Drug Metabolism and Disposition最新文献

Gut bacterial β-glucuronidase (GUS) enzymes contribute to the intestinal toxicity and/or enterohepatic recycling of glucuronidated compounds by cleaving glucuronide conjugates excreted into the intestinal lumen. The activities and substrate specificities of several GUS isoforms have been recently described. However, the extent of intraindividual and interindividual variability in gut microbial deglucuronidation activity has remained poorly characterized. In this study, we used pan-GUS reporter substrates as well as drug and steroid glucuronides to study the deglucuronidation activities of fecal lysates produced from individual fecal samples from healthy donors (n = 12), and sequential samples collected from fecal microbiota transplantation (FMT) donors (n = 3) and patients with recurrent Clostridioides difficile infection who underwent FMT (n = 7). To determine relationships between fecal deglucuronidation activity and gut microbiota composition, we used 16S rRNA gene sequencing to characterize the healthy donors' fecal microbiotas. Although we observed considerable interindividual variability specifically in the processing of steroid glucuronides, intraindividual variability in the fecal deglucuronidation activity of FMT donors was relatively modest. We observed the female sex and Alistipes, Faecalibacterium, and Gemmiger taxa to be associated with higher deglucuronidation activity, whereas the abundance of Roseburia correlated negatively with deglucuronidation activity. In addition, the baseline deglucuronidation activity of patients with recurrent C. difficile infection was low but increased by FMT treatment. The results of this study further highlight deglucuronidation as a function of a healthy gut microbiota. Moreover, these results improve our understanding of deglucuronidation activity as a source of individual variability in the pharmacokinetics and pharmacodynamics of glucuronidated drugs that undergo enterohepatic recycling. SIGNIFICANCE STATEMENT: Gut microbial deglucuronidation rates of specific compounds may vary considerably between individuals. Deglucuronidation activity is relatively stable within healthy individuals for ≥1 year, but fecal microbiota transplantation can significantly alter the deglucuronidation activity of an individual.

Imatinib is a kinase inhibitor used in the treatment of chronic myeloid leukemia and other cancers. Although its pharmacokinetics is generally predictable, substantial interindividual variability in clearance and exposure remains. In this study, we investigated the impact of cytochrome P450 (P450) enzymes CYP2C8, CYP3A4, and CYP3A5 phenotypes and genotypes on imatinib metabolism using both human liver microsomes (HLMs) and primary human hepatocytes (PHHs). Imatinib clearance and N-desmethyl imatinib formation were quantified by liquid chromatography-tandem mass spectrometry and correlated with enzyme activity, protein concentration, and compared by genotype groups. In single-donor HLMs (n = 21), imatinib clearance varied 45-fold between donors and was strongly associated with CYP2C8 (r = 0.91) and CYP3A (r = 0.90) protein concentrations and CYP2C8 (r = 0.66) and CYP3A (r = 0.86) enzyme activities. A multiple linear regression model identified CYP3A activity and biological sex as significant predictors of imatinib clearance (adjusted R² = 0.90, P < .0001). In PHH (n = 14), imatinib clearance varied 10-fold and was significantly correlated with CYP2C8 activity and protein concentration, but not with CYP3A activity. CYP2C8∗3 carriers had significantly lower clearance than ∗1/∗1 donors (P = .012). N-Desmethyl imatinib formation was consistently associated with both CYP2C8 and CYP3A protein concentration and enzyme activity in HLM and PHH. These findings provide further insight into the enzymes driving imatinib metabolism and highlight the relevance of CYP2C8 and CYP3A variability to interindividual differences in drug disposition. These results support the integration of enzyme phenotyping into predictive models to inform imatinib precision dosing approaches. SIGNIFICANCE STATEMENT: This study highlights the influence of CYP2C8 and CYP3A enzymes on interindividual variability in imatinib metabolism in human liver microsomes and primary human hepatocytes. Our findings provide evidence that CYP2C8 phenotypic measures (enzyme activity and protein concentration) are effective in predicting imatinib metabolism in vitro in primary human hepatocytes. Future studies are warranted to examine how preemptive testing of P450 parameters, such as phenotypes and genotypes, in patients before drug administration could aid in therapy optimization and reduction of drug toxicities.

