Pharmacokinetic variability of anticancer agents

Flaxseed Lignans as Important Dietary Polyphenols for Cancer Prevention and Treatment: Chemistry, Pharmacokinetics, and Molecular Targets

Cancer causes considerable morbidity and mortality across the world. Socioeconomic, environmental, and lifestyle factors contribute to the increasing cancer prevalence, bespeaking a need for effective prevention and treatment strategies. Phytochemicals like plant polyphenols are generally considered to have anticancer, anti-inflammatory, antiviral, antimicrobial, and immunomodulatory effects, which explain their promotion for human health. The past several decades have contributed to a growing evidence base in the literature that demonstrate ability of polyphenols to modulate multiple targets of carcinogenesis linking models of cancer characteristics (i.e., hallmarks and nutraceutical-based targeting of cancer) via direct or indirect interaction or modulation of cellular and molecular targets. This evidence is particularly relevant for the lignans, an ubiquitous, important class of dietary polyphenols present in high levels in food sources such as flaxseed. Literature evidence on lignans suggests potential benefit in cancer prevention and treatment. This review summarizes the relevant chemical and pharmacokinetic properties of dietary polyphenols and specifically focuses on the biological targets of flaxseed lignans. The consolidation of the considerable body of data on the diverse targets of the lignans will aid continued research into their potential for use in combination with other cancer chemotherapies, utilizing flaxseed lignan-enriched natural products.

Mesenchymal stem cell therapies in brain disease

As treatments for diseases throughout the body progress, treatment for many brain diseases has been at a standstill due to difficulties in drug delivery. While new drugs are being discovered in vitro, these therapies are often hindered by inefficient tissue distribution and, more commonly, an inability to cross the blood brain barrier. Mesenchymal stem cells are thus being investigated as a delivery tool to directly target therapies to the brain to treat wide array of brain diseases. This review discusses the use of mesenchymal stem cells in hypoxic disease (hypoxic ischemic encephalopathy), an inflammatory neurodegenerative disease (multiple sclerosis), and a malignant condition (glioma).

Mathematical Analysis of a Mathematical Model of Chemovirotherapy: Effect of Drug Infusion Method

A mathematical model for the treatment of cancer using chemovirotherapy is developed with the aim of determining the efficacy of three drug infusion methods: constant, single bolus, and periodic treatments. The model is in the form of ODEs and is further extended into DDEs to account for delays as a result of the infection of tumor cells by the virus and chemotherapeutic drug responses. Analysis of the model is carried out for each of the three drug infusion methods. Analytic solutions are determined where possible and stability analysis of both steady state solutions for the ODEs and DDEs is presented. The results indicate that constant and periodic drug infusion methods are more efficient compared to a single bolus injection. Numerical simulations show that with a large virus burst size, irrespective of the drug infusion method, chemovirotherapy is highly effective compared to either treatments. The simulations further show that both delays increase the period within which a tumor can be cleared from body tissue.

Polytherapy and Targeted Cancer Drug Resistance

A current challenge in cancer treatment is drug resistance. Even the most effective therapies often fail to produce a complete and durable tumor response and ultimately give rise to therapy resistance and tumor relapse. However, how resistance arises in cancer remains incompletely understood. While drug resistance in cancer is thought to be driven by irreversible genetic mutations, emerging evidence also implicates reversible proteomic and epigenetic mechanisms in the development of drug resistance. Tumor microenvironment-mediated mechanisms and tumor heterogeneity can significantly contribute to cancer treatment resistance. Here, we discuss the diverse and dynamic strategies that cancers use to evade drug response, the promise of upfront combination and intermittent therapies and therapy switching in forestalling resistance, and epigenetic reprogramming to combat resistance.

How can we best monitor 5-FU administration to maximize benefit to risk ratio?

INTRODUCTION

5-Fluorouracil (5-FU) is currently used as a chemotherapy in several cancers such as head-and-neck (H&N) and colorectal cancers. 5-FU dosing is traditionally based on body surface area (BSA), but this strategy is usually associated with severe toxicities. 5-FU is mainly catabolized by dihydropyrimidine dehydrogenase (DPD), and 5-FU dosage adaptation according to DPD status at the first cycle of treatment is now recommended. To further optimize 5-FU-based chemotherapy, a body of evidences justifies therapeutic drug monitoring (TDM). Areas covered: 5-FU pharmacokinetics, relationships between pharmacokinetics and efficacy or toxicity of 5-FU, proofs of interest of 5-FU TDM and its practical considerations are discussed. Expert opinion: BSA-adjusted 5-FU administration is associated with a large inter-individual variability, and according to this strategy, many patients experience under- or overexposure. Moreover, relationships between 5-FU area under the curve (AUC) and its toxicity or efficacy have been demonstrated, at least in patients with colorectal or H&N cancers. 5-FU therapeutic index has been validated and algorithms of 5-FU dosage adaptation according to its AUC are now available. Advances in pre-analytical and analytical steps of 5-FU TDM make its use feasible in clinical practice. Thus, there are consistent evidences to recommend 5-FU TDM in patients with advanced colorectal or H&N cancers.

