Pharmacokinetics of paclitaxel and carboplatin in a dose-escalating and dose-sequencing study in patients with non-small-cell lung cancer. The European Cancer Centre

Using maximum plasma concentration (Cmax) to personalize taxane treatment and reduce toxicity

Taxanes are a widely used class of anticancer agents that play a vital role in the treatment of a variety of cancers. However, toxicity remains a major concern of using taxane drugs as some toxicities are highly prevalent, they can not only adversely affect patient prognosis but also compromise the overall treatment plan. Among all kinds of factors that associated with taxane toxicity, taxane exposure has been extensively studied, with different pharmacokinetic (PK) parameters being used as toxicity predictors. Compared to other widely used predictors such as the area under the drug plasma concentration curve versus time (AUC) and time above threshold plasma drug concentration, maximum plasma concentration (Cmax) is easier to collect and shows promise for use in clinical practice. In this article, we review the previous research on using Cmax to predict taxane treatment outcomes. While Cmax and toxicity have been extensively studied, research on the relationship between Cmax and efficacy is lacking. Most of the articles find a positive relationship between Cmax and toxicity but several articles have contradictory findings. Future clinical trials are needed to validate the relationship between Cmax and treatment outcome and determine whether Cmax can serve as a useful surrogate endpoint of taxane treatment efficacy.

Paclitaxel therapeutic drug monitoring - International association of therapeutic drug monitoring and clinical toxicology recommendations

Paclitaxel, one of the most frequently used anticancer drugs, is dosed by body surface area, which leads to substantial inter-individual variability in systemic drug exposure. We evaluated clinical evidence regarding the scientific rationale and clinical benefit of individualized paclitaxel dosing based on measured systemic concentrations, known as therapeutic drug monitoring (TDM). In retrospective studies, higher systemic exposure is associated with greater toxicity and efficacy of paclitaxel treatment across several disease types and dosing regimens. In prospective trials, TDM reduces variability in systemic exposure, and has been demonstrated to reduce toxicity while retaining treatment efficacy for 3-weekly dosing in patients with advanced non-small cell lung cancer. Despite the demonstrated benefits of paclitaxel TDM, clinical adoption has been limited due to the challenges with sample collection and analysis. Based on our review, we strongly recommend TDM for patients receiving every 3-week paclitaxel in combination with a platinum agent for advanced NSCLC, due to the prospectively demonstrated clinical benefits, and find moderate evidence to recommend TDM for paclitaxel 3-hour infusions for other tumor types and preliminary evidence suggesting potential usefulness for paclitaxel administered by 1-hour infusions.

Potential Drug-Drug Interactions in Outpatient Lung Cancer Patients in a University Hospital

INTRODUCTION

Concomitant use of drugs in the same or different indications can sometimes lead to undesirable interactions. The prevalence of drug interactions is high in cancer patients. In this study, we aimed to determine the frequency and clinical severity of drug interactions in outpatient lung cancer patients.

METHODS

The drugs used, kidney and liver blood analysis results of 160 outpatient lung cancer patients over the age of 18 years who received chemotherapy between October 2020 and July 2021 were evaluated. The Lexi-Interact online database was used to identify the types of clinically significant drug interactions, frequently interacting drugs, and clinical outcomes predicted by the databases.

RESULTS

The average number of drugs per patient was 4.2 ± 2.3. It was determined that there was a relationship between multidrug use and comorbidity, and the number of drugs used increased as the number of diagnoses increased. A relationship was also found between potential drug-drug interactions (pDDIs), which we observed in 52.5% of the patients, and the number of drugs used and age. The most common clinically significant C- (36.9%), D- (16.9%), and X- (10.6%) type pDDIs were detected between conventional paclitaxel-hydrochlorothiazide, conventional paclitaxel-carboplatin, and ipratropium-tiotropium, respectively.

CONCLUSIONS

The use of frequently interacting drugs in outpatient lung cancer patients can lead to pDDIs. In these patients, the application of therapy by observing the drug-drug interaction may improve the quality of life.

Paclitaxel and Therapeutic Drug Monitoring with Microsampling in Clinical Practice

Paclitaxel is an anticancer agent efficacious in various tumors. There is large interindividual variability in drug plasma concentrations resulting in a wide variability in observed toxicity in patients. Studies have shown the time the concentration of paclitaxel exceeds 0.05 µM is a predictive parameter of toxicity, making dose individualization potentially useful in reducing the adverse effects. To determine paclitaxel drug concentration, a venous blood sample collected 24 h following the end of infusion is required, often inconvenient for patients. Alternatively, using a microsampling device for self-sampling would facilitate paclitaxel monitoring regardless of the patient's location. We investigated the feasibility of collecting venous and capillary samples (using a Mitra® device) from cancer patients to determine the paclitaxel concentrations. The relationship between the venous plasma and whole blood and venous and capillary blood (on Mitra®) paclitaxel concentrations, defined by a Passing-Bablok regression, were 0.8433 and 0.8569, respectively. Demonstrating a clinically acceptable relationship between plasma and whole blood paclitaxel concentration would reduce the need to establish new target concentrations in whole blood. However, in this study, comparison of venous and capillary blood using Mitra® for sampling displayed wide confidence intervals suggesting the results from the plasma and whole blood on this device may not be interchangeable.

Model-based approach to identify predictors of paclitaxel-induced myelosuppression in "real-world" administration

Taxanes are currently the most frequently used chemotherapeutic agents in cancer care, where real-world use has focused on minimizing adverse events and standardizing the delivery. Myelosuppression is a well-characterized, adverse pharmacodynamic effect of taxanes. Electronic health records (EHRs) comprise data collected during routine clinical care that include patients with heterogeneous demographic, clinical, and treatment characteristics. Application of pharmacokinetic/pharmacodynamic (PK/PD) modeling to EHR data promises new insights on the real-world use of taxanes and strategies to improve therapeutic outcomes especially for populations who are typically excluded from clinical trials, including the elderly. This investigation: (i) leveraged previously published PK/PD models developed with clinical trial data and addressed challenges to fit EHR data, and (ii) evaluated predictors of paclitaxel-induced myelosuppression. Relevant EHR data were collected from patients treated with paclitaxel-containing chemotherapy at Inova Schar Cancer Institute between 2015 and 2019 (n = 405). Published PK models were used to simulate mean individual exposures of paclitaxel and carboplatin, which were linearly linked to absolute neutrophil count (ANC) using a published semiphysiologic myelosuppression model. Elderly patients (≥70 years) constituted 21.2% of the dataset and 2274 ANC measurements were included in the analysis. The PD parameters were estimated and matched previously reported values. The baseline ANC and chemotherapy regimen were significant predictors of paclitaxel-induced myelosuppression. The nadir ANC and use of supportive treatments, such as growth factors and antimicrobials, were consistent across age quantiles suggesting age had no effect on paclitaxel-induced myelosuppression. In conclusion, EHR data could complement clinical trial data in answering key therapeutic questions.

Time above threshold plasma concentrations as pharmacokinetic parameter in the comparison of oral and intravenous docetaxel treatment of breast cancer tumors

BACKGROUND

Prolonging the time which plasma concentrations of antimitotic drugs, such as the taxanes, exceed cytotoxic threshold levels may be beneficial for their efficacy. Orally administered docetaxel offers an undemanding approach to optimize such time above threshold plasma concentrations (t C>threshold ).

