Ritonavir is the best alternative to ketoconazole as an index inhibitor of cytochrome P450-3A in drug-drug interaction studies

Mechanism-based inactivation of cytochromes P450: implications in drug interactions and pharmacotherapy

Cytochrome P40 (CYP) enzymes dominate the metabolism of numerous endogenous and xenobiotic substances. While it is commonly believed that CYP-catalysed reactions result in the detoxication of foreign substances, these reactions can also yield reactive intermediates that can bind to cellular macromolecules to cause cytotoxicity or irreversibly inactivate CYPs that create them.Mechanism-based inactivation (MBI) produces either irreversible or quasi-irreversible inactivation and is commonly caused by CYP metabolic bioactivation to an electrophilic reactive intermediate. Many drugs that have been known to cause MBI in CYPs have been discovered as perpetrators in drug-drug interactions throughout the last 20-30 years.This review will highlight the key findings from the recent literature about the mechanisms of CYP enzyme inhibition, with a focus on the broad mechanistic elements of MBI for widely used drugs linked to the phenomenon. There will also be a brief discussion of the clinical or pharmacokinetic consequences of CYP inactivation with regard to drug interaction and toxicity risk.Gaining knowledge about the selective inactivation of CYPs by common therapeutic drugs helps with the assessment of factors that affect the systemic clearance of co-administered drugs and improves comprehension of anticipated interactions with other drugs or xenobiotics.

Pharmacokinetic analysis of antiviral drug ritonavir across the blood-brain barrier and its interaction with Scutellaria baicalensis using multisite microdialysis in rats

Ritonavir, an excellent inhibitor of CYP3A4, has recently been combined with nirmatrelvir to form Paxlovid for the treatment of severe acute respiratory syndrome coronavirus 2 infections. The root of Scutellaria baicalensis Georgi (S. baicalensis), a traditional Chinese medicinal (TCM) herb commonly used to treat heat/inflammation in the lung and digestive tracts, which are major organs targeted by viral infections, contains flavones that can influence the CYP3A metabolism pathway. To investigate the ability of ritonavir to cross the bloodbrain barrier (BBB) and its potential herb-drug interactions with an equivalent TCM clinical dose of S. baicalensis, multisite microdialysis coupled with an LCMS/MS system was developed using rat model. Pretreatment with S. baicalensis extract for 5 days, which contains less flavones than those used in previous studies, had a significant influence on ritonavir, resulting in a 2-fold increase in the total concentration of flavones in the blood and brain. Treatment also boosted the maximum blood concentration of flavones by 1.5-fold and the maximum brain concentration of flavones by 2-fold, all the while exerting no noticeable influence on the transfer ratio across the bloodbrain barrier. These experimental results demonstrated that the use of a typical traditional Chinese medicinal dose of S. baicalensis is sufficient to influence the metabolic pathway and synergistically increase the concentration of ritonavir in rats.

Effect of Strong CYP3A4 Inhibition, CYP3A4 Induction, and OATP1B1/3 Inhibition on the Pharmacokinetics of a Single Oral Dose of Sotorasib

Sotorasib is a small molecule that irreversibly inhibits the Kirsten rat sarcoma viral oncogene homolog (KRAS) protein with a G12C amino acid substitution mutant protein. The impact of cytochrome P450 (CYP) 3A4 inhibition and induction on sotorasib pharmacokinetics (PKs) was evaluated in 2 separate studies in healthy volunteers (N = 14/study). The impact of CYP3A4 inhibition was interrogated utilizing repeat doses of 200 mg of itraconazole, a strong CYP3A4 inhibitor, on 360 mg of sotorasib PKs. The impact of CYP3A4 induction was interrogated utilizing multiple doses of 600 mg of rifampin, a strong CYP3A4 inducer. Additionally, the impact of organic anion transporting polypeptide (OATP) 1B1/3 inhibition on 960 mg of sotorasib PKs was interrogated after a single dose of 600 mg of rifampin. CYP3A4 inhibition did not significantly impact sotorasib Cmax but did lead to a 26% increase in sotorasib AUCinf. CYP3A4 induction decreased sotorasib Cmax by 35% and AUCinf by 51%. OATP1B1/3 inhibition decreased sotorasib Cmax and AUCinf by 16% and 23%, respectively. These results support that sotorasib can be given together with strong CYP3A4 and OATP1B1/3 inhibitors but the co-administration of sotorasib and strong CYP3A4 inducers should be avoided.

Effects of Quinidine or Rifampin Co-administration on the Single-Dose Pharmacokinetics and Safety of Rilzabrutinib (PRN1008) in Healthy Participants

This open-label, phase 1 study was conducted with healthy adult participants to evaluate the potential drug-drug interaction between rilzabrutinib and quinidine (an inhibitor of P-glycoprotein [P-gp] and CYP2D6) or rifampin (an inducer of CYP3A and P-gp). Plasma concentrations of rilzabrutinib were measured after a single oral dose of rilzabrutinib 400 mg administered on day 1 and again, following a wash-out period, after co-administration of rilzabrutinib and quinidine or rifampin. Specifically, quinidine was given at a dose of 300 mg every 8 hours for 5 days from day 7 to day 11 (N = 16) while rifampin was given as 600 mg once daily for 11 days from day 7 to day 17 (N = 16) with rilzabrutinib given in the morning of day 10 (during quinidine dosing) or day 16 (during rifampin dosing). Quinidine had no significant effect on rilzabrutinib pharmacokinetics. Rifampin decreased rilzabrutinib exposure (the geometric mean of Cmax and AUC0-∞ decreased by 80.5% and 79.5%, respectively). Single oral doses of rilzabrutinib, with or without quinidine or rifampin, appeared to be well tolerated. These findings indicate that rilzabrutinib is a substrate for CYP3A but not a substrate for P-gp.

Pharmacokinetic Evaluation of the CYP3A4 and CYP2C9 Drug-Drug Interaction of Avacopan in 2 Open-Label Studies in Healthy Participants

Avacopan, a complement 5a receptor (C5aR) antagonist approved for treating severe active antineutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis, was evaluated in 2 clinical drug-drug interaction studies. The studies assessed the impact of avacopan on the pharmacokinetics (PK) of CYP3A4 substrates midazolam and simvastatin and CYP2C9 substrate celecoxib, and the influence of CYP3A4 inhibitor itraconazole and inducer rifampin on the PKs of avacopan. The results indicated that twice-daily oral administration of 30 mg of avacopan increased the area under the curve (AUC) of midazolam by 1.81-fold and celecoxib by 1.15-fold when administered without food, and twice-daily oral administration of 30 or 60 mg of avacopan increased the AUC of simvastatin by approximately 2.6-3.5-fold and the AUC of the active metabolite β-hydroxy-simvastatin acid by approximately 1.4-1.7-fold when co-administered with food. Furthermore, the AUC of avacopan increased by approximately 2.19-fold when co-administered with itraconazole and decreased by approximately 13.5-fold when co-administered with rifampin. These findings provide critical insights into the potential drug-drug interactions involving avacopan, which could have significant implications for patient care and treatment planning. (NCT06207682).

Posaconazole-ibrutinib interaction cannot be avoided by staggered dosing: How to optimize ibrutinib dose during posaconazole treatment

AIMS

Ibrutinib is used in the treatment of certain B-cell malignancies. Due to its CYP3A4-mediated metabolism and highly variable pharmacokinetics, it is prone to potentially harmful drug-drug interactions.

METHODS

In a randomized, placebo-controlled, three-phase crossover study, we examined the effect of the CYP3A4-inhibiting antifungal posaconazole on ibrutinib pharmacokinetics. Eleven healthy participants ingested repeated doses of 300 mg of posaconazole either in the morning or in the evening, or placebo. A single dose of ibrutinib (30, 70 or 140 mg, respectively) was administered at 9 AM, 1 or 12 h after the preceding posaconazole/placebo dose.

RESULTS

On average, morning posaconazole increased the dose-adjusted geometric mean area under the plasma concentration-time curve from zero to infinity (AUC0-∞ ) and peak plasma concentration (Cmax ) of ibrutinib 9.5-fold (90% confidence interval [CI] 6.3-14.3, P < 0.001) and 8.5-fold (90% CI 5.7-12.8, P < 0.001), respectively, while evening posaconazole increased those 10.3-fold (90% CI 6.7-16.0, P < 0.001) and 8.2-fold (90% CI 5.2-13.2, P < 0.001), respectively. Posaconazole had no significant effect on the half-life of ibrutinib, but substantially reduced the metabolite PCI-45227 to ibrutinib AUC0-∞ ratio. There were no significant differences in ibrutinib pharmacokinetics between morning and evening posaconazole phases.

CONCLUSIONS

Posaconazole increases ibrutinib exposure substantially, by about 10-fold. This interaction cannot be avoided by dosing the drugs 12 h apart. In general, a 70-mg daily dose of ibrutinib should not be exceeded during posaconazole treatment to avoid potentially toxic systemic ibrutinib concentrations.