[Venous thromboembolism and urological cancer: Epidemiology and therapeutically management]

INTRODUCTION

Active cancer is a risk factor in the occurrence of venous thromboembolism (VTE). This is the second cause of death for these patients. In onco-urology, some cancers are associated with an increased risk of VTE. The aim of this study was to propose a focus of epidemiology and VTE therapy management.

MATERIAL AND METHODS

A systematic analysis of the PubMed^® database was performed through the PRISMA methodology using the followings keywords : "neoplasm", "venous thromboembolism", "prophylaxis", "pulmonary embolism", "urology". The original papers were included with a priority on: meta-analyzes, literature reviews, randomized controlled trials and good-level proof cohort studies. Only publications in English or French have been selected.

RESULTS

The incidence of VTE was more important in case of renal carcinomas (3.5%/year). When surgery was proposed cystectomy was the riskiest procedure (2.6 to 11.6% VTE). Chemotherapy alone was an important risk factor increasing by a factor of six the occurrence of VTE. Hormonotherapy also increased this risk by induced hypogonadism. The curative treatment for VTE associated with cancers has to be performed through the injection of low molecular weight heparin. The implantation of a prophylactic treatment was not systematic among patients diagnosed with urological cancer.

CONCLUSION

The understanding of mechanisms associated with the occurrence of VTE among these patients has enabled to improve patient management, especially those suffering from urological cancer. Undeniably, frequency of VTE is probably underestimated by urologists during clinical practice.

Precision Medicine with Imprecise Therapy: Computational Modeling for Chemotherapy in Breast Cancer

Medical oncology is in need of a mathematical modeling toolkit that can leverage clinically-available measurements to optimize treatment selection and schedules for patients. Just as the therapeutic choice has been optimized to match tumor genetics, the delivery of those therapeutics should be optimized based on patient-specific pharmacokinetic/pharmacodynamic properties. Under the current approach to treatment response planning and assessment, there does not exist an efficient method to consolidate biomarker changes into a holistic understanding of treatment response. While the majority of research on chemotherapies focus on cellular and genetic mechanisms of resistance, there are numerous patient-specific and tumor-specific measures that contribute to treatment response. New approaches that consolidate multimodal information into actionable data are needed. Mathematical modeling offers a solution to this problem. In this perspective, we first focus on the particular case of breast cancer to highlight how mathematical models have shaped the current approaches to treatment. Then we compare chemotherapy to radiation therapy. Finally, we identify opportunities to improve chemotherapy treatments using the model of radiation therapy. We posit that mathematical models can improve the application of anticancer therapeutics in the era of precision medicine. By highlighting a number of historical examples of the contributions of mathematical models to cancer therapy, we hope that this contribution serves to engage investigators who may not have previously considered how mathematical modeling can provide real insights into breast cancer therapy.

Drug metabolizing enzymes and their inhibitors' role in cancer resistance

Despite continuous research on chemotherapeutic agents, different mechanisms of resistance have become a major pitfall in cancer chemotherapy. Although, exhaustive efforts are being made by several researchers to target resistance against chemotherapeutic agents, there is another class of resistance mechanism which is almost carrying on unattended. This class of resistance includes pharmacokinetics resistance such as efflux by ABC transporters and drug metabolizing enzymes. ABC transporters are the membrane bound proteins which are responsible for the movement of substrates through the cell membrane. Drug metabolizing enzymes are an integral part of phase-II metabolism that helps in the detoxification of exogenous, endogenous and xenobiotics substrates. These include uridine diphospho-glucuronosyltransferases (UGTs), glutathione-S-transferases (GSTs), dihydropyrimidine dehydrogenases (DPDs) and thiopurine methyltransferases (TPMTs). These enzymes may affect the role of drugs in both positive as well negative manner, depending upon the type of tissue and cells present and when present in tumors, can result in drug resistance. However, the underlying mechanism of resistance by drug metabolizing enzymes is still not clear. Here, we have tried to cover various aspects of these enzymes in relation to anticancer drugs.

Population Pharmacokinetic-Pharmacodynamic Modeling of 5-Fluorouracil for Toxicities in Rats

BACKGROUND AND OBJECTIVES

Myelosuppression is a dose-limiting toxicity of 5-fluorouracil (5-FU). Predicting the inter- and intra-patient variability in pharmacokinetics and toxicities of 5-FU may contribute to the individualized medicine. This study aimed to establish a population pharmacokinetic-pharmacodynamic model that could evaluate the inter- and intra-individual variability in the plasma 5-FU concentration, 5-FU-induced body weight loss and myelosuppression in rats.

METHOD

Plasma 5-FU concentrations, body weight loss, and blood cell counts in rats following the intravenous administration of various doses of 5-FU for 4 days were used to develop the population pharmacokinetic-pharmacodynamic model.

