A polymorphism in ABCA2 is associated with neutropenia induced by capecitabine in Japanese patients with colorectal cancer.

Purpose: Capecitabine is a prodrug that converts to 5-fluorouracil (5-FU) in three steps. A previous study showed that ABCA2 rs2271862 (C > T) and ABCG5 rs6720173 were associated with increased clearance of 5-FU and 5'-deoxy-5-fluorouridine, respectively, in Spanish patients with colorectal cancer (CRC) (Br J Clin Pharmacol 2021) and reported that ABCA2 rs2271862 was associated with decreased risk of capecitabine-induced neutropenia. Other studies have reported that ABCB1 rs1128503, rs2032592, and rs1045642 were associated with capecitabine-induced toxicity in Spanish CRC patients (Oncotarget 2015, Phamacogenomics 2010). Here, we prospectively examined the effects of ABC transporter genes polymorphisms on capecitabine pharmacokinetics and toxicity.

Methods: We enrolled patients with postoperative CRC treated with adjuvant capecitabine plus oxaliplatin (CapeOX) and patients with metastatic CRC receiving CapeOX. Pharmacokinetic analysis of the first capecitabine dose (1000 mg/m) was performed on day 1. We analyzed plasma concentrations of capecitabine and its three metabolites by high-performance liquid chromatography and ABC transporter genes polymorphisms using direct sequencing.

Results: Patients with ABCA2 rs2271862 T/T genotype had significantly lower area under the plasma concentration-time curve of capecitabine, but not of its metabolites, which were divided by the dose of the parent drug, than patients with C/C or C/T genotype (P = 0.0238). Frequency of ≥ grade 2 neutropenia was significantly lower in patients with ABCA2 rs2271862 T/T genotype (P = 0.00915). Polymorphisms in ABCG5 and ABCB1 were not associated with capecitabine pharmacokinetics and toxicity.

Conclusions: We found that ABCA2 polymorphism was significantly associated with systemic exposure to capecitabine and capecitabine-induced neutropenia in Japanese patients with CRC.