Onradivir (ZSP1273) is a novel antiviral agent with broad-spectrum activity, favorable pharmacokinetics, and potential for treating influenza virus infections. This study developed a population pharmacokinetic model to evaluate the impact of factors on onradivir pharmacokinetics, explore exposure-efficacy and exposure-safety relationships, and inform pediatric dose selection in clinical trial. Six clinical trial datasets were pooled for population pharmacokinetic analysis. Covariates were subsequently screened. The impact of significant covariates on exposure was assessed through simulation. Safety and efficacy endpoints were defined as the incidence rate of adverse events and the average viral load (baseline-adjusted) over T, respectively. Binary endpoints were analyzed using logistic regression and continuous endpoints using scatter plots and the sigmoid E_max model. Pediatric dosing was determined through allometric scaling and simulations referencing adult exposure. Significant covariates included weight, health status, sex, and formulation process, but their impact on exposure did not warrant dose adjustments. Diarrhea was the main mild and transient side effect. Antiviral modeling suggested a flat or saturated exposure-response relationship within the studied exposure window. Proposed pediatric dosing regimens for clinical trial evaluation are 600 mg once daily (>40 kg), 400 mg once daily (20-40 kg), and 200 mg once daily (10-20 kg). This analysis provides a preliminary basis for onradivir dose selection in pediatric clinical trials, indicating possible directions for dose adjustment and informing future research and development efforts. SIGNIFICANCE STATEMENT: This study establishes the first population pharmacokinetic model for onradivir, identifying weight, health status, and sex as key covariates without necessitating dose adjustments. It provides weight-based pediatric dosing suggestions (200-600 mg once daily) in a pediatric clinical trial.

The unbound (free) drug hypothesis is now correctly termed the unbound drug principle. Despite it offering a basic and simple mechanism for the action of drugs both in vitro and in vivo, there are still misconceptions. The literature provides a challenge to the unbound drug principle in addressing the common preclinical finding of phospholipidosis associated with basic compounds. Similar agents (differentiated mainly by pKa) with identical unbound plasma concentrations, in vivo, can show very different effects. In this commentary we explain how this finding is in keeping with unbound drug principles, as the change in pKa inversely correlates to Kd and enhanced affinity for phospholipid. The majority of a basic drug, associated with tissue, is reversibly bound to abundant acidic phospholipid rather than interstitial and cytosolic proteins. Total tissue concentrations may therefore correlate with phospholipidosis better than unbound plasma drug concentrations, however, once phospholipid Kd is considered the correlation becomes obvious. In the specific case of phospholipidosis, measurement of tissue concentrations for basic drugs provides a direct measure of target occupancy. SIGNIFICANCE STATEMENT: The importance of this commentary is to address what may be seen as an exception to the unbound (free) drug principle and has been quoted as such. By explaining the role of unbound drug and target (phospholipid) affinity the anomaly is clarified. Moreover, the total tissue concentrations in phospholipidosis are rationalized as actually a measure of target occupancy, acidic phospholipids.