RESULTS

The population pharmacokinetic model consisting of a two-compartment model with Michaelis-Menten elimination kinetics successfully characterized the individual and population predictions of the plasma concentration of 5-FU and provided credible parameter estimates. The estimates of inter-individual variability in maximal rate of saturable metabolism and residual variability were 8.1 and 22.0%, respectively. The population pharmacokinetic-pharmacodynamic model adequately described the individual complete time-course of alterations in body weight loss, erythrocyte, leukocyte, and lymphocyte counts in rats treated with various doses of 5-FU. The inter-individual variability of the drug effects in the pharmacodynamic model for body weight loss was 82.6%, which was relatively high. The results of the present study suggest that not only individual fluctuations in the 5-FU concentration but also the cell sensitivity would affect the onset and degree of 5-FU-induced toxicity.

CONCLUSION

This population pharmacokinetic-pharmacodynamic model could evaluate the inter- and intra-individual variability in drug-induced toxicity and guide the assessments of novel anticancer agents in drug development.

On the design principles of peptide-drug conjugates for targeted drug delivery to the malignant tumor site

Cancer is the second leading cause of death affecting nearly one in two people, and the appearance of new cases is projected to rise by >70% by 2030. To effectively combat the menace of cancer, a variety of strategies have been exploited. Among them, the development of peptide–drug conjugates (PDCs) is considered as an inextricable part of this armamentarium and is continuously explored as a viable approach to target malignant tumors. The general architecture of PDCs consists of three building blocks: the tumor-homing peptide, the cytotoxic agent and the biodegradable connecting linker. The aim of the current review is to provide a spherical perspective on the basic principles governing PDCs, as also the methodology to construct them. We aim to offer basic and integral knowledge on the rational design towards the construction of PDCs through analyzing each building block, as also to highlight the overall progress of this rapidly growing field. Therefore, we focus on several intriguing examples from the recent literature, including important PDCs that have progressed to phase III clinical trials. Last, we address possible difficulties that may emerge during the synthesis of PDCs, as also report ways to overcome them.

Biomimetic nanoparticles with enhanced affinity towards activated endothelium as versatile tools for theranostic drug delivery

Activation of the vascular endothelium is characterized by increased expression of vascular adhesion molecules and chemokines. This activation occurs early in the progression of several diseases and triggers the recruitment of leukocytes. Inspired by the tropism of leukocytes, we investigated leukocyte-based biomimetic nanoparticles (i.e., leukosomes) as a novel theranostic platform for inflammatory diseases.

Methods: Leukosomes were assembled by combining phospholipids and membrane proteins from leukocytes. For imaging applications, phospholipids modified with rhodamine and gadolinium were used. Leukosomes incubated with antibodies blocking lymphocyte function-associated antigen 1 (LFA-1) and CD45 were administered to explore their roles in targeting inflammation. In addition, relaxometric assessment of NPs was evaluated.

Results: Liposomes and leukosomes were both spherical in shape with sizes ranging from 140-170 nm. Both NPs successfully integrated 8 and 13 µg of rhodamine and gadolinium, respectively, and demonstrated less than 4% variation in physicochemical features. Leukosomes demonstrated a 16-fold increase in breast tumor accumulation relative to liposomes. Furthermore, quantification of leukosomes in tumor vessels demonstrated a 4.5-fold increase in vessel lumens and a 14-fold increase in vessel walls. Investigating the targeting mechanism of action revealed that blockage of LFA-1 on leukosomes resulted in a 95% decrease in tumor accumulation. Whereas blockage of CD45 yielded a 60% decrease in targeting and significant increases in liver and spleen accumulation. In addition, when administered in mice with atherosclerotic plaques, leukosomes exhibited a 4-fold increase in the targeting of inflammatory vascular lesions. Lastly, relaxometric assessment of NPs demonstrated that the incorporation of membrane proteins into leukosomes did not impact the r₁ and r₂ relaxivities of the NPs, demonstrating 6 and 30 mM^-1s^-1, respectively.

Conclusion: Our study demonstrates the ability of leukosomes to target activated vasculature and exhibit superior accumulation in tumors and vascular lesions. The versatility of the phospholipid backbone within leukosomes permits the incorporation of various contrast agents. Furthermore, leukosomes can potentially be loaded with therapeutics possessing diverse physical properties and thus warrant further investigation toward the development of powerful theranostic agents.

Combination Cancer Therapy Can Confer Benefit via Patient-to-Patient Variability without Drug Additivity or Synergy

Combination cancer therapies aim to improve the probability and magnitude of therapeutic responses and reduce the likelihood of acquired resistance in an individual patient. However, drugs are tested in clinical trials on genetically diverse patient populations. We show here that patient-to-patient variability and independent drug action are sufficient to explain the superiority of many FDA-approved drug combinations in the absence of drug synergy or additivity. This is also true for combinations tested in patient-derived tumor xenografts. In a combination exhibiting independent drug action, each patient benefits solely from the drug to which his or her tumor is most sensitive, with no added benefit from other drugs. Even when drug combinations exhibit additivity or synergy in pre-clinical models, patient-to-patient variability and low cross-resistance make independent action the dominant mechanism in clinical populations. This insight represents a different way to interpret trial data and a different way to design combination therapies.

