Genotyping NUDT15*3 rs1166855232 reveals higher frequency of potential adverse effects of thiopurines in Natives and Mestizos from Mexico.

BACKGROUND: Thiopurines are effectively prescribed for immune and oncology diseases but their toxicity leads to severe myelosuppression. Therefore, TPMT genetic variants have been used to adjust dosing for poor and intermediate metabolizers, significantly preventing adverse drug reactions. In 2018, the Clinical Pharmacogenetics Implementation Consortium included NUDT15 rs116855232 to also guide thiopurines dosing. This variant is not present in Caucasians but have been identified in 10% of Asian and Latin American populations. Despite research efforts to portrait the world's genetic variation, few studies include the investigation of NUDT15 in large samples. METHODS: Fifteen NUDT15 and TPMT variants were retrieved for 1270 Mestizos and 20 Natives genotyped from previous studies using the GSA-Illumina microarray. After bioinformatic quality controls, genotypes were available for 12 variants, TPMT rs2842949, rs2842950, rs2842934, rs1800460, rs12201199, rs12663332, rs2518463, rs4449636, rs12529220, rs3931660, rs200591577, and NUD15 rs116855232. Allele frequencies and haplotypes were assessed using PLINK, R, and Haploview. Dosing inferences were described according to the Clinical Pharmacogenomics Implementation Consortium. RESULTS: We report relevant populations differences in actionable TPMT*3B and NUDT15 rs116855232 as the allele frequency of the former is higher in Mestizos compared to Caucasians, and for the latter we report twofold and 1.35-fold higher allele frequencies in Natives and Mestizos compared to Mexicans from Los Angeles. CONCLUSIONS: TPMT*3B and NUDT15 rs116855232 actionable markers showed population differences that ought to be considered as dosing inferences highlight the relevance of routine genotyping of these variants for the prescription of thiopurines in Mexican populations.

Pharmacogenomics: Current Actionable Variants

Pharmacogenomics (PGx), one of the several tools of precision medicine, has been slowly implemented in the clinic during the past decades. This process generally starts with direct and indirect genotype-phenotype associations of gene variants and drug efficacy, or adverse drug reactions, followed by replication and validation studies. Institutional efforts led by the PGx Research Network, The PGx Knowledge Base, and The Clinical Pharmacogenetics Implementation Consortium, mine all available data for further validation or research in additional populations. This data mining gives rise to a detailed classification of over 200 drug-gene pairs which, with enough documentation, may become part of a publishable guideline to aid clinicians in drug selection and dosing using genetics. The US Food and Drug Administration utilizes these guidelines to issue warnings and recommendations for specific drugs and their cautioning serves clinicians and pharmacists worldwide. Here, we aim to discuss the steps of this process and list existing actionable drug-gene pairs. Moreover, we describe the current status of PGx knowledge in populations from Mexico for actionable variants on the 19 genes listed by present PGx guidelines affecting 47 drugs. Our review collects current allele frequency information for these actionable variants, lists gaps of PGx information for relevant markers, and highlights the importance of continuing PGx research in Native and Mestizo populations. (REV INVEST CLIN. 2020;72(5):271-9)