Effects of Genetic Polymorphisms of Cathepsin A on Metabolism of Tenofovir Alafenamide

Cathepsin A (CatA) is important as a drug-metabolizing enzyme responsible for the activation of prodrugs, such as the anti-human immunodeficiency virus drug Tenofovir Alafenamide (TAF). The present study was undertaken to clarify the presence of polymorphisms of the CatA gene in healthy Japanese subjects and the influence of gene polymorphism on the expression level of CatA protein and the drug-metabolizing activity. Single-strand conformation polymorphism method was used to analyze genetic polymorphisms in healthy Japanese subjects. Nine genetic polymorphisms were identified in the CatA gene. The polymorphism (85_87CTG>-) in exon 2 was a mutation causing a deletion of leucine, resulting in the change of the leucine 9-repeat (Leu9) to 8-repeat (Leu8) in the signal peptide region of CatA protein. The effect of Leu8 on the expression level of CatA protein was evaluated in Flp-In-293 cells with a stably expressed CatA, resulting in the expression of CatA protein being significantly elevated in variant 2 with Leu8 compared with Leu9. Higher concentrations of tenofovir alanine (TFV-Ala), a metabolite of TAF, were observed in the Leu8-expressing cells than in the Leu9-expressing cells using LC/MS/MS. Our findings suggest that the drug metabolic activity of CatA is altered by the genetic polymorphism.

Anti-inflammatory Effects in LPS-treated RAW 264.7 Cells and the Influences on Drug Metabolizing Enzyme Activities by the Traditional Herbal Formulas, Yongdamsagan-Tang and Paljung-san

Objectives: Yongdamsagan-tang (YST) and Paljung-san (PJS) in traditional medicine and finasteride in modern medicine are used to treat benign prostatic hyperplasia (BPH). In recent, the use of combination herbal remedies with conventional drugs has been increasing. Therefore, we investigated the anti-inflammatory effects of these drugs to treat BPH and the influence of herbal formulas on finasteride metabolism.Methods: The inhibitory effects of the herbal formulas and finasteride on the production of inflammatory mediators and cytokines were determined in lipopolysaccharide (LPS)-treated RAW 264.7 cells. Additionally, the influence of herbal formulas on activities of human drug metabolizing enzymes (DMEs) was assessed using human microsomal enzymes.Results: We observed that YST, PJS and finasteride inhibited the production of nitric oxide (NO), prostaglandin E2 (PGE2) and interleukin-6 (IL-6) in RAW 264.7 cells. The half maximal inhibitory concentration (IC50) of YST on PGE2 production was calculated to be below 25 μg/mL. YST inhibited the activity of uridine diphosphateglucuronosyltransterase (UGT) 1A4 with an IC50 value of 49.35 μg/mL. The activities of cytochrome P450 (CYP) 1A2, CYP2B6, CYP2C19, CYP3A4, and UGT1A1 were inhibited by PJS (IC50 < 100 μg/mL, each). Although PJS and YST inhibited the activities of CYP3A4 and UGT1A4, respectively, these formulas may not influence the metabolism of finasteride because the IC50 values of herbal formulas on DMEs are too high to affect metabolism.Conclusions: Our results suggest that the combination of finasteride and YST or PJS might not influence their drug metabolism and that the drugs may have synergistic effects against BPH.

A Novel System for Evaluating the Inhibition Effect of Drugs on Cytochrome P450 Enzymes in vitro Based on Human-Induced Hepatocytes (hiHeps)

