Effects of genetic and clinical factors on thiopurine drugs pharmacokinetics in Tunisian patients.

Thiopurine drugs are used in the treatment of various diseases including inflammatory bowel disease. Thiopurine-S-methyltransferase (TPMT) and inosine triphosphate pyrophosphatase (ITPA) are the crucial enzymes involved in thiopurines metabolism. The present study aims to investigate in Tunisian patients, the influence of genetic and nongenetic factors on thiopurine drugs pharmacokinetics. We have included patients having received thiopurine drugs and have undergone 6-thioguanine nucleotides (6-TGN) concentration monitoring. The identification of TPMT and ITPA polymorphisms was performed using the polymerase chain reaction-restriction fragment length polymorphism method. The impact of both genetic and nongenetic factors on the variability of the 6-TGN C/D ratio was analyzed through a stepwise multiple regression model. One hundred and twenty-three patients were included in the study. For TPMT, the most frequent variant allele was TPMT*3B (3.3%). For ITPA, the predominant polymorphism was the c.IVS2 + 21A> C (7%). We have demonstrated that only gender, the and alleles are significantly involved on the variability of thiopurines pharmacokinetics. Our study is the first to evaluate, in African patients, the impact of both genetic and nongenetic factors on the thiopurine drugs pharmacokinetics. Considering the narrow therapeutic range of these drugs, TPMT genotyping combined with 6-TGN blood concentration monitoring may enhance their efficacy and safety.