A population pharmacokinetic model for doxorubicin and doxorubicinol in the presence of a novel MDR modulator, zosuquidar trihydrochloride (LY335979)

Comparative study on ABCB1-dependent efflux of anthracyclines and their metabolites: consequences for cancer resistance

1. ABCB1 (P-glycoprotein, MDR1) is one of the most important transporter involved in cancer multi-drug resistance. It also plays a significant role in cancer resistance against anthracyclines, an anticancer group of drugs, including doxorubicin and daunorubicin. Several intracellular enzymes metabolise anthracyclines to carbonyl-reduced, hydroxy metabolites, which have impaired cytotoxic properties. However, metabolite efflux by ABCB1 transporter is not well characterised, while it may be the mechanism responsible for the metabolites' lack of activity.2. In this study recombinant ABCB1 ATPase transporter assay; anthracyclines accumulation assay in resistant cells overexpressing ABCB1; and molecular modelling were used to investigate anthracyclines: doxorubicin and daunorubicin and their carbonyl-reduced metabolites (doxorubicinol, daunorubicinol) susceptibility for ABCB1-dependent efflux.3. Based on the kinetics parameters of ATPase activity of ABCB1, it was found that daunorubicinol exerted an exceptionally high potential for being effluxed by the ABCB1 transporter. ABCB1 significantly affected the accumulation pattern of studied chemicals in resistant cancer cells. Doxorubicin and daunorubicinol accumulation were influenced by the activity of ABCB1 modulator - valspodar.4. Results indicate that ABCB1 activity affects not only anthracyclines but also their metabolites. Therefore crosstalk between the process of anthracyclines metabolism and metabolite efflux may be the mechanism of impairing anticancer properties of anthracyclines metabolites.

A model-based head-to-head comparison of single-agent lurbinectedin in the pivotal ATLANTIS Study

Introduction

Lurbinectedin is a selective inhibitor of oncogenic transcription U.S. Food and Drug Administration (FDA)-approved for patients with relapsed small cell lung cancer (SCLC) as monotherapy at 3.2 mg/m² every 3 weeks (q3wk). ATLANTIS was a phase 3 study in SCLC with lurbinectedin 2.0 mg/m² plus doxorubicin 40 mg/m² q3wk vs physician's choice, with overall survival (OS) as the primary endpoint and objective response rate (ORR) as the secondary endpoint. This work aimed to dissect the contribution of lurbinectedin and doxorubicin to antitumor effects in SCLC, and to predict the efficacy of single-agent lurbinectedin at 3.2 mg/m² in ATLANTIS to allow for a head-to-head comparison with the control arm.

Methods

The dataset included exposure and efficacy data from 387 patients with relapsed SCLC (ATLANTIS, n=288; study B-005, n=99). Patients in the ATLANTIS control arm (n=289) were used for comparison. Unbound plasma lurbinectedin area under the concentration-time curve (AUC_u) and total plasma doxorubicin area under the concentration-time curve (AUC_DOX) were used as exposure metrics. Univariate and multivariate analyses were conducted to determine the best predictors and predictive model for OS and ORR. OS baseline hazard was best described by a log-logistic distribution, with chemotherapy-free interval (CTFI), lactate dehydrogenase, albumin, brain metastases, neutrophils/lymphocytes ratio, AUC_u, and the interaction between AUC_u and AUC_DOX as predictors. Effect of AUC_u on ORR best fitted to a sigmoid-maximal response (E_max) logistic model, where E_max was dependent on CTFI.

Results

Head-to-head comparisons with predicted 3.2 mg/m² lurbinectedin resulted in a positive outcome in ATLANTIS, with hazard ratio (95% prediction intervals [95% PI]) for OS of 0.54 (0.41, 0.72), and odds ratio (95% PI) for ORR of 0.35 (0.25, 0.5).

Conclusion

These results support the superiority of lurbinectedin monotherapy for relapsed SCLC over other approved therapies.

Inflammation and aging: signaling pathways and intervention therapies

Aging is characterized by systemic chronic inflammation, which is accompanied by cellular senescence, immunosenescence, organ dysfunction, and age-related diseases. Given the multidimensional complexity of aging, there is an urgent need for a systematic organization of inflammaging through dimensionality reduction. Factors secreted by senescent cells, known as the senescence-associated secretory phenotype (SASP), promote chronic inflammation and can induce senescence in normal cells. At the same time, chronic inflammation accelerates the senescence of immune cells, resulting in weakened immune function and an inability to clear senescent cells and inflammatory factors, which creates a vicious cycle of inflammation and senescence. Persistently elevated inflammation levels in organs such as the bone marrow, liver, and lungs cannot be eliminated in time, leading to organ damage and aging-related diseases. Therefore, inflammation has been recognized as an endogenous factor in aging, and the elimination of inflammation could be a potential strategy for anti-aging. Here we discuss inflammaging at the molecular, cellular, organ, and disease levels, and review current aging models, the implications of cutting-edge single cell technologies, as well as anti-aging strategies. Since preventing and alleviating aging-related diseases and improving the overall quality of life are the ultimate goals of aging research, our review highlights the critical features and potential mechanisms of inflammation and aging, along with the latest developments and future directions in aging research, providing a theoretical foundation for novel and practical anti-aging strategies.

Population pharmacokinetics of doxorubicin: A systematic review

Because of the high interindividual pharmacokinetic variability, several population pharmacokinetic (PopPK) models of doxorubicin (DOX) were developed to characterize factors influencing such variability. However, significant predictors for DOX pharmacokinetics identified using PopPK models varied across studies. Thus, this review aims to summarize PopPK models of DOX and its metabolites (if any) as well as significant covariates influencing DOX (and its metabolites) pharmacokinetic variability. A systematic search from PubMed, CINAHL Complete, Science Direct, and SCOPUS databases identified 503 studies. Of these, 16 studies met the inclusion criteria and were included in this review. DOX pharmacokinetics was described with two- or three-compartment models. Most studies found a significant increase in DOX clearance with an increase in body surface area from the median value of 1.8 m² . Moreover, this review identified that while a 10-year increase in patient age resulted in a decrease in DOX clearance in adults and the elderly, younger children had lower DOX clearance compared to older children. Further, low DOX exposure was observed in pregnant women, and thus dosage adjustment is required. Concerning model applicability, predictive performance assessment of these published models should be performed before implementing such models in clinical practice.

