Pharmacogenomics of autoimmune diseases

Abstract

Autoimmune diseases such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and psoriasis cause a considerable degree of morbidity worldwide. Although the treatment of these conditions has shown progress over the last decade with the steady trickle of new drug molecules, drug therapy is far from satisfactory due to the reduced effi cacy and maximal toxicity in certain patients. Several factors are known to infl uence the effi cacy and toxicity of these drugs such as age, gender, liver and kidney function, and concomitant drug therapy. Another crucial factor infl uencing drug response of the patient is the genetic constitution of the patient. For example, polymorphisms in the gene MTHFR such as 677T > C can increase methotrexate serum levels and lead to toxicity in a patient with RA. Similarly polymorphisms in the drug transporter ABCB1 are associated with decreased effi cacy to methotrexate. Polymorphisms within the TNF promoter region have been shown to modify the clinical effi cacy and toxicity of anti-TNF therapy in RA patients. SLE patients with polymorphic TPMT gene may require a reduced dose of azathioprine to circumvent the catastrophe of fatal bone marrow suppression. Polymorphisms in the TYMS gene could lead to reduced effi cacy with methotrexate in psoriatic arthritis patients. Although our understanding of autoimmune diseases has improved considerably over the last decade and several studies in pharmacogenomics of autoimmune diseases have been carried out, the only clinical application is TPMT testing for azathioprine. Yet with improved methodology adopted in pharmacogenomics studies coupled with novel technologies, the fi eld of pharmacogenomics does appear to offer signifi cant promise in the coming years towards the dream of personalized medicine in autoimmune diseases.