Effect of genetic polymorphisms on effectiveness of low-dose azathioprine in Japanese patients with systemic lupus erythematosus

Abstract

The effect of genetic polymorphisms on the effectiveness of low-dose azathioprine in Japanese patients with systemic lupus erythematosus (SLE) was studied. Sixty-one unrelated Japanese patients with SLE treated with azathioprine were included in the study. The selected genetic polymorphisms evaluated in the analysis were ITPA 138G>A, ITPA 563G>A, IMPDH 1575A>G, XO 837C>T, XO 2211C>T, XO 3030C>T, and MRP4 2269G>A. The DNA isolation and genotyping procedures for ITPA 94C>A and TPMT*3C were the same as those in a previous study. Genotyping of ITPA 138G>A, ITPA 563G>A, IMPDH 1575A>G, MRP4 2269G>A, XO 837C>T, XO 2211C>T, and XO 3030C>T was performed using a validated genotyping assay. The SLE disease activity index (SLEDAI) score was used as a marker for the efficacy of azathioprine treatment, and the correlations between the changes in the SLEDAI score and the considered polymorphisms were evaluated. The mean SLE duration, SLEDAI score, and azathioprine dosage prescribed were 5.6 years, 6.0, and 1 mg/kg/day, respectively. Small (but not significant) p values suggested a tendency for the reduction in the SLEDAI score to be greater in patients with the ITPA 94A allele. Further, the ITPA 94C>A polymorphism correlated highly with the change in the SLEDAI score. However, there were no significant associations among TPMT*3C, ITPA 138G>A, ITPA 563G>A, IMPDH 1575A>G, XO 837C>T, XO 2211C>T, and XO 3030C>T and the mean changes in the SLEDAI score over the one-year investigation period. The ITPA 94C>A polymorphism was found to possibly influence the clinical response to low-dose azathioprine in Japanese patients with SLE. The other studied single-nucleotide polymorphisms appeared to have little influence on the effectiveness of azathioprine.