A Quantitative Systems Pharmacology Framework for Optimal Doxorubicin Granulocyte Colony-Stimulating Factor Regimens in Triple-Negative Breast Cancer

INTRODUCTION

To mitigate the risk of neutropenia during chemotherapy treatment of triple-negative breast cancer, prophylactic and supportive therapy with granulocyte colony-stimulating factor (G-CSF) is administered concomitant to chemotherapy. The proper timing of combined chemotherapy and G-CSF is crucial for treatment outcomes.

METHODS

Leveraging our established mathematical model of neutrophil production by G-CSF, we developed quantitative systems pharmacology (QSP) framework to investigate how modulating chemotherapy dose frequency and intensity can maximize antitumour effects. To establish schedules that best control tumour size while minimizing neutropenia, we combined Gompertzian tumour growth with pharmacokinetic/pharmacodynamic models of doxorubicin and G-CSF, and our QSP model of neutrophil production.

RESULTS

We optimized a range of chemotherapeutic cycle lengths and dose sizes to establish regimens that simultaneously reduced tumour burden while minimizing neutropenia. Our results suggest that cytotoxic chemotherapy with doxorubicin 45 mg/m2 every 14 days provides effective control of tumour growth while mitigating neutropenic risks.

CONCLUSION

This work suggests future avenues for optimal regimens of chemotherapy with prophylactic G-CSF support. Importantly, the algorithmic approach that we developed can aid in balancing the anticancer and the neutropenic effects of both drugs, and therefore contributes to rational considerations in clinical decision-making in triple-negative breast cancer.

Characterization of P-Glycoprotein Inhibitors for Evaluating the Effect of P-Glycoprotein on the Intestinal Absorption of Drugs

For developing oral drugs, it is necessary to predict the oral absorption of new chemical entities accurately. However, it is difficult because of the involvement of efflux transporters, including P-glycoprotein (P-gp), in their absorption process. In this study, we conducted a comparative analysis on the inhibitory activities of seven P-gp inhibitors (cyclosporin A, GF120918, LY335979, XR9576, WK-X-34, VX-710, and OC144-093) to evaluate the effect of P-gp on drug absorption. GF120918, LY335979, and XR9576 significantly decreased the basal-to-apical transport of paclitaxel, a P-gp substrate, across Caco-2 cell monolayers. GF120918 also inhibited the basal-to-apical transport of mitoxantrone, a breast cancer resistance protein (BCRP) substrate, in Caco-2 cells, whereas LY335979 hardly affected the mitoxantrone transport. In addition, the absorption rate of paclitaxel after oral administration in wild-type mice was significantly increased by pretreatment with LY335979, and it was similar to that in mdr1a/1b knockout mice. Moreover, the absorption rate of topotecan, a BCRP substrate, in wild-type mice pretreated with LY335979 was similar to that in mdr1a/1b knockout mice but significantly lower than that in bcrp knockout mice. These results indicate that LY335979 has a selective inhibitory activity for P-gp, and would be useful for evaluating the contribution of P-gp to drug absorption.

Phase I feasibility study of Magnetic Resonance guided High Intensity Focused Ultrasound-induced hyperthermia, Lyso-Thermosensitive Liposomal Doxorubicin and cyclophosphamide in de novo stage IV breast cancer patients: study protocol of the i-GO study

INTRODUCTION

In breast cancer, local tumour control is thought to be optimised by administering higher local levels of cytotoxic chemotherapy, in particular doxorubicin. However, systemic administration of higher dosages of doxorubicin is hampered by its toxic side effects. In this study, we aim to increase doxorubicin deposition in the primary breast tumour without changing systemic doxorubicin concentration and thus without interfering with systemic efficacy and toxicity. This is to be achieved by combining Lyso-Thermosensitive Liposomal Doxorubicin (LTLD, ThermoDox, Celsion Corporation, Lawrenceville, NJ, USA) with mild local hyperthermia, induced by Magnetic Resonance guided High Intensity Focused Ultrasound (MR-HIFU). When heated above 39.5°C, LTLD releases a high concentration of doxorubicin intravascularly within seconds. In the absence of hyperthermia, LTLD leads to a similar biodistribution and antitumour efficacy compared with conventional doxorubicin.

METHODS AND ANALYSIS

This is a single-arm phase I study in 12 chemotherapy-naïve patients with de novo stage IV HER2-negative breast cancer. Previous endocrine treatment is allowed. Study treatment consists of up to six cycles of LTLD at 21-day intervals, administered during MR-HIFU-induced hyperthermia to the primary tumour. We will aim for 60 min of hyperthermia at 40°C-42°C using a dedicated MR-HIFU breast system (Profound Medical, Mississauga, Canada). Afterwards, intravenous cyclophosphamide will be administered. Primary endpoints are safety, tolerability and feasibility. The secondary endpoint is efficacy, assessed by radiological response.This approach could lead to optimal loco-regional control with less extensive or even no surgery, in de novo stage IV patients and in stage II/III patients allocated to receive neoadjuvant chemotherapy.

ETHICS AND DISSEMINATION

This study has obtained ethical approval by the Medical Research Ethics Committee Utrecht (Protocol NL67422.041.18, METC number 18-702). Informed consent will be obtained from all patients before study participation. Results will be published in an academic peer-reviewed journal.

TRIAL REGISTRATION NUMBERS

NCT03749850, EudraCT 2015-005582-23.

