Association of the Q141K polymorphism of the ABCG2 gene with the effectiveness of urate-lowering therapy in patients with gout (a pilot study)

Abstract

Achieving the target serum uric acid (UA) level is a priority in the treatment of gout.Objective: to study the relationship of the ABCG2 gene polymorphism (rs2231142) with the efficacy of allopurinol and febuxostat in patients with gout.Patients and methods. The study included 82 patients with gout over 18 years of age with serum UA level >360 μmol/L who did not take uratelowering therapy.All patients were prescribed allopurinol 100 mg daily, followed by its titration until the target UA level was reached (<360 μmol/L or <300 μmol/L in patients with chronic tofus gout), up to a maximum of 900 mg/day, in patients with glomerular filtration rate <60 ml/min/1.73 m2 – up to 300 mg/day. Patients who did not reach the target UA level when using allopurinol were prescribed febuxostat 80 mg/day, which, if necessary, was increased to 120 mg/day. Monitoring of each patient was continued until the target serum UA level was reached.All patients underwent genotyping of the C>A polymorphism (rs2231142) of the ABCG2 gene. We compared the probability of achieving the target UA level, the mean values of a decrease in the serum UA level, and the mean doses of urate-lowering drugs in patients with different genotypes (CC, CA, AA) of the ABCG2 gene.Results and discussion. The target UA level in 45 (55%) of 82 patients was defined as <300 μmol/L, in the remaining 37 – as <360 μmol/L.In 26 patients, the dose of allopurinol did not exceed 300 mg/day. In 28 (34%) patients treated with allopurinol, the target UA level was achieved, in the remaining 54 (66%) patients, allopurinol was substituted by febuxostat, and in 22 (41%) of them the UA level decreased and was below the target.The CC genotype of the ABCG2 gene was detected in 51 (62%) patients, the CA genotype in 30 (37%) and the minor genotype AA in 1 (1%).The probability of achieving the target UA level during therapy with allopurinol in carriers of homozygous CC genotype and genotypes CA or AA did not differ: 17 (33%) and 11 (35%) cases, respectively, but patients with CA and AA genotypes required a significantly higher dose of allopurinol (365±102 mg/day) than patients with the CC genotype (290±85 mg/day), p=0.002. Of the 54 patients who took febuxostat and did not reach the target UA level, 30 (56%) had the CC genotype and 24 (44%) had the CA genotype, the probability of reaching the target UA level was also comparable (p=0.22).Conclusion. The probability of reaching the target serum UA level in patients with gout taking allopurinol is not associated with the C>A polymorphism of the ABCG2 gene, but the presence of CA and AA genotypes is identified with a higher dose of the drug. The C>A (rs2231142) polymorphism of the ABCG2 gene does not affect the ability to achieve the goal of therapy when using febuxostat in patients with allopurinol ineffectiveness.