METHODS

A nonsystematic literature screen was performed to identify studies reporting in-vitro half-maximal inhibitory concentration (IC 50 ) values for docetaxel. Pharmacokinetics of intravenously (i.v.) docetaxel (75 mg/m 2 ) and orally administered docetaxel (ModraDoc006) co-administered with ritonavir (r) given twice daily (30 + 20 mg concomitant with 100 mg ritonavir bis in die) were simulated using previously developed population models. T C>threshold was calculated for a range of relevant thresholds in terms of in-vitro cytotoxicity and plasma concentrations achieved after i.v. and oral administration of docetaxel. A published tumor growth inhibition model for i.v. docetaxel was adapted to predict the effect of attainment of time above threshold levels on tumor dynamics.

RESULTS

Identified studies reported a wide range of in vitro IC 50 values [median 0.04 µmol/L, interquartile range (IQR): 0.0046-0.62]. At cytotoxic thresholds <0.078 µmol/L oral docetaxel shows up to ~7.5-fold longer t C>threshold within each 3-week cycle for a median patient compared to i.v.. Simulations of tumor dynamics showed the increased relative potential of oral docetaxel for inhibition of tumor growth at thresholds of 0.075, 0.05 and 0.005 µmol/L.

CONCLUSION

ModraDoc006/r is superior to i.v. docetaxel 75 mg/m 2 in terms of median time above cytotoxic threshold levels <0.078 µmol/L. This may indicate superior cytotoxicity and inhibition of tumor growth compared to i.v. administration for relatively docetaxel-sensitive tumors.

Paclitaxel exposure-toxicity analysis reveals a pharmacokinetic determinant for dose-limiting neutropenia in East-Asian solid tumor patients: results from two prospective, phase II studies

PURPOSE

The time of a paclitaxel (PTX) concentration remains above 0.05 μM (Tc > 0.05) has been associated with PTX-induced adverse effects in Caucasians, while limited studies were reported in Asians. This study was aimed to explore the characteristics of Tc > 0.05 and the relationship between PTX exposure and toxicity in East-Asian patients.

METHODS

This study was based on two prospective phase II clinical trials and patients with advanced nasopharyngeal cancer (NPC) and non-small cell lung cancer (NSCLC) who were naïve to PTX were included independently. Eligible patients receive PTX (175 mg/m²) and carboplatin (AUC = 5) treatment every 3 weeks. PTX pharmacokinetic analysis was accessed. The relationship between PTX exposure and toxicities after first cycle as well as clinical efficacy was evaluated.

RESULTS

A total of 93 NPC and 40 NSCLC patients were enrolled. PTX exposure was consistent in two trials with average Tc > 0.05 duration of 38.8 h and 38.4 h, respectively. Average Tc > 0.05 in patients with grade 3/4 neutropenia was significantly higher than those without severe neutropenia in NPC patients (P = 0.003) and NSCLC patients (P = 0.007). Cut-off value of Tc > 0.05 were identified from the NPC cohort and then verified in the NSCLC cohort, dividing patients into high exposure Tc > 0.05 group (> 39 h) and low exposure group (≤ 39 h). Incidence of grade 3/4 neutropenia were significantly higher in the high exposure group in NPC cohort (43.3% vs 10.0%, P < 0.001) and NSCLC cohort (42.1% vs 9.5%, P = 0.028). No significant relationship between Tc > 0.05 and efficacy were observed.

CONCLUSION

Patients with PTX Tc > 0.05 duration above 39 h experience more severe neutropenia than those under 39 h. Prospective studies are needed to verify this threshold.

Development of a population pharmacokinetic/pharmacodynamic model for various oral paclitaxel formulations co-administered with ritonavir and thrombospondin-1 based on data from early phase clinical studies

Purpose

Orally administered paclitaxel offers increased patient convenience while providing a method to prolong exposure without long continuous, or repeated, intravenous infusions. The oral bioavailability of paclitaxel is improved through co-administration with ritonavir and application of a suitable pharmaceutical formulation, which addresses the dissolution-limited absorption of paclitaxel. We aimed to characterize the pharmacokinetics of different paclitaxel formulations, co-administered with ritonavir, and to investigate a pharmacodynamic relationship between low-dose metronomic (LDM) treatment with oral paclitaxel and the anti-angiogenic marker thrombospondin-1 (TSP-1).

Methods

Fifty-eight patients treated with different oral paclitaxel formulations were included for pharmacokinetic analysis. Pharmacodynamic data was available for 36 patients. All population pharmacokinetic/pharmacodynamic modelling was performed using non-linear mixed-effects modelling.

Results

A pharmacokinetic model consisting of gut, liver, central, and peripheral compartments was developed for paclitaxel. The gastrointestinal absorption rate was modelled with a Weibull function. Relative gut bioavailabilities of the tablet and capsule formulations, as fractions of the gut bioavailability of the drinking solution, were estimated to be 0.97 (95%CI: 0.67–1.33) and 0.46 (95%CI: 0.34–0.61), respectively. The pharmacokinetic/pharmacodynamic relationship between paclitaxel and TSP-1 was modelled using a turnover model with paclitaxel plasma concentrations driving an increase in TSP-1 formation rate following an E_max relationship with an EC₅₀ of 284 ng/mL (95%CI: 122–724).

Conclusion

The developed pharmacokinetic model adequately described the paclitaxel plasma concentrations for the different oral formulations co-administered with ritonavir. This model, and the established pharmacokinetic/pharmacodynamic relationship with TSP-1, may facilitate future development of oral paclitaxel.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00280-022-04445-z.

Optimized Dosing: The Next Step in Precision Medicine in Non-Small-Cell Lung Cancer

In oncology, and especially in the treatment of non-small-cell lung cancer (NSCLC), dose optimization is often a neglected part of precision medicine. Many drugs are still being administered in "one dose fits all" regimens or based on parameters that are often only minor determinants for systemic exposure. These dosing approaches often introduce additional pharmacokinetic variability and do not add to treatment outcomes. Fortunately, pharmacological knowledge is increasing, providing valuable information regarding the potential of, for example, therapeutic drug monitoring. This article focuses on the evidence for the most promising and easily implemented optimized dosing approaches for the small-molecule inhibitors, chemotherapeutic agents, and monoclonal antibodies as treatment options currently approved for NSCLC. Despite limitations such as investigations having been conducted in oncological diseases other than NSCLC or the retrospective origin of many analyses, an alternative dosing regimen could be beneficial for treatment outcomes, prescriber convenience, or financial burden on healthcare systems. This review of the literature provides recommendations on the implementation of dose optimization and advice regarding promising strategies that deserve further research in NSCLC.

A continued learning approach for model-informed precision dosing: updating models in clinical practice

Model-informed precision dosing (MIPD) is a quantitative dosing framework that combines prior knowledge on the drug-disease-patient system with patient data from therapeutic drug/biomarker monitoring (TDM) to support individualized dosing in ongoing treatment. Structural models and prior parameter distributions used in MIPD approaches typically build on prior clinical trials that involve only a limited number of patients selected according to some exclusion/inclusion criteria. Compared to the prior clinical trial population, the patient population in clinical practice can be expected to include also altered behavior and/or increased interindividual variability, the extent of which, however, is typically unknown. Here, we address the question of how to adapt and refine models on the level of the model parameters to better reflect this real-world diversity. We propose an approach for continued learning across patients during MIPD using a sequential hierarchical Bayesian framework. The approach builds on two stages to separate the update of the individual patient parameters from updating the population parameters. Consequently, it enables continued learning across hospitals or study centers, since only summary patient data (on the level of model parameters) need to be shared, but no individual TDM data. We illustrate this continued learning approach with neutrophil-guided dosing of paclitaxel. The present study constitutes an important step towards building confidence in MIPD and eventually establishing MIPD increasingly in everyday therapeutic use.