Cytochrome P450 (CYP) is the most important phase I drug-metabolizing enzyme, and the effect of drugs on CYP enzymes can lead to decreased pharmacological efficacy or enhanced toxicity of drugs, but there are many deficiencies in the evaluation models of CYP enzymes in vitro. Human-induced hepatocytes (hiHeps) derived from human fibroblasts by transdifferentiation have mature hepatocyte characteristics. The aim was to establish a novel evaluation system for the effect of drugs on CYP3A4, 1A2, 2B6, 2C9, and 2C19 in vitro based on hiHeps. Curcumin can inhibit many CYP enzymes in vitro, and so the inhibition of curcumin on CYP enzymes was compared by human liver microsomes, human hepatocytes, and hiHeps using UPLC-MS and the cocktail method. The results showed that the IC50 values of CYP enzymes in the hiHeps group were similar to those in the hepatocytes group, which proved the effectiveness and stability of the novel evaluation system in vitro. Subsequently, the evaluation system was applied to study the inhibitory activity of notoginseng total saponins (NS), safflower total flavonoids (SF), and the herb pair of NS–SF on five CYP enzymes. The mechanism of improving efficacy after NS and SF combined based on CYP enzymes was elucidated in vitro. The established evaluation system will become a powerful tool for the research of the effect of drugs on the activity of CYP enzymes in vitro, which has broad application prospects in drug research.

CLINICAL OPPORTUNITIES FOR GERMLINE PHARMACOGENETICS AND MANAGEMENT OF DRUG-DRUG INTERACTIONS IN PATIENTS WITH ADVANCED SOLID CANCERS

PURPOSE: Precision medicine approaches, including germline pharmacogenetics (PGx) and management of drug-drug interactions (DDIs), are likely to benefit advanced cancer patients who are frequently prescribed multiple concomitant medications to treat cancer and associated conditions. Our objective was to assess the potential opportunities for PGx and DDI management within a cohort of adults with advanced cancer. PATIENTS AND METHODS: Medication data were collected from the electronic health records (EHRs) for 481 subjects since their first cancer diagnosis. All subjects were genotyped for variants with clinically actionable recommendations in Clinical Pharmacogenetics Implementation Consortium (CPIC) guidelines for 13 pharmacogenes. DDIs were defined as concomitant prescription of strong inhibitors or inducers with sensitive substrates of the same drug-metabolizing enzyme and were assessed for six major cytochrome P450 (CYP) enzymes. RESULTS: Approximately 60% of subjects were prescribed at least one medication with CPIC recommendations, and ~14% of subjects had an instance for actionable PGx, defined as prescription of a drug in a subject with an actionable genotype. The overall subject-level prevalence of DDIs and serious DDIs were 50.3% and 34.8%, respectively. Serious DDIs were most common for CYP3A, CYP2D6, and CYP2C19, occurring in 24.9%, 16.8%, and 11.7% of subjects, respectively. When assessing PGx and DDIs together, ~40% of subjects had at least one opportunity for a precision medicine-based intervention and ~98% of subjects had an actionable phenotype for at least one CYP enzyme. CONCLUSION: Our findings demonstrate numerous clinical opportunities for germline PGx and DDI management in adults with advanced cancer.

Pharmacogenetic and Clinical Predictors of Ondansetron Failure in a Diverse Pediatric Oncology Population

Purpose: Chemotherapy induced nausea and vomiting (CINV) is a frequently seen burdensome adverse event of cancer therapy. The 5-HT3 receptor antagonist ondansetron has improved the rates of CINV but, unfortunately, up to 30% of patients do not obtain satisfactory control. This study examined whether genetic variations in a relevant drug metabolizing enzyme (CYP2D6), transporter (ABCB1) or receptor (5-HT3) were associated with ondansetron failure. Methods: DNA was extracted from blood and used to genotype: ABCB1 (3435C>T (rs1045642) and G2677A/T (rs2032582)), 5-HT3RB (rs3758987 T>C and rs45460698 (delAAG/dupAAG)) and CYP2D6 variants. Ondansetron failure was determined by review of the medical records and by patient-reported outcomes (PROs). Results: 129 patients were approached; 103 consented. Participants were less than 1 to 33 years (mean 6.85). 39.8% were female, 58.3% were White (22.3% Black, 19.4% other); and 24.3% were Hispanic. A majority had leukemia or lymphoma, and 41 (39.8%) met the definition of ondansetron failure. Of variants tested, rs45460698 independently showed a significant difference in risk of ondansetron failure between a mutant (any deletion) and normal allele (p=0.0281, OR 2.67). Age and BMI were both predictive of ondansetron failure (Age > 12 (OR 1.12, p=0.0012) and higher BMI (OR 1.13, p=0.0119)). In multivariate analysis, age > 12 was highly predictive of ondansetron failure (OR 7.108, p=0.0008). rs45460698 was predictive when combined with an increased nausea phenotype variant of rs1045642 (OR 3.45, p=0.0426). Conclusion: Select phenotypes of 5-HT3RB and ABCB1, age, and potentially BMI can help predict increased risk for CINV in a diverse pediatric oncology population.

