Folate metabolic pathway single nucleotide polymorphisms: a predictive pharmacogenetic marker of methotrexate response in Indian (Asian) patients with rheumatoid arthritis.

Aim: We evaluated the pharmacogenetic influence of genetic polymorphisms in folate pathway genes in Indian rheumatoid arthritis patients receiving methotrexate (MTX).

Patients & Methods: Twelve polymorphisms within nine folate pathway genes were analyzed for association with MTX response in 322 Indian rheumatoid arthritis (RA) patients and MTX pharmacokinetics in 94 RA patients.

Results: Polymorphisms in GGH, SHMT1 and TS were associated with MTX-related adverse events while SNPs in MTHFR and RFC1/SLC19A1 were associated with MTX efficacy. TS5'UTR and SHMT1 polymorphisms were associated with higher plasma levels of MTX.

Conclusion: Polymorphisms in folate-MTX pathway genes contribute to MTX response and affect MTX concentrations in Indian RA patients. A toxicogenetic index could identify patients who develop adverse events to MTX.