Midazolam as a Probe for Heterotropic Drug-Drug Interactions Mediated by CYP3A4

EIDD-1931 Treatment Tweaks CYP3A4 and CYP2C8 in Arthritic Rats to Expedite Drug Interaction: Implication in Oral Therapy of Molnupiravir

EIDD-1931 is the active form of molnupiravir, an orally effective drug approved by the United States Food and Drug Administration (USFDA) against COVID-19. Pharmacokinetic alteration can cause untoward drug interaction (drug-drug/disease-drug), but hardly any information is known about this recently approved drug. Therefore, we first investigated the impact of the arthritis state on the oral pharmacokinetics of EIDD-1931 using a widely accepted complete Freund's adjuvant (CFA)-induced rat model of rheumatoid arthritis (RA) after ascertaining the disease occurrence by paw swelling measurement and X-ray examination. Comparative oral pharmacokinetic assessment of EIDD-1931 (normal state vs arthritis state) showed that overall plasma exposure was augmented (1.7-fold) with reduced clearance (0.54-fold), suggesting its likelihood of dose adjustment in arthritis conditions. In order to elucidate the effect of EIDD-1931 treatment at a therapeutic regime (normal state vs arthritis state) on USFDA-recommended panel of cytochrome P450 (CYP) enzymes (CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP3A4) for drug interaction using the same disease model, we monitored protein and mRNA expressions (rat homologs) in liver tissue by western blotting (WB) and real time-polymerase chain reaction (RT-PCR), respectively. Results reveal that EIDD-1931 treatment could strongly influence CYP3A4 and CYP2C8 among experimental proteins/mRNAs. Although CYP2C8 regulation upon EIDD-1931 treatment resembles similar behavior under the arthritis state, results dictate a potentially reverse phenomenon for CYP3A4. Moreover, the lack of any CYP inhibitory effect by EIDD-1931 in human/rat liver microsomes (HLM/RLM) helps to ascertain EIDD-1931 treatment-mediated disease-drug interaction and the possibility of drug-drug interaction with disease-modifying antirheumatic drugs (DMARDs) upon coadministration. As elevated proinflammatory cytokine levels are prevalent in RA and nuclear factor-kappa B (NF-kB) and nuclear receptors control CYP expressions, further studies should focus on understanding the regulation of affected CYPs to subside unexpected drug interaction.

Assessing the role of residue Phe108 of cytochrome P450 3A4 in allosteric effects of midazolam metabolism

Cytochrome P450 3A4 (CYP3A4) is involved in the metabolism of more drugs in clinical use than any other xenobiotic-metabolizing enzyme. CYP3A4-mediated drug metabolism is usually allosterically modulated by substrate concentration (homotropic allostery) and other drugs (heterotropic allostery), exhibiting unusual kinetic profiles and regiospecific metabolism. Recent studies suggest that residue Phe108 (F108) of CYP3A4 may have an important role in drug metabolism. In this work, residue mutations were coupled with well-tempered metadynamics simulations to assess the importance of F108 in the allosteric effects of midazolam metabolism. Comparing the simulation results of the wild-type and mutation systems, we identify that the π-π interaction and steric effect between the F108 side chain and midazolam is favorable for the stable binding of substrate in the active site. F108 also plays an important role in the transition of substrate binding mode, which mainly induces the transition of substrate binding mode by forming π-π interactions with multiple aromatic rings of the substrate. Moreover, the side chain of F108 is closely related to the radius and depth of the 2a and 2f channels, and F108 may further regulate drug metabolism by affecting the pathway, orientation, or time of substrate entry into the CYP3A4 active site or product egress from the active site. Altogether, we suggest that F108 affects drug metabolism and regulatory mechanisms by affecting substrate binding stability, binding mode transition, and channel characteristics of CYP3A4. Our findings could promote the understanding of complicated allosteric mechanisms in CYP3A4-mediated drug metabolism, and the knowledge could be used for drug development and disease treatment.

Evaluation of the potential drug-drug interactions of carotegrast methyl with midazolam, prednisolone or atorvastatin in healthy adults

AIMS

This study evaluated drug-drug interactions between the CYP3A4 inhibitor carotegrast methyl and the other CYP3A4 substrates, midazolam, atorvastatin and prednisolone.

METHODS

A total of 88 healthy volunteers orally received carotegrast methyl 960 mg 3 times daily for 14 days. A single oral (5 mg) or intravenous (0.017 mg kg-1 ) midazolam, oral (5 mg) prednisolone or oral (10 mg) atorvastatin was administered before, with and after carotegrast methyl treatment. When the 90% confidence interval (CI) for the geometric mean ratios of the pharmacokinetic (PK) parameters with coadministration with carotegrast methyl (Day 14) to those before carotegrast methyl administration was between 0.80 and 1.25, no PK interaction were deemed.