Pharmacokinetic analysis of placental transfer of ritonavir as a component of paxlovid using microdialysis in pregnant rats

Background

Ritonavir is one of the most potent CYP3A4 inhibitor currently on the market, and is often used together with other antiviral drugs to increase their bioavailability and efficacy. Paxlovid, consisting of nirmatrelvir and ritonavir, was approved for the treatment of COVID-19. As previous studies regarding the use of ritonavir during pregnancy were limited to ex-vivo experiments and systemic safety data, to fully explore the detailed pharmacokinetics of ritonavir in pregnant rats' blood and conceptus, an analytical method consisted of multi-microdialysis coupled with UHPLC-MS/MS were developed to analyze the pharmacokinetics of ritonavir, both as a component of Paxlovid and by itself. 17 days pregnant female Sprague-Dawley rats were randomly split into three experimental group: normal dosage of ritonavir alone (7 mg kg-1), normal dosage of Paxlovid (ritonavir 7 mg kg-1 + nirmatrelvir 15 mg kg-1), and 3× dosage of ritonavir (21 mg kg-1).

Results

3× dosage of ritonavir produced a more than 3× increase in rats' blood and placenta. Transfer rate of ritonavir to the placenta, amniotic fluid, and fetus were determined to be 20.7%, 13.8%, and 4.7% respectively. Concentration of ritonavir in the placenta, amniotic fluid, and fetus did not significantly go down after 8 h.

Significance

Overall, ritonavir's metabolism was not influenced by the presence of nirmatrelvir in pregnant rats. A 3× increase in dosage produced a concentration of roughly 4×, most likely a result of ritonavir's auto-inhibition effect on cytochrome P450 proteins. Accumulation of ritonavir is possible in placenta, amniotic fluid, and fetus.

Simultaneous Prediction Method for Intestinal Absorption and Metabolism Using the Mini-Ussing Chamber System

Many evaluation tools for predicting human absorption are well-known for using cultured cell lines such as Caco-2, MDCK, and so on. Since the combinatorial chemistry and high throughput screening system, pharmacological assay, and pharmaceutical profiling assay are mainstays of drug development, PAMPA has been used to evaluate human drug absorption. In addition, cultured cell lines from iPS cells have been attracting attention because they morphologically resemble human intestinal tissues. In this review, we used human intestinal tissues to estimate human intestinal absorption and metabolism. The Ussing chamber uses human intestinal tissues to directly assay a drug candidate's permeability and determine the electrophysiological parameters such as potential differences (PD), short circuit current (Isc), and resistance (R). Thus, it is an attractive tool for elucidating human intestinal permeability and metabolism. We have presented a novel prediction method for intestinal absorption and metabolism by utilizing a mini-Ussing chamber using human intestinal tissues and animal intestinal tissues, based on the transport index (TI). The TI value was calculated by taking the change in drug concentrations on the apical side due to precipitation and the total amounts accumulated in the tissue (Tcorr) and transported to the basal side (Xcorr). The drug absorbability in rank order, as well as the fraction of dose absorbed (Fa) in humans, was predicted, and the intestinal metabolism of dogs and rats was also predicted, although it was not quantitative. However, the metabolites formation index (MFI) values, which are included in the TI values, can predict the evaluation of intestinal metabolism and absorption by using ketoconazole. Therefore, the mini-Ussing chamber, equipped with human and animal intestinal tissues, would be an ultimate method to predict intestinal absorption and metabolism simultaneously.

Effects of nirmatrelvir/ritonavir on midazolam and dabigatran pharmacokinetics in healthy participants

AIMS

To evaluate pharmacokinetics (PK) and safety after coadministration of nirmatrelvir/ritonavir or ritonavir alone with midazolam (a cytochrome P450 3A4 substrate) and dabigatran (a P-glycoprotein substrate).

METHODS

PK was studied in 2 phase 1, open-label, fixed-sequence studies in healthy adults. Single oral doses of midazolam 2 mg (n = 12) or dabigatran 75 mg (n = 24) were administered alone and after steady state (i.e. ≥2 days) of nirmatrelvir/ritonavir 300 mg/100 mg and ritonavir 100 mg. Midazolam and dabigatran plasma concentrations and adverse events were analysed for each treatment.

RESULTS

After administration of midazolam with nirmatrelvir/ritonavir (test) or alone (reference), midazolam geometric mean area under the concentration-time curve extrapolated to infinity (AUCinf ) and maximum plasma concentration (Cmax ) increased 14.3-fold and 3.7-fold, respectively. Midazolam coadministered with ritonavir (test) or alone (reference) resulted in 16.5-fold and 3.9-fold increases in midazolam geometric mean AUCinf and Cmax , respectively. After administration of dabigatran with nirmatrelvir/ritonavir (test) or alone (reference), dabigatran geometric mean AUCinf and Cmax increased 1.9-fold and 2.3-fold, respectively. Dabigatran coadministered with ritonavir (test) or alone (reference) resulted in a 1.7-fold increase in dabigatran geometric mean AUCinf and Cmax . Midazolam or dabigatran exposures were generally comparable when coadministered with nirmatrelvir/ritonavir or ritonavir alone, with a slightly higher dabigatran Cmax with nirmatrelvir/ritonavir vs. ritonavir alone. Nirmatrelvir/ritonavir was generally safe when administered with or without midazolam or dabigatran. No serious or severe adverse events were reported.

CONCLUSION

Coadministration of midazolam or dabigatran with nirmatrelvir/ritonavir increased systemic exposure of midazolam or dabigatran. Midazolam exposures were comparable when coadministered with nirmatrelvir/ritonavir or ritonavir alone, suggesting no incremental effect of nirmatrelvir. Dabigatran Cmax was slightly higher when coadministered with nirmatrelvir/ritonavir compared with of ritonavir alone, suggesting a minor incremental effect of nirmatrelvir.

Pharmacokinetic boosting of olaparib: A randomised, cross-over study (PROACTIVE-study)

BACKGROUND

Pharmacokinetic (PK) boosting is the intentional use of a drug-drug interaction to enhance systemic drug exposure. PK boosting of olaparib, a CYP3A-substrate, has the potential to reduce PK variability and financial burden. The aim of this study was to investigate equivalence of a boosted, reduced dose of olaparib compared to the non-boosted standard dose.

METHODS

This cross-over, multicentre trial compared olaparib 300 mg twice daily (BID) with olaparib 100 mg BID boosted with the strong CYP3A-inhibitor cobicistat 150 mg BID. Patients were randomised to the standard therapy followed by the boosted therapy, or vice versa. After seven days of each therapy, dense PK sampling was performed for noncompartmental PK analysis. Equivalence was defined as a 90% Confidence Interval (CI) of the geometric mean ratio (GMR) of the boosted versus standard therapy area under the plasma concentration-time curve (AUC0-12 h) within no-effect boundaries. These boundaries were set at 0.57-1.25, based on previous pharmacokinetic studies with olaparib capsules and tablets.

RESULTS

Of 15 included patients, 12 were eligible for PK analysis. The GMR of the AUC0-12 h was 1.45 (90% CI 1.27-1.65). No grade ≥3 adverse events were reported during the study.

CONCLUSIONS

Boosting a 100 mg BID olaparib dose with cobicistat increases olaparib exposure 1.45-fold, compared to the standard dose of 300 mg BID. Equivalence of the boosted olaparib was thus not established. Boosting remains a promising strategy to reduce the olaparib dose as cobicistat increases olaparib exposure Adequate tolerability of the boosted therapy with higher exposure should be established.

Evaluation of the Cytochrome P450 3A and P-glycoprotein Drug-Drug Interaction Potential of Futibatinib

Futibatinib, a selective, irreversible fibroblast growth factor receptor 1-4 inhibitor, is being investigated for tumors harboring FGFR aberrations and was recently approved for the treatment of FGFR2 fusion/rearrangement-positive intrahepatic cholangiocarcinoma. In vitro studies identified cytochrome P450 (CYP) 3A as the major CYP isoform in futibatinib metabolism and indicated that futibatinib is likely a P-glycoprotein (P-gp) substrate and inhibitor. Futibatinib also showed time-dependent inhibition of CYP3A in vitro. Phase I studies investigated the drug-drug interactions of futibatinib with itraconazole (a dual P-gp and strong CYP3A inhibitor), rifampin (a dual P-gp and strong CYP3A inducer), or midazolam (a sensitive CYP3A substrate) in healthy adult participants. Compared with futibatinib alone, coadministration of futibatinib with itraconazole increased futibatinib mean peak plasma concentration and area under the plasma concentration-time curve by 51% and 41%, respectively, and coadministration of futibatinib with rifampin lowered futibatinib mean peak plasma concentration and area under the plasma concentration-time curve by 53% and 64%, respectively. Coadministration of midazolam with futibatinib had no effect on midazolam pharmacokinetics compared with midazolam administered alone. These findings suggest that concomitant use of dual P-gp and strong CYP3A inhibitors/inducers with futibatinib should be avoided, but futibatinib can be concomitantly administered with other drugs metabolized by CYP3A. Drug-drug interaction studies with P-gp-specific substrates and inhibitors are planned.

