Phenotyping drug disposition in oncology

Cytotoxicity and induction of proinflammatory cytokines in placental explant cells following azathioprine exposure

Immunosuppressive drugs offer hope for the survival and motherhood of women with various disorders. Although the systemic side effects of these drugs on mothers have been studied, their impact on the placenta remains poorly understood, which can negatively affect fetal and postnatal development. This study investigated the effects of Azathioprine, an immunosuppressive drug, on the chorionic villi of human placentas from healthy pregnancies, focusing on cellular vitality and pro-inflammatory cytokines expression. Chorionic villi from term placentas were cultured and treated with Azathioprine at concentrations ranging from 0 to 100 ng/mL for 24 h. Azathioprine reduced mitochondrial metabolic activity (MTT assay) at all concentrations tested (p < 0.05) and increased cellular injury rates (LDH assay) at 50 and 100 ng/mL (p < 0.05). It also elevated protein (at 12.5 and 25 ng/mL, p < 0.05) and gene expression levels of interleukin (IL)-1β (12.5 ng/mL, p < 0.05). Protein levels of IL-18 increased significantly following Azathioprine exposure (p < 0.05), along with cleaved Caspase-1 (p = 0.003) and phosphorylated NF-κB levels (p < 0.05), compared to controls. IL-18 gene expression was elevated only at 12.5 ng/mL (p < 0.0005). These findings suggest that Azathioprine creates a cytotoxic microenvironment that disrupts the metabolism of chorionic villi, leading to injury and activation of pro-inflammatory cytokine expression. Such changes may contribute to an imbalance in placental homeostasis, potentially associated with adverse maternal and neonatal outcomes that warrant further investigation.

Exploring the Pharmacogenomic Map of Croatia: PGx Clustering of 522-Patient Cohort Based on UMAP + HDBSCAN Algorithm

Pharmacogenetics is a branch of genomic medicine aiming to personalize drug prescription guidelines based on individual genetic information. This concept might lead to a reduction in adverse drug reactions, which place a heavy burden on individual patients' health and the economy of the healthcare system. The aim of this study was to present insights gained from the pharmacogenetics-based clustering of over 500 patients from the Croatian population. The data used in this article were obtained by the pharmacogenetic testing of 522 patients from the Croatian population. The patients were clustered based on the genotypes of 28 pharmacologically relevant genes. Dimensionality reduction was employed using the UMAP algorithm, after which clusters were defined using HDBSCAN. Validation of clustering was performed by decision tree analysis and predictive modeling using the RandomForest, XGBoost, and ExtraTrees classification algorithms. The clustering algorithm defined six clusters of patients based on two UMAP components (silhouette score = 0.782). Decision tree analysis demonstrated CYP2D6 and SLCO1B1 genotypes as the main points of cluster determination. Predictive modeling demonstrated an excellent ability to discern the cluster of each patient based on all genes (avg. ROC-AUC = 0.998), CYP2D6 and SLCO1B1 (avg. ROC-AUC = 1.000), and CYP2D6 alone (avg. ROC-AUC = 0.910). Membership in each cluster provided clinically relevant information, in the context of ruling out certain favorable or unfavorable phenotypes. However, this study's main limitation is its cohort size. Through further research and investigation of a larger number of patients, more accurate and clinically applicable associations between pharmacogenetic genotypes and phenotypes might be discovered.

Towards better dose individualisation: metabolic phenotyping to predict cabazitaxel pharmacokinetics in men with prostate cancer

BACKGROUND

Cabazitaxel is approved for treatment of castration-resistant metastatic prostate cancer. The current dosing strategy of cabazitaxel is based on body surface area (BSA). Body surface area is known as a poor predictor for total systemic exposure to drugs, since it does not take into account variability in activity of metabolising enzymes, necessary for clearance of drugs. As exposure to cabazitaxel is related to treatment response, it is essential to develop a better individualised dosing strategy.