Feasibility of pharmacometabolomics to identify potential predictors of paclitaxel pharmacokinetic variability

PURPOSE

Paclitaxel is a commonly used chemotherapy drug with substantial variability in pharmacokinetics (PK) that affects treatment efficacy and toxicity. Pharmacometabolomic signatures that explain PK variability could be used to individualize dosing to improve therapeutic outcomes. The objective of this study was to identify pretreatment metabolites or metabolomic signatures that explain variability in paclitaxel PK.

METHODS

This analysis was conducted using data previously collected on a prospective observational study of 48 patients with breast cancer receiving weekly 80 mg/m² paclitaxel infusions. Paclitaxel plasma concentrations were measured during the first infusion to estimate paclitaxel time above threshold (T_c>0.05) and maximum concentration (C_max). Metabolites measured in pretreatment whole blood by nuclear magnetic resonance spectrometry were analyzed for an association with T_c>0.05 and C_max using Pearson correlation followed by stepwise linear regression.

RESULTS

Pretreatment creatinine, glucose, and lysine concentrations were positively correlated with T_c>0.05, while pretreatment betaine was negatively correlated and lactate was positively correlated with C_max (all uncorrected p < 0.05). After stepwise elimination, creatinine was associated with T_c>0.05, while betaine and lactate were associated with C_max (all p < 0.05).

CONCLUSION

This study identified pretreatment metabolites that may be associated with paclitaxel PK variability demonstrating feasibility of a pharmacometabolomics approach for understanding paclitaxel PK. However, identification of more robust pharmacometabolomic predictors will be required for broad and routine application for the clinical dosing of paclitaxel.

Reinforcement learning and Bayesian data assimilation for model-informed precision dosing in oncology

Model-informed precision dosing (MIPD) using therapeutic drug/biomarker monitoring offers the opportunity to significantly improve the efficacy and safety of drug therapies. Current strategies comprise model-informed dosing tables or are based on maximum a posteriori estimates. These approaches, however, lack a quantification of uncertainty and/or consider only part of the available patient-specific information. We propose three novel approaches for MIPD using Bayesian data assimilation (DA) and/or reinforcement learning (RL) to control neutropenia, the major dose-limiting side effect in anticancer chemotherapy. These approaches have the potential to substantially reduce the incidence of life-threatening grade 4 and subtherapeutic grade 0 neutropenia compared with existing approaches. We further show that RL allows to gain further insights by identifying patient factors that drive dose decisions. Due to its flexibility, the proposed combined DA-RL approach can easily be extended to integrate multiple end points or patient-reported outcomes, thereby promising important benefits for future personalized therapies.

Role of TDM-based dose adjustments for taxane anticancer drugs

The classical taxanes (paclitaxel, docetaxel), the newer taxane cabazitaxel and the nanoparticle-bound nab-paclitaxel are among the most widely used anticancer drugs. Still, the optimal use and the value of pharmacological personalization of the taxanes is still controversial. We give an overview on the pharmacological properties of the taxanes, including metabolism, pharmacokinetics-pharmacodynamic relations and aspects in the clinical use of taxanes. The latter includes the ongoing debate on the most effective and safe regimen, the recommended initial dose, and pharmacological dosing individualization. The taxanes are among the most widely used anticancer drugs in patients with solid malignancies. Despite their longtime use in clinical routine, the optimal dosing strategy (weekly versus 3-weekly) or optimal average dose (cabazitaxel, nab-paclitaxel) has not been fully resolved, as it may differ according to tumour entity and line of treatment. The value of pharmacological individualization of the taxanes (TDM, TCI) has been partly explored for 3-weekly paclitaxel and docetaxel, but remains mostly unexplored for cabazitaxel and nab-paclitaxel at present.

Randomized study of individualized pharmacokinetically-guided dosing of paclitaxel compared with body-surface area dosing in Chinese patients with advanced non-small cell lung cancer

AIMS

This prospective, randomized study was initiated to assess the impact of pharmacokinetically (PK)-guided paclitaxel (PTX) dosing on toxicity and efficacy compared with body-surface area (BSA)-based dosing in Chinese non-small cell lung cancer patients.

METHODS

A total of 319 stage IIIB/IV non-small cell lung cancer patients receiving first-line chemotherapy were enrolled. Patients were randomized to receive 3-weekly carboplatin plus PTX at a starting dose of 175 mg/m² with subsequent PTX dosing based on either BSA or PK-guided dosing targeting time above a PTX plasma concentration of 0.05 μmol/L (PTX_Tc > 0.05 ) between 26 and 31 hours. The primary safety endpoint was grade 4 haematological toxicity. The secondary endpoints were neuropathy, objective response rate, progression-free survival and overall survival.

RESULTS

In total, 275 (86%) patients completed ≥2 cycles of chemotherapy (140 in BSA arm and 135 in PK arm). In cycle 1, with the same PTX dose, average PTX_Tc > 0.05 was 37 hours (range = 18-57 hours). Over cycles 2-4, patients in the PK arm had significantly lower average PTX doses and exposure compared with the BSA arm (128 vs 161 mg/m² , P < .0001 and 29 vs 35 hours, P < .0001). PK-guided dosing significantly reduced the cumulative incidence of grade 4 haematological toxicity (15% vs 24%, P = .004), grade 4 neutropenia (15% vs 23%, P = .009) and grade ≥ 2 neuropathy (8% vs 21%, P = .005). Objective response rate (32% vs 26%, P = .28) and overall survival (21.0 vs 24.0 months, P = .815) were similar in PK and BSA arms. Progression-free survival was slightly improved in PK arm (4.67 vs 4.17 months, P = .026).

CONCLUSION

PK-guided PTX dosing significantly reduced grade 4 haematological toxicities and grade ≥ 2 neuropathy without an adverse impact on clinical outcomes.

Validation of a Commercial Assay and Decision Support Tool for Routine Paclitaxel Therapeutic Drug Monitoring (TDM)

BACKGROUND

The value of therapeutic drug monitoring (TDM) for paclitaxel (PTX) was recently demonstrated in the largest TDM trial ever conducted in oncology. The trial demonstrated significant reduction in neuropathy when using TDM. Dose adjustment for PTX was based on time above a threshold concentration (Tc>0.05). Tc>0.05 must be calculated with a pharmacokinetic model and complex nonlinear mixed-effects software. The use of the software and chromatographic methods to measure PTX requires specialized expertise. User-friendly methods to quantitate PTX and calculate Tc>0.05 could simplify the introduction of TDM into routine clinical practice.

METHODS

The immunoassay (MyPaclitaxel) was used to quantitate PTX in samples from the clinical trial; the results were used to calculate Tc>0.05 using a stand-alone computer program with a simple, friendly graphical user interface for nonlinear mixed-effects pharmacokinetic calculations (MyCare Drug Exposure Calculator). The resulting dose recommendations from the calculated Tc>0.05 were compared with those using liquid chromatography-ultraviolet detection and NONMEM to examine the efficacy of the simpler tools for TDM.

RESULTS

There was a good agreement between the immunoassay and liquid chromatography-ultraviolet detection: Passing-Bablok regression slope was 1.045 and intercept was -6.00, R was 0.9757, and mean bias was -1.77 ng/mL (-2.07 nmol/L). Dosing recommendations were identical for 70% of the cycles and within 10% for 89% of the samples. All Tc>0.05 values were at the same or adjacent medical decision points.