Evaluation of the performance of elastomeric pumps in practice: are we under-delivering on chemotherapy treatments?

BACKGROUND AND AIMS

Elastomeric pumps are widely used to facilitate ambulatory chemotherapy, and studies have shown that they are safe and well received by patients. Despite these advantages, their end of infusion time can fluctuate significantly. The aim of this research was to observe the performance of these pumps in real practice and to evaluate patients' satisfaction.

METHODS

This was a two-phase study conducted at three cancer units over 6 months. Phase-1 was an observational study recording the status of pumps at the scheduled disconnection time and noting remaining volume of infusion. Phase-2 was a survey of patients and their perception/satisfaction. Ethical approval was granted.

RESULTS

A total of 92 cases were observed covering 50 cases disconnected at hospital and 42 disconnected at home. The infusion in 40% of hospital disconnection cases was slow, with patients arriving at hospital with unfinished pumps; 58% of these had an estimated remaining volume which exceeded 10 mL with 35% exceeded 20 mL. In 73% of these cases, and regardless of the remaining volume, the patient was disconnected and the pump was discarded.

CONCLUSIONS

The performance of pumps varied, which affected nurse workload and patients' waiting-times. A smart system is an option to monitor the performance of pumps and to predict their accuracy.

Comparison of the Pharmacokinetics of the Phase II and Phase III Capsule Formulations of Selumetinib and the Effects of Food on Exposure: Results From Two Randomized Crossover Trials in Healthy Male Subjects

PURPOSE

Selumetinib (AZD6244, ARRY-142886), an oral, potent, and highly selective mitogen-activated protein kinase 1/2 inhibitor with a short half-life, has shown activity across various tumor types. Before initiation of Phase III trials, the site, scale, and color (hypromellose shell from white [Phase II] to blue [Phase III]) of the selumetinib 25mg capsule manufacture was changed. We present 2 crossover trials evaluating Phase III capsules in healthy subjects.

METHODS

The relative bioavailability trial was a Phase I, open-label, randomized, 3-treatment, 4-period, 6-sequence crossover trial in healthy male subjects (aged 18-55 years). Subjects received selumetinib 75mg (3 × 25 mg) Phase II or Phase III capsules, or a 35mg oral solution, during 4 dosing periods in 1 of 6 randomized treatment sequences. The food effect trial was a Phase I, open-label, randomized, 2-period crossover trial in healthy male subjects (aged 18-45 years). Subjects were randomized to 1 of 2 sequences to receive selumetinib 75mg (3 × 25 mg) Phase III capsules. In sequence 1, subjects received selumetinib after 10 hours of fasting. Following a washout period, selumetinib was administered after a high-fat meal. In sequence 2, subjects received selumetinib in the fed state, before the fasted state. Pharmacokinetic parameters were determined from serial blood sampling.

FINDINGS

Twenty-seven subjects were randomized to the relative bioavailability trial; 26 completed all dosing periods. Mean selumetinib AUC was unchanged (geometric least squares mean ratio [GLSMR], 90.01% [90% CI, 81.74-99.11]). C_max was 18% lower with the Phase III capsules (GLSMR, 81.97% [90% CI, 69.01-97.36]). A post hoc exploratory statistical analysis excluding outlying observations with later T_max showed that Phase II and III capsules produced similar exposure in terms of C_max and AUC. High intrasubject variability for C_max attributed to the pharmacokinetic sampling schedule was judged to have impacted on the estimated GLSMR. In the food effect trial, 34 subjects completed both study periods. A high-fat meal reduced selumetinib C_max compared with the fasted state (GLSMR, 49.76% [90% CI, 43.82-56.51]); AUC was minimally changed (GLSMR, 84.08% [90% CI, 80.72-87.59]). Median T_max was prolonged by 1.49 hours. No deaths or serious adverse events were reported.

IMPLICATIONS

Selumetinib 75mg (3 × 25 mg) Phase III capsules are being used in ongoing pivotal Phase III trials and should be administered in the fasted state. Based on findings from the relative bioavailability trial, pharmacokinetic sampling frequency was increased for healthy subject trials, including the food effect trial. ClinicalTrials.gov identifiers: NCT01635023 (relative bioavailability) and NCT01974349 (food effect).

A framework for understanding and targeting residual disease in oncogene-driven solid cancers

Molecular targeted therapy has the potential to dramatically improve survival in patients with cancer. However, complete and durable responses to targeted therapy are rare in individuals with advanced-stage solid cancers. Even the most effective targeted therapies generally do not induce a complete tumor response, resulting in residual disease and tumor progression that limits patient survival. We discuss the emerging need to more fully understand the molecular basis of residual disease as a prelude to designing therapeutic strategies to minimize or eliminate residual disease so that we can move from temporary to chronic control of disease, or a cure, for patients with advanced-stage solid cancers. Ultimately, we propose a shift from the current reactive paradigm of analyzing and treating acquired drug resistance to a pre-emptive paradigm of defining the mechanisms that result in residual disease, to target and limit this disease reservoir.