Physiologically based pharmacokinetic modeling to assess the drug-drug interactions of anaprazole with clarithromycin and amoxicillin in patients undergoing eradication therapy of H. pylori infection

OBJECTIVE

This study aimed to assess the pharmacokinetic (PK) interactions of anaprazole, clarithromycin, and amoxicillin using physiologically based pharmacokinetic (PBPK) models.

METHODS

The PBPK models for anaprazole, clarithromycin, and amoxicillin were constructed using the GastroPlus™ software (Version 9.7) based on the physicochemical data and PK parameters obtained from literature, then were optimized and validated in healthy subjects to predict the plasma concentration-time profiles of these three drugs and assess the predictive performance of each model. According to the analysis of the properties of each drug, the developed and validated models were applied to evaluate potential drug-drug interactions (DDIs) of anaprazole, clarithromycin, and amoxicillin.

RESULTS

The developed PBPK models properly described the pharmacokinetics of anaprazole, clarithromycin, and amoxicillin well, and all predicted PK parameters (Cmax,ss, AUC0-τ,ss) ratios were within 2.0-fold of the observed values. Furthermore, the application of these models to predict the anaprazole-clarithromycin and anaprazole-amoxicillin DDIs demonstrates their good performance, with the predicted DDI Cmax,ss ratios and DDI AUC0-τ,ss ratios within 1.25-fold of the observed values, and all predicted DDI Cmax,ss, and AUC0-τ,ss ratios within 2.0-fold. The simulated results show no need to adjust the dosage when co-administered with anaprazole in patients undergoing eradication therapy of H. pylori infection since the dose remained in the therapeutic range.

CONCLUSION

The whole-body PBPK models of anaprazole, clarithromycin, and amoxicillin were built and qualified, which can predict DDIs that are mediated by gastric pH change and inhibition of metabolic enzymes, providing a mechanistic understanding of the DDIs observed in the clinic of clarithromycin, amoxicillin with anaprazole.

Pharmacokinetics of the Akt Serine/Threonine Protein Kinase Inhibitor, Capivasertib, Administered to Healthy Volunteers in the Presence and Absence of the CYP3A4 Inhibitor Itraconazole

Capivasertib is a potent, selective inhibitor of all 3 Akt isoforms (Akt1/2/3), and it is currently being tested in Phase III trials for the treatment of prostate and breast cancer. To investigate the effect of a cytochrome P450 3A4 (CYP3A4) inhibitor on the pharmacokinetics of capivasertib, a Phase I drug-drug interaction study of capivasertib and itraconazole was conducted in 11 healthy volunteers (median age, 54 years). The 8-day study had 3 stages: Participants received a single dose of capivasertib 80 mg in Stage 1, 4 doses of itraconazole 200 mg over 3 days in Stage 2, and a final dose of capivasertib 80 mg coadministered with itraconazole 200 mg in Stage 3. Capivasertib pharmacokinetics were examined in Stages 1 and 3. Itraconazole coadministration increased the maximum plasma concentration of capivasertib and total capivasertib exposure (area under the concentration-time curve from time of administration to infinity) by 1.70-fold (90% confidence interval, 1.56-1.86) and 1.95-fold (90% confidence interval, 1.82-2.10), respectively.

Effects of itraconazole and carbamazepine on the pharmacokinetics of nirmatrelvir/ritonavir in healthy adults

AIMS

The objective of this study was to evaluate the effects of a strong cytochrome P450 family (CYP) 3A4 inhibitor (itraconazole) and inducer (carbamazepine) on the pharmacokinetics and safety of nirmatrelvir/ritonavir.

METHODS

Pharmacokinetics were measured in two phase 1, open-label, fixed-sequence studies in healthy adults. During Period 1, oral nirmatrelvir/ritonavir 300 mg/100 mg twice daily was administered alone; during Period 2, it was administered with itraconazole or carbamazepine. Nirmatrelvir/ritonavir was administered as repeated doses or one dose in the itraconazole and carbamazepine studies, respectively. Nirmatrelvir and ritonavir plasma concentrations and adverse event (AE) rates in both periods were analysed.

RESULTS

Each study included 12 participants. Following administration of nirmatrelvir/ritonavir with itraconazole (Test) or alone (Reference), test/reference ratios of the adjusted geometric means (90% CIs) for nirmatrelvir AUCtau and Cmax were 138.82% (129.25%, 149.11%) and 118.57% (112.50%, 124.97%), respectively. After administration of nirmatrelvir/ritonavir with carbamazepine (Test) or alone (Reference), test/reference ratios (90% CIs) of the adjusted geometric means for nirmatrelvir AUCinf and Cmax were 44.50% (33.77%, 58.65%) and 56.82% (47.04%, 68.62%), respectively. Nirmatrelvir/ritonavir was generally safe when administered with or without itraconazole or carbamazepine. No serious or severe AEs were reported.

CONCLUSIONS

Coadministration of a strong CYP3A4 inhibitor with a strong CYP3A inhibitor used for pharmacokinetic enhancement (i.e., ritonavir) resulted in small increases in plasma nirmatrelvir exposure, whereas coadministration of a strong inducer substantially decreased systemic nirmatrelvir and ritonavir exposures suggesting a contraindication in the label with CYP3A4 strong inducers. Administration of nirmatrelvir/ritonavir alone or with itraconazole or carbamazepine was generally safe.

Assessment of Drug-Drug Interaction Risk Between Intravenous Fentanyl and the Glecaprevir/Pibrentasvir Combination Regimen in Hepatitis C Patients Using Physiologically Based Pharmacokinetic Modeling and Simulations

INTRODUCTION

An unsafe injection practice is one of the major contributors to new hepatitis C virus (HCV) infections; thus, people who inject drugs are a key population to prioritize to achieve HCV elimination. The introduction of highly effective and well-tolerated pangenotypic direct-acting antivirals, including glecaprevir/pibrentasvir (GLE/PIB), has revolutionized the HCV treatment landscape. Glecaprevir is a weak cytochrome P450 3A4 (CYP3A4) inhibitor, so there is the potential for drug-drug interactions (DDIs) with some opioids metabolized by CYP3A4, such as fentanyl. This study estimated the impact of GLE/PIB on the pharmacokinetics of intravenous fentanyl by building a physiologically based pharmacokinetic (PBPK) model.

METHODS

A PBPK model was developed for intravenous fentanyl by incorporating published information on fentanyl metabolism, distribution, and elimination in healthy individuals. Three clinical DDI studies were used to verify DDIs within the fentanyl PBPK model. This model was integrated with a previously developed GLE/PIB PBPK model. After model validation, DDI simulations were conducted by coadministering GLE 300 mg + PIB 120 mg with a single dose of intravenous fentanyl (0.5 µg/kg).

RESULTS

The predicted maximum plasma concentration ratio between GLE/PIB + fentanyl and fentanyl alone was 1.00, and the predicted area under the curve ratio was 1.04, suggesting an increase of only 4% in fentanyl exposure.

CONCLUSION

The administration of a therapeutic dose of GLE/PIB has very little effect on the pharmacokinetics of intravenous fentanyl. This negligible increase would not be expected to increase the risk of fentanyl overdose beyond the inherent risks related to the amount and purity of the fentanyl received during recreational use.

The premise of capsid assembly modulators towards eliminating HBV persistence

INTRODUCTION

The burden of chronic hepatitis B virus (HBV) results in almost a million deaths per year. The most common treatment for chronic hepatitis B infection is long-term nucleoside analogs (NUC) or one-year interferon-alpha (pegylated or non-pegylated) therapy before or after NUC therapy. Unfortunately, these therapies rarely result in HBV functional cure because they do not eradicate HBV from the nucleus of the hepatocytes, where the covalently closed circular DNA (cccDNA) is formed and/or where the integrated HBV DNA persists in the host genome. Hence, the search continues for novel antiviral therapies that target different steps of the HBV replication cycle to cure chronically infected HBV individuals and eliminate HBV from the liver reservoirs.

AREAS COVERED

The authors focus on capsid assembly modulators (CAMs). These molecules are unique because they impact not only one but several steps of HBV viral replication, including capsid assembly, capsid trafficking into the nucleus, reverse transcription, pre-genomic RNA (pgRNA), and polymerase protein co-packaging.

EXPERT OPINION

Mono- or combination therapy, including CAMs with other HBV drugs, may potentially eliminate hepatitis B infections. Nevertheless, more data on their potential effect on HBV elimination is needed, especially when used daily for 6-12 months.

Individuals at risk for severe COVID-19 in whom ritonavir-containing therapies are contraindicated or may lead to interactions with concomitant medications: a retrospective analysis of German health insurance claims data

Background

Nirmatrelvir/ritonavir is authorized for the treatment of COVID-19 but has several contraindications and potential drug-drug interactions (pDDIs) due to ritonavir-induced irreversible inhibition of cytochrome P450 3A4. We aimed to assess the prevalence of individuals with one or more risk factors for severe COVID-19 along with contraindications and pDDIs due to ritonavir-containing COVID-19 therapy.

