A Molecular Dynamic Simulation, Structural Analysis, and Ex Vivo Insights into the P-glycoprotein-Mediated Interactions of Dietary Polyphenols with Cyclin-dependent Kinase Inhibitors: A Potential Strategy to Counteract Drug Efflux.

INTRODUCTION: P-glycoprotein, an ATP-dependent efflux transporter, plays a crucial role in eliminating cellular toxins and affects the intracellular concentration and bioavailability of CDK 4/6 inhibitors. Moreover, dietary flavonoids are natural bio-enhancers that can effectively inhibit the efflux function of these transporters. Therefore, this study aimed to assess the impact of dietary polyphenols on the inhibition of P-glycoprotein and the subsequent efflux of CDK inhibitors palbociclib and ribociclib. METHODS: A molecular docking approach was implemented to evaluate the binding interaction characteristics of CDK4/6 inhibitors in the presence of dietary polyphenols at the ATP binding site. Furthermore, the stability of the complexes was evaluated in two conformations of P-glycoprotein, followed by an ex vivo everted gut sac experiment. RESULTS: The findings demonstrated that the binding of curcumin and quercetin with high affinity (-51.63 and 47.16 Kcal/mol) to ATP binding sites of P-glycoprotein-palbociclib and ribociclib inward conformation complexes resulted in good stability of complex and minimal fluctuation throughout the course of the simulation. It was evident from the everted gut sac ex vivo study that the presence of 100µM of curcumin resulted in an increase of 1.77 and 4.20-fold in the intestinal transit of palbociclib and ribociclib, respectively. CONCLUSION: The study emphasizes the significance of curcumin and quercetin as inhibitors of P-glycoprotein, demonstrating their potential to decrease the efflux of palbociclib and ribociclib, consequently contributing to their bioavailability enhancement.

Strategy to Improve the Oral Pharmacokinetics of Cyclin-Dependent Kinase 4/6 Inhibitors: Enhancing Permeability and CYP450 Inhibition by a Natural Bioenhancer.

Palbociclib and ribociclib an orally bioavailable, potent cyclin-dependent kinase 4/6 inhibitors, with low oral bioavailability due to substrate specificity towards CYP3A and P-glycoprotein. Thus, current research aims to examine the effect of a bioenhancer (naringin), on oral pharmacokinetics of palbociclib and ribociclib. Naringin's affinity for CYP3A4 and P-glycoprotein was studied using molecular docking; its impact on palbociclib/ribociclib CYP3A metabolism and P-glycoprotein-mediated efflux was examined using in vitro preclinical models; and its oral pharmacokinetics in rats were assessed following oral administration of palbociclib/ribociclib in presence of naringin (50 and 100 mg/kg). Naringin binds optimally to both proteins with the highest net binding energy of - 1477.23 and - 1607.47 kcal/mol, respectively. The microsomal intrinsic clearance of palbociclib and ribociclib was noticeably reduced by naringin (5-100 µM), by 3.0 and 2.46-folds, respectively. Similarly, naringin had considerable impact on the intestinal transport and efflux of both drugs. The pre-treatment with 100 mg/kg naringin increased significantly (p < 0.05) the oral exposure of palbociclib (2.0-fold) and ribociclib (1.95-fold). Naringin's concurrent administration of palbociclib and ribociclib increased their oral bioavailability due to its dual inhibitory effect on CYP3A4 and P-glycoprotein; thus, concurrent naringin administration may represent an innovative strategy for enhancing bioavailability of cyclin-dependent kinase inhibitors.

Estimation of CDK inhibitors by RP-HPLC: application for pharmacokinetic interactions studies with PPIs.

