Docetaxel, cyclophosphamide, and epirubicin: application of PBPK modeling to gain new insights for drug-drug interactions

The new adjuvant chemotherapy of docetaxel, epirubicin, and cyclophosphamide has been recommended for treating breast cancer. It is necessary to investigate the potential drug-drug Interactions (DDIs) since they have a narrow therapeutic window in which slight differences in exposure might result in significant differences in treatment efficacy and tolerability. To guide clinical rational drug use, this study aimed to evaluate the DDI potentials of docetaxel, cyclophosphamide, and epirubicin in cancer patients using physiologically based pharmacokinetic (PBPK) models. The GastroPlus™ was used to develop the PBPK models, which were refined and validated with observed data. The established PBPK models accurately described the pharmacokinetics (PKs) of three drugs in cancer patients, and the predicted-to-observed ratios of all the PK parameters met the acceptance criterion. The PBPK model predicted no significant changes in plasma concentrations of these drugs during co-administration, which was consistent with the observed clinical phenomenon. Besides, the verified PBPK models were then used to predict the effect of other Cytochrome P450 3A4 (CYP3A4) inhibitors/inducers on these drug exposures. In the DDI simulation, strong CYP3A4 modulators changed the exposure of three drugs by 0.71-1.61 fold. Therefore, patients receiving these drugs in combination with strong CYP3A4 inhibitors should be monitored regularly to prevent adverse reactions. Furthermore, co-administration of docetaxel, cyclophosphamide, or epirubicin with strong CYP3A4 inducers should be avoided. In conclusion, the PBPK models can be used to further investigate the DDI potential of each drug and to develop dosage recommendations for concurrent usage by additional perpetrators or victims.

Prediction of Drug-Drug Interaction Potential of Tegoprazan Using Physiologically Based Pharmacokinetic Modeling and Simulation

This study aimed to develop a physiologically based pharmacokinetic (PBPK) model of tegoprazan and to predict the drug-drug interaction (DDI) potential between tegoprazan and cytochrome P450 (CYP) 3A4 perpetrators. The PBPK model of tegoprazan was developed using SimCYP Simulator^® and verified by comparing the model-predicted pharmacokinetics (PKs) of tegoprazan with the observed data from phase 1 clinical studies, including DDI studies. DDIs between tegoprazan and three CYP3A4 perpetrators were predicted by simulating the difference in tegoprazan exposure with and without perpetrators, after multiple dosing for a clinically used dose range. The final PBPK model adequately predicted the biphasic distribution profiles of tegoprazan and DDI between tegoprazan and clarithromycin. All ratios of the predicted-to-observed PK parameters were between 0.5 and 2.0. In DDI simulation, systemic exposure to tegoprazan was expected to increase about threefold when co-administered with the maximum recommended dose of clarithromycin or ketoconazole. Meanwhile, tegoprazan exposure was expected to decrease to ~30% when rifampicin was co-administered. Based on the simulation by the PBPK model, it is suggested that the DDI potential be considered when tegoprazan is used with CYP3A4 perpetrator, as the acid suppression effect of tegoprazan is known to be associated with systemic exposure.

Effect of ketoconazole on the pharmacokinetic profile of buprenorphine following administration of a once-weekly buprenorphine transdermal system

BACKGROUND AND OBJECTIVE

Buprenorphine is extensively metabolized by cytochrome P450 (CYP) 3A4. This study evaluated the effect of ketoconazole, a CYP3A4 inhibitor, on the metabolism of buprenorphine following the administration of a buprenorphine transdermal system 10 μg/hour (BTDS 10).

METHODS

This single-centre study enrolled 20 healthy subjects who had demonstrated ketoconazole-mediated CYP3A4 inhibition via an erythromycin breath test. Subjects were randomized into a placebo-controlled, two-treatment, two-period crossover study. Subjects participated in a 7- to 14-day screening period, two baseline evaluations (day 0 [period 1] and day 16 [period 2]), two 12-day treatment periods (periods 1 and 2) separated by a 4-day washout period, and a study completion visit. Subjects received one BTDS 10 for 7 days per treatment period, administered concomitantly with either ketoconazole 200 mg twice daily or matching placebo. The main outcome measures were the ratios of geometric means for area under the plasma drug concentration versus time curve (AUC) from time zero to time of last measurable concentration (AUC(last)), AUC from time zero to infinity (AUC(∞)), and maximum plasma drug concentration (C(max)).