Methods

Retrospective observational study of individuals with one or more risk factors according to Robert Koch Institute criteria for severe COVID-19 according to German statutory health insurance (SHI) claims data from the pre-pandemic years 2018-2019 based on the German Analysis Database for Evaluation and Health Services Research. Prevalence was extrapolated to the entire SHI population using age-adjusted and sex-adjusted multiplication factors.

Results

Nearly 2.5 million fully insured adults, representing 61 million people in the German SHI population, were included in the analysis. In 2019, prevalence of individuals that would have been at risk of severe COVID-19 was 56.4%. Amongst them, the prevalence of contraindications for treatment with ritonavir-containing COVID-19 therapy was approximately 2% according to presence of somatic comorbidities (severe liver or kidney disease). Prevalence of intake of medicines contraindicated for their potential interactions with ritonavir-containing COVID-19 therapy was 16.5% according to Summary of Product Characteristics and 31.8% according to previously published data. The prevalence of individuals at risk of pDDIs during ritonavir-containing COVID-19 therapy without adjustment of their concomitant therapy was 56.0% and 44.3%, respectively. Prevalence data for 2018 were similar.

Conclusion

Administering ritonavir-containing COVID-19 therapy can be challenging as thorough medical record review and close monitoring are required. In some cases, ritonavir-containing treatment may not be appropriate due to contraindications, risk of pDDIs, or both. For those individuals, an alternative ritonavir-free treatment should be considered.

The inhibitory and inducing effects of ritonavir on hepatic and intestinal CYP3A and other drug-handling proteins

Ritonavir, originally developed as HIV protease inhibitor, is widely used as a booster in several HIV pharmacotherapy regimens and more recently in Covid-19 treatment (e.g., Paxlovid). Its boosting capacity is due to the highly potent irreversible inhibition of the cytochrome P450 (CYP) 3 A enzyme, thereby enhancing the plasma exposure to coadministered drugs metabolized by CYP3A. Typically used booster doses of ritonavir are 100-200 mg once or twice daily. This review aims to address several aspects of this booster drug, including the possibility to use lower ritonavir doses, 20 mg for instance, resulting in partial CYP3A inactivation in patients. If complete CYP3A inhibition is not needed, lower ritonavir doses could be used, thereby reducing unwanted side effects. In this context, there are contradictory reports on the actual recovery time of CYP3A activity after ritonavir discontinuation, but probably this will take at least one day. In addition to ritonavir's CYP3A inhibitory effect, it can also induce and/or inhibit other CYP enzymes and drug transporters, albeit to a lesser extent. Although ritonavir thus exhibits gene induction capacities, with respect to CYP3A activity the inhibition capacity clearly predominates. Another potent CYP3A inhibitor, the ritonavir analog cobicistat, has been reported to lack the ability to induce enzyme and transporter genes. This might result in a more favorable drug-drug interaction profile compared to ritonavir, although the actual benefit appears to be limited. Indeed, ritonavir is still the clinically most used pharmacokinetic enhancer, indicating that its side effects are well manageable, even in chronic administration regimens.

Drug-drug interactions that alter the exposure of glucuronidated drugs: Scope, UDP-glucuronosyltransferase (UGT) enzyme selectivity, mechanisms (inhibition and induction), and clinical significance

Drug-drug interactions (DDIs) arising from the perturbation of drug metabolising enzyme activities represent both a clinical problem and a potential economic loss for the pharmaceutical industry. DDIs involving glucuronidated drugs have historically attracted little attention and there is a perception that interactions are of minor clinical relevance. This review critically examines the scope and aetiology of DDIs that result in altered exposure of glucuronidated drugs. Interaction mechanisms, namely inhibition and induction of UDP-glucuronosyltransferase (UGT) enzymes and the potential interplay with drug transporters, are reviewed in detail, as is the clinical significance of known DDIs. Altered victim drug exposure arising from modulation of UGT enzyme activities is relatively common and, notably, the incidence and importance of UGT induction as a DDI mechanism is greater than generally believed. Numerous DDIs are clinically relevant, resulting in either loss of efficacy or an increased risk of adverse effects, necessitating dose individualisation. Several generalisations relating to the likelihood of DDIs can be drawn from the known substrate and inhibitor selectivities of UGT enzymes, highlighting the importance of comprehensive reaction phenotyping studies at an early stage of drug development. Further, rigorous assessment of the DDI liability of new chemical entities that undergo glucuronidation to a significant extent has been recommended recently by regulatory guidance. Although evidence-based approaches exist for the in vitro characterisation of UGT enzyme inhibition and induction, the availability of drugs considered appropriate for use as 'probe' substrates in clinical DDI studies is limited and this should be research priority.

Pharmacokinetic Interaction of Chiglitazar with CYP3A4 Inducer or Inhibitor: An Open-Label, Sequential Crossover, Self-Control, 3-Period Study in Healthy Chinese Volunteers

Chiglitazar, a pan agonist of non-thiazolidinedione peroxisome proliferator-activated receptor, has the potential to regulate blood sugar, improve lipid metabolism, and reduce cardiovascular complications. This study aimed to examine the effect of cytochrome P450 (CYP) 3A4 inhibitors/inducers on the in vivo metabolism of chiglitazar and provide a reference for the clinical combination use of chiglitazar. A single-center, open-label, sequential crossover, and self-control study was carried out in 24 healthy subjects to determine the pharmacokinetics of chiglitazar dosed with and without CYP3A4 inhibitors and inducers. The findings showed that the CYP3A4 inhibitor itraconazole had no apparent pharmacokinetic drug interaction with chiglitazar, whereas rifampicin did. When combined with rifampicin after continuous dosing, chiglitazar exposure was not theoretically reduced but increased compared to a single dose of chiglitazar. The possible explanation may be the transporters of bile salt export pump, but this needs to be confirmed. The safety of chiglitazar in single or combination doses was well tolerated. The findings of this study provide a basis for clinical combinations of chiglitazar with CYP3A4 inhibitors or inducers.

Drug-Drug Interaction Studies to Evaluate the Effect of Inhibition of UGT1A1 and CYP3A4 and Induction of CYP3A4 on the Pharmacokinetics of Tropifexor in Healthy Subjects

Tropifexor, a farnesoid X receptor agonist, is currently under clinical development for the treatment of nonalcoholic steatohepatitis. Tropifexor undergoes glucuronidation by uridine 5'-diphosphoglucuronosyltransferase (UGT) 1A1 and oxidation by cytochrome P450 (CYP) 3A4, as reported in in vitro studies. Here, we report the results from 2 drug-drug interaction studies. Study 1 enrolled 20 healthy subjects to investigate the effect of the UGT1A1 inhibitor atazanavir (ATZ) on tropifexor pharmacokinetics (PK). Study 2 had 2 cohorts with 16 healthy subjects each to investigate the effect of the strong CYP3A4 inhibitor itraconazole and strong CYP3A4 inducer rifampin on the PK of tropifexor. Coadministration of ATZ reduced the maximum plasma concentration (C_max ) of tropifexor by 40%; however, it did not lead to increased exposure of tropifexor (both area under the plasma concentration-time curve [AUC] from time 0 to the last quantifiable concentration [AUC_last ] and AUC from time 0 to infinity [AUC_inf ] reduced by only 10%), suggesting minor relevance of the UGT1A1 pathway for clearance of tropifexor and no expected drug-drug interactions based on UGT1A1 inhibition. Inhibition of CYP3A4 by itraconazole increased the C_max of tropifexor by only 9% and exposure (both AUC_last and AUC_inf ) by 47%, suggesting a weak effect of strong CYP3A4 inhibitors on tropifexor PK. Inducing CYP3A4 with rifampin decreased C_max (55%) and AUC (AUC_last by 79% and AUC_inf by 77%). Coadministration of tropifexor with either ATZ, itraconazole, or rifampin was well tolerated.

Effects of CYP3A Inhibition, CYP3A Induction, and Gastric Acid Reduction on the Pharmacokinetics of Ripretinib, a Switch Control KIT Tyrosine Kinase Inhibitor

Ripretinib is a switch control KIT kinase inhibitor approved for treatment of adults with advanced gastrointestinal stromal tumors who received prior treatment with 3 or more kinase inhibitors, including imatinib. Ripretinib and its active metabolite (DP-5439) are cleared mainly via cytochrome P450 enzyme 3A4/5 (CYP3A4/5), and ripretinib solubility is pH-dependent, thus the drug-drug interaction potentials of ripretinib with itraconazole (strong CYP3A inhibitor), rifampin (strong CYP3A inducer), and pantoprazole (proton pump inhibitor) were each evaluated in open-label, fixed-sequence study designs. Overall, 20 participants received ripretinib 50 mg alone and with itraconazole 200 mg once daily, 24 participants received ripretinib 100 mg alone and with rifampin 600 mg once daily, and 25 participants received ripretinib 50 mg alone and with pantoprazole 40 mg once daily. Ripretinib exposure increased with concomitant itraconazole, with geometric least-squares (LS) mean ratios of ripretinib area under the concentration-time curve from 0 to ∞ (AUC_0-∞ ) and maximum observed concentration (C_max ) of 199% and 136%. Ripretinib exposure decreased with concomitant rifampin: geometric LS mean ratios for ripretinib AUC_0-∞ and C_max were 39% and 82%. Pantoprazole coadministration had no effect on ripretinib pharmacokinetics. No unexpected safety signals occurred. No dose adjustment is required for ripretinib coadministered with gastric acid reducers and strong CYP3A inhibitors; patients also receiving strong CYP3A inhibitors should be monitored more frequently for adverse reactions. Concomitant ripretinib use with strong CYP3A inducers should be avoided. Prescribers should refer to approved labeling for specific dose recommendations with concomitant use of strong and moderate CYP3A inducers.