CONCLUSIONS

MyPaclitaxel assay and MyCare Drug Exposure Calculator are convenient, user-friendly tools that may be suitable for routine TDM of PTX in clinical care.

Standardization of the infusion sequence of antineoplastic drugs used in the treatment of breast and colorectal cancers

The definition of antineoplastic administration sequences can help planning of therapeutic regimens in a more rational way, and thus optimize chemotherapy effects on patients, increasing efficacy and reducing toxic effects. In this way, this study aimed to evaluate the infusion order of antineoplastic agents of the main therapeutic protocols used in the treatment of colorectal and breast cancer which are used in a tertiary hospital, identifying possible interactions dependent on the infusion sequence. For the definition of protocols adopted in the hospital, medical prescriptions were used in the period of January to March 2016 and a literature review was conducted to search for studies assessing the sequence of administering the selected regimens. The databases used were SciELO, LILACS and MEDLINE, in addition to Micromedex Solutions® and UpToDate®. A total of 19 protocols were identified for antineoplastic therapy, 11 for colorectal cancer and 8 for breast cancer. The selected articles provided evidence for administration order of 19 protocols, and three protocols did no report relevance of infusion sequence. Sequence-dependent interactions were mainly related to toxicity, pharmacokinetics and efficacy of the drug combination. The definition of the infusion sequence has a great impact on the optimization of therapy, increasing efficacy and safety of the protocols containing combined antineoplastic therapies.

Taxanes and platinum derivatives impair Schwann cells via distinct mechanisms

Impairment of peripheral neurons by anti-cancer agents, including taxanes and platinum derivatives, has been considered to be a major cause of chemotherapy-induced peripheral neuropathy (CIPN), however, the precise underlying mechanisms are not fully understood. Here, we examined the direct effects of anti-cancer agents on Schwann cells. Exposure of primary cultured rat Schwann cells to paclitaxel (0.01 μM), cisplatin (1 μM), or oxaliplatin (3 μM) for 48 h induced cytotoxicity and reduced myelin basic protein expression at concentrations lower than those required to induce neurotoxicity in cultured rat dorsal root ganglion (DRG) neurons. Similarly, these anti-cancer drugs disrupted myelin formation in Schwann cell/DRG neuron co-cultures without affecting nerve axons. Cisplatin and oxaliplatin, but not paclitaxel, caused mitochondrial dysfunction in cultured Schwann cells. By contrast, paclitaxel led to dedifferentiation of Schwann cells into an immature state, characterized by increased expression of p75 and galectin-3. Consistent with in vitro findings, repeated injection of paclitaxel increased expression of p75 and galectin-3 in Schwann cells within the mouse sciatic nerve. These results suggest that taxanes and platinum derivatives impair Schwan cells by inducing dedifferentiation and mitochondrial dysfunction, respectively, which may be important in the development of CIPN in conjunction with their direct impairment in peripheral neurons.

Mass spectrometry in the pharmacokinetic studies of anticancer natural products

In the history of medicine, nature has represented the main source of medical products. Indeed, the therapeutic use of plants certainly goes back to the Sumerian and Hippocrates and nowadays nature still represents the major source for new drugs discovery. Moreover, in the cancer treatment, drugs are either natural compounds or have been developed from naturally occurring parent compounds firstly isolated from plants and microbes from terrestrial and marine environment. A critical element of an anticancer drug is represented by its severe toxicities and, after administration, the drug concentrations have to remain in an appropriate range to be effective. Anyway, the drug dosage defined during the clinical studies could be inappropriate for an individual patient due to differences in drug absorption, metabolism and excretion. For this reason, personalized medicine, based on therapeutic drug monitoring (TDM), represents one of most important challenges in cancer therapy. Mass spectrometry sensitivity, specificity and fastness lead to elect this technique as the Golden Standard for pharmacokinetics and drug metabolism studies therefore for TDM. This review focuses on the mass spectrometry-based methods developed for pharmacokinetic quantification in human plasma of anticancer drugs derived from natural sources and already used in clinical practice. Particular emphasis was placed both on the pre-analytical and analytical steps, such as: sample preparation procedures, sample size required by the analysis and the limit of quantification of drugs and metabolites to give some insights on the clinical practice applicability. © 2015 Wiley Periodicals, Inc. Mass Spec Rev. 36:213-251, 2017.

Polymorphism of CYP3A4 and ABCB1 genes increase the risk of neuropathy in breast cancer patients treated with paclitaxel and docetaxel

BACKGROUND

Interindividual variability of pharmacogenetics may account for unpredictable neurotoxicities of taxanes.

METHODS

From March 2011 to June 2015, female patients with operable breast cancer who had received docetaxel- or paclitaxel-containing adjuvant chemotherapy were included in this study. All patients were treated with single-agent paclitaxel intravenously (IV) 175 mg/m(2) every 3 weeks for four cycles, or IV 80 mg/m(2) weekly for 12 cycles, and IV 100 mg/m(2) docetaxel for four cycles as adjuvant treatment. We evaluated the relationship between neurotoxicity of taxanes and single-nucleotide polymorphisms of ABCB1, CYP3A4, ERCC1, ERCC2, FGFR4, TP53, ERBB2, and CYP2C8 genes. Taxane-induced neurotoxicity during the treatment was evaluated according to the National Cancer Institute Common Toxicity Criteria version 4.03 prior to each cycle. Chi-squared tests were used to compare the two groups, and multivariate binary logistic regression models were used for determining possible risk factors of neuropathy.

RESULTS

Pharmacogenetic analysis was performed in 219 females. ABCB1 3435 TT genotype had significantly higher risk for grade ≥2 neurotoxicity (odds ratio [OR]: 2.759, 95% confidence interval [CI]: 1.172-6.493, P: 0.017) compared to TC and CC genotype, and also CYP3A4 392 AA and AG genotype had significantly higher risk for grade ≥2 neurotoxicity (OR: 2.259, 95% CI: 1.033-4.941, P: 0.038) compared to GG genotype. For FDGF4 gene with AG and GG genotype, OR was 1.879 (95% CI: 1.001-3.525, P: 0.048) compared to AA genotype with regard to any grade of neuropathy risk. We could not find any other association of other genotypes with neurotoxicity grades.

CONCLUSION

ABCB1 3435 TT genotype and CYP3A4 392 AA/AG genotypes may be used as predictors of neurotoxicity during taxane chemotherapy.

Nanocarriers in cancer clinical practice: a pharmacokinetic issue

The advent of nanocarriers for drug delivery has given rise to new intriguing scenarios in the cancer field. Nanocarriers indeed partly overcome the limits of traditional cytotoxic drugs principally changing the pharmacokinetic behavior of the parental drug. The peculiar characteristics of these systems strongly minimize the adverse reactions and ensure a more precise release of the compound to the tumor site. Several nanocarriers have been developed for the delivery of cytotoxic drugs such as paclitaxel and doxorubicin in order to improve both the outcome and the patients' quality of life. The aims of this review are to describe in detail the pharmacokinetics of nanocarriers, already marketed or in advanced clinical phases, for paclitaxel and doxorubicin, to highlight the main differences with the parental drugs, and to underline, in a critical manner, benefits and disadvantages related to the use of these new drug delivery systems.

Review : Pharmacokinetics and pharmacodynamics of the taxanes

Objectives. To review the pharmacokinetics and pharmacodynamics of docetaxel and paclitaxel.

Data Sources. We reviewed the literature through a MEDLINE search from 1982 to 1996. The terms docetaxel, paclitaxel, taxanes, and taxoids were used in the search. Relevant articles cited in literature obtained by MEDLINE searching, as well as new articles published in early 1997 in specific oncology journals, were also considered.