Molecular mechanisms for tumour resistance to chemotherapy

Chemotherapy is one of the prevailing methods used to treat malignant tumours, but the outcome and prognosis of tumour patients are not optimistic. Cancer cells gradually generate resistance to almost all chemotherapeutic drugs via a variety of distinct mechanisms and pathways. Chemotherapeutic resistance, either intrinsic or acquired, is caused and sustained by reduced drug accumulation and increased drug export, alterations in drug targets and signalling transduction molecules, increased repair of drug-induced DNA damage, and evasion of apoptosis. In order to better understand the mechanisms of chemoresistance, this review highlights our current knowledge of the role of altered drug metabolism and transport and deregulation of apoptosis and autophagy in the development of tumour chemoresistance. Reduced intracellular activation of prodrugs (e.g. thiotepa and tegafur) or enhanced drug inactivation by Phase I and II enzymes contributes to the development of chemoresistance. Both primary and acquired resistance can be caused by alterations in the transport of anticancer drugs which is mediated by a variety of drug transporters such as P-glycoprotein (P-gp), multidrug resistance associated proteins, and breast cancer resistance protein. Presently there is a line of evidence indicating that deregulation of programmed cell death including apoptosis and autophagy is also an important mechanism for tumour resistance to anticancer drugs. Reversal of chemoresistance is likely via pharmacological and biological approaches. Further studies are warranted to grasp the full picture of how each type of cancer cells develop resistance to anticancer drugs and to identify novel strategies to overcome it.

Associations of High-Dose Melphalan Pharmacokinetics and Outcomes in the Setting of a Randomized Cryotherapy Trial

High-dose melphalan followed by autologous stem cell transplantation remains the standard of care for eligible patients with multiple myeloma, but disease response and toxicity, including severe mucositis, varies among patients. Our randomized trial investigated duration of cryotherapy (2 and 6 h) for reduction of mucositis prevalence and severity and explored factors associated with variability in pharmacokinetics and outcomes from melphalan therapy. The results demonstrate that 2-h is at least as effective as 6-h cryotherapy in decreasing severe mucositis. From a population pharmacokinetic model, we identified that fat-free mass, hematocrit, and creatinine clearance were significant covariates, as reported previously. Furthermore, we observed the rs4240803 SLC7A5 polymorphism was significantly associated with pharmacokinetic variability, and pharmacokinetics was associated with both mucositis and neutropenia. However, melphalan exposure was not associated with progression-free or overall survival in our dataset. These findings contribute to ongoing efforts to personalize melphalan dosing in transplant patients.

Repurposing itraconazole for the treatment of cancer

The repurposing of drugs is becoming increasingly attractive as it avoids the lengthy process and cost implications associated with bringing a novel drug to market. Itraconazole is a broad-spectrum anti-fungal agent. An emerging body of in vivo, in vitro and clinical evidence have confirmed that it also possesses antineoplastic activities and has a synergistic action when combined with other chemotherapeutic agents. It acts via several mechanisms to prevent tumour growth, including inhibition of the Hedgehog pathway, prevention of angiogenesis, decreased endothelial cell proliferation, cell cycle arrest and induction of auto-phagocytosis. These allow itraconazole, either alone or in combination with other cytotoxic agents, to increase drug efficacy and overcome drug resistance. This study reviews the reported literature on the use of itraconazole in a variety of malignancies and highlights the recent insights into the critical pathways acted upon to prevent tumour growth.

Molecular design and synthesis of self-assembling camptothecin drug amphiphiles

The conjugation of small molecular hydrophobic anticancer drugs onto a short peptide with overall hydrophilicity to create self-assembling drug amphiphiles offers a new prodrug strategy, producing well-defined, discrete nanostructures with a high and quantitative drug loading. Here we show the detailed synthesis procedure and how the molecular structure can influence the synthesis of the self-assembling prodrugs and the physicochemical properties of their assemblies. A series of camptothecin-based drug amphiphiles were synthesized via combined solid- and solution-phase synthetic techniques, and the physicochemical properties of their self-assembled nanostructures were probed using a number of imaging and spectroscopic techniques. We found that the number of incorporated drug molecules strongly influences the rate at which the drug amphiphiles are formed, exerting a steric hindrance toward any additional drugs to be conjugated and necessitating extended reaction time. The choice of peptide sequence was found to affect the solubility of the conjugates and, by extension, the critical aggregation concentration and contour length of the filamentous nanostructures formed. In the design of self-assembling drug amphiphiles, the number of conjugated drug molecules and the choice of peptide sequence have significant effects on the nanostructures formed. These observations may allow the fine-tuning of the physicochemical properties for specific drug delivery applications, ie systemic vs local delivery.