The Mechanism-Based Inactivation of CYP3A4 by Ritonavir: What Mechanism?

Ritonavir is the most potent cytochrome P450 (CYP) 3A4 inhibitor in clinical use and is often applied as a booster for drugs with low oral bioavailability due to CYP3A4-mediated biotransformation, as in the treatment of HIV (e.g., lopinavir/ritonavir) and more recently COVID-19 (Paxlovid or nirmatrelvir/ritonavir). Despite its clinical importance, the exact mechanism of ritonavir-mediated CYP3A4 inactivation is still not fully understood. Nonetheless, ritonavir is clearly a potent mechanism-based inactivator, which irreversibly blocks CYP3A4. Here, we discuss four fundamentally different mechanisms proposed for this irreversible inactivation/inhibition, namely the (I) formation of a metabolic-intermediate complex (MIC), tightly coordinating to the heme group; (II) strong ligation of unmodified ritonavir to the heme iron; (III) heme destruction; and (IV) covalent attachment of a reactive ritonavir intermediate to the CYP3A4 apoprotein. Ritonavir further appears to inactivate CYP3A4 and CYP3A5 with similar potency, which is important since ritonavir is applied in patients of all ethnicities. Although it is currently not possible to conclude what the primary mechanism of action in vivo is, it is unlikely that any of the proposed mechanisms are fundamentally wrong. We, therefore, propose that ritonavir markedly inactivates CYP3A through a mixed set of mechanisms. This functional redundancy may well contribute to its overall inhibitory efficacy.

Roles of cytochrome P450 enzymes in pharmacology and toxicology: Past, present, and future

The development of the cytochrome P450 (P450) field has been remarkable in the areas of pharmacology and toxicology, particularly in drug development. Today it is possible to use the knowledge base and relatively straightforward assays to make intelligent predictions about drug disposition prior to human dosing. Much is known about the structures, regulation, chemistry of catalysis, and the substrate and inhibitor specificity of human P450s. Many aspects of drug-drug interactions and side effects can be understood in terms of P450s. This knowledge has also been useful in pharmacy practice, as well as in the pharmaceutical industry and medical practice. However, there are still basic and practical questions to address regarding P450s and their roles in pharmacology and toxicology. Another aspect is the discovery of drugs that inhibit P450 to treat diseases.

Foerster K, Terstegen T, Vogt C, Said A, Schulz M, E. Haefeli W. Oral Drugs Against COVID-19

BACKGROUND

Five-day oral therapies against early COVID-19 infection have recently been conditionally approved in Europe. In the drug combination nirmatrelvir + ritonavir (nirmatrelvir/r), the active agent, nirmatrelvir, is made bioavailable in clinically adequate amounts by the additional administration of a potent inhibitor of its first-pass metabolism by way of cytochrome P450 [CYP] 3A in the gut and liver. In view of the central role of CYP3A in the clearance of many different kinds of drugs, and the fact that many patients with COVID-19 are taking multiple drugs to treat other conditions, it is important to assess the potential for drug interactions when nirmatrelvir/r is given, and to minimize the risks associated with such interactions.

METHODS

We defined the interaction profile of ritonavir on the basis of information derived from two databases (Medline, GoogleScholar), three standard electronic texts on drug interactions, and manufacturer-supplied drug information. We compiled a list of drugs and their potentially relevant interactions, developed a risk min - imization algorithm, and applied it to the substances in question. We also compiled a list of commonly prescribed drugs for which there is no risk of interaction with nirmatrelvir/r.

RESULTS

Out of 190 drugs and drug combinations, 57 do not need any special measures when given in combination with brief, low-dose ritonavir treatment, while 15 require dose modification or a therapeutic alternative, 8 can be temporarily discontinued, 9 contraindicate ritonavir use, and 102 should preferably be combined with a different treatment.

CONCLUSION

We have proposed measures that are simple to carry out for the main types of drug that can interact with ritonavir. These measures can be implemented under quarantine conditions before starting a 5-day treatment with nirmatrelvir/r.

A Phase 1, Open-Label Study to Evaluate the Effect of Food and Concomitant Itraconazole Administration on the Pharmacokinetics of AMG 986 in Healthy Subjects

This phase 1, open-label study evaluated the effect of food and administration of the cytochrome P450 3A4 and P-glycoprotein inhibitor itraconazole (ITZ) on the pharmacokinetics of AMG 986. In cohort 1, 12 healthy subjects received a single oral dose of AMG 986 200 mg ± food on days 1 and 10. In cohort 2, 15 healthy subjects received oral ITZ 200 mg once daily on days 8 to 15 and a single oral dose of AMG 986 10 mg on days 1 and 11. The geometric least squares mean ratios of fed/fasted for AMG 986 maximum observed concentration (C_max ) and area under the plasma concentration-time curve from time 0 to infinity (AUC_inf ) were 0.76 (90%CI, 0.61-0.95) and 1.07 (90%CI, 0.94-1.22), respectively. The geometric least squares mean ratios of AMG 986 10 mg plus ITZ 200 mg/AMG 986 10 mg alone for AMG 986 C_max and AUC_inf were 1.36 (90%CI, 1.25-1.48) and 5.13 (90%CI, 4.71-5.59), respectively. Overall, 3 subjects experienced mild treatment-related adverse events; there were no serious or fatal adverse events. In conclusion, food had no apparent effect on the exposure of AMG 986 200 mg; therefore, food restrictions are not required. Potent cytochrome P450 3A4 and/or P-glycoprotein inhibitors may warrant AMG 986 dose reduction and should be coadministered with caution in patients with heart failure treated with AMG 986.

Using nirmatrelvir/ritonavir in patients with epilepsy: an update from the Israeli ILAE Chapter

Presented herein are recommendations for use of nirmatrelvir/ritonavir in patients with epilepsy, as issued by the Steering Committee of the Israeli chapter of the International League Against Epilepsy. The recommendations suggest that patients on moderate‐to‐strong enzyme‐inducing antiseizure medications (ASMs) and everolimus should not be treated with nirmatrelvir/ritonavir; rectal diazepam may be used as an alternative to buccal midazolam; doses of ASMs that are cytochrome P450 (CYP3A4) substrates might be adjusted; and patients treated with combinations of nirmatrelvir/ritonavir and ASMs that are CYP3A4 substrates or lamotrigine should be monitored for drug efficacy and adverse drug reactions.

A Phase 1 Pharmacokinetic Drug Interaction Study of Belumosudil Coadministered With CYP3A4 Inhibitors and Inducers and Proton Pump Inhibitors

Belumosudil is a selective Rho-associated protein kinase 2 inhibitor. Inhibition of Rho-associated protein kinase 2 has emerged as a promising treatment for chronic graft-versus-host disease by restoring immune homeostasis and reducing fibrosis. In vitro assessments have suggested that metabolism of belumosudil is primarily dependent on cytochrome P450 (CYP) 3A4 activity and that the solubility of belumosudil is pH dependent. As such, this 2-part clinical drug-drug interaction study was conducted to assess the effect of itraconazole (a strong CYP3A4 inhibitor), rifampicin (a strong CYP3A4 inducer), rabeprazole, and omeprazole (both proton pump inhibitors) on the pharmacokinetics of belumosudil. No clinically relevant change in belumosudil exposure was observed following a 200-mg single oral dose of belumosudil with itraconazole; however, exposure of main metabolite, KD025m2, was decreased. Consistent with the proposed metabolic pathway of belumosudil, the strong CYP3A4 inducer rifampicin significantly decreased exposure of belumosudil and KD025m2 and increased KD025m1 exposure. When a 200-mg single oral dose of belumosudil was coadministered with both rabeprazole and omeprazole, parent and metabolite exposures were largely reduced, suggesting that belumosudil dosage should be increased when given with PPIs. Administration of belumosudil with and without perpetrator drugs was safe, and no notable adverse events were reported.