CYP3A4∗22 Genotyping in Clinical Practice: Ready for Implementation?

Cytochrome P450 3A4 (CYP3A4) is the most important drug metabolizing enzyme in the liver, responsible for the oxidative metabolism of ∼50% of clinically prescribed drugs. Therefore, genetic variation in CYP3A4 could potentially affect the pharmacokinetics, toxicity and clinical outcome of drug treatment. Thus far, pharmacogenetics for CYP3A4 has not received much attention. However, the recent discovery of the intron 6 single-nucleotide polymorphism (SNP) rs35599367C &gt; T, encoding the CYP3A4∗22 allele, led to several studies into the pharmacogenetic effect of CYP3A4∗22 on different drugs. This allele has a relatively minor allele frequency of 3-5% and an effect on CYP3A4 enzymatic activity. Thus far, no review summarizing the data published on several drugs is available yet. This article therefore addresses the current knowledge on CYP3A4∗22. This information may help in deciding if, and for which drugs, CYP3A4∗22 genotype-based dosing could be helpful in improving drug therapy. CYP3A4∗22 was shown to significantly influence the pharmacokinetics of several drugs, with currently being most thoroughly investigated tacrolimus, cyclosporine, and statins. Additional studies, focusing on toxicity and clinical outcome, are warranted to demonstrate clinical utility of CYP3A4∗22 genotype-based dosing.

Nonclinical Safety Profile of Sotorasib, a KRASG12C-Specific Covalent Inhibitor for the Treatment of KRAS p.G12C-Mutated Cancer

Sotorasib is a first-in-class KRASG12C covalent inhibitor in clinical development for the treatment of tumors with the KRAS p.G12C mutation. A comprehensive nonclinical safety assessment package, including secondary/safety pharmacology and toxicology studies, was conducted to support the marketing application for sotorasib. Sotorasib was negative in a battery of genotoxicity assays and negative in an in vitro phototoxicity assay. Based on in vitro assays, sotorasib had no off-target effects against various receptors, enzymes (including numerous kinases), ion channels, or transporters. Consistent with the tumor-specific target distribution (ie, KRASG12C), there were no primary pharmacology-related on-target effects identified. The kidney was identified as a target organ in the rat but not the dog. Renal toxicity in the rat was characterized by tubular degeneration and necrosis restricted to a specific region suggesting that the toxicity was attributed to the local formation of a putative toxic reactive metabolite. In the 3-month dog study, adaptive changes of hepatocellular hypertrophy due to drug metabolizing enzyme induction were observed in the liver that was associated with secondary effects in the pituitary and thyroid gland. Sotorasib was not teratogenic and had no direct effect on embryo-fetal development in the rat or rabbit. Human, dog, and rat circulating metabolites, M24, M10, and M18, raised no clinically relevant safety concerns based on the general toxicology studies, primary/secondary pharmacology screening, an in vitro human ether-à-go-go-related gene assay, or mutagenicity assessment. Overall, the results of the nonclinical safety program support a high benefit/risk ratio of sotorasib for the treatment of patients with KRAS p.G12C-mutated tumors.