Previous reports have stated that cytochrome P4502C8 (CYP2C8) catalyzes the hydroxylation of repaglinide at the 3-position of the piperidine ring, and this metabolite has been used as a marker for CYP2C8 catalytic activity in vitro and in vivo. However, data shown in the present report demonstrate unequivocally that the actual site of hydroxylation is on the adjacent 4-position. The metabolite was biosynthesized using CYP2C8, isolated, and evaluated by high resolution mass spectrometry and 1D and 2D NMR spectroscopy. Definitive assignment of the structure required 2D heteronuclear single quantum correlation NMR analysis conducted at low temperature and the data for the isolated metabolite were contrasted with data gathered for the synthetic standard of 3'-hydroxyrepaglinide diastereomers. Repaglinide 4'-hydroxylation was measured in pooled human liver microsomes and recombinant CYP2C8 with Michaelis constants of 10.2 and 5.4 μM, respectively. Because repaglinide hydroxylation is an important drug metabolism reaction that probes CYP2C8 activity, it is critical that the correct structure of the CYP2C8 generated metabolite is known. SIGNIFICANCE STATEMENT: Previous studies have misassigned the structure of the main hydroxy metabolite of repaglinide that is generated by human P4502C8 (CYP2C8). This transformation has been used as a marker for CYP2C8 in clinical and in vitro studies. These data unequivocally demonstrate that the absolute structure of the hydroxyrepaglinide metabolite generated by CYP2C8 is 4'-hydroxymetabolite, not 3'-hydroxyrepaglinide as previously claimed.

FDA018, a novel trophoblast cell surface antigen 2-targeted antibody-drug conjugate, is designed for treating trophoblast cell surface antigen 2-positive solid tumors, including triple-negative breast cancer, lung cancer, and gastric cancer. In this study, a single-center, open-label, dose-escalation clinical study was conducted to evaluate the pharmacokinetics (PK) and immunogenicity of FDA018 injection in patients with advanced or metastatic epithelial malignant solid tumors, using an "accelerated titration" design and a standard "3+3" design across 6 dose cohorts (2.5, 5, 7.5, 10, 12 and 15 mg/kg). PK profiles were investigated for a topoisomerase I inhibitor (SN-38)-conjugated antibody, total antibody, unconjugated SN-38, a glucuronate metabolite of SN-38 (SN-38G), and total SN-38. To evaluate the impact of immunogenicity on PK profiles of FDA018, immunogenicity was assessed with an electrochemiluminescence-based bridging immunoassay. PK results showed that the exposure of the SN-38-conjugated antibody increased linearly with dose escalation. The terminal half-life of the SN-38-conjugated antibody (about 30 hours) was significantly shorter than that of the total antibody (about 85 hours). The terminal half-life of the SN-38-conjugated antibody and total antibody appeared to be prolonged after multiple administrations. The exposure of unconjugated SN-38 accounted for approximately 1% of total SN-38, indicating that most SN-38 remained conjugated to the monoclonal antibody in the systemic circulation, and the off-target toxicity was controllable. The accumulation analysis results showed that total antibody accumulated after multiple administrations. For immunogenicity assessment, among 20 patients receiving doses from 7.5 to 15 mg/kg, 15% tested positive for anti-drug antibodies. Anti-drug antibody-positive results did not significantly affect the PK profiles of FDA018. In conclusion, FDA018 demonstrated promising PK and immunogenicity profiles and laid a solid foundation for further clinical research. SIGNIFICANCE STATEMENT: This study comprehensively evaluated the clinical pharmacokinetic and immunogenicity of the trophoblast cell surface antigen 2-targeted antibody-drug conjugate, FDA018, for the first time, to the authors' knowledge. Compared with the commercially available trophoblast cell surface antigen 2-targeted antibody-drug conjugate sacituzumab govitecan, FDA018 showed promising pharmacokinetic properties with higher exposure of conjugated antibody and lower exposure of unconjugated SN-38 in vivo, implying better efficacy and lower off-target toxicity.