Praziquantel for Schistosomiasis: Single-Drug Metabolism Revisited, Mode of Action, and Resistance

Schistosomiasis, a major neglected tropical disease, affects more than 250 million people worldwide. Treatment of schistosomiasis has relied on the anthelmintic drug praziquantel (PZQ) for more than a generation. PZQ is the drug of choice for the treatment of schistosomiasis; it is effective against all major forms of schistosomiasis, although it is less active against juvenile than mature parasites. A pyrazino-isoquinoline derivative, PZQ is not considered to be toxic and generally causes few or transient, mild side effects. Increasingly, mass drug administration targeting populations in sub-Saharan Africa where schistosomiasis is endemic has led to the appearance of reduced efficacy of PZQ, which portends the selection of drug-resistant forms of these pathogens. The synthesis of improved derivatives of PZQ is attracting attention, e.g., in the (i) synthesis of drug analogues, (ii) rational design of pharmacophores, and (iii) discovery of new compounds from large-scale screening programs. This article reviews reports from the 1970s to the present on the metabolism and mechanism of action of PZQ and its derivatives against schistosomes.

Towards better dose individualisation: metabolic phenotyping to predict cabazitaxel pharmacokinetics in men with prostate cancer

BACKGROUND

Cabazitaxel is approved for treatment of castration-resistant metastatic prostate cancer. The current dosing strategy of cabazitaxel is based on body surface area (BSA). Body surface area is known as a poor predictor for total systemic exposure to drugs, since it does not take into account variability in activity of metabolising enzymes, necessary for clearance of drugs. As exposure to cabazitaxel is related to treatment response, it is essential to develop a better individualised dosing strategy.

METHODS

Ten patients with metastatic castration-resistant prostate cancer, who received cabazitaxel dosed on BSA as a part of routine palliative care, were enrolled in this study. Midazolam was administered as phenotyping probe for cytochrome P450 isoenzyme 3A (CYP3A). The relationship between midazolam and cabazitaxel clearance was investigated using non-linear mixed effects modelling.

RESULTS

The clearance of Midazolam highly correlated with cabazitaxel clearance (R=0.74). Midazolam clearance significantly (P<0.004) explained the majority (∼60%) of the inter-individual variability in cabazitaxel clearance in the studied population.

CONCLUSIONS

Metabolic phenotyping of CYP3A using midazolam is a promising strategy to individualise cabazitaxel dosing. Before clinical application, a randomised study is warranted.

Mesenchymal stromal/stem cells in drug therapy: New perspective

Mesenchymal stromal/stem cells (MSC) have emerged as a class of cells suitable for cellular delivery of nanoparticles, drugs and micro-RNA cargo for targeted treatments such as tumor and other protective mechanisms. The special properties of MSC underscore the current use for various clinical applications. Examples of applications include but are not limited to regenerative medicine, immune disorders and anti-cancer therapies. In recent years, there has been intense research in modifying MSC to achieve targeted and efficient clinical outcomes. This review discusses effects of MSC in an inflammatory microenvironment and then explains how these properties could be important to the overall application of MSC in cell therapy. The article also advises caution in the application of these cells because of their role in tumorigenesis. The review stresses the use of MSC as vehicles for drug delivery and discusses the accompanying challenges, based on the influence of the microenvironment on MSC.

Feasibility of spatial frequency domain imaging (SFDI) for optically characterizing a preclinical oncology model

Determination of chemotherapy efficacy early during treatment would provide more opportunities for physicians to alter and adapt treatment plans. Diffuse optical technologies may be ideally suited to track early biological events following chemotherapy administration due to low cost and high information content. We evaluated the use of spatial frequency domain imaging (SFDI) to characterize a small animal tumor model in order to move towards the goal of endogenous optical monitoring of cancer therapy in a controlled preclinical setting. The effects of key measurement parameters including the choice of imaging spatial frequency and the repeatability of measurements were evaluated. The precision of SFDI optical property extractions over repeat mouse measurements was determined to be within 3.52% for move and replace experiments. Baseline optical properties and chromophore values as well as intratumor heterogeneity were evaluated over 25 tumors. Additionally, tumor growth and chemotherapy response were monitored over a 45 day longitudinal study in a small number of mice to demonstrate the ability of SFDI to track treatment effects. Optical scattering and oxygen saturation increased as much as 70% and 25% respectively in treated tumors, suggesting SFDI may be useful for preclinical tracking of cancer therapies.