Gender differences in doxorubicin pharmacology for subjects with chemosensitive cancers of young adulthood

PURPOSE

For many cancers, adolescents and young adults (AYA) have worse outcomes than for children and adults. Many factors may contribute to the AYA survival gap, including differences in biology, therapeutic intent, and adherence to therapy. It has been observed that male AYAs have poorer outcomes than females. The purpose of this work was to test the proposition that gender-related pharmacologic factors may account for a component of the AYA survival gap.

PATIENTS AND METHODS

A prospective, multi-institutional pharmacologic study of 79 patients in total with chemosensitive cancers (Ewing sarcoma, osteosarcoma and Hodgkin lymphoma) was conducted, with conventional doxorubicin treatment. Pharmacokinetic data of 13 children, 40 AYAs and 13 adults were valid for analysis. Population pharmacokinetics models were developed for doxorubicin and its metabolite doxorubicinol based on the data created in this study. Consequently, model-based analysis was conducted to investigate the relevant topics.

RESULTS

The clearance of doxorubicinol (normalized to body surface area), the main active metabolite of doxorubicin, appears faster in male AYAs than female (p = 0.04, 95% CI 0.1-3.9 L/h). The exposure of doxorubicinol (normalized to dose) is lower in male AYA than female (p = 0.03, 95% CI - 0.005 to - 0.0002 h/L). These might be correlated to the observed difference on nadir neutrophil count between male AYA and female (p = 0.027, 95% CI 0.09-1.4).

CONCLUSION

Gender-related differences in doxorubicin pharmacology may account for worse outcomes for male AYAs with chemosensitive cancers compared to females. These findings may reduce the AYA survival gap compared to other age groups.

Simple and rapid monitoring of doxorubicin using streptavidin-modified microparticle-based time-resolved fluorescence immunoassay

Developing a simple analytical method suitable for therapeutic drug monitoring in a clinical setting is key to establishing guidelines on accurate dose administration and the advancement of precision medicine. We devised a simple rapid analytical method through the combination of streptavidin-modified microparticles and a time-resolved fluorescence immunoassay for therapeutic drug monitoring. The analytical performance of this method was investigated and validated using clinical samples. By determination of doxorubicin concentration, the proposed assay has shown a satisfactory linear range of detection (3.8-3000 ng mL-1) with a limit of detection of 3.8 ng mL-1 and an IC50 of 903.9 ng mL-1. The intra and inter-assay coefficients of variation were 4.12-5.72% and 5.48-6.91%, respectively, and the recovery was acceptable. The applicability of the proposed assay was assessed by comparing the determined results with those measured by LC-MS/MS, presenting a satisfactory correlation (R 2 = 0.9868). The proposed assay, which shows satisfactory analytical performance, has great potential for application in the field of TDM in the future.

Metabolic carbonyl reduction of anthracyclines - role in cardiotoxicity and cancer resistance. Reducing enzymes as putative targets for novel cardioprotective and chemosensitizing agents

Anthracycline antibiotics (ANT), such as doxorubicin or daunorubicin, are a class of anticancer drugs that are widely used in oncology. Although highly effective in cancer therapy, their usefulness is greatly limited by their cardiotoxicity. Possible mechanisms of ANT cardiotoxicity include their conversion to secondary alcohol metabolites (i.e. doxorubicinol, daunorubicinol) catalyzed by carbonyl reductases (CBR) and aldo-keto reductases (AKR). These metabolites are suspected to be more cardiotoxic than their parent compounds. Moreover, overexpression of ANT-reducing enzymes (CBR and AKR) are found in many ANT-resistant cancers. The secondary metabolites show decreased cytotoxic properties and are more susceptible to ABC-mediated efflux than their parent compounds; thus, metabolite formation is considered one of the mechanisms of cancer resistance. Inhibitors of CBR and AKR were found to reduce the cardiotoxicity of ANT and the resistance of cancer cells, and therefore are being investigated as prospective cardioprotective and chemosensitizing drug candidates. In this review, the significance of a two-electron reduction of ANT, including daunorubicin, epirubicin, idarubicin, valrubicin, amrubicin, aclarubicin, and especially doxorubicin, is described with respect to toxicity and efficacy of therapy. Additionally, CBR and AKR inhibitors, including monoHER, curcumin, (−)-epigallocatechin gallate, resveratrol, berberine or pixantrone, and their modulating effect on the activity of ANT is characterized and discussed as potential mechanism of action for novel therapeutics in cancer treatment.

Pharmacokinetic and pharmacodynamic study of doxorubicin in children with cancer: results of a "European Pediatric Oncology Off-patents Medicines Consortium" trial

Purpose

Doxorubicin is a key component in many pediatric oncology treatment regimens; still pharmacology data on which current dosing regimens are based are very limited.

Methods

We conducted a multinational pharmacokinetic study investigating age dependency of doxorubicin metabolism and elimination in children with cancer. One hundred and one patients treated with doxorubicin according to a cancer-specific national or European therapeutic trial were recruited. Doses of doxorubicin ranged from 10.4 to 57.7 mg/m². Blood samples for measurement of doxorubicin and its metabolite doxorubicinol were collected after two administrations, with five samples collected in children <3 years and eight in children ≥3 years. A population pharmacokinetic approach was used for analysis, including pharmacogenetic covariates. Natriuretic peptides and cardiac troponins were measured to evaluate their role as early indicators of cardiotoxicity.

Results

Age dependence of doxorubicin clearance was demonstrated, with children less than 3 years having a statistically significant lower clearance (21.1 ± 5.8 l/h/m²) than older children (26.6 ± 6.7 l/h/m²) (p = 0.0004) after correcting for body surface area. No effect of the investigated genetic polymorphisms on the pharmacokinetics could be observed. Although natriuretic peptides were transiently elevated after each doxorubicin administration and troponin levels increased with increasing doxorubicin exposure, only limited correlation could be observed between their blood levels and doxorubicin pharmacokinetics.