Use of Modeling and Simulation to Predict the Influence of Triazole Antifungal Agents on the Pharmacokinetics of Crizotinib

Crizotinib is used for the treatment of c-ros oncogene 1-positive advanced non-small-cell lung cancer. Triazole antifungal agents are widely used for invasive fungal infections in clinical practice. To predict the potential influence of different triazoles (voriconazole, fluconazole, and itraconazole) on the pharmacokinetics of crizotinib by modeling and simulation the physiologically based pharmacokinetic models were established and validated in virtual cancer subjects through Simcyp software based on the essential physicochemical properties and pharmacokinetic data collected. The validated physiologically based pharmacokinetic models were applied to predict the drug-drug interactions between crizotinib and different triazoles (voriconazole, fluconazole, or itraconazole) in patients with cancer. Crizotinib and triazole antifungal agents were administered orally. The predicted plasma concentration vs time profiles of crizotinib, voriconazole, fluconazole, and itraconazole showed good agreement with observed, respectively. The geometric mean area under the plasma concentration-time curve (AUC) of crizotinib was increased by 84%, 58%, and 79% when coadministered with voriconazole, fluconazole, or itraconazole at multiple doses, respectively. The drug-drug interaction results showed increased pharmacokinetic exposure (maximum plasma concentration and area under the plasma concentration-time curve) of crizotinib when coadministrated with different triazoles (voriconazole > itraconazole > fluconazole). Among the 3 triazoles, voriconazole exhibited the most significant influence on the pharmacokinetic exposure of crizotinib. In clinic, adverse drug reactions and toxicity related to crizotinib should be carefully monitored, and therapeutic drug monitoring for crizotinib is recommended to guide dosing and optimize treatment when coadministered with voriconazole, fluconazole, or itraconazole.

Evaluation of the Pharmacokinetics of Felcisetrag (TAK-954), a 5-HT4 Receptor Agonist, in the Presence and Absence of Itraconazole, a Potent CYP3A4 Inhibitor

The 5-hydroxytryptamine type-4 receptor agonist felcisetrag (TAK-954) is being investigated for improving gastrointestinal motility in postoperative gastrointestinal dysfunction. Polypharmacy often occurs in this setting, and as in vitro data indicate, felcisetrag is primarily metabolized by cytochrome P450 (CYP) 3A4, its CYP3A4-mediated drug-drug interaction potential requires consideration. This phase 1, fixed-sequence, open-label, crossover trial (ClinicalTrials.gov identifier NCT03173170) investigated the effect of itraconazole, a potent CYP3A4 inhibitor, on felcisetrag pharmacokinetics in healthy adults. Over 2 study periods (period 1, 6 days; period 2, 9 days), participants received a single felcisetrag 0.2-mg intravenous dose (day 1, period 1; and day 4, period 2), and once-daily oral itraconazole 200-mg doses (days 1-8, period 2). For felcisetrag alone, felcisetrag total systemic exposure was lower than with itraconazole coadministration. The geometric mean ratio for area under the plasma concentration-time curve from time 0 to infinity of felcisetrag plus itraconazole: felcisetrag alone was 1.49 (90% confidence interval, 1.39-1.60). Peak exposure was similar between regimens (geometric mean ratio, 1.06; 90% confidence interval, 0.96-1.18), and both treatments were well tolerated. These data suggest limited CYP3A4-mediated drug-drug interaction inhibition for felcisetrag.

The role of pharmacogenetics in Efficacy and safety of protease inhibitor based therapy in human immunodeficiency virus type (HIV) infection

Antiretroviral therapy has markedly reduced morbidity and mortality for persons living with human immunodeficiency virus (HIV). HIV can now be classified as a chronic disease; until a cure is found, patients are likely to require life-long therapy. However, despite these undoubted advances, there are many issues that need to be resolved, including the problems associated with long-term efficacy and toxicity. Moreover, pharmacotherapy of patients infected with HIV is challenging because a great number of comorbidities increase polypharmacy and the risk for drug-drug interactions. There is considerable interindividual variability in patient outcomes in terms of drug disposition, drug efficacy and adverse events. The basis of these differences is multifactorial, but host genetics are believed to play a significant part. HIV-infected population consists of ethnically diverse individuals on complex and potentially toxic antiretroviral regimens on a long-term basis. These individuals would benefit greatly from predictive tests that identify the most durable regimens. Pharmacogenetics holds that promise. Thus, detailed understanding of the metabolism and transport of antiretrovirals and the influence of genetics on these pathways is important. To this end, this review provides an up-to-date overview of the metabolism of antiHIV therapeutics of the protease inhibitors Lopinavir and Ritonavir and the impact of genetic variation in drug metabolism and transport on the treatment of HIV.

Optimized pharmacological control over the AAV-Gene-Switch vector for regulable gene therapy

Gene therapy in its current design is an irreversible process. It cannot be stopped in case of unwanted side effects, nor can expression levels of therapeutics be adjusted to individual patient’s needs. Thus, the Gene-Switch (GS) system for pharmacologically regulable neurotrophic factor expression was established for treatment of parkinsonian patients. Mifepristone, the synthetic steroid used to control transgene expression of the GS vector, is an approved clinical drug. However, pharmacokinetics and -dynamics of mifepristone vary considerably between different experimental animal species and depend on age and gender. In humans, but not in any other species, mifepristone binds to a high-affinity plasma carrier protein. We now demonstrate that the formulation of mifepristone can have robust impact on its ability to activate the GS system. Furthermore, we show that a pharmacological booster, ritonavir (Rtv), robustly enhances the pharmacological effect of mifepristone, and allows it to overcome gender- and species-specific pharmacokinetic and -dynamic issues. Most importantly, we demonstrate that the GS vector can be efficiently controlled by mifepristone in the presence of its human plasma carrier protein, α1-acid glycoprotein, in a “humanized” rat model. Thus, we have substantially improved the applicability of the GS vector toward therapeutic use in patients.

An automated cocktail method for in vitro assessment of direct and time-dependent inhibition of nine major cytochrome P450 enzymes - application to establishing CYP2C8 inhibitor selectivity

We developed an in vitro high-throughput cocktail assay with nine major drug-metabolizing CYP enzymes, optimized for screening of time-dependent inhibition. The method was applied to determine the selectivity of the time-dependent CYP2C8 inhibitors gemfibrozil 1-O-β-glucuronide and clopidogrel acyl-β-D-glucuronide. In vitro incubations with CYP selective probe substrates and pooled human liver microsomes were conducted in 96-well plates with automated liquid handler techniques and metabolite concentrations were measured with quantitative UHPLC-MS/MS analysis. After determination of inter-substrate interactions and K_m values for each reaction, probe substrates were divided into cocktails I (tacrine/CYP1A2, bupropion/CYP2B6, amodiaquine/CYP2C8, tolbutamide/CYP2C9 and midazolam/CYP3A4/5) and II (coumarin/CYP2A6, S-mephenytoin/CYP2C19, dextromethorphan/CYP2D6 and astemizole/CYP2J2). Time-dependent inhibitors (furafylline/CYP1A2, selegiline/CYP2A6, clopidogrel/CYP2B6, gemfibrozil 1-O-β-glucuronide/CYP2C8, tienilic acid/CYP2C9, ticlopidine/CYP2C19, paroxetine/CYP2D6 and ritonavir/CYP3A) and direct inhibitor (terfenadine/CYP2J2) showed similar inhibition with single substrate and cocktail methods. Established time-dependent inhibitors caused IC₅₀ fold shifts ranging from 2.2 to 30 with the cocktail method. Under time-dependent inhibition conditions, gemfibrozil 1-O-β-glucuronide was a strong (>90% inhibition) and selective (<< 20% inhibition of other CYPs) inhibitor of CYP2C8 at concentrations ranging from 60 to 300 μM, while the selectivity of clopidogrel acyl-β-D-glucuronide was limited at concentrations above its IC₈₀ for CYP2C8. The time-dependent IC₅₀ values of these glucuronides for CYP2C8 were 8.1 and 38 µM, respectively. In conclusion, a reliable cocktail method including the nine most important drug-metabolizing CYP enzymes was developed, optimized and validated for detecting time-dependent inhibition. Moreover, gemfibrozil 1-O-β-glucuronide was established as a selective inhibitor of CYP2C8 for use as a diagnostic inhibitor in in vitro studies.

Effects of Itraconazole and Rifampin on the Pharmacokinetics of Mobocertinib (TAK-788), an Oral Epidermal Growth Factor Receptor Inhibitor, in Healthy Volunteers

Mobocertinib (TAK‐788) is an investigational oral tyrosine kinase inhibitor targeting epidermal growth factor receptor and human epidermal growth factor 2. A phase 1 open‐label, 2‐period, fixed‐sequence, 2‐part study (NCT03928327) characterized effects of a strong CYP3A4 inhibitor (itraconazole) and inducer (rifampin) on the pharmacokinetics (PK) of mobocertinib and its active metabolites, AP32960 and AP32914. Healthy volunteers (n = 12 per part) received a single dose of mobocertinib alone (20 mg, part 1; 160 mg, part 2) and with multiple doses of itraconazole 200 mg once daily (part 1) or rifampin 600 mg once daily (part 2). Coadministration of itraconazole with mobocertinib increased the combined molar area under the plasma concentration‐time curve from time 0 to infinity (AUC_0‐∞) of mobocertinib, AP32960, and AP32914 by 527% (geometric least‐squares mean [LSM] ratio, 6.27; 90% confidence interval [CI], 5.20‐7.56). Coadministration of rifampin with mobocertinib decreased the combined molar AUC_0‐∞ of mobocertinib, AP32960, and AP32914 by 95% (geometric LSM ratio, 0.05; 90%CI, 0.04‐0.07). Based on these results, the strong CYP3A inhibitor itraconazole and inducer rifampin significantly influenced the PK of mobocertinib and its active metabolites. Coadministration of mobocertinib with moderate and strong CYP3A inhibitors or inducers is not recommended in ongoing clinical trials.