High-dose methotrexate (HD-MTX) is essential in treating acute lymphoblastic leukemia (ALL), but its pharmacokinetics and toxicity are influenced by transporter and metabolic enzyme gene polymorphisms. This study examines the impact of gene polymorphisms in the MTX metabolic pathway on toxicity and pharmacokinetics in Chinese patients with ALL to aid individualized therapy in order to ensure the safety of patients. We prospectively collected 273 serum MTX concentration data from 92 patients with ALL (15-71 years) undergoing HD-MTX. Differences in liver and kidney toxicity markers were analyzed across gene polymorphisms. A population pharmacokinetic model was developed using nonlinear mixed-effect modeling to explore the impact of demographic, biochemical, and genetic covariates. Patients who were homozygous for γ-glutamyl hydrolase gene rs13248452 (GG + AA genotypes) had higher urea levels. SLCO1B1 mutant allele carriers had elevated alanine aminotransferase and aspartate aminotransferase levels compared with homozygous patients. SLC19A1 rs2838957 CT genotype patients had significantly higher aspartate aminotransferase. Population pharmacokinetic analysis indicated that the glomerular filtration rate significantly affected the MTX clearance, whereas gene polymorphisms did not significantly alter the clearance rate or volume of distribution of MTX. In conclusion, gene polymorphisms in SLCO1B1, SLC19A1, and γ-glutamyl hydrolase correlate with MTX-induced alterations in liver and kidney function indicators, but the toxicity mechanisms may be independent of systemic pharmacokinetics. In clinical practice, dosage adjustments should be made based on glomerular filtration rate, with enhanced monitoring for high-risk genotypes. Genetic markers should be combined with renal function monitoring to optimize individualized MTX therapy and improve safety. SIGNIFICANCE STATEMENT: This study identifies γ-glutamyl hydrolase/SLCO1B1/SLC19A1 polymorphisms as key predictors of methotrexate toxicity in Chinese acute lymphoblastic leukemia patients, whereas population pharmacokinetic reveals glomerular filtration rate-not genetics-drives clearance. Findings advocate for genotype-toxicity monitoring and glomerular filtration rate-based dosing to improve safety.

Aldehyde oxidase (AOX) oxidizes nitrogen-containing heterocyclic drugs and reduces electron-deficient nitroaromatic drugs. The aim of this study was to elucidate the mode of inhibition of benzothiazepines such as quetiapine and clozapine, which are known inhibitors of AOX, to predict drug-drug interactions between AOX substrates and inhibitors. Quetiapine and its metabolites inhibited the oxidation and reduction activities of AOX (inhibitory effects: quetiapine ≈ norquetiapine > quetiapine sulfoxide > quetiapine carboxylic acid). The inhibition mode of quetiapine was noncompetitive for phthalazine oxidation (K_i, 5.72 ± 0.88 μM) and competitive for flunitrazepam reduction (K_i, 5.71 ± 0.34 μM). Although a mixed inhibition mode was indicated for the reduction of AOX by clozapine (K_i, 30.91 ± 4.02 μM), the affinity for the enzyme-substrate complex was estimated to be lower than its affinity for the substrate-free enzyme. On the basis of these results, we expected that benzothiazepines would inhibit activity by becoming trapped in the pocket of AOX, where the electron donor resides. Quetiapine and its metabolites did not inhibit xanthine oxidase activity, and it is assumed that there are significant structural differences in the sites where the reduction reactions of AOX and xanthine oxidase occur. To our knowledge, this is the first study to identify drugs that competitively inhibit the AOX-mediated reduction reactions. The affinities of the inhibitors, especially quetiapine, were higher than those of flunitrazepam used in this study. When evaluating the combined effects of competitive inhibitors on substrate drugs, attention should be paid to the concentrations of both the substrate and the inhibitor. SIGNIFICANCE STATEMENT: Quetiapine inhibited the oxidative reaction of aldehyde oxidase noncompetitively and the reductive reaction competitively, suggesting that benzothiazepines tend to bind to the reductive pocket of aldehyde oxidase.