Utilizing In Vitro Dissolution-Permeation Chamber for the Quantitative Prediction of pH-Dependent Drug-Drug Interactions with Acid-Reducing Agents: a Comparison with Physiologically Based Pharmacokinetic Modeling

For many orally administered basic drugs with pH-dependent solubility, concurrent administration with acid-reducing agents (ARAs) can significantly impair their absorption and exposure. In this study, pH-dependent drug-drug interaction (DDI) prediction methods, including in vitro dissolution-permeation chamber (IVDP) and physiologically based pharmacokinetic (PBPK) modeling, were evaluated for their ability to quantitatively predict the clinical DDI observations using 11 drugs with known clinical pH-dependent DDI data. The data generated by IVDP, which consists of a gastrointestinal compartment and a systemic compartment separated by a biomimic membrane, significantly correlated with the clinical DDI observations. The gastrointestinal compartment AUC ratio showed strong correlation with clinical AUC ratio (R=0.72 and P=0.0056), and systemic compartment AUC ratio showed strong correlation with clinical C_max ratio (R=0.91 and P=0.0003). PBPK models were also developed for the 11 test compounds. The simulations showed that the predictions from PBPK model with experimentally measured parameters significantly correlated with the clinical DDI observations. Future studies are needed to evaluate predictability of Z-factor-based PBPK models for pH-dependent DDI. Overall, these data suggested that the severity of pH-dependent DDI can be predicted by in vitro and in silico methods. Proper utilization of these methods before clinical DDI studies could allow adequate anticipation of pH-dependent DDI, which helps with minimizing pharmacokinetic variation in clinical studies and ensuring every patient with life-threatening diseases receives full benefit of the therapy.

Preclinical anticancer effectiveness of a fraction from Casearia sylvestris and its component Casearin X: in vivo and ex vivo methods and microscopy examinations

ETHNOPHARMACOLOGICAL RELEVANCE

Casearia sylvestris (Salicaceae) is found in South America and presents antiulcerogenic, cytotoxic, antimicrobial, anti-inflammatory and antihypertensive activities.

AIM OF THE STUDY

To assess the in vivo and ex vivo antitumor action of a fraction with casearins (FC) and its main component - Casearin X-isolated from C. sylvestris leaves.

MATERIALS AND METHODS

Firstly, Sarcoma 180 bearing Swiss mice were treated with FC and Cas X for 7 days. Secondly, BALB/c nude animals received hollow fibers with colon carcinoma (HCT-116) or glioblastoma (SF-295) cells and were treated with FC for 4 days. On 5th day, proliferation was determined by MTT assay.

RESULTS

FC 10 and 25mg/kg/day i.p. and 50mg/kg/day oral and Cas X 25mg/kg/day i.p. and 50mg/kg/day oral revealed tumor growth inhibition rates of 35.8, 86.2, 53.7, 90.0 and 65.5% and such tumors demonstrated rare mitoses and coagulation necrosis areas. Similarly, FC reduced multiplying of HCT-116 and SF-295 cells when evaluated by the Hollow Fiber Assay (2.5 and 5mg/kg/day i.p. and 25 and 50mg/kg/day oral), with cell growth inhibition rates ranging from 33.3 to 67.4% (p<0.05). Flow cytometry experiments revealed that FC reduced membrane integrity and induced DNA fragmentation and mitochondrial depolarization (p<0.05).

CONCLUSIONS

FC and Cas X were efficient antitumor substances against murine and human cancer cells and caused reversible morphological changes in liver, kidneys and spleens, emphasizing clerodane diterpenes as an emerging class of anticancer molecules.

Mechanisms of Drug Resistance Related to the Microenvironment of Solid Tumors and Possible Strategies to Inhibit Them

Drug resistance can occur at the individual cellular level or as a result of properties of the tumor microenvironment. The convoluted vasculature within tumors results in robustly proliferating well-nourished cells located proximal to functional blood vessels and regions of slowly proliferating (often hypoxic) cells located distal to functional blood vessels. Irregular blood flow and large distances between functional blood vessels in solid tumors lead to poor drug distribution within them such that cells distal from functional blood vessels are exposed to ineffective concentrations of drug, resulting in therapeutic resistance. Strategies to improve or complement the distribution of anticancer drugs within tumors hold promise for increasing antitumor effects without corresponding increases in normal tissue toxicity. In particular, use of hypoxia-targeted agents and modulation of autophagy have shown promising results in enhancing the distribution of drug activity within solid tumors and hence antitumor efficacy. In this review, we describe causes of resistance to chemotherapy that relate to the microenvironment of solid tumors and the potential to improve antitumor effects by countering such mechanisms of resistance.

Effect of food and acid-reducing agents on the absorption of oral targeted therapies in solid tumors

Oral targeted therapies represent an increasingly important group of drugs within modern oncology. With the shift from intravenously to orally administered drugs, drug absorption is a newly introduced factor in drug disposition. The process of absorption can have a large effect on inter- and intrasubject variability in drug exposure and thereby potentially treatment benefit or the severity of toxicities. The intake of oral targeted therapies with food and concomitant use of acid-reducing agents (ARAs) can significantly affect drug absorption. The size and direction of the effect of food and ARAs on drug absorption varies among drugs as a result of different chemical characteristics. Therefore, an awareness and understanding of these effects for each drug is essential to optimize patient outcomes.