Data Extraction. We have reviewed the current literature with regard to the chemistry, mechanisms of action and pharmacology, pharmacokinetics, clini cal use, adverse effects, drug interactions, formula tion, dosage, administration, and pharmaceutical is sues of the taxanes.

Conclusion. Both docetaxel and paclitaxel are novel antineoplastic agents with significant activity in many types of cancer. The pharmacokinetics of both agents are best characterized by a three-compartment disposition profile. However, the pharmacokinetics of paclitaxel, not docetaxel, are non-linear and can be described by a saturation process in distribution and elimination. The nonlinearity appears to be associated more frequently with shorter infusions and/or higher doses. There is evidence suggesting that the time duration of paclitaxel concentrations maintained above 0.1 μM/L (T>0.1 μM ) is associated with improved survival and development of toxicity. On the other hand, currently there is no information relating opti mal systemic exposure of docetaxel to efficacy and toxicity. In addition, these pharmacokinetic-pharma codynamic relationship may change with therapy with antineoplastic agents and other agents adminis tered concurrently, and necessitates additional phar macokinetic-pharmacodynamic investigations.

Urinary excretion of paclitaxel and metabolites in a large series study

Objective. Paclitaxel is an antineoplastic agent with significant activity against several tumour types. The major portion of the drug disposition (80-90%) in volves metabolism and biliary excretion. The purpose of this study was to investigate the relationships between the mean urinary paclitaxel excretion frac tion and the administered dose, creatinine clearance, or the measured paclitaxel area under the plasma concentration versus time curve.

Design. The design used was a retrospective convenience sample study.

Setting. The setting for this study was a hospi talised care center.

Patients. A total of 103 24-hour urine collections from 60 patients treated with paclitaxel were used to investigate these relationships.

Results. In this large series study, the paclitaxel urinary fraction was 5 ± 3% (mean ± SD) as a fraction of the administered paclitaxel dose. No correlations were found between the paclitaxel urinary excretion fraction and the administered dose, creatinine clear ance, and plasma concentration-time curve. In addi tion, the paclitaxel metabolites 6α-hydroxypaclitaxel, 3'- p-hydroxypaclitaxel and some unidentified com pounds were detected in the 24-hour urine samples of two patients, of whom one had a mild impaired renal function.

Conclusions. Considering the low urinary ex cretion of paclitaxel, it is anticipated that patients with renal dysfunction require no dose adjustments. Metabolites were found in the urine.

SNPs associated with activity and toxicity of cabazitaxel in patients with advanced urothelial cell carcinoma

AIM

We aimed to identify SNPs associated with cabazitaxel toxicity and response within a Phase II clinical trial using this compound in advanced transitional cell carcinoma after progression to a platinum-based regimen.

PATIENTS & METHODS

Eleven SNPs in CYP3A4, CYP3A5, CYP2C8, ABCB1 and TUBB1 were genotyped in 45 patients.

RESULTS

CYP3A5 rs776746 A allele was associated with protection against gastrointestinal toxicity (odds ratio: 0.06, 95% CI: 0.007-0.63, p = 0.018) and with reduced progression-free survival (hazard ratio: 5.1, 95% CI: 1.7-15.1, p = 0.0038, multivariable analysis). ABCB1 SNPs were associated with total number of grade 3-4 toxicity events (p-values of 0.009, 0.041 and 0.043, respectively).

CONCLUSION

Polymorphisms in CYP3A5 and ABCB1 may define a subset of patients with different cabazitaxel toxicity and efficacy and therefore could be used as markers for treatment optimization.

Pharmacokinetics of Selected Anticancer Drugs in Elderly Cancer Patients: Focus on Breast Cancer

Background: Elderly patients receiving anticancer drugs may have an increased risk to develop treatment-related toxicities compared to their younger peers. However, a potential pharmacokinetic (PK) basis for this increased risk has not consistently been established yet. Therefore, the objective of this study was to systematically review the influence of age on the PK of anticancer agents frequently administered to elderly breast cancer patients. Methods: A literature search was performed using the PubMed electronic database, Summary of Product Characteristics (SmPC) and available drug approval reviews, as published by EMA and FDA. Publications that describe age-related PK profiles of selected anticancer drugs against breast cancer, excluding endocrine compounds, were selected and included. Results: This review presents an overview of the available data that describe the influence of increasing age on the PK of selected anticancer drugs used for the treatment of breast cancer. Conclusions: Selected published data revealed differences in the effect and magnitude of increasing age on the PK of several anticancer drugs. There may be clinically-relevant, age-related PK differences for anthracyclines and platina agents. In the majority of cases, age is not a good surrogate marker for anticancer drug PK, and the physiological state of the individual patient may better be approached by looking at organ function, Charlson Comorbidity Score or geriatric functional assessment.

Treatment regimens of classical and newer taxanes

The classical taxanes (paclitaxel, docetaxel), the newer taxane cabazitaxel and the nanoparticle-bound nab-paclitaxel are among the most widely used anticancer drugs. The taxanes share the characteristics of extensive hepatic metabolism and biliary excretion, the need for dose adaptation in patients with liver dysfunction, and a substantial pharmacokinetic variability even after taking into account known covariates. Data from clinical studies suggest that optimal scheduling of the taxanes is dependent not only on the specific taxane compound, but also on the tumor type and line of treatment. Still, the optimal dosing regimen (weekly vs 3 weekly) and optimal dose of the taxanes are controversial, as is the value of pharmacological personalization of taxane dosing. In this article, an overview is given on the pharmacological properties of the taxanes, including metabolism, pharmacokinetics-pharmacodynamics and aspects in the clinical use of taxanes. The latter includes the ongoing debate on the most active and safe regimen, the recommended initial dose and the issue of therapeutic drug dosing.

Personalizing chemotherapy dosing using pharmacological methods

PURPOSE

Given the toxic nature and narrow therapeutic index of traditional chemotherapeutics, better methods of dose and therapy selection are critical. Pharmacological methods, including pharmacogenomics and pharmacokinetics, offer a practical method to enrich drug exposure, reduce toxicity, and improve quality of life for patients.

METHODS

PubMed and key abstracts from the American Society of Clinical Oncology (ASCO) and American Association for Cancer Research (AACR) were searched until July 2015 for clinical data relating to pharmacogenomic- and/or pharmacokinetic-guided dosing of anticancer drugs.

RESULTS

Based on the results returned from a thorough search of the literature and the plausibility of utilizing pharmacogenomic and/or pharmacokinetic methods to personalize chemotherapy dosing, we identified several chemotherapeutic agents with the potential for therapy individualization. We highlight the available data, clinical validity, and utility of using pharmacogenomics to personalize therapy for tamoxifen, 5-fluorouracil, mercaptopurine, and irinotecan, in addition to using pharmacokinetics to personalize dosing for 5-fluorouracil, busulfan, methotrexate, taxanes, and topotecan.

CONCLUSION

A concerted effort should be made by researchers to further elucidate the role of pharmacological methods in personalizing chemotherapy dosing to optimize the risk-benefit profile. Clinicians should be aware of the clinical validity, utility, and availability of pharmacogenomic- and pharmacokinetic-guided therapies in clinical practice, to ultimately allow optimal dosing for each and every cancer patient.