Conclusion

In the European framework of funding and regulatory support, an add-on study to existing therapeutic trials was developed. The pediatric need concerning missing PK data could be addressed with limited burden for the patients. Empirically used dose adaptations for infants were generally found to be justified based on our PK analyses.

Electronic supplementary material

The online version of this article (doi:10.1007/s00280-016-3174-8) contains supplementary material, which is available to authorized users.

Pharmacokinetic Interactions for Drugs with a Long Half-Life—Evidence for the Need of Model-Based Analysis

Pharmacokinetic drug-drug interactions (DDIs) can lead to undesired drug exposure, resulting in insufficient efficacy or aggravated toxicity. Accurate quantification of DDIs is therefore crucial but may be difficult when full concentration-time profiles are problematic to obtain. We have compared non-compartmental analysis (NCA) and model-based predictions of DDIs for long half-life drugs by conducting simulation studies and reviewing published trials, using antituberculosis drug bedaquiline (BDQ) as a model compound. Furthermore, different DDI study designs were evaluated. A sequential design mimicking conducted trials and a population pharmacokinetic (PK) model of BDQ and the M2 metabolite were utilized in the simulations where five interaction scenarios from strong inhibition (clearance fivefold decreased) to strong induction (clearance fivefold increased) were evaluated. In trial simulations, NCA systematically under-predicted the DDIs’ impact. The bias in average exposure was 29–96% for BDQ and 20–677% for M2. The model-based analysis generated unbiased predictions, and simultaneous fitting of metabolite data increased precision in DDI predictions. The discrepancy between the methods was also apparent for conducted trials, e.g., lopinavir/ritonavir was predicted to increased BDQ exposure 22% by NCA and 188% by model-based methods. In the design evaluation, studies with parallel designs were considered and shown to generally be inferior to sequential/cross-over designs. However, in the case of low inter-individual variability and no informative metabolite data, a prolonged parallel design could be favored. Model-based analysis for DDI assessments is preferable over NCA for victim drugs with a long half-life and should always be used when incomplete concentration-time profiles are part of the analysis.

Population pharmacokinetics of doxorubicin and doxorubicinol in patients diagnosed with non-Hodgkin's lymphoma

AIMS

The aims of the study were: (i) to characterize the pharmacokinetics (PK) of doxorubicin (DOX) and doxorubicinol (DOXol) in patients diagnosed with non-Hodgkin's lymphoma (NHL) using a population approach; (ii) to evaluate the influence of various covariates on the PK of DOX; and (iii) to evaluate the role of DOX and DOXol exposure in haematological toxicity.

METHODS

Population PK modelling (using NONMEM) was performed using DOX and DOXol plasma concentration-time data from 45 NHL patients treated with R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone). The influence of drug exposure on haematological toxicity was analysed using the Mann-Whitney-Wilcoxon test.

RESULTS

A five-compartment model, three for DOX and two for DOXol, with first-order distribution and elimination for both entities best described the data. Population estimates for parent drug (CL) and metabolite (CL_m ) clearance were 62 l h^-1 and 27 l h^-1 , respectively. The fraction metabolized to DOXol (F_m ) was estimated at 0.22. While bilirubin and aspartate aminotransferase showed an influence on the CL and CL_m , the objective function value decrease was not statistically significant. A trend towards an association between the total area under the concentration-time curve (AUC_total ), the area under the concentration-time curve for DOX (AUC) plus the area under the concentration-time curve for DOXol (AUC_m ), and the neutropenia grade (P = 0.068) and the neutrophil counts (P = 0.089) was observed, according to an exponential relationship.

CONCLUSIONS

The PK of DOX and DOXol were well characterized by the model developed, which could be used as a helpful tool to optimize the dosage of this drug. The results suggest that the main active metabolite of DOX, DOXol, is involved in the haematological toxicity of the parent drug.

Pharmacokinetic-pharmacodynamic modelling of acute N-terminal pro B-type natriuretic peptide after doxorubicin infusion in breast cancer

AIMS

The aim of the present study was to develop a pharmacokinetic-pharmacodynamic (PK-PD) model to characterize the relationship between plasma doxorubicin and N-terminal pro B-type natriuretic peptide (NT-proBNP) concentrations within 48 h of doxorubicin treatment.

METHODS

The study enrolled 17 female patients with stages 1-3 breast cancer and receiving adjuvant doxorubicin (60 mg m(-2) ) and cyclophosphamide (600 mg m(-2) ) every 14 days for four cycles. In two consecutive cycles, plasma concentrations of doxorubicin, doxorubicinol, troponin and NT-proBNP were collected before infusion, and up to 48 h after the end of doxorubicin infusion. Nonlinear mixed-effects modelling was used to describe the PK-PD relationship of doxorubicin and NT-proBNP.

RESULTS

A three-compartment parent drug with a one-compartment metabolite model best described the PK of doxorubicin and doxorubicinol. Troponin concentrations remained similar to baseline. An indirect PD model with transit compartments best described the relationship of doxorubicin exposure and acute NT-proBNP response. Estimated PD parameters were associated with large between-subject variability (total assay variability 38.8-73.9%). Patient clinical factors, including the use of enalapril, were not observed to be significantly associated with doxorubicin PK or NT-proBNP PD variability.

CONCLUSION

The relationship between doxorubicin concentration and the acute NT-proBNP response was successfully described with a population PK-PD model. This model will serve as a valuable framework for future studies to identify clinical factors associated with the acute response to doxorubicin. Future studies are warranted to examine the relationship between this acute response and subsequent heart failure. Should such a relationship be established, this model could provide useful information on patients' susceptibility to doxorubicin-induced long-term cardiotoxicity.

