Abstract

This article discusses rheumatoid arthritis (RA) as a chronic, systemic autoimmune disease leading to progressive joint damage and multi-organ complications. The complex pathogenesis of the disease is presented, involving the interaction of environmental, genetic, and immunological factors, including the role of autoantibodies and proinflammatory cytokines. Particular attention is paid to leflunomide, a disease-modifying antirheumatic drug (DMARD), which primarily works by inhibiting the DHODH enzyme, leading to reduced T and B cell proliferation. The additional anti-inflammatory properties of the drug’s active metabolite, teriflunomide, and its impact on signaling pathways related to the immune response are also discussed. This article examines the variability in patient responses to leflunomide treatment in terms of both efficacy and toxicity, with particular emphasis on the potential role of pharmacogenetic factors. It was pointed out that polymorphisms in genes related to drug metabolism, transport, and mechanism of action may influence the pharmacokinetics and safety of the therapy. It was also emphasized that the available data are primarily derived from observational studies and small cohorts, and the results are often inconsistent. Although some genetic variants and plasma teriflunomide concentrations show potential as predictors of treatment response, the current level of evidence does not support the routine use of pharmacogenetic testing in clinical practice. The article emphasizes that the pharmacogenetics of leflunomide represents a promising, yet still exploratory, avenue of research in the context of personalized RA therapy. It emphasizes the need for larger, well-designed clinical trials and the development of standardized guidelines, which would be necessary before the potential implementation of such strategies in routine clinical practice.

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