Carboplatin and taxol resistance develops more rapidly in functional BRCA1 compared to dysfunctional BRCA1 ovarian cancer cells

A major risk factor for ovarian cancer is germline mutations of BRCA1/2. It has been found that (80%) of cellular models with acquired platinum or taxane resistance display an inverse resistance relationship, that is collateral sensitivity to the other agent. We used a clinically relevant comparative selection strategy to develop novel chemoresistant cell lines which aim to investigate the mechanisms of resistance that arise from different exposures of carboplatin and taxol on cells having BRCA1 function (UPN251) or dysfunction (OVCAR8). Resistance to carboplatin and taxol developed quicker and more stably in UPN251 (BRCA1-wildtype) compared to OVCAR8 (BRCA1-methylated). Alternating carboplatin and taxol treatment delayed but did not prevent resistance development when compared to single-agent administration. Interestingly, the sequence of drug exposure influenced the resistance mechanism produced. UPN251-6CALT (carboplatin first) and UPN251-6TALT (taxol first) have different profiles of cross resistance. UPN251-6CALT displays significant resistance to CuSO4 (2.3-fold, p=0.004) while UPN251-6TALT shows significant sensitivity to oxaliplatin (0.6-fold, p=0.01). P-glycoprotein is the main mechanism of taxol resistance found in the UPN251 taxane-resistant sublines. UPN251 cells increase cellular glutathione levels (3.0-fold, p=0.02) in response to carboplatin treatment. However, increased glutathione is not maintained in the carboplatin-resistant sublines. UPN251-7C and UPN251-6CALT are low-level resistant to CuSO4 suggesting alterations in copper metabolism. However, none of the UPN251 sublines have alterations in the protein expression of ATP7A or CTR1. The protein expression of BRCA1 and MRP2 is unchanged in the UPN251 sublines. The UPN251 sublines remain sensitive to parp inhibitors veliparib and CEP8983 suggesting that these agents are candidates for the treatment of platinum/taxane resistant ovarian cancer patients.

Metabolism of the taxanes including nab-paclitaxel

INTRODUCTION

The classical taxanes (paclitaxel, docetaxel), the newer taxane cabazitaxel and the nanoparticle-bound nab-paclitaxel are among the most widely used anticancer drugs. Despite years of research, the optimal dosing regimen (weekly vs 3-weekly) and optimal dose is still controversial, as is the value of pharmacological personalization of taxane dosing.

AREAS COVERED

This review provides an overview of the pharmacological properties of the taxanes, including metabolism, pharmacokinetics-pharmacodynamics and aspects in the clinical use of taxanes. The latter includes the ongoing debate on the most active and safe regimen (paclitaxel, docetaxel, nab-paclitaxel), the recommended initial dose (cabazitaxel) and pharmacological dosing individualization.

EXPERT OPINION

Taxanes share the characteristics of extensive hepatic metabolism and biliary excretion, the need for dose adaptation in patients with liver dysfunction, and substantial pharmacokinetic variability even after taking into account known covariates. Data from clinical studies suggest that optimal scheduling of the taxanes is dependent not only on the specific taxane compound, but also on the tumor type and line of treatment. Finally, treating oncologists should be aware of the substantial risk for drug-drug interactions that is a direct consequence of the complex hepatic metabolism of the taxanes.

"Effect of the drug transporters ABCB1, ABCC2, and ABCG2 on the disposition and brain accumulation of the taxane analog BMS-275,183"

BMS-275,183 is a novel oral C-4 methyl carbonate analogue of paclitaxel. Recently, a drug-drug interaction between BMS-275,183 and benzimidazole proton pump inhibitors (PPIs) was suggested in clinical trials resulting in elevated drug exposure and toxicity. We explored whether the interaction takes place at the level of P-glycoprotein (Pgp, MDR1, ABCB1), Breast Cancer Resistance Protein (BCRP, ABCG2) and MRP2 (ABCC2) using in vitro and in vivo models. In vitro cell survival, drug accumulation, efflux and transport studies with BMS-275,183 were performed employing MDCKII (wild-type, MDR1, BCRP, MRP2) and LLCPK (wild-type and MDR1) cells. In vivo the pharmacokinetics and tissue distribution of BMS-275,183 after p.o. and i.v. administration were explored in Mdr1a/1b(-/-) and wild-type mice, in presence or absence of the PPI pantoprazole. Results In vitro, BMS-275,183 was found to be a good substrate for MDR1, a moderate substrate for MRP2 and not a substrate for BCRP. In vivo, oral bioavailability, plasma AUC0-6h and brain concentrations were significantly 1.5-, 4-, and 2-fold increased, respectively, in Mdr1a/1b(-/-) compared with wild-type mice (p < 0.001). However, oral co-administration of pantoprazole (40 mg/kg) did not alter the pharmacokinetics of BMS-275,183 in wild-type mice. Conclusions BMS-275,183 is efficiently transported by Pgp and to a lesser extent by MRP2 in vitro. Genetic deletion of Pgp significantly altered the pharmacokinetics and brain distribution of p.o. and i.v. administered BMS-275,183 in Mdr1a/1b-/- compared to wild-type mice. Oral co-administration of BMS-275,183 with pantoprazole did not affect the pharmacokinetics of BMS-275,183 in wild-type mice, suggesting no interaction with PPI at the dose employed.

Pharmacogenetics, enzyme probes and therapeutic drug monitoring as potential tools for individualizing taxane therapy

The taxanes are a class of chemotherapeutic agents that are widely used in the treatment of various solid tumors. Although taxanes are highly effective in cancer treatment, their use is associated with serious complications attributable to large interindividual variability in pharmacokinetics and a narrow therapeutic window. Unpredictable toxicity occurrence necessitates close patient monitoring while on therapy and adverse effects frequently require decreasing, delaying or even discontinuing taxane treatment. Currently, taxane dosing is based primarily on body surface area, ignoring other factors that are known to dictate variability in pharmacokinetics or outcome. This article discusses three potential strategies for individualizing taxane treatment based on patient information that can be collected before or during care. The clinical implementation of pharmacogenetics, enzyme probes or therapeutic drug monitoring could enable clinicians to personalize taxane treatment to enhance efficacy and/or limit toxicity.

Pharmacokinetic evaluation of Paclitaxel in South Indian cancer patients: a prospective study

Paclitaxel is a promising drug in the treatment of different solid tumors. It exhibits nonlinear pharmacokinetics, particularly when administered as a constant rate infusion for shorter duration (e.g., 3 h). Because of the nonlinearity, relatively small changes in dose may lead to large changes in peak plasma concentration and total drug exposure. The study was conducted to evaluate the pharmacokinetics of different doses of paclitaxel administered intravenously as an infusion. A prospective study was conducted in 23 cancer patients aged between 28 and 74 years, treated with paclitaxel (130, 200, 230, and 260 mg/m²) over 3 h as constant rate infusion. Plasma samples were collected from all patients at 0, 1, and 3 h and for five patients at 5 and 13 h and paclitaxel concentrations were determined using high-performance liquid chromatography method. The overall mean clearance was found to be 47.5847 ± 142.028 l/h; the mean volume of distribution was 142.028 ± 73.438 l; mean elimination rate constant was 0.336 ± 0.002/h; mean half-life was 2.086 ± 0.009 h; mean area under the curve (AUC) was 5.5917 ± 2.707 mg/ml*h; and the mean of mean residence time was 2.980 ± 0.0131 h. Paclitaxel showed nonlinear kinetics and the pharmacokinetic parameters calculated were similar to those quoted in the literature. The peak plasma concentration at 130 mg dose level was 2 μ/ml, but an increase in dose was not associated with proportional increase in plasma concentration. No significant difference was found between pharmacokinetic parameters such as clearance, volume of distribution, and AUC at different dose levels.