RESULTS

The ratio of geometric means (BTDS 10 with ketoconazole/BTDS 10 with placebo) was 99.4 (90% confidence interval [CI] 87.2, 113.3) for AUC(last) and 97.8 (90% CI 87.7, 109.1) for C(max). The ratio of geometric means for AUC(∞) was 86.7 (90% CI 70.7, 106.2). The plasma concentrations of the metabolites norbuprenorphine and norbuprenorphine-3β-glucuronide were slightly elevated following ketoconazole administration. BTDS 10 with ketoconazole was well tolerated and no apparent safety concerns were noted.

CONCLUSION

The lack of a clinically significant CYP3A4 interaction with ketoconazole following transdermal delivery of buprenorphine is consistent with the parenteral administration of a high clearance drug bypassing exposure to gut wall and hepatic CYP3A4 first-pass effects. Metabolism of buprenorphine during therapy with BTDS is also not expected to be affected by co-administration of other CYP3A4 inhibitors.

Effect of ketoconazole on the pharmacokinetic profile of buprenorphine following administration of a once-weekly buprenorphine transdermal system

BACKGROUND AND OBJECTIVE

Buprenorphine is extensively metabolized by cytochrome P450 (CYP) 3A4. This study evaluated the effect of ketoconazole, a CYP3A4 inhibitor, on the metabolism of buprenorphine following the administration of a buprenorphine transdermal system 10 μg/hour (BTDS 10).

METHODS

This single-centre study enrolled 20 healthy subjects who had demonstrated ketoconazole-mediated CYP3A4 inhibition via an erythromycin breath test. Subjects were randomized into a placebo-controlled, two-treatment, two-period crossover study. Subjects participated in a 7- to 14-day screening period, two baseline evaluations (day 0 [period 1] and day 16 [period 2]), two 12-day treatment periods (periods 1 and 2) separated by a 4-day washout period, and a study completion visit. Subjects received one BTDS 10 for 7 days per treatment period, administered concomitantly with either ketoconazole 200 mg twice daily or matching placebo. The main outcome measures were the ratios of geometric means for area under the plasma drug concentration versus time curve (AUC) from time zero to time of last measurable concentration (AUC(last)), AUC from time zero to infinity (AUC(∞)), and maximum plasma drug concentration (C(max)).

RESULTS

The ratio of geometric means (BTDS 10 with ketoconazole/BTDS 10 with placebo) was 99.4 (90% confidence interval [CI] 87.2, 113.3) for AUC(last) and 97.8 (90% CI 87.7, 109.1) for C(max). The ratio of geometric means for AUC(∞) was 86.7 (90% CI 70.7, 106.2). The plasma concentrations of the metabolites norbuprenorphine and norbuprenorphine-3β-glucuronide were slightly elevated following ketoconazole administration. BTDS 10 with ketoconazole was well tolerated and no apparent safety concerns were noted.

CONCLUSION

The lack of a clinically significant CYP3A4 interaction with ketoconazole following transdermal delivery of buprenorphine is consistent with the parenteral administration of a high clearance drug bypassing exposure to gut wall and hepatic CYP3A4 first-pass effects. Metabolism of buprenorphine during therapy with BTDS is also not expected to be affected by co-administration of other CYP3A4 inhibitors.

Ascending single-dose study of the safety profile, tolerability, and pharmacokinetics of bosutinib coadministered with ketoconazole to healthy adult subjects

BACKGROUND

Bosutinib (SKI-606) is an orally bioavailable, competitive tyrosine kinase inhibitor that selectively targets both Src and Abl tyrosine kinases. Bosutinib is metabolized primarily through the cytochrome P450 3A4 pathway. Inhibition of bosutinib metabolism by coadministration with the potent cytochrome P450 3A4 inhibitor ketoconazole could potentially increase plasma concentrations of bosutinib, allowing for the study of bosutinib tolerability at supratherapeutic concentrations in a healthy subject population.