Curcumin-docetaxel co-loaded nanosuspension for enhanced anti-breast cancer activity

PURPOSE

A curcumin-docetaxel co-loaded nanosuspension with increased anti-breast cancer activity was developed. Curcumin is a potential anticancer agent with p-glycoprotein (p-gp) inhibiting activity may be co-administered with docetaxel as a nanosuspension to enhance its anticancer effect by increasing the oral bioavailability and decreasing drug efflux.

METHODS

Nanosuspensions of curcumin and docetaxel were prepared by precipitation-homozenisation technique and evaluated for particle size, polydispersity, zeta potential and drug release. The in vitro MTT assay was conducted using MCF-7 for anti-breast cancer activity. The in vivo biodistribution by radiolabeling and tumor inhibition study was conducted in mice.

RESULTS

Homogenous nanosuspensions of 80 ± 20 nm were obtained with increased solubility. The drugs as nanosuspensions showed higher cytotoxicity on MCF-7 cell line compared to their suspensions due to the increased in vitro cellular uptake. Due to this increased solubility, sensitization of tumor cells and inhibition of p-gp the in-vivo results showed greater tumor inhibition rate of up to 70% in MCF-7 treated mice. Histopathological results showed higher apoptotic activity and reduced level of angiogenesis.

CONCLUSIONS

The in vitro and in vivo study of the nanosuspensions has shown that Co-administration of Curcumin as a p-gp inhibitor with docetaxel may have the potential to increase the anti-breast cancer efficacy of both drugs.

Effects of the inhibition of intestinal P-glycoprotein on aliskiren pharmacokinetics in cynomolgus monkeys

Aliskiren is a substrate for P-glycoprotein (P-gp) and is metabolized via cytochrome P450 3A4 (CYP3A4). The aim of the present study was to assess whether P-gp influenced the pharmacokinetics of aliskiren and also if drug-drug interactions (DDIs) mediated through P-gp could be reproduced in cynomolgus monkeys. The study investigated the pharmacokinetics of aliskiren in mdr1a/1b gene-deficient (P-gp KO) and wild-type (WT) mice. The area under the plasma concentration-time curve (AUC) following the oral administration of aliskiren was 6.9-fold higher in P-gp KO mice than in WT mice, while no significant differences were observed in the AUC or total plasma clearance following the intravenous administration of aliskiren to P-gp KO mice. Then the pharmacokinetics of aliskiren were evaluated and DDIs between aliskiren and P-gp inhibitors, such as cyclosporin A (CsA) and zosuquidar, examined in cynomolgus monkeys. The AUC for aliskiren were 8.3- and 42.1-fold higher after the oral administration of aliskiren with the concomitant oral administration of zosuquidar and CsA at doses of 10 and 30 mg/kg, respectively. In contrast, the AUC after the intravenous and oral administration of aliskiren was not significantly affected by the oral administration of zosuquidar or intravenous administration of CsA, respectively. These results indicated that P-gp strictly limited the intestinal absorption of aliskiren in mice and monkeys, and also that the effects of intestinal P-gp inhibition by CsA or zosuquidar on the pharmacokinetics of aliskiren were sensitively reproduced in monkeys. In conclusion, aliskiren can be used as a sensitive substrate to evaluate intestinal P-gp inhibition in monkeys.

Validation and clinical evaluation of a UHPLC method with fluorescence detector for plasma quantification of doxorubicin and doxorubicinol in haematological patients

A rapid and simple UHPLC-fluorescence detection method for the quantification of doxorubicin and its main metabolite, doxorubicinol, in human plasma has been developed. The method was also validated for its application in therapeutic drug monitoring, a clinical approach used in the optimization of oncologic treatments. Following a single protein precipitation step, chromatographic separation was achieved using a C18 column (50mm×2.10mm, particle size 1.7μm) at 50°C with a mobile phase consisting of water (containing 0.4% triethylamine and 0.4% orthophosphoric acid)/acetonitrile (77:23, v/v). Flow rate was 0.50mL/min and fluorescence detection with an excitation wavelength of 470nm and an emission wavelength of 548nm was used. The method met the specifications of linearity, selectivity, sensitivity, accuracy, precision and stability of the FDA and EMA guidelines for the validation of bioanalytical methods. Linearity for the drug (8-3000ng/mL) and the metabolite (3-150ng/mL) was observed (R(2)>0.992) and the maximum intra-day and inter-day precision coefficients of variation were less than 14% for both. The lower limits of quantification were 8 and 3ng/mL for doxorubicin and doxorubicinol, respectively. The method was successfully applied to the quantify plasma concentrations of doxorubicin and doxorubicinol in 33 patients diagnosed with haematological malignancies in which broad ranges for drug (8.3-2766.0ng/mL) and metabolite (4.8-104.9ng/mL) levels were measured adequately.

Model-based drug development applied to oncology

Model-based drug development (MBDD) is an approach that is used to organize the vast and complex data streams that feed the drug development pipelines of small molecule and biotechnology sponsors. Such data streams are ultimately reviewed by the global regulatory community as evidence of a drug's potential to treat and/or harm patients. Some of this information is captured in the scientific literature and prescribing compendiums forming the basis of how new and existing agents will ultimately be administered and further evaluated in the broader patient community. As this data stream evolves, the details of data qualification, the assumptions and/or critical decisions based on these data are lost under conventional drug development paradigms. MBDD relies on the construction of quantitative relationships to connect data from discrete experiments conducted along the drug development pathway. These relationships are then used to ask questions relevant at critical development stages, hopefully, with the understanding that the various scenarios explored represent a path to optimal decision making. Oncology, as a therapeutic area, presents a unique set of challenges and perhaps a different development paradigm as opposed to other disease targets. The poor attrition of development compounds in the recent past attests to these difficulties and provides an incentive for a different approach. In addition, given the reliance on multimodal therapy, oncological disease targets are often treated with both new and older agents spanning several drug classes. As MBDD becomes more integrated into the pharmaceutical research community, a more rational explanation for decisions regarding the development of new oncology agents as well as the proposed treatment regimens that incorporate both new and existing agents can be expected. Hopefully, the end result is a more focussed clinical development programme, which ultimately provides a means to optimize individual patient care.

