AIMSTacrolimus (TAC) is one of the most successful immunosuppressive drugs in transplantation. Its pharmacokinetics (PK) and pharmacogenetics (PG) have been extensively studied, with many studies showing the influence of CYP3A5 on TAC metabolism and bioavailability. However, data concerning the functional significance of ABCB1 polymorphisms are uncertain due to inconsistent results. We evaluated the association between ABCB1 diplotypes, CYP3A5 polymorphisms and TAC disposition in a cohort of Brazilian transplant recipients. METHODSIndividuals were genotyped for the CYP3A5*3 allele and ABCB1 polymorphisms (2677G>A/T, 1236C>T, 3435C/T) using a TaqMan® PCR technique. Diplotypes were analyzed for correlation with the TAC dose-normalized ratio (Co : dose). RESULTSWe genotyped 108 Brazilian kidney recipients for CYP3A5 (11% CYP3A5*1/*1; 31% CYP3A5*1/*3 and 58% CYP3A5*3/*3) and ABCB1 haplotypes (42% CGC/CGC; 41% GCG/TTT and 17% TTT/TTT). Homozygous subjects for the CYP3A5*3 allele or carriers of the ABCB1 TTT/TTT diplotype showed a higher Co : dose ratio compared with wild type subjects [median (interquartile range) 130.2 (97.5-175.4) vs. 71.3 (45.6-109.0), P < 0.0001 and 151.8 (112.1-205.6) vs. 109.6 (58.1-132.9), P = 0.01, respectively]. When stratified for the CYP3A5*3 group, ABCB1 TTT/TTT individuals showed a higher Co : dose ratio compared with non-TTT/TTT individuals [167.8 (130.4-218.0) vs. 119.4 (100.2-166.3), P = 0.04]. Multivariate linear regression analysis showed that the effects of CYP3A5 polymorphisms and ABCB1 diplotypes remained significant after correction for confounding factors. CONCLUSIONSCYP3A5 is the major enzyme responsible for the marked interindividual variability in TAC PK, but it cannot be considered alone when predicting dose adjustment because ABCB1 diplotypes also affect TAC disposition, showing independent and additive effects on the TAC dose-normalized concentration. WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT• Tacrolimus disposition results largely from the actions of CYP3A5 enzymes and P-glycoprotein (PGP1). Several clinical studies have reported that homozygous carriers of the CYP3A5*3 allele require lower doses of tacrolimus to achieve similar target blood concentrations. In contrast, ABCB1 polymorphism studies have shown controversial results, and few studies have addressed the interaction between ABCB1 diplotype and tacrolimus (TAC) pharmacokinetics. WHAT THIS STUDY ADDS• This study shows that individuals carrying the homozygote variant diplotype (TTT/TTT) present a higher TAC dose-normalized concentration. We also show that the effects of CYP3A5 polymorphism and ABCB1 diplotype on TAC dose-normalized concentration are independent and additive.

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Plasma concentration data points (n = 2,640) from 16 healthy adults were used to develop and validate limited sampling strategies (LSS) for estimation of phenotypic metrics for CYP enzymes and the ABCB1 transporter, using a cocktail of subtherapeutic doses of the selective probes caffeine (CYP1A2), metoprolol (CYP2D6), midazolam (CYP3A), losartan (CYP2C9), omeprazole (CYP2C19), and fexofenadine (ABCB1). All-subsets linear regression modelling was applied to estimate the AUC 0-12h for caffeine, fexofenadine, and midazolam, and the AUC 0-12h ratio of metoprolol: a-OH metoprolol and omeprazole:5-OH omeprazole. LSS-derived metrics were compared with the parameters' 'best estimates' obtained by non-compartmental analysis using all plasma concentration data points. The correlation coefficient (R 2) was used to identify the LSS equations that provided the best fit for n timed plasma samples, and the jack-knife statistics was used as an additional validation procedure for the LSS models. Single timepoint LSS models provided R 2 values greater than 0.95 (R 2 > 0.95) for the AUC 0-12h ratio of metoprolol:a-OH metoprolol and omeprazole:5-OH omeprazole, whereas 2 time-point models were required for R 2 > 0.95 for the AUC 0-12h of caffeine, fexofenadine, and midazolam. Increasing the number of sampling points to three led to minor increases in R 2 and/or the bias or prediction of the estimates. In conclusion, the LSS models provided accurate prediction of phenotypic indices for CYP1A2, CYP2C19, CYP2D6, CYP3A, and ABCB1, when using subtherapeutic doses of selective probes for these enzymes and transporter.

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A toxicologia forense atua na investigação post mortem para identificação e quantificação de substâncias exógenas, buscando correlacioná-las com a causa mortis. Para tanto são realizados exames toxicológicos em diversos fluidos ou tecidos biológicos, denominados matrizes. Os exemplos mais comuns e amplamente estudados de matrizes biológicas são sangue, plasma e urina, classificadas como matrizes convencionais. Outros tipos de matrizes como humor vítreo e saliva têm surgido como alternativa analítica e sua importância têm aumentado nas últimas décadas. O humor vítreo (HV) é uma substância gelatinosa e incolor que se encontra no segmento posterior dos olhos. Devido suas vantagens anatômicas e analíticas, o HV tem sido alvo de pesquisas para análise de concentração de drogas de abuso em casos post mortem. No entanto, mesmo sendo utilizado como matriz alternativa por mais de 50 anos, a quantidade de literatura ainda é limitada, principalmente a respeito da difusão de xenobióticos e sua correlação com as concentrações plasmáticas. O objetivo deste trabalho é realizar um levantamento bibliográfico dos estudos elaborados por pesquisadores brasileiros utilizando o humor vítreo como matriz alternativa para detecção post mortem de drogas de abuso no período de 2010 a 2020. Foram encontrados, no total, 187 artigos dos quais 07 foram estavam relacionados a cientistas brasileiros, evidenciando a deficiência deste tema de pesquisa na área de toxicologia forense em nosso país.

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CUSINATO, D.A.C Association of CYP3A5 and PGP polymorphisms and haplotypes with tacrolimus pharmacokinetics, acute nephrotoxicity and allograft rejection after kidney transplantation. 2012. 90 f. Dissertação (Mestrado)