Single nucleotide polymorphisms of ABCB1 gene and response to etanercept treatment in patients with ankylosing spondylitis in a Chinese Han population

Background: Etanercept was highly recommended for patients with ankylosing spondylitis (AS), as its efficacy has been confirmed in AS, while genetic polymorphisms, by affecting drug metabolism or drug receptor, lead to interindividual variability in drug disposition and efficacy. Therefore, this study aims to investigate whether ABCB1 gene polymorphisms can predict therapeutic response to etanercept in patients with AS. Methods: A total of 185 patients with AS in our hospital were recruited into our study from December 2012 to May 2015. The frequency distributions of genotype and allele of rs2032582, rs1128503, and rs1045642 were detected by polymerase chain reaction (PCR) and electrophoresis verification enzyme products method. AS patients received etanercept treatment for 12 weeks, followed by this would be evaluated by the bath AS disease activity index (BASDAI) score improvement and the assessment of spondyloArthritis international society 20/50/70 (ASAS20/50/70) score improvements to explore the relationship between genotype of ABCB1 gene polymorphisms and therapeutic response to etanercept in patients with AS. Results: After 12 weeks, the BASDAI score mean improvement value of rs2032582 A/A genotype was 2.87 +/- 0.52. The ratios of patients with rs2032582 A/A genotype reaching the BASDAI50 and ASAS20 evaluation criteria were 64.29% and 92.86%, respectively. The results indicated that efficacy of etanercept was promoted in rs2032582 A/A genotype. The BASDAI score mean improvement value of rs1128503 C/C genotype was 2.79 +/- 0.54 after 12 weeks. The ratios of patients with rs1128503 C/C genotype reaching the BASDAI50 and ASAS20 evaluation criteria were 66.67% and 93.94%, respectively. The results indicated that efficacy of etanercept was promoted in rs1128503 C/C genotype. However, no significant associations were observed between rs1045642 and therapeutic response to etanercept in AS patients. Conclusion: ABCB1 gene rs2032582 and rs1128503 polymorphisms may be associated with the efficacy of etanercept in AS patients. ABCB1 gene polymorphisms can act as biological indicators of etanercept efficacy. Abbreviations: AS = Ankylosing spondylitis, BASDAI = Bath Ankylosing Spondylitis Disease Activity Index, CRP = C-reactive protein, ESR = erythrocyte sedimentation rate, PCR = Polymerase chain reactions, SNP = Single nucleotide polymorphism.