METHODS

Ten patients with metastatic castration-resistant prostate cancer, who received cabazitaxel dosed on BSA as a part of routine palliative care, were enrolled in this study. Midazolam was administered as phenotyping probe for cytochrome P450 isoenzyme 3A (CYP3A). The relationship between midazolam and cabazitaxel clearance was investigated using non-linear mixed effects modelling.

RESULTS

The clearance of Midazolam highly correlated with cabazitaxel clearance (R=0.74). Midazolam clearance significantly (P<0.004) explained the majority (∼60%) of the inter-individual variability in cabazitaxel clearance in the studied population.

CONCLUSIONS

Metabolic phenotyping of CYP3A using midazolam is a promising strategy to individualise cabazitaxel dosing. Before clinical application, a randomised study is warranted.

Therapeutic drug monitoring and tyrosine kinase inhibitors

The therapeutic activity of drugs can be optimized by establishing an individualized dosage, based on the measurement of the drug concentration in the serum, particularly if the drugs are characterized by an inter-individual variation in pharmacokinetics that results in an under- or overexposure to treatment. In recent years, several tyrosine kinase inhibitors (TKIs) have been developed to block intracellular signaling pathways in tumor cells. These oral drugs are candidates for therapeutic drug monitoring (TDM) due to their high inter-individual variability for therapeutic and toxic effects. Following a literature search on PubMed, studies on TKIs and their pharmacokinetic characteristics, plasma quantification and inter-individual variability was studied. TDM is commonly used in various medical fields, including cardiology and psychiatry, but is not often applied in oncology. Plasma concentration monitoring has been thoroughly studied for imatinib, in order to evaluate the usefulness of TDM. The measurement of plasma concentration can be performed by various analytical techniques, with liquid chromatography-mass spectrometry being the reference method. This method is currently used to monitor the efficacy and tolerability of imatinib treatments. Although TDM is already being used for imatinib, additional studies are required in order to improve this practice with the inclusion of other TKIs.

Breath tests to phenotype drug disposition in oncology

Breath tests (BTs) have been investigated as diagnostic tools to phenotype drug disposition in cancer patients in the pursuit to individualize drug treatment. The choice of the right phenotype probe is crucial and depends on the metabolic pathway of the anticancer agent of interest. BTs using orally or intravenously administered selective non-radioactive (13)C-labeled probes to non-invasively evaluate dihydropyrimidine dehydrogenase, cytochrome P450 (CYP) 3A4, and CYP2D6 enzyme activity have been published. Clinically, a (13)C-dextromethorphan BT to predict endoxifen levels in breast cancer patients and a (13)C-uracil BT to predict fluoropyrimidine toxicity in colorectal cancer patients are most promising. However, the clinical benefit and cost effectiveness of these phenotype BTs need to be determined in order to make the transition from an experimental setting to clinical practice as companion diagnostic tests.

OATP1B1 polymorphism as a determinant of erythromycin disposition

Previous studies have demonstrated that the pharmacokinetic profile of erythromycin, a probe for CYP3A4 activity, is affected by inhibitors or inducers of hepatic solute carriers. We hypothesized that these interactions are mediated by OATP1B1 (gene symbol, SLCO1B1), a polypeptide expressed on the basolateral surface of hepatocytes. Using stably transfected Flp-In T-Rex293 cells, erythromycin was found to be a substrate for OATP1B1*1A (wild type) with a Michaelis-Menten constant of ~13 µmol/l, and that its transport was reduced by ~50% in cells expressing OATP1B1*5 (V174A). Deficiency of the ortholog transporter Oatp1b2 in mice was associated with a 52% decrease in the metabolic rate of erythromycin (P = 0.000043). In line with these observations, in humans the c.521T>C variant in SLCO1B1 (rs4149056), encoding OATP1B1*5, was associated with a decline in erythromycin metabolism (P = 0.0072). These results suggest that impairment of OATP1B1 function can alter erythromycin metabolism, independent of changes in CYP3A4 activity.