Paclitaxel-loaded polymeric micelle (230 mg/m(2)) and cisplatin (60 mg/m(2)) vs. paclitaxel (175 mg/m(2)) and cisplatin (60 mg/m(2)) in advanced non-small-cell lung cancer: a multicenter randomized phase IIB trial

INTRODUCTION

The development of paclitaxel-loaded polymeric micelle (PPM) has circumvented many of the infusion-related difficulties associated with standard solvent-based paclitaxel. PPM plus cisplatin combination chemotherapy showed significant antitumor activity in phase I and II studies. This prospective randomized controlled phase IIB study assessed the noninferiority of the efficacy and tolerability of high-dose PPM plus cisplatin to a standard dose of paclitaxel plus cisplatin.

PATIENTS AND METHODS

Patients with stage IIIB/IV or recurrent non-small-cell lung cancer (NSCLC) who were chemonaive were eligible for participation. The patients were randomly assigned to receive PPM 230 mg/m(2) plus cisplatin 60 mg/m(2) or paclitaxel 175 mg/m(2) plus cisplatin 60 mg/m(2) once every 3-week cycle. The primary endpoint was to compare the response rate (RR) between the groups with coprimary analyses to assess noninferiority. Secondary endpoints included progression-free survival, overall survival, and safety.

RESULTS

A total of 276 patients were randomized to PPM plus cisplatin (n = 140) or paclitaxel plus cisplatin (n = 136). RR was 43.6% in the PPM plus cisplatin group and 41.9% in the paclitaxel plus cisplatin group. Noninferiority of PPM plus cisplatin compared with paclitaxel plus cisplatin was confirmed for RR. There were no differences in progression-free survival and overall survival between the groups. Although there was a higher rate of grade 3 neutropenia in the PPM plus cisplatin group, the overall rate of adverse events was comparable between the 2 groups.

CONCLUSION

PPM in combination with cisplatin was well tolerated, and its response rate was noninferior to that of paclitaxel plus cisplatin in patients with advanced NSCLC and who were chemonaive.

Feasibility of prior administration of cyclophosphamide in TC combination treatment

BACKGROUND

TC (docetaxel 75 mg/m(2) and cyclophosphamide 600 mg/m(2) q3w) combination is used for neoadjuvant/adjuvant chemotherapy in primary breast cancer. The incidence of allergic reaction is reportedly more common in patients who receive docetaxel before cyclophosphamide. This study aims to determine the significance of cyclophosphamide and docetaxel administration sequence.

METHODS

Prospective analysis was performed of 49 consecutive patients treated with TC for stage I-IIB breast cancer from March 2010 to June 2011. Premedication was administered with granisetron, dexamethasone, and chlorpheniramine. Patient charts were reviewed for completion rate and adverse events. Two-tailed Fisher exact test was used to evaluate adverse events between prior cyclophosphamide and prior docetaxel.

RESULTS

Of 49 patients, 26 received docetaxel prior to cyclophosphamide and 23 received cyclophosphamide before docetaxel. There were no differences in patient characteristics between the two groups. Completion rates were 95.6 % in the prior cyclophosphamide group, and 100 % in the prior docetaxel group. The relative dose intensities of docetaxel and cyclophosphamide were 94.5 and 94.8 % in the prior cyclophosphamide group, and 98.5 and 98.7 % in the prior docetaxel group (p < 0.01). In the prior cyclophosphamide group, severe neutropenia occurred in 96 % of patients, but in only 46 % of patients in the prior docetaxel group (p < 0.01). Significantly fewer cases of skin eczema (27 versus 61 %), nausea (8 versus 48 %), stomatitis (23 versus 61 %), and diarrhea (4 versus 30 %) were observed in the prior docetaxel group as compared with the prior cyclophosphamide group (p < 0.01). Decreased incidences of fatigue (50 versus 65 %) and edema (19 versus 35 %) were found in the prior docetaxel group (p < 0.05). No difference was observed in allergic reaction or neuropathy between the two groups.

CONCLUSION

Patients receiving cyclophosphamide prior to docetaxel were at increased risk of several toxicities as compared with patients receiving docetaxel prior to cyclophosphamide in TC combination therapy.

Phase II Clinical Trial of Genexol® (Paclitaxel) and Carboplatin for Patients with Advanced Non-small Cell Lung Cancer

Purpose

This phase II clinical trial was conducted to evaluate the activity and safety of a combination treatment of paclitaxel (Genexol®) plus carboplatin in patients with advanced non-small cell lung cancer.

Materials and Methods

Chemotherapy-naïve patients having histologically confirmed advanced or metastatic non-small cell lung cancer were enrolled. Genexol® was administered at 225 mg/m² intravenous (IV) infusion over 3 hours, followed by carboplatin (area under the concentration-time curve=6) IV on day 1 every 3 weeks.

Results

Twenty-eight patients were enrolled between January 2003 and January 2005. A total of 110 cycles of chemotherapy were given. The median number of chemotherapy cycles was 4. A total of 25 study patients were evaluable. On an intent-to-treat basis, there were ten partial responses (response rate 35.7%). The median time-to-progression was 3.2 months (95% confidence interval [CI], 1.5 to 4.9) and the median overall survival was 8.2 months (95% CI, 4.1 to 12.3). The main hematologic grade 3/4 toxicity was neutropenia, which was observed in 14 (50.0%) patients. The main non-hematologic toxicity was peripheral neuropathy, which was observed in 12 patients (42.9%). Grade 3/4 neuropathy occurred in 8 patients (28.6%) and three patients discontinued treatment because of neuropathy.

Conclusion

In this trial, the combination of Genexol® and carboplatin showed significant activity as first line treatment for patients with advanced or metastatic non-small cell lung cancer. However, a modest dose reduction of Genexol® is needed due to sensory neuropathy.

Enhanced oral absorption of paclitaxel in N-deoxycholic acid-N, O-hydroxyethyl chitosan micellar system

The overall goal of this study was to develop a micellar system of paclitaxel (PTX) to enhance its oral absorption. An amphiphilic chitosan derivative, N-deoxycholic acid-N, O-hydroxyethyl chitosan (DHC), was synthesized and characterized by FTIR, (1)H NMR, elemental analysis, and X-ray diffraction (XRD) techniques. The degree of substitution (DS) of hydroxyethyl group and deoxycholic acid group ranged from 89.5-114.5% and 1.11-8.17%, respectively. The critical micelle concentration (CMC) values of DHC decreased from 0.26 to 0.16 mg/mL as the DS of deoxycholic acid group increased. PTX was successfully loaded in DHC micelles with a high drug loading (31.68 ± 0.14%) and entrapment efficiency (77.57 ± 0.51%). The particle size of PTX-loaded DHC micelles ranged from 203.35 ± 2.19 to 236.70 ± 3.40 nm as the DS of deoxycholic acid group increased. After orally administration of PTX-loaded DHC micelles, the bioavailability was threefold compared with that of an orally dosed Taxol®. The single-pass intestinal perfusion studies (SPIP) showed that the intestinal absorption of micelles was via endocytosis involving a saturable process and a p-glycoprotein (P-gp)-independent way. All these indicated that the DHC micelles might be a promising tool for oral delivery of poorly water-soluble drugs.