OBJECTIVE

This study assessed the safety profile, tolerability, and pharmacokinetics of different dose combinations of bosutinib coadministered with ketoconazole in healthy adults, and determined whether supratherapeutic concentrations of bosutinib can be achieved with ketoconazole.

METHODS

This was a randomized, Phase I, double-blind, placebo-controlled, sequential-group study conducted in healthy adults. Single oral doses of bosutinib 100, 200, 300, 400, 500, and 600 mg or placebo were administered with ketoconazole and food on day 1; daily single oral doses of ketoconazole 400 mg were administered on days -1 and 1 through 4.

RESULTS

Forty-eight subjects were enrolled. Their mean (SD) age was 32.0 (10.7) years (range, 18-50 years). The majority of the subjects (n = 44 [92%]) were white, 2 (4%) were black or African American, and 2 (4%) were of other races. Bosutinib was associated with acceptable tolerability at doses from 100 to 600 mg, with adverse events either mild (n = 30 [63%]) or moderate (n = 12 [25%]) in severity; no subject discontinued treatment due to adverse events, and no serious events were reported. Mean (SD) values for bosutinib 100 to 600 mg ranged from 58.4 (13.3) to 426 (100) ng/mL for C(max) and 2980 (802) to 23,000 (4020) ng·h/mL for AUC(0-∞); mean AUC(0-24) and AUC(0-last) ranged from 876 (234) to 7080 (1640) ng· h/mL and from 2740 (854) to 22,200 (3630) ng · h/mL, respectively. C(max) and AUC were linear and dose proportional. Mean C(max) at 600 mg was 2.1-fold higher than the steady-state C(max) previously observed for patients with chronic myelogenous leukemia who received bosutinib 500 mg once daily with food.

CONCLUSIONS

Single doses of bosutinib up to 600 mg coadministered with multiple doses of ketoconazole were acceptably well tolerated in this small, selected group of healthy male volunteers. In addition, supratherapeutic exposure was achieved within this range for bosutinib when coadministered with ketoconazole. ClinicalTrials.gov identifier: NCT00777530.

Pharmacokinetics of oral neratinib during co-administration of ketoconazole in healthy subjects

AIM

The primary objective was to evaluate the pharmacokinetics of a single dose of neratinib, a potent, low-molecular-weight, orally administered, irreversible pan-ErbB (ErbB-1, -2, -4) receptor tyrosine kinase inhibitor, during co-administration with ketoconazole, a potent CYP3A4 inhibitor.

METHODS

This was an open-label, randomized, two-period, crossover study. Fasting healthy adults received a single oral dose of neratinib 240 mg alone and with multiple oral doses of ketoconazole 400 mg. Blood samples were collected up to 72 h after each neratinib dose. Plasma concentration data were analyzed using a noncompartmental method. The least square geometric mean ratios [90% confidence interval (CI)] of C(max) (neratinib+ketoconazole): C(max) (neratinib alone), and AUC(neratinib+ketoconazole): AUC(neratinib alone) were assessed.

RESULTS

Twenty-four subjects were enrolled. Compared with neratinib administered alone, co-administration of ketoconazole increased neratinib C(max) by 3.2-fold (90% CI: 2.4, 4.3) and AUC by 4.8-fold (3.6, 6.5). Median t(max) was 6.0 h with both regimens. Ketoconazole decreased mean apparent oral clearance of neratinib from 346 lh(-1) to 87.1 lh(-1) and increased mean elimination half-life from 11.7 h to 18.0 h. The incidence of adverse events was comparable between the two regimens (50% neratinib alone, 65% co-administration with ketoconazole).

CONCLUSION

Co-administration of neratinib with ketoconazole, a potent CYP3A inhibitor, increased neratinib C(max) by 3.2-fold and AUC by 4.8-fold compared with administration of neratinib alone. These results indicate that neratinib is a substrate of CYP3A and is susceptible to interaction with potent CYP3A inhibitors and, thus, dose adjustments may be needed if neratinib is administered with such compounds.