Background: The study investigated pharmacokinetic interactions between palbociclib and ribociclib with proton pump inhibitors (PPIs) using the reverse-phase high-performance liquid chromatography (RP-HPLC) method.Methods: Developed RP-HPLC method quantified palbociclib and ribociclib in biological matrices. In vitro metabolic stability assays and in vivo studies in rats evaluated effect of omeprazole and esomeprazole on pharmacokinetics of palbociclib and ribociclib.Results: The RP-HPLC method was sensitive, accurate and linear. Esomeprazole and omeprazole decreased metabolic clearance of palbociclib and ribociclib by several folds. In vivo, esomeprazole elevated Cmax of palbociclib and ribociclib by 90.1% and 86.4%, whereas omeprazole reduced it by 32.0% and 16.8%, respectively.Conclusion: The RP-HPLC method was used to analyze in vitro and in vivo samples. Long-term treatment with PPIs affects pharmacokinetics of palbociclib and ribociclib, necessitating optimal chemotherapy regimen.

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Differential effects of dietary polyphenols on oral pharmacokinetics of cyclin-dependent kinase inhibitors in rats: a mechanistic framework for in vitro-in vivo extrapolation.

OBJECTIVES: Cyclin-dependent kinase inhibitors are subject to rapid first-pass metabolism, and their oral absorption is hindered by intestinal CYP3A4 and P-gp. The present study investigates the impact of dietary polyphenols on the oral pharmacokinetics of palbociclib and ribociclib, considering their potential as modulators of CYP3A4 and P-gp. METHODS: Therefore, potential inhibitory effects of dietary polyphenols on drug metabolism and efflux of these drugs were investigated using molecular docking; in vitro preclinical assay using rat liver microsomes and Caco-2 cell monolayers; in vivo, pharmacokinetic parameters were determined in rats pretreated with dietary polyphenols. KEY FINDINGS: Curcumin and quercetin have the highest binding affinities to the PXR's AF-2 region cluster. Curcumin and quercetin significantly inhibited both intestinal efflux and CYP3A4-mediated metabolism of palbociclib and ribociclib (P < .05). In rats pretreated with curcumin, Cmax of palbociclib exhibited a 5.13% increase, while the AUC0-24h of ribociclib showed a significant increase of 18.83% (P < .05). Quercetin administration, notably, impedes the pharmacokinetics of palbociclib. However, the pharmacokinetics of ribociclib remains unaffected by quercetin. CONCLUSIONS: In conclusion, the utilization of curcumin as a bioenhancer can enhance the bioavailability of dual substrates of P-gp and CYP3A4.

Molecular Insights into the Mechanism of Modulatory Effects of Proton Pump Inhibitors on P-glycoprotein Mediated Drug Transport of Palbociclib and Ribociclib.

BACKGROUND: Palbociclib and ribociclib are substrates of efflux transporter P-glycoprotein which plays a key role in absorption and transport of these drugs. Proton pump inhibitors, when co-administered with them are known to show inhibitory effect on P-glycoprotein. OBJECTIVE: Therefore, this study aims to investigate the role of proton pump inhibitors in inhibition of P-glycoprotein mediated efflux of palbociclib and ribociclib. METHOD: A combined approach of molecular docking and ex vivo everted gut sac model was implemented to predict the potential of proton pump inhibitors i.e., omeprazole, esomeprazole, lansoprazole, pantoprazole and rabeprazole to inhibit the P-glycoprotein mediated intestinal transport of palbociclib and ribociclib and study the molecular basis of interaction taking place. RESULTS: Molecular docking studies revealed that omeprazole, rabeprazole and pantoprazole bound to the ATP site of nucleotide binding domain with binding energies of -27.53, -29.56 and -38.44 Kcal/mol respectively. In ex vivo studies, rabeprazole and omeprazole, affected the absorptive permeability of palbociclib by 3.04 and 1.26 and ribociclib by 1.76 and 2.54 folds, respectively. Results of molecular docking studies and ex vivo studies highlighted that proton pump inhibitors bound to the ATP binding site to block its hydrolysis thereby inhibiting the P-glycoprotein mediated efflux of palbociclib and ribociclib. CONCLUSION: The experimental evidence presented highlights the fact that proton pump inhibitors have potential to inhibit P-glycoprotein, giving rise to drug interactions with palbociclib and ribociclib. Hence, monitoring is required while proton pump inhibitors and cyclin-dependent kinase inhibitors are being co-administered to avoid adverse events.