Pilot study evaluating the interaction between paclitaxel and protease inhibitors in patients with human immunodeficiency virus-associated Kaposi's sarcoma: an Eastern Cooperative Oncology Group (ECOG) and AIDS Malignancy Consortium (AMC) trial

PURPOSE

Paclitaxel, a cytotoxic agent metabolized by cytochrome P450 hepatic enzymes, is active for the treatment of human immunodeficiency (HIV) associated Kaposi's sarcoma. Protease inhibitors are commonly used to treat HIV infection and are known to inhibit cytochrome P450. We sought to determine whether protease inhibitors alter the pharmacokinetics of paclitaxel.

METHODS

Patients with advanced HIV-associated KS received paclitaxel (100 mg/m(2)) by intravenous infusion over 3 h, and plasma samples were collected to measure paclitaxel concentration. The area under the curve (AUC) was calculated using a combination of the log and linear trapezoidal rule, and clearance was calculated as the dose/AUC. Pharmacokinetics were compared with respect to antiretroviral therapy and toxicity,

RESULTS

Thirty-four patients received paclitaxel, of whom 20 had no prior paclitaxel therapy and were assessable for response. Twenty-seven had pharmacokinetic studies performed. Paclitaxel exposure was higher in patients taking protease inhibitors compared to those who were not taking protease inhibitors. The increased exposure did not correlate with efficacy or toxicity. Of the 20 patients assessable for response, 6 (30%) had an objective response and median progression-free survival was 7.8 months (95% confidence interval, 5.6, 21.0 months).

CONCLUSION

Despite higher exposure to paclitaxel, patients on protease inhibitors did not experience enhanced toxicity or efficacy.

Phase 1b study of dulanermin (recombinant human Apo2L/TRAIL) in combination with paclitaxel, carboplatin, and bevacizumab in patients with advanced non-squamous non-small-cell lung cancer

PURPOSE

To determine the safety, pharmacokinetics (PK), and maximum-tolerated dose (MTD) up to a prespecified target dose of dulanermin in combination with paclitaxel, carboplatin, and bevacizumab (PCB) in patients with previously untreated, nonsquamous, stage IIIb (with pleural effusion)/IV or recurrent non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

In this phase 1b study, patients (n = 24) received PCB on day 1 of each 21-day cycle then dulanermin at 4 or 8 mg/kg/d for 5 consecutive days or 15 or 20 mg/kg/d for 2 consecutive days per assigned treatment cohort. Incidence of dose-limiting toxicities (DLTs), adverse events, and antidulanermin antibodies were assessed. PK parameters were recorded for each agent. Tumor response was measured by modified Response Evaluation Criteria in Solid Tumors.

RESULTS

Twenty-four patients received at least one dose of dulanermin plus PCB, six in each treatment cohort. There were no DLTs. An MTD was not reached, and the drug combination was well tolerated. Treatment-emergent adverse events were generally as expected for the PCB regimen. Adverse events attributed to dulanermin were grade 1/2; no significant hepatotoxicity occurred. There was minimal impact of PCB on the PK of dulanermin. There was one confirmed complete response and 13 confirmed partial responses. The overall response rate was 58% (95% CI, 37 to 78). Median progression-free survival was 7.2 months (95% CI, 4.7 to 10.3).

CONCLUSION

Dulanermin plus PCB was well tolerated with no occurrence of DLTs and demonstrated antitumor activity in this patient population. Dulanermin at 8 mg/kg/d for 5 days and 20 mg/kg/d for 2 days every 3 weeks in combination with PCB is being studied in a phase II trial.

The ABCB1 3435 T allele does not increase the risk of paclitaxel-induced neurotoxicity

Paclitaxel is a frequently used anticancer drug with considerable inter-individual variability in terms of drug efficiency and toxicity. The reasons for this variability have not been fully explained. The purpose of this study was to evaluate the possible relationship between paclitaxel-induced neurotoxicity and the distribution of genetic variations with reported functional significance in the ABCB1, CYP2C8 and CYP3A4 genes that are all implicated in taxol metabolism. Women (n=36) experiencing paclitaxel-induced neurotoxicity were included in the study, and the ABCB1 G2677A/T and C3435T as well as CYP2C8(*)3 and CYP3A4(*)1b allele frequencies were determined using PCR-RFLP and DNA sequence analysis. We showed that the ABCB1 3435T allele, previously reported as a risk allele for neurotoxicity, did not correlate with the occurrence of neurotoxicity in our patient sample (Chi-square test, p=0.61). Furthermore, we showed that neither the CYP2C8(*)3 nor CYP3A4(*)1b alleles, that both lead to diminished enzyme activity, correlated with paclitaxel-induced neurotoxicity. The occurrence and variation in severity of neurotoxicity in our Swedish patient sample could therefore not be explained by the reported functional polymorphisms in the ABCB1, CYP2C8 and CYP3A4 genes.

A phase I dose escalation and pharmacokinetic study of vatalanib (PTK787/ZK 222584) in combination with paclitaxel in patients with advanced solid tumors

PURPOSE

To define the maximum-tolerated dose (MTD) for weekly paclitaxel administered in combination with daily vatalanib (PTK787/ZK 222584, PTK/ZK) and assess for a drug-drug interaction.

METHODS

Patients were treated with escalating doses of weekly paclitaxel (75-85 mg/m(2)), and daily PTK/ZK (250-1,000 mg). During the first cycle only, paclitaxel was given on days 1 and 15, and PTK/ZK on days 3-28. Pharmacokinetic studies were conducted on cycle 1 days 1 and 15 for paclitaxel, and on cycle 1 day 15 for PTK/ZK. Therapy was given until disease progression.

RESULTS

Twenty-seven patients were accrued to four dose levels. Two of five patients treated with paclitaxel 85 mg/m(2) and PTK/ZK 1,000 mg had Grade 3 transaminase elevation as dose-limiting toxicity. Paired PK analyses demonstrated a significant increase in paclitaxel clearance on day 15 (p = 0.006). Activity included one partial response and 11 patients with stable disease > or =4 months, including patients previously treated with paclitaxel.

CONCLUSIONS

The MTD for weekly paclitaxel plus daily PTK/ZK is 75 mg/m(2) and 750 mg. PK analysis revealed a significant drug-drug interaction, with an increase in paclitaxel clearance. This combination was well tolerated with evidence of anti-cancer activity and provides guidance for phase 2 planning.

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.

Pharmacogenetic studies of Paclitaxel in the treatment of ovarian cancer

The purpose of this study was to evaluate the role of sequence variants in the CYP2C8, ABCB1 and CYP3A4 genes and the CYP3A4 phenotype for the pharmacokinetics and toxicity of paclitaxel in ovarian cancer patients. Thirty-eight patients were treated with paclitaxel and carboplatin. The genotypes of CYP2C8*1B, *1C, *2, *3, *4, *5, *6, *7, *8 and P404A, ABCB1 G2677T/A and C3435T, as well as CYP3A4*1B, were determined by pyrosequencing. Phenotyping of CYP3A4 was performed in vivo with quinine as a probe. The patients were monitored for toxicity and 23 patients underwent a more extensive neurotoxicity evaluation. Patients heterozygous for G/A in position 2677 in ABCB1 had a significantly higher clearance of paclitaxel than most other ABCB1 variants. A lower clearance of paclitaxel was found for patients heterozygous for CYP2C8*3 when stratified according to the ABCB1 G2677T/A genotype. In addition, the CYP3A4 enzyme activity in vivo affected which metabolic pathway was dominant in each patient, but not the total clearance of paclitaxel. The exposure to paclitaxel correlated to the degree of neurotoxicity. Our findings suggest that interindividual variability in paclitaxel pharmacokinetics might be predicted by ABCB1 and CYP2C8 genotypes and provide useful information for individualized chemotherapy.