Background: Tacrolimus is metabolized by the CYP3A5 pathway, of which different genomic variants have been described: CYP3A5*3/*3 “non expresser” do not express functional protein, but not: CYP3A4*1/*1 AND CYP3A5*1/ *3 They are functional genotypes. A risk factor for presenting specific anti-donor antibodies, as well as rejection episodes, is the variability in serum levels of tacrolimus. Variability can be expressed as: Standard deviation, (SD) Coefficient of variability, or (CV) Time in therapeutic range, (TTR).

Objectives: To find the association or not between the CYP3A5 polymorphisms studied with the formation of ADES de Novo and the presence of rejection.

Material and methods: Kidney transplant recipient patients from January 1, 2010 to January 1, 2020. Take variability with different measurements of tacrolimus, according to the different types of CYP3A5*1 and CYP3A5*3 polymorphisms. Study time: 3,6,12 months post transplant, and with different variability index.

Results: Student's T analysis of independent variables was performed, reporting an O.R. of 3.5, with a 95% confidence interval of (-12.29 – 19.37), with a p value of 0.653, the association not being significant. In turn, Student's t-test was performed, with independent variables, where an O.R. of 3.5, with a 95% confidence interval of (-12.29 – 19.37), with a p value of 0.653, the association not being significant.No significant association was found in the univariate analysis between greater variability of serum tacrolimus, allelic status, with the development of de novo ADES and renal graft rejection. Statistical significance was found between the CYP3A5 variant and the intrapatient tacrolimus serum variability coefficient percentage.

Discussion: Previous studies have reported a significant association, between greater intrapatient serum tacrolimus variability, with the development of de novo ADES, as well as with a higher incidence of renal graft rejection. A significant association was found between the CYP3A5 variant and the intrapatient tacrolimus serum variability coefficient percentage.

Conclusion: In the present study, no significant association was found in the univariate analysis between greater variability of serum tacrolimus, allelic status, with the development of de novo ADES and renal graft rejection. Statistical significance was found between the CYP3A5 variant and the intrapatient tacrolimus serum variability coefficient percentage, which, together with a longer follow-up time, could, associated with other previously mentioned risk factors, manifest as rejection events. kidney graft and development of de novo ADEs, when presenting a subtherapeutic level of tacrolimus, for longer periods of time.