Population-Based Assessments of Clinical Drug-Drug Interactions: Qualitative Indices or Quantitative Measures?

Population-based assessments of drug-drug interactions have become more common since the introduction and acceptance of the population pharmacokinetic approach. Unlike traditional methods, population-based studies provide clinically relevant results that can be applied directly to a target patient population. Furthermore, population-based studies do not demand the traditional requirements of intensive pharmacokinetic sampling, rigorous inpatient stays, or stringent assessment schedules. As such, the population-based approach can effectively be used to confirm known drug-drug interactions and further characterize anticipated interactions. A prospectively designed analysis can also reveal drug-drug interactions that might otherwise have gone undetected with traditional methods. Ultimately, these results could help to alleviate clinicians' concerns about using widely marketed drugs in combination therapies and also reduce patients' risk of experiencing unacceptable side effects. This article intends to provide a balanced overview of the population-based approach and its merits, drawbacks, and potential utility in the assessment of drug-drug interactions during clinical drug development.

Population pharmacokinetics of doxorubicin: establishment of a NONMEM model for adults and children older than 3 years

PURPOSE

The aim of the current investigation was to develop a population pharmacokinetic model for doxorubicin and doxorubicinol that could provide improved estimated values for the pharmacokinetic parameters clearance of doxorubicin, volume of distribution of the central compartment, clearance of doxorubicinol and volume of distribution of the metabolite compartment for adults and children older than 3 years. A further aim was to investigate the potential influence of the covariates body surface area, body weight, body height, age, body mass index, sex and lean body mass on the pharmacokinetic parameters.

METHODS

Three different datasets, two containing data from adults and one containing data from adults and children, were merged and the combined dataset was analysed retrospectively. In total, the combined dataset contained 934 doxorubicin and 935 doxorubicinol plasma concentrations from 82 patients [64 adults and 18 children (<18 years)]. With this combined dataset, a population pharmacokinetic model was developed, using NONMEM(®) 7.2 and a predefined model-building strategy. Different structural models, error models and estimation methods were tested, and the inter-individual and the inter-occasion variability (variability between separate (two or three) doxorubicin infusions) were tested. Using a subset of 52 patients, the influence of different covariates on the pharmacokinetic parameters was investigated. The pharmacokinetic parameter estimates obtained from doxorubicin concentrations with the best model were fixed, and an additional compartment for doxorubicinol was added to the model. With the final model for both substances, a potential age dependency and body mass index dependency of the clearance of doxorubicin and doxorubicinol as well as of the volumes of distribution of the central and the metabolite compartment were evaluated.

RESULTS

A four-compartment model best described the doxorubicin and doxorubicinol data of the combined dataset. This model included a proportional residual error model and an inter-individual variability on the clearance of doxorubicin, on the inter-compartmental clearances of the peripheral compartments, on the clearance of doxorubicinol and on the volumes of distribution of the central, one peripheral and the metabolite compartment. Furthermore, the body surface area as covariate on all pharmacokinetic parameters and an inter-occasion variability for the clearance of doxorubicin and the volume of distribution of the central compartment were incorporated in the model. For a patient with the body surface area of 1.8 m², the clearance of doxorubicin was 53.3 L/h (inter-individual variability 31%, inter-occasion variability 13%) and the volume of distribution of the central compartment was 17.7 L (inter-individual variability 19%, inter-occasion variability 21%), respectively. The residual variability of the model was 22% for doxorubicin and 26% for doxorubicinol. The clearance of doxorubicinol was estimated at 44 L/h (inter-individual variability 50%) and the volume of distribution of the metabolite compartment at 1,150 L (inter-individual variability 57%). The evaluation of a possible age dependency and body mass index dependency showed a trend to a smaller volume of distribution of the central compartment (normalised to the body surface area) and a higher volume of distribution of the metabolite compartment (normalised to the body weight) in younger patients.

CONCLUSIONS

A four-compartment NONMEM(®) model for doxorubicin and doxorubicinol adequately described the plasma concentrations in adults and children (>3 years). No pronounced effects of age on the clearance of doxorubicin or doxorubicinol were found, and the analysis did not support the modification of the dosing strategies presently used in children and adults.

[Populational pharmacokinetics of doxorubicin applied to personalised its dosing in cancer patients]

OBJECTIVE

To develop and internally validate a population pharmacokinetic model for doxorubicin and to evaluate its predictive performance for dose individualization in cancer patients.

METHODS

Doxorubicin plasma concentrations were determined in thirty-three cancer patients treated with intravenous doxorubicin. A three-compartment pharmacokinetic model was implemented in the NONMEN VI programme to determine the doxorubicin pharmacokinetic parameters. The identifiability of the parameters was assessed by parametric bootstrap and model validation was performed using nonparametric bootstrap, visual predictive check, and numerical predictive check. The final model's predictive performance was evaluated in terms of accuracy and precision of plasma concentration predictions during the first and second cycles of chemotherapy.

RESULTS

Doxorubicin clearance was 58.8 L/h, with interpatient variability of 29.2% and intrapatient variability of 18.9%. The estimated volume of distribution at steady state was 2294 L, with inter-and intrapatient variability of 7.3% and 26.1%, respectively. Internal validation confirmed that the population pharmacokinetic model is appropriate to describe the time course of the doxorubicin plasma concentrations and its variability in this population. The accuracy and precision of an a posteriori prediction of doxorubicin plasma concentrations improved by 63% and 41% compared to the a priori prediction.

CONCLUSION

The Bayesian population pharmacokinetic model characterised the time course of doxorubicine plasma concentrations and can be accurately and precisely used to optimise doxorubicine dosing regimens in cancer patients.

