an exciting field which is progressing productively and rapidly. Pharmacogenomic approaches offer powerful tools to optimize drug therapy in individual patients.