RESULTS

The Cmax and AUC0-t of oral midazolam before administration of carotegrast methyl were 30.9 ± 9.8 ng mL-1 and 74.5 ± 21.9 ng h mL-1 , respectively. The geometric mean ratio of the Cmax and AUC0-t of midazolam on Day 14 to those on Day -1 was 1.86 (90% CI, 1.64-2.11) and 3.07 (90% CI, 2.81-3.35), which did not fall within the range of 0.80-1.25, suggesting that carotegrast methyl had a PK interaction with midazolam. Similar PK interactions were found for intravenous midazolam and atorvastatin, but not for prednisolone. The inhibitory effect of carotegrast methyl on CYP3A4-mediated metabolism of midazolam and atorvastatin had almost disappeared by 14 days after the end of administration.

CONCLUSION

Carotegrast methyl was classified as a moderate CYP3A4 inhibitor in humans. Carotegrast methyl might enhance the action of drugs that are metabolized by CYP3A4.

Factors influencing the detergent-free membrane protein isolation using synthetic nanodisc-forming polymers

The detergent-free isolation of membrane proteins using synthetic polymers is becoming the desired approach for functional and structural studies of membrane proteins. Since the expression levels for many membrane proteins are low and a high yield of functionalized reconstituted membrane proteins is essential for in vitro studies, it is crucial to optimize the experimental conditions for a given polymer to solubilize target membranes/proteins effectively. The factors that affect membrane solubilization and subsequently the isolation of a target membrane protein include polymer concentration, polymer charge, temperature, pH, and concentration of divalent metal ions. Therefore, it is important to have knowledge about the efficacy of different types of polymers in solubilizing cell membranes. In this study, we evaluate the efficacy of inulin-based non-ionic polymers in solubilizing E. coli membranes enriched with rat flavin mononucleotide binding-domain (FBD) of cytochrome-P450-reductase (CPR) and rabbit cytochrome-b5 (Cyt-b5) under various solubilization conditions. Our results show that a 1:1 (w/w) membrane:polymer ratio, low temperature, high pH and sub-millimolar concentration of metal ions favor the solubilization of E. coli membranes enriched with FBD or Cyt-b5. Conversely, the presence of excess divalent metal ions affected the final protein levels in the polymer-solubilized samples. We believe that the results from this study provide knowledge to assess and plan the use of non-ionic polymers in membrane protein studies.

Pharmacogenomics of Dementia: Personalizing the Treatment of Cognitive and Neuropsychiatric Symptoms

Dementia is a syndrome of global and progressive deterioration of cognitive skills, especially memory, learning, abstract thinking, and orientation, usually affecting the elderly. The most common forms are Alzheimer's disease, vascular dementia, and other (frontotemporal, Lewy body disease) dementias. The etiology of these multifactorial disorders involves complex interactions of various environmental and (epi)genetic factors and requires multiple forms of pharmacological intervention, including anti-dementia drugs for cognitive impairment, antidepressants, antipsychotics, anxiolytics and sedatives for behavioral and psychological symptoms of dementia, and other drugs for comorbid disorders. The pharmacotherapy of dementia patients has been characterized by a significant interindividual variability in drug response and the development of adverse drug effects. The therapeutic response to currently available drugs is partially effective in only some individuals, with side effects, drug interactions, intolerance, and non-compliance occurring in the majority of dementia patients. Therefore, understanding the genetic basis of a patient's response to pharmacotherapy might help clinicians select the most effective treatment for dementia while minimizing the likelihood of adverse reactions and drug interactions. Recent advances in pharmacogenomics may contribute to the individualization and optimization of dementia pharmacotherapy by increasing its efficacy and safety via a prediction of clinical outcomes. Thus, it can significantly improve the quality of life in dementia patients.

Impact of Heterotropic Allosteric Modulation on the Time-Dependent Inhibition of Cytochrome P450 3A4

The current study was designed to investigate the influence of allosteric effectors on the metabolism of the prototypical cytochrome P450 (CYP) 3A4 substrate midazolam (MDZ), and on the determination in vitro time-dependent inhibition (TDI) of CYP3A4 using human liver microsomes (HLM). As the concentration of midazolam increased to 250 µM in HLMs, homotropic cooperativity resulted in a decrease in the 1'-hydroxymidazolam to 4-hydroxymidazolam ratio to a maximum of 1.1. The presence of varying concentrations of testosterone, progesterone (PGS), or carbamazepine (CBZ) in HLMs with MDZ could recapitulate the effect of homotropic cooperativity such that the formation rates of the 1'hydroxymidazolam and 4-hydroxymidazolam were equal even at low concentrations of MDZ. The presence of PGS (10 or 100 µM) and CBZ (100 or 1000 µM) in in vitro TDI determination of four known CYP3A4 time-dependent inactivators (clarithromycin, troleandomycin, mibefradil, raloxifene) simultaneously decreased potency and inactivation rate constant, resulting in fold changes in inactivation efficiency on average of 1.6-fold and 13-fold for the low and high concentrations of allosteric modulator tested, respectively. The formation of a metabolic-intermediate complex (MIC) for clarithromycin and troleandomycin decreased in the presence of the allosteric modulators in a concentration-dependent manner, reaching a new steady state formation that could not be overcome with increased incubation time. Maximum reduction of the MIC formed by clarithromycin was up to ∼91%, while troleandomycin MIC decreased up to ∼31%. These findings suggest that the absence of endogenous allosteric modulators may contribute to the poor translation of HLM-based drug-drug interaction predictions. SIGNIFICANCE STATEMENT: The reported overprediction of in vitro human liver microsome time-dependent inhibition of CYP3A4 and observed drug interactions in vivo remains an issue in drug development. We provide characterization of allosteric modulators on the CYP3A4 metabolism of the prototypical substrate midazolam, demonstrating the ability of the modulators to recapitulate the homotropic cooperativity of midazolam. Furthermore, we demonstrate that allosteric heterotropic cooperativity of CYP3A4 can impact the time-dependent inhibition kinetics of known mechanisms-based inhibitors, providing a potential mechanism to explain the overprediction.