Antisense oligonucleotides (ASOs) are selective small biological drugs used to decrease targeted proteins by suppressing mRNA expression. In this study, a quantitative framework was developed to characterize the disposition and effects of such drugs in the central nervous system across species to facilitate the translation of preclinical pharmacology to the clinic. A minimal physiologically based pharmacokinetic (PK)-pharmacodynamic (PD) model for ASOs was developed using published drug and species-specific physiological information, including PK of nusinersen and preclinical PK and mRNA expression for an investigational compound targeting glutamate receptor subunit 1. The model describes relevant pharmacological processes, including (1) clathrin-dependent/independent endocytosis, (2) exocytosis, (3) exonuclease metabolism, (4) macropinocytosis, and (5) knockdown of the targeted protein. Most physiological values were obtained from literature, and drug-specific parameters were estimated. The model captured PK data in preclinical species (mice, rats, and monkeys), infants, and pediatric subjects from phase 1 and 2 studies. Renal clearances were fixed to 2.07, 25.2, 170.7, and 405 mL/h for mice, rats, monkeys, and humans, which were based on prior published values for oligonucleotides. Glutamate receptor subunit 1 mRNA and protein expression in rats were well characterized using a precursor-dependent indirect response model assuming maximal inhibition (I_max) set to 1. Overall, the biodistribution of 2 ASOs across species were characterized by implementing allometric scaling and minimal physiologically based PK concepts. The final model provides insights into the role of specific disposition processes in controlling ASO PK-PD properties in the central nervous system. SIGNIFICANCE STATEMENT: Antisense oligonucleotides enable central nervous system-targeted gene therapy and precision medicine. Using a translational multispecies minimal physiologically based PK-PD model, drug- and system-specific factors were identified that influence the biodistribution of antisense oligonucleotides in preclinical species and humans. The final model can readily translate preclinical data to anticipate human drug exposures in the brain and plasma, help in lead and backup compound selection, project first-in-human dose levels, interpret early human PK-PD data, and facilitate the identification of recommended phase 2 doses.

Pharmacogenomics has emerged as a vital field within precision medicine and forensics, focusing on how an individual's genome affects their response to drugs. This field is essential in enhancing treatment efficacy and minimizing side effects, particularly for cancer patients with gliomas, who often face narrow therapeutic windows for anticancer agents and have a limited Food and Drug Administration-approved treatment option. Among the cytochrome P450 enzyme superfamily, CYP2B6 metabolizes drugs such as cyclophosphamide, efavirenz, methadone, and ecstasy. Genetic variation in P450 genes influences individual's drug-metabolizing capacity, making it crucial to understand CYP2B6 and its regulation to ensure the effectiveness and safety of drug therapies and determine the cause of death in drug-related cases. Previous studies have shown that activating transcription factor 5 (ATF5), a basic leucine zipper transcription factor, transactivates CYP2B6 in liver cells. Additionally, a cell-penetrating dominant-negative ATF5 (CP-DN-ATF5) peptide was developed and successfully interfered with the ATF5-mediated stabilization of antiapoptotic proteins. Our study aimed to establish the ATF5-mediated regulation of CYP2B6 in glioblastoma cells and to determine whether CP-DN-ATF5 could also promote the downregulation of CYP2B6. We used the Tat cell-penetrating peptide from HIV-1 transactivator of transcription (TAT) form, which was N-terminally fused with DN-ATF5 (TAT-CP-DN-ATF5), for our investigation. We found that ATF5 regulates CYP2B6, and the TAT-CP-DN-ATF5 peptide effectively downregulates CYP2B6 protein levels in certain glioblastoma cell lines, LN229 and GBM5. These findings suggest the potential for targeting CYP2B6 with TAT-CP-DN-ATF5 to slow drug metabolism, allowing for personalized dosing and coadministration strategies to improve treatment efficiency and reduce side effects. SIGNIFICANCE STATEMENT: The study found that the transcription factor activating transcription factor 5 regulates CYP2B6 expression in glioblastoma cell lines. Introducing a transactivator of transcription-fused cell-penetrating dominant-negative activating transcription factor 5 peptide downregulates CYP2B6 protein expression, suggesting its potential for personalized dosing strategies by targeting CYP2B6.