Pharmacokinetics of daunorubicin and daunorubicinol in infants with leukemia treated in the interfant 99 protocol

BACKGROUND

There is an extreme paucity of pharmacokinetic data for anticancer agents in infants. Therefore, we aimed at characterizing the pharmacokinetics for daunorubicin in infants and examined their relationship to age, body weight, and body surface area.

PROCEDURE

Leukemia patients treated according to the Interfant 99 protocol received 30 mg/m(2) daunorubicin, with dose reduction to 3/4 for patients 6-12 months old and 2/3 for patients <6 months, respectively. Plasma samples from 21 patients (aged 0.05-1.88 years) were collected and analyzed for daunorubicin and daunorubicinol. Samples from 12 children (age 1.6-18.8 years), who received daunorubicin in an earlier investigation, were used for pharmacokinetic model building using the software NONMEM.

RESULTS

Plasma concentration time profiles could be described using a two compartment model. Daunorubicin clearance was 43.9 L hr(-1) m(-2) +/- 65% and central volume of distribution 16.4 L m(-2) +/- 46%, whereas apparent clearance of daunorubicinol was 19.1 L hr(-1) m(-2) +/- 32% and apparent volume of distribution 228 L m(-2) +/- 80% (mean +/- interindividual variability). No age-dependency in any of the BSA-normalized pharmacokinetic parameters was observed. Consequently, due to the empirical dose reduction in infants the overall exposure to daunorubicinol in infants was smaller than would be expected from older children. Patients aged <6 months experienced more infections in the induction phase than the group aged 6-12 months at diagnosis. Other toxicities were similar in both groups.

CONCLUSION

We observed no indication of an age-dependency in the pharmacokinetics of daunorubicin. Pediatr Blood Cancer 2010;54:355-360.

Phase I/II trial of a P-glycoprotein inhibitor, Zosuquidar.3HCl trihydrochloride (LY335979), given orally in combination with the CHOP regimen in patients with non-Hodgkin's lymphoma

A phase I/II trial was performed to investigate the safety and tolerance of zosuquidar.3HCL, a potent inhibitor of P-glycoprotein (P-gp), when administered orally alone and in combination with the CHOP regimen in patients with untreated non-Hodgkin's lymphoma and to determine whether zosuquidar.3HCL affects pharmacokinetics of doxorubicin and vincristine. Doses of CHOP remained constant and the doses of zosuquidar.3HCL were increased from 200 to 500 mg per dose. A total of 15 patients were treated at three dose levels. A target dose providing peak and trough levels compatible with prolonged modulation of P-gp function was obtained in patients receiving three doses of 500 mg of zosuquidar.3HCL p.o. At this dose level, toxicity was minimal and no enhancement of CHOP-related toxicity was observed. Zosuquidar.3HCL did not significantly affect the pharmacokinetics of doxorubicin and had moderate effects on the pharmacokinetics of vincristine. Zosuquidar.3HCL can be safely administered with CHOP therapy using a 24-h schedule.

Modulation of Oral Drug Bioavailability: From Preclinical Mechanism to Therapeutic Application

Currently, more than one fourth of all anticancer drugs are developed as oral formulations, and it is expected that this number will increase substantially in the near future. To enable oral drug therapy, adequate oral bioavailability must be achieved. Factors that have proved to be important in limiting the oral bioavailability are the presence of ATP-binding cassette drug transporters (ABC transporters) and the cytochrome P450 enzymes. We discuss the tissues distribution and physiological function of the ABC transporters in the human body, their expression in tumors, currently known polymorphisms and drugs that are able to inhibit their function as transporter. Furthermore, the role of the ABC transporters and drug-metabolizing enzymes as mechanisms to modulate the pharmacokinetics of anticancer agents, will be reviewed. Finally, some clinical examples of oral drug modulation are discussed. Among these examples are the coadministration of paclitaxel with CsA, a CYP3A4 substrate with P-glycoprotein (P-gp) modulating activity, and topotecan combined with the BCRP/P-gp transport inhibitor elacridar. Both are good examples of improvement of oral drug bioavailability by temporary inhibition of drug transporters in the gut epithelium.

Evaluation of anticancer effects of newly synthesized dihydropyridine derivatives in comparison to verapamil and doxorubicin on T47D parental and resistant cell lines in vitro

Failure of current anticancer drugs mandates screening for new compounds of synthetic or biological origin to be used in cancer therapy. Multidrug resistance (MDR) is one of the main obstacles in the chemotherapy of cancer. Efflux of cytotoxic agents mediated by P-glycoprotein (P-gp or MDR1) is believed to be an important mechanism of multidrug resistance. Therefore, we decided to investigate the antiproliferative effects of seven newly synthesized 1,4-dihydropyridine (DHP) derivatives in comparison to verapamil (VP) and doxorubicin (DOX) on human breast cancer T47D cells and its MDR1 overexpressed and moderately resistant cells (RS cells) using MTT cytotoxicity assay. We also examined the effects of these compounds on cytotoxicity of DOX in these two cell types. The cytotoxicity assays using MTT showed that most of the tested new DHP derivatives and VP at 10 microM concentration had varying levels of toxicity on both T47D and RS cells. The toxicity was mostly in the range of 10-25%. However, the cytotoxicity of these DHP derivatives, similar to VP, was significantly less than DOX when comparing IC(50) values. Furthermore, these compounds in general had relatively more cytotoxicity on T47D vs RS cells at 10-microM concentration. Among new DHPs, compounds 7a (3,5-dibenzoyl-4-(2-methylthiazol-4-yl)-1,4-dihydro-2,6-dimethylpyridine) and 7d (3,5-diacetyl-4-[2-(2-chlorophenyl)thiazol-4-yl)]-1,4-dihydro-2,6-dimethylpyridine) showed noticeable potentiation of DOX cytotoxicity (reduction of DOX IC(50)) compared to DOX alone in both cells, particularly in RS cells. This effect was similar to that of VP, a known prototype of MDR1 reversal agent. In other words, compounds 7a and 7d resensitized RS cells to DOX or reversed their resistance. Results indicate that compound 7d exerts highest effect on RS cells. Therefore, these two newly synthesized DHP derivatives, compounds 7a and 7d, are promising as potential new MDR1 reversal agents and should be further studied on other highly resistant cells due to MDR1 overexpression and with further molecular investigation.

