Recombinant human enzymes for characterization of drug metabolism in US patient populations

Drug metabolism is significantly variable across genetically polymorphic population groups, especially those seen in the US patient population. Several drugs demonstrate genotype-dependent differences in drug metabolism, leading to individual variability in drug disposition and response. Important drugs such as clopidogrel, warfarin, tamoxifen, and irinotecan show differences in metabolism, efficacy, and toxicity due to genetic differences across different patient groups. These cases underscore the need for pharmacogenetic testing and personalized medicine to optimize therapy and reduce adverse reactions. While the Food and Drug Administration (FDA) recommends comprehensive in vitro and in vivo testing of drug metabolism during drug development, current approaches do not employ testing strategies to include genetically polymorphic populations, leading to potential disparities in drug safety and efficacy for patient groups with rare alleles or unique haplotypes. Additionally, in vitro metabolism studies typically employ liver microsomes or hepatocytes from genetically similar donors, limiting applicability to other patient groups. This project aims to bridge these shortcomings by developing recombinant human enzyme panels representing genetic variants in drug-metabolizing enzymes present in the US patient population, particularly those populations with less common alleles. In this Phase I application, we will leverage recombinant human proteins representing different genotypes and develop commercially viable kits representing polymorphic drug metabolizing enzymes shown to exhibit variability. In Aim 1, we will design and generate recombinant enzymes, including cytochrome P450s, N-acetyltransferases, and thiopurine S-methyltransferase, using mammalian cell-based expression systems and standardized protein engineering techniques. The expression of individual proteins will be measured using validated quantitative proteomics assays. In Aim 2a, we will compare the enzyme expression and activity between individual recombinant enzymes and multiple lots of human liver microsomes and cytosol samples representing genetically polymorphic donors. In Aim 2b, we will package the recombinant enzyme panels with quality controls and pre-aliquoted reagents into kits that are compatible with standard drug metabolism assays and screening platforms. These kits will enable pharmaceutical companies to assess genetic variability in drug metabolism and optimize drug development for genetically polymorphic populations. The successful completion of this project will provide innovative recombinant protein kits as a translational tool for improving health outcomes, by enabling personalized medicine tailored to unique patient needs. In particular, the in vitro data generated using recombinant human enzymes representing different genotypes can be leveraged in predicting drug metabolism and pharmacokinetics in genetically polymorphic populations using physiologically-based pharmacokinetic modeling of investigational drugs.