Inhibition of CYP3A mRNA and protein expression, and enzymatic activity, by enrofloxacin in chickens

This study was to investigate the effect of enrofloxacin (EF) on CYP3A in chicken by using quantitative reverse transcription-polymerase chain reaction and immunodetected. The treated chickens were given 5, 25 and 125 mg/kg of EF while the control chickens were treated with the same volume saline. There was no significant difference between the low dose group and controls in the concentration of hepatic microsome protein and total CYP content, while the middle and high dose EF caused the down regulation. Depression of the CYP3A activity, mRNA and protein were observed in treated chickens, and the inhibition degree was different from each group. It was concluded that EF caused the inhibition of CYP3A both in genetic transcription and protein levels. But the inhibition metabolism still needs further researches.

Effect of ketoconazole on the pharmacokinetics of oral bosutinib in healthy subjects

Bosutinib (SKI-606), a dual inhibitor of Src and Abl tyrosine kinases, is being developed for the treatment of chronic myelogenous leukemia. The effect of coadministration of ketoconazole on the pharmacokinetic (PK) profile of bosutinib was evaluated in an open-label, randomized, 2-period, crossover study. Healthy subjects (fasting) received a single dose of oral bosutinib 100 mg alone and with multiple once-daily doses of oral ketoconazole 400 mg. PK sampling occurred through 96 hours. The least square geometric mean treatment ratios (90% confidence interval [CI]) of C(max(bosutinib+ketoconazole))/C(max(bosutinib alone)), AUC(T(bosutinib+ketoconazole))/AUC(T(bosutinib alone)), and AUC((bosutinib+ketoconazole))/AUC((bosutinib alone)) were assessed. Compared with bosutinib administered alone, coadministration with ketoconazole increased bosutinib C(max) 5.2-fold, AUC(T) 7.6-fold, and AUC 8.6-fold. Ketoconazole coadministration decreased the mean apparent clearance of bosutinib approximately 9-fold and increased the mean (SD) terminal half-life from 46.2 (16.4) hours to 69.0 (29.1) hours. The incidence of adverse events (AEs) was comparable between the 2 treatments. The most common AEs were headache, nausea, and increased blood creatinine. No safety-related discontinuations or serious AEs occurred. These PK results indicate that bosutinib is susceptible to interaction with potent CYP3A4 inhibitors.

Quantitative clinical pharmacology is transforming drug regulation

Prior to 1970s, development and regulation of new drugs was devoid of a fully quantitative, pathophysiological conceptual foundation. Malcolm Rowland pioneered, in collaboration with colleagues and friends, our modern understanding of drug clearance concepts, and equipped drug development and regulatory scientists with key investigative tools such as physiologically-based pharmacokinetic (PBPK) modeling, standardized approaches to characterizing drug metabolism, and microdosing. From the 1970s to the present, Malcolm Rowland has contributed to key advances in pharmacokinetics that have had transformational impacts on drug regulatory science. These advances include concepts that have led to the fundamental understanding that mechanistically derived, quantitative variations in drug concentrations, rather than assigned dosage alone, drive pharmacodynamic effects (PKPD)-including disease biomarkers and clinical outcomes. This body of knowledge has transformed drug development and regulatory science theory and practice from naïve empiricism to a mechanism/model-based, quantitative scientific discipline. As a result, it is now possible to incorporate pre-clinical in vitro data on drug physico-chemical properties, metabolizing enzymes, transporters and permeability properties into PBPK-based simulations of expected PK distributions and drug-drug interactions in human populations. The most comprehensive application of PK-PD is in the modeling and simulation of clinical trials in the context of model-based drug development and regulation, imbedded in the "learn-confirm paradigm". Regulatory agencies have embraced these advances and incorporated them into regulatory requirements, approval acceleration pathways and regulatory decisions. These developments are reviewed here, with emphasis on key contributions of Malcolm Rowland that facilitated this transformation.