International Society of Geriatric Oncology Chemotherapy Taskforce: evaluation of chemotherapy in older patients--an analysis of the medical literature

The elderly comprise the majority of patients with cancer and are the recipients of the greatest amount of chemotherapy. Unfortunately, there is a lack of data to make evidence-based decisions with regard to chemotherapy. This is due to the minimal participation of older patients in clinical trials and that trials have not systematically evaluated chemotherapy. This article reviews the available information with regard to chemotherapy and aging provided by a task force of the International Society of Geriatric Oncology (SIOG). Due to the lack of prospective data, the conclusions and recommendations made are a consensus of the participants. Extrapolation of data from younger to older patients is necessary, particularly to those patients older than 80 years, for which data is almost entirely lacking. The classes of drugs reviewed include alkylators, antimetabolites, anthracyclines, taxanes, camptothecins, and epipodophyllotoxins. Clinical trials need to incorporate an analysis of chemotherapy in terms of the pharmacokinetic and pharmacodynamic effects of aging. In addition, data already accumulated need to be reanalyzed by age to aid in the management of the older cancer patient.

Modeling methadone pharmacokinetics in rats in presence of P-glycoprotein inhibitor valspodar

PURPOSE

To quantify the in vivo role of P-glycoprotein (P-gp) in the pharmacokinetics of methadone after intravenous and oral administration, using valspodar as a P-gp inhibitor.

MATERIALS AND METHODS

Methadone plasma concentrations after intravenous (0.35 mg/kg) and oral (6 mg/kg) administration were analyzed, in absence and presence of valspodar, using nonlinear mixed effects modeling (NONMEM V). Non-parametric bootstrap analysis and posterior predictive check were employed as model evaluation techniques.

RESULTS

The pharmacokinetics of methadone in the rat was successfully modeled using a two-compartmental model with a linear elimination from the central compartment and a first-order absorption process with lag time. Valspodar increased methadone F by 122% (95%CI: 34-269%) and decreased the V ( c ) and V ( p ) by 35% (95%CI: 16-49%) and 81% (95%CI: 63-93%), respectively. No effect of valspodar on other pharmacokinetic parameters was discernible. The non-parametric bootstrap analysis confirmed the absence of bias on the parameter estimates, and visual predictive check evidence the adequacy of the model to reproduce the observed time course of methadone plasma concentrations.

CONCLUSION

Valspodar increased methadone's bioavailability as consequence of P-gp inhibition, which resulted in an increased analgesic effect of methadone.

Pharmacokinetics/Pharmacodynamics and the stages of drug development: role of modeling and simulation

Pharmacokinetic (PK) and pharmacodynamic (PD) modeling and simulation (M&S) are well-recognized powerful tools that enable effective implementation of the learn-and-confirm paradigm in drug development. The impact of PK/PD M&S on decision making and drug development risk management is dependent on the question being asked and on the availability and quality of data accessible at a particular stage of drug development. For instance, M&S methodologies can be used to capture uncertainty and use the expected variability in PK/PD data generated in preclinical species for projection of the plausible range of clinical dose; clinical trial simulation can be used to forecast the probability of achieving a target response in patients based on information obtained in early phases of development. Framing the right question and capturing the key assumptions are critical components of the "learn-and-confirm" paradigm in the drug development process and are essential to delivering high-value PK/PD M&S results. Selected works of PK/PD modeling and simulation from preclinical to phase III are presented as case examples in this article.

Population pharmacokinetic model for daunorubicin and daunorubicinol coadministered with zosuquidar.3HCl (LY335979)

PURPOSE

The impact of zosuquidar.3HCl, an inhibitor of P-glycoprotein, on the pharmacokinetics of daunorubicin and daunorubicinol was examined in a phase I trial using a population approach. Pharmacokinetic and pharmacodynamic properties of zosuquidar.3HCl were also determined.

METHODS

The pharmacokinetics of daunorubicin and daunorubicinol were studied following daunorubicin administration on day 1 (50 mg/m2 i.v. infusion over 10 min) alone and on day 3 concomitantly with zosuquidar.3HCl (i.v. 200 or 300 mg/m2 over 6 h or 400 mg over 3 h). Of a total of 18 patients entered, 16 with acute leukemia completed the study.

RESULTS

A three-compartment pharmacokinetic model adequately described daunorubicin concentration-time profiles. Five- and four-compartment models adequately described the daunorubicin-daunorubicinol pharmacokinetics in the absence and presence of zosuquidar.3HCl, respectively. The impact of zosuquidar.3HCl on coadministered daunorubicin was minimal, with a 10% reduction in daunorubicin clearance. The model predicted a 50% decrease in daunorubicinol apparent clearance in the presence of zosuquidar.3HCl. A direct concentration-effect relationship between zosuquidar.3HCl concentrations and inhibition of rhodamine 123 (Rh123) efflux in CD56 lymphocytes was defined by a sigmoid E(max) model. The IC(50) was 31.7 microg/l. The zosuquidar.3HCl dosing regimen led to concentrations in excess of the IC(90) (169.6 microg/l) and provided maximal P-glycoprotein inhibition during the distribution phases of daunorubicin.

CONCLUSIONS

The decrease in daunorubicin and daunorubicinol clearance in the presence of zosuquidar.3HCl likely reflects inhibition of P-glycoprotein in the bile canaliculi impeding their biliary excretion. The results need to be interpreted carefully due to the sequential nature of daunorubicin administration and analysis.