Evaluation of Drug-Drug Interaction Liability for Buprenorphine Extended-Release Monthly Injection Administered by Subcutaneous Route

Buprenorphine extended‐release (BUP‐XR) formulation is a once‐monthly subcutaneous injection for the treatment of opioid use disorder (OUD). Buprenorphine undergoes extensive cytochrome P450 (CYP) 3A4 metabolism, leading to potential drug‐drug interactions (DDIs) as reported for sublingual buprenorphine. Sublingual buprenorphine is subject to first‐pass extraction, as a significant proportion of the dose is swallowed. Because subcutaneous administration avoids first‐pass extraction, the DDI with CYP3A4 inhibitors is expected to be less than the 2‐fold increase reported for the sublingual route. The objective of this analysis was to predict the magnitude of DDI following coadministration of BUP‐XR with a strong CYP3A4 inhibitor or inducer using physiologically based pharmacokinetic (PBPK) modeling. Models were developed and verified by comparing predicted and observed data for buprenorphine following intravenous and sublingual dosing. Comparison of predicted and observed pharmacokinetic (PK) profiles and PK parameters demonstrated acceptable predictive performance of the models (within 1.5‐fold). Buprenorphine plasma concentrations following administration of a single dose of BUP‐XR (300 mg) were simulated using a series of intravenous infusions. Daily coadministration of strong CYP3A4 inhibitors with BUP‐XR predicted mild increases in buprenorphine exposures (AUC, 33%‐44%; C_max, 17‐28%). Daily coadministration of a strong CYP3A4 inducer was also associated with mild decreases in buprenorphine AUC (28%) and C_max (22%). In addition, the model predicted minimal increases in buprenorphine AUC (8%‐11%) under clinical conditions of 2 weeks’ treatment with CYP3A4 inhibitors administered after initiation of BUP‐XR. In conclusion, the PBPK predictions indicate that coadministration of BUP‐XR with strong CYP3A4 inhibitors or inducers would not result in clinically meaningful interactions.

Pharmacoenhancement of Low Crizotinib Plasma Concentrations in Patients with Anaplastic Lymphoma Kinase-Positive Non-Small Cell Lung Cancer using the CYP3A Inhibitor Cobicistat

The inhibitor of anaplastic lymphoma kinase (ALK) crizotinib significantly increases survival in patients with ALK-positive non-small cell lung cancer (NSCLC). When evaluating crizotinib pharmacokinetics (PKs) in patients taking the standard flat oral dose of 250 mg b.i.d., interindividual PK variability is substantial and patient survival is lower in the quartile with the lowest steady-state trough plasma concentrations (Cmin,ss ), suggesting that concentrations should be monitored and doses individualized. We investigated whether the CYP3A inhibitor cobicistat increases Cmin,ss of the CYP3A substrate crizotinib in patients with low exposure. Patients with ALK-positive NSCLC of our outpatient clinic treated with crizotinib were enrolled in a phase I trial (EudraCT 2016-002187-14, DRKS00012360) if crizotinib Cmin,ss was below 310 ng/mL and treated with cobicistat for 14 days. Crizotinib plasma concentration profiles were established before and after a 14-day co-administration of cobicistat to construct the area under the plasma concentration-time curve in the dosing interval from zero to 12 hours (AUC0-12 ). Patients were also monitored for adverse events by physical examination, laboratory tests, and 12-lead echocardiogram. Enrolment was prematurely stopped because of the approval of alectinib, a next-generation ALK-inhibitor with superior efficacy. In the only patient enrolled, cobicistat increased Cmin,ss from 158 ng/mL (before cobicistat) to 308 ng/mL (day 8) and 417 ng/mL (day 14 on cobicistat), concurrently the AUC0-12 increased by 78% from 2,210 ng/mL*h to 3,925 ng/mL*h. Neither safety signals nor serious adverse events occurred. Pharmacoenhancement with cobicistat as an alternative for dose individualisation for patients with NSCLC with low crizotinib exposure appears to be safe and is cost-effective and feasible.

Pharmacokinetics and Toxicities of Oral Docetaxel Formulations Co-Administered with Ritonavir in Phase I Trials

Introduction

Docetaxel is widely used as intravenous (IV) chemotherapy. Oral docetaxel is co-administered with the cytochrome P450 3A4 and P-glycoprotein inhibitor ritonavir to increase oral bioavailability. This research explores the relationship between the pharmacokinetics (PK) and toxicity of this novel oral chemotherapy.

Methods

The patients in two phase I trials were treated with different oral docetaxel formulations in combination with ritonavir in different dose levels, ranging from 20 to 80 mg docetaxel with 100 to 200 mg ritonavir a day. The patients were categorized based on the absence or occurrence of severe treatment-related toxicity (grade ≥3 or any grade leading to treatment alterations). The docetaxel area under the plasma concentration–time curve (AUC) and maximum plasma concentration (C_max) were associated with toxicity.

Results

Thirty-four out of 138 patients experienced severe toxicity, most frequently observed as mucositis, fatigue, diarrhea, nausea and vomiting. The severe toxicity group had a significantly higher docetaxel AUC (2231 ± 1405 vs 1011 ± 830 ng/mL*h, p<0.0001) and C_max (218 ± 178 vs 119 ± 77 ng/mL, p<0.0001) as compared to the patients without severe toxicity. When extrapolated from IV PK data, the patients without severe toxicity had a similar cumulative docetaxel AUC as with standard 3-weekly IV docetaxel, while the C_max was up to 10-fold lower with oral docetaxel and ritonavir.

Conclusion

Severe toxicity was observed in 25% of the patients treated with oral docetaxel and ritonavir. This toxicity seems related to the PK, as the docetaxel AUC_0-inf and C_max were up to twofold higher in the severe toxicity group as compared to the non-severe toxicity group. Future randomized trials will provide a further evaluation of the toxicity and efficacy of the new weekly oral docetaxel and ritonavir regimen in comparison to standard IV docetaxel.

Rational Design of CYP3A4 Inhibitors: A One-Atom Linker Elongation in Ritonavir-Like Compounds Leads to a Marked Improvement in the Binding Strength

Inhibition of the major human drug-metabolizing cytochrome P450 3A4 (CYP3A4) by pharmaceuticals and other xenobiotics could lead to toxicity, drug–drug interactions and other adverse effects, as well as pharmacoenhancement. Despite serious clinical implications, the structural basis and attributes required for the potent inhibition of CYP3A4 remain to be established. We utilized a rational inhibitor design to investigate the structure–activity relationships in the analogues of ritonavir, the most potent CYP3A4 inhibitor in clinical use. This study elucidated the optimal length of the head-group spacer using eleven (series V) analogues with the R₁/R₂ side-groups as phenyls or R₁–phenyl/R₂–indole/naphthalene in various stereo configurations. Spectral, functional and structural characterization of the inhibitory complexes showed that a one-atom head-group linker elongation, from pyridyl–ethyl to pyridyl–propyl, was beneficial and markedly improved K_s, IC₅₀ and thermostability of CYP3A4. In contrast, a two-atom linker extension led to a multi-fold decrease in the binding and inhibitory strength, possibly due to spatial and/or conformational constraints. The lead compound, 3h, was among the best inhibitors designed so far and overall, the strongest binder (K_s and IC₅₀ of 0.007 and 0.090 µM, respectively). 3h was the fourth structurally simpler inhibitor superior to ritonavir, which further demonstrates the power of our approach.

Inhibitory effect of ketoconazole, quinidine and 1-aminobenzotriazole on pharmacokinetics of l-tetrahydropalmatine and its metabolite in rats

l-tetrahydropalmatine (l-THP) is mainly metabolised by CYP450 enzymes.This study was to investigate the possible effect of co-administered CYP inhibitors on the pharmacokinetics of l-THP and its metabolites in rats.An established LC-MS/MS method has been applied for the evaluation of drug-drug interaction between l-THP and CYP inhibitors. Following the administration of CYP inhibitors, a single dose of l-THP (9 mg/kg) was orally administrated.With regard to l-THP, the AUC_0-48 were significantly increased by 4.3, 3.79, and 11.39 folds, and C_max were increased by 4.74, 3.64, and 2.76 folds in the ketoconazole group (KET), quinidine group (QD), and 1-aminobenzotriazole group (ABT), respectively. KET and QD both significantly increased the AUC_0-48 of 2-DM and 2-DM-Glu by 1.38 ∼ 2.43 times, while C_max was significantly decreased by 41.3 and 78.0% in the ABT group, respectively. The C_max of 3-DM was reduced by 51.38, 48.02, and 63.31% after pre-treatment with KET, QD, and ABT, respectively, and C_max of 3-DM-Glu decreased correspondingly by 29.6, 22.1, and 58.0%.Results indicated that CYP inhibitors could markedly influence the systemic level of l-THP and its metabolites. To guarantee the safe use of l-THP, attention should be paid when l-THP was co-administered with CYP inhibitors, particularly with CYP3A4 and 2D6 inhibitors.