Factors influencing the detergent-free membrane protein isolation using synthetic nanodisc-forming polymers

The detergent-free isolation of membrane proteins using synthetic polymers is becoming the desired approach for functional and structural studies of membrane proteins. Since the expression levels for many membrane proteins are low and a high yield of functionalized reconstituted membrane proteins is essential for in vitro studies, it is crucial to optimize the experimental conditions for a given polymer to effectively solubilize target membranes/proteins. The factors that affect membrane solubilization and subsequently the isolation of a target membrane protein include polymer concentration, polymer charge, temperature, pH, and concentration of divalent metal ions. Therefore, it is important to have knowledge about the efficacy of different types of polymers in solubilizing cell membranes. In this study, we evaluate the efficacy of inulin-based non-ionic polymers in solubilizing E. coli membranes enriched with rat flavin mononucleotide binding-domain (FBD) of cytochrome-P450-reductase (CPR) and rabbit cytochrome-b5 (Cyt-b5) under various solubilization conditions. Our results show that a 1:1 (w/w) membrane:polymer ratio, low temperature, high pH and sub-millimolar concentration of metal ions favor the solubilization of E. coli membrane enriched with FBD or Cyt-b5. Conversely, the presence of excess divalent metal ions affected the final protein levels in the polymer-solubilized samples. We believe that the results from this study provides knowledge to assess and plan the use of non-ionic polymers in membrane protein studies.

Molecular Insights into the Heterotropic Allosteric Mechanism in Cytochrome P450 3A4-Mediated Midazolam Metabolism

Cytochrome P450 3A4 (CYP3A4) is the main P450 enzyme for drug metabolism and drug-drug interactions (DDIs), as it is involved in the metabolic process of approximately 50% of drugs. A detailed mechanistic elucidation of DDIs mediated by CYP3A4 is commonly believed to be critical for drug optimization and rational use. Here, two typical probes, midazolam (MDZ, substrate) and testosterone (TST, allosteric effector), are used to investigate the molecular mechanism of CYP3A4-mediated heterotropic allosteric interactions, through conventional molecular dynamics (cMD) and well-tempered metadynamics (WT-MTD) simulations. Distance monitoring shows that TST can stably bind in two potential peripheral sites (Site 1 and Site 2) of CYP3A4. The binding of TST at these two sites can induce conformational changes in CYP3A4 flexible loops on the basis of conformational analysis, thereby promoting the transition of the MDZ binding mode and affecting the ratio of MDZ metabolites. According to the results of the residue interaction network, multiple allosteric communication pathways are identified that can provide vivid and applicable insights into the heterotropic allostery of TST on MDZ metabolism. Comparing the regulatory effects and the communication pathways, the allosteric effect caused by TST binding in Site 2 seems to be more pronounced than in Site 1. Our findings could provide a deeper understanding of CYP3A4-mediated heterotropic allostery at the atomic level and would be helpful for rational drug use as well as the design of new allosteric modulators.

Detergent-Free Isolation of Membrane Proteins and Strategies to Study Them in a Near-Native Membrane Environment

Atomic-resolution structural studies of membrane-associated proteins and peptides in a membrane environment are important to fully understand their biological function and the roles played by them in the pathology of many diseases. However, the complexity of the cell membrane has severely limited the application of commonly used biophysical and biochemical techniques. Recent advancements in NMR spectroscopy and cryoEM approaches and the development of novel membrane mimetics have overcome some of the major challenges in this area. For example, the development of a variety of lipid-nanodiscs has enabled stable reconstitution and structural and functional studies of membrane proteins. In particular, the ability of synthetic amphipathic polymers to isolate membrane proteins directly from the cell membrane, along with the associated membrane components such as lipids, without the use of a detergent, has opened new avenues to study the structure and function of membrane proteins using a variety of biophysical and biological approaches. This review article is focused on covering the various polymers and approaches developed and their applications for the functional reconstitution and structural investigation of membrane proteins. The unique advantages and limitations of the use of synthetic polymers are also discussed.