Active targeting of chemotherapy to disseminated tumors using nanoparticle-carrying T cells

Tumor cells disseminate into compartments that are poorly accessible from circulation, which necessitates high doses of systemic chemotherapy. However, the effectiveness of many drugs, such as the potent topoisomerase I poison SN-38, is hampered by poor pharmacokinetics. To deliver SN-38 to lymphoma tumors in vivo, we took advantage of the fact that healthy lymphocytes can be programmed to phenocopy the biodistribution of the tumor cells. In a murine model of disseminated lymphoma, we expanded autologous polyclonal T cells ex vivo under conditions that retained homing receptors mirroring lymphoma cells, and functionalized these T cells to carry SN-38-loaded nanocapsules on their surfaces. Nanocapsule-functionalized T cells were resistant to SN-38 but mediated efficient killing of lymphoma cells in vitro. Upon adoptive transfer into tumor-bearing mice, these T cells served as active vectors to deliver the chemotherapeutic into tumor-bearing lymphoid organs. Cell-mediated delivery concentrated SN-38 in lymph nodes at levels 90-fold greater than free drug systemically administered at 10-fold higher doses. The live T cell delivery approach reduced tumor burden significantly after 2 weeks of treatment and enhanced survival under conditions where free SN-38 and SN-38-loaded nanocapsules alone were ineffective. These results suggest that tissue-homing lymphocytes can serve as specific targeting agents to deliver nanoparticles into sites difficult to access from the circulation, and thus improve the therapeutic index of chemotherapeutic drugs with unfavorable pharmacokinetics.

Separation and simultaneous quantification of nine furanocoumarins from Radix Angelicae dahuricae using liquid chromatography with tandem mass spectrometry for bioavailability determination in rats

Radix Angelicae dahuricae is a well-known medicinal herb in a number of herb preparations for medical uses. In this study, a rapid and selective method using liquid chromatography with tandem mass spectrometry was developed for the separation and simultaneous quantitation of nine furanocoumarins from Radix A. dahuricae, namely imperatorin, isoimperatorin, oxypeucedanin hydrate, bergapten, oxypeucedanin, xanthotoxol, xanthotoxin, isopimpinellin, and psoralen. Chromatographic separation was achieved on a CAPCELL PAK MG II C18 analytical column. Detection was performed using positive electrospray ion source in the multiple reaction monitoring mode. The method was fully validated for analyzing these principles in rat plasma with a lower limit of quantification from 0.5 to 5 ng/mL. The intra- and interbatch precisions were less than 10%, and the accuracies ranged from -7.5 to 8.0%. The extraction recovery of the analytes was above 70% without a significant matrix effect. The method was used to determine the oral and intravenous pharmacokinetic profiles of these furanocoumarins after dosing with Radix A. dahurica extract. The bioavailability of these furanocoumarins ranged from 10.1 to 82.8%. These data provide critical information for a better understanding of the pharmacological mechanisms and herb-drug interaction potential of Radix A. dahurica.

Inhibition of OATP-1B1 and OATP-1B3 by tyrosine kinase inhibitors

BACKGROUND

The potential of tyrosine kinase inhibitors (TKIs) interacting with other therapeutics through hepatic uptake transporter inhibition has not been fully delineated in drug-drug interactions (DDIs). This study was designed to estimate the half-maximal inhibitory concentration (IC50) values of five small-molecule TKIs (pazopanib, nilotinib, vandetanib, canertinib and erlotinib) interacting with organic anion-transporting polypeptides (OATPs): OATP-1B1 and -1B3.

METHODS

The IC50 values of TKIs and rifampicin (positive control) were determined by concentration-dependent inhibition of TKIs on cellular accumulation of radiolabeled probe substrates [3H]estrone sulfate and [3H]cholecystokinin octapeptide. Chinese hamster ovary cells transfected with humanized OATP-1B1 and OATP-1B3 transporter proteins, respectively, were utilized to carry out these studies.

RESULTS

Pazopanib and nilotinib show inhibitory activity on OATP-1B1 transporter protein. IC50 values for rifampicin, pazopanib and nilotinib were 10.46±1.15, 3.89±1.21 and 2.78±1.13 μM, respectively, for OATP-1B1 transporter. Vandetanib, canertinib and erlotinib did not exhibit any inhibitory potency toward OATP-1B1 transporter protein. Only vandetanib expressed inhibitory potential toward OATP-1B3 transporter protein out of the five selected TKIs. IC50 values for rifampicin and vandetanib for OATP-1B3 transporter inhibition were 3.67±1.20 and 18.13±1.21 μM, respectively. No significant inhibition in the presence of increasing concentrations of pazopanib, nilotinib, canertinib and erlotinib were observed for OATP-1B3 transporter.

CONCLUSIONS

Because selected TKIs are inhibitors of OATP-1B1 and -1B3 expressed in hepatic tissue, these compounds can be regarded as molecular targets for transporter-mediated DDIs. These findings provide the basis for further preclinical and clinical studies investigating the transporter-based DDI potential of TKIs.

Resistance to cