[Pharmacogenetics and pharmacogenomics of methotrexate. Current status and novel aspects].

Since its introduction as a disease-modifying drug, methotrexate (MTX), a folate antagonist, is regarded as a major pillar of anti-rheumatic pharmacotherapy. This has not been changed in the current era of biologicals based on recombinant proteins. Despite most promising therapeutic progress about half of rheumatoid arthritis patients still display insufficient response to anti-rheumatic drugs. Specifically, about one in four patients on MTX shows lack of sufficient therapeutic efficacy which may lead to drug discontinuation. In addition, adjustment of therapy may be necessary due to individual drug toxicity. In this context and in light of recent advances concerning the use of genetic analysis in clinical practice, the development of novel strategies which implement individualized pharmacotherapy has become a major issue for translational and clinical research. Accordingly, numerous studies have been performed in recent years analyzing genetic polymorphisms of cellular parameters which relate to MTX efficacy and toxicity. Data currently available demonstrate the potential and the limitations of clinical genetic polymorphism analyses.