A Review: Effects of Macrolides on CYP450 Enzymes

As a kind of haemoglobin, cytochrome P450 enzymes (CYP450) participate in the metabolism of many substances, including endogenous substances, exogenous substances and drugs. It is estimated that 60% of common prescription drugs require bioconversion through CYP450. The influence of macrolides on CYP450 contributes to the metabolism and drug-drug interactions (DDIs) of macrolides. At present, most studies on the effects of macrolides on CYP450 are focused on CYP3A, but a few exist on other enzymes and drug combinations, such as telithromycin, which can decrease the activity of hepatic CYP1A2 and CYP3A2. This article summarizes some published applications of the influence of macrolides on CYP450 and the DDIs of macrolides caused by CYP450. And the article may subsequently guide the rational use of drugs in clinical trials. To a certain extent, poisoning caused by adverse drug interactions can be avoided. Unreasonable use of macrolide antibiotics may enable the presence of residue of macrolide antibiotics in animal-origin food. It is unhealthy for people to eat food with macrolide antibiotic residues. So it is of great significance to guarantee food safety and protect the health of consumers by the rational use of macrolides. This review gives a detailed description of the influence of macrolides on CYP450 and the DDIs of macrolides caused by CYP450. Moreover, it offers a perspective for researchers to further explore in this area.

Investigating the interaction between nifedipine- and ritonavir-containing antiviral regimens: A physiologically based pharmacokinetic/pharmacodynamic analysis

AIMS

Hypertension is a common comorbidity of patients with COVID-19, SARS or HIV infection. Such patients are often concomitantly treated with antiviral and antihypertensive agents, including ritonavir and nifedipine. Since ritonavir is a strong inhibitor of CYP3A and nifedipine is mainly metabolized via CYP3A, the combination of ritonavir and nifedipine can potentially cause drug-drug interactions. This study provides guidance on nifedipine treatment during and after coadministration with ritonavir-containing regimens, using a physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) analysis.

METHODS

The PBPK/PD models for 3 formations of nifedipine were developed based on the Simcyp nifedipine model and the models were verified using published data. The effects of ritonavir on nifedipine exposure and systolic blood pressure (SBP) were assessed for instant-release, sustained-release and controlled-release formulations in patients. Various nifedipine regimens were investigated when coadministered with or without ritonavir.

RESULTS

PBPK/PD models for 3 formulations of nifedipine were successfully established. The predicted maximum concentration (C_max ), area under plasma concentration-time curve (AUC), maximum reduction in SBP and area under effect-time curve were all within 0.5-2.0-fold of the observed data. Model simulations showed that the inhibitory effect of ritonavir on CYP3A4 increased the C_max of nifedipine 17.92-48.85-fold and the AUC 63.30-84.01-fold at steady state and decreased the SBP by >40 mmHg. Thus, the combination of nifedipine and ritonavir could lead to severe hypotension.

CONCLUSION

Ritonavir significantly affects the pharmacokinetics and antihypertensive effect of nifedipine. It is not recommended for patients to take nifedipine- and ritonavir-containing regimens simultaneously.

Open-Label Assessment of the Effects of Itraconazole and Rifampicin on Balovaptan Pharmacokinetics in Healthy Volunteers

INTRODUCTION

Balovaptan, an investigational vasopressin 1a receptor antagonist that has been evaluated for improvement of social communication and interaction, is primarily metabolized by cytochrome P450 3A4 (CYP3A4).

METHODS

Two single-center, non-randomized, two-period, phase 1 studies assessed the effect of the strong CYP3A4 inhibitor itraconazole (study NCT03579719) or the strong CYP3A4 inducer rifampicin (study NCT03586726) at steady state on the pharmacokinetics (PK) of steady-state balovaptan in healthy volunteers. Participants received balovaptan (5 or 10 mg/day) alone for 10 days, or in combination with itraconazole (200 mg/day) for 15 days, or rifampicin (600 mg/day) for 10 days, following balovaptan washout and itraconazole/rifampicin pre-dosing. Geometric mean ratios (GMRs) and 90% confidence intervals (90% CIs) for the area under the concentration-time curve over the dosing interval (AUC) and maximum plasma concentration (C_max) of balovaptan dosed with vs. without itraconazole/rifampicin were estimated from a mixed effects model.

RESULTS

Both studies comprised 15-16 healthy male and female volunteers. Itraconazole 200 mg/day elevated steady-state exposure to 5 mg/day balovaptan approximately 4.5-5.5-fold (Day 15 GMR [90% CI], 4.46 [4.06-4.90] for C_max and 5.57 [5.00-6.21] for AUC) and extended the time to steady state from ~ 5 days to ~ 13-14 days. Rifampicin 600 mg/day resulted in ~ 90% reductions in both the C_max (Day 10 GMR [90% CI], 0.14 [0.12-0.15]) and AUC (0.07 [0.06-0.07]) of balovaptan 10 mg/day. Time to balovaptan steady state could not be determined with rifampicin. There were no clinically significant safety findings in either study.

CONCLUSIONS

Strong modulators of CYP3A4 activity will significantly alter the PK of balovaptan, with the effect of CYP3A4 induction greater than that of inhibition. Caution should be taken when concomitantly dosing balovaptan with moderate or strong CYP3A4 inducers or strong CYP3A4 inhibitors.

TRIAL REGISTRATION NUMBER

NCT03579719; NCT03586726.

Potential Drug-Drug Interactions with Combination Volasertib + Itraconazole: A Phase I, Fixed-sequence Study in Patients with Solid Tumors

PURPOSE

This drug-drug interaction study determined whether the metabolism and distribution of the Polo-like kinase 1 inhibitor, volasertib, is affected by co-administration of the P-glycoprotein and cytochrome P-450 3A4 inhibitor, itraconazole.

METHODS

This was an uncontrolled, open-label, fixed-sequence trial of two 21-day treatment cycles in patients with various solid tumors. In cycle 1 (test), eligible patients were administered volasertib (day 1) plus itraconazole (days -3 to 15). In cycle 2 (reference), patients received volasertib monotherapy. The primary end point was the influence of co-administration of itraconazole on the pharmacokinetic profile (AUC0-tz; Cmax) of volasertib and its main metabolite, CD 10899, compared with that of volasertib monotherapy. Other end points included tolerability and preliminary therapeutic efficacy.

FINDINGS

Concurrent administration of itraconazole resulted in a slight reduction in the AUC0-tz (geometric mean ratio, 93.6%; 90% CI, 82.1%-106.8%) and a 20% reduction in Cmax (geometric mean ratio, 79.4%; 90% CI, 64.9%-97.1%) of volasertib compared with monotherapy. Of note, concurrent administration of itraconazole + volasertib had no effect on the AUC0-∞ of volasertib. More patients reported at least one drug-related adverse event in cycle 1 than in cycle 2 (75% vs 71%). The most commonly reported drug-related adverse events (cycles 1 and 2) were thrombocytopenia (68% and 33%, respectively), leukopenia (50% and 46%), and anemia (36% and 33%). No objective responses were observed. Stable disease was observed in 25 of 28 patients (89%).

IMPLICATIONS

While there was no clear evidence of a pharmacokinetic interaction between volasertib and itraconazole, co-administration reduced the tolerability of volasertib. Clinicaltrials.gov identifier: NCT01772563.

Physiologically Based Pharmacokinetic Modeling of Doravirine and Its Major Metabolite to Support Dose Adjustment With Rifabutin

Doravirine, a novel nonnucleoside reverse transcriptase inhibitor for the treatment of human immunodeficiency virus 1 (HIV-1), is predominantly cleared by cytochrome P450 (CYP) 3A4 and metabolized to an oxidative metabolite (M9). Coadministration with rifabutin, a moderate CYP3A4 inducer, decreased doravirine exposure. Based on nonparametric superposition modeling, a doravirine dose adjustment from 100 mg once daily to 100 mg twice daily during rifabutin coadministration was proposed. However, M9 exposure may also be impacted by induction, in addition to the dose adjustment. As M9 concentrations have not been quantified in previous clinical studies, a physiologically based pharmacokinetic model was developed to investigate the change in M9 exposure when doravirine is coadministered with CYP3A inducers. Simulations demonstrated that although CYP3A induction increases doravirine clearance by up to 4.4-fold, M9 exposure is increased by only 1.2-fold relative to exposures for doravirine 100 mg once daily in the absence of CYP3A induction. Thus, a 2.4-fold increase in M9 exposure relative to the clinical dose of doravirine is anticipated when doravirine 100 mg twice daily is coadministered with rifabutin. In a subsequent clinical trial, doravirine and M9 exposures, when doravirine 100 mg twice daily was coadministered with rifabutin, were found to be consistent with model predictions using rifampin and efavirenz as representative inducers. These findings support the dose adjustment to doravirine 100 mg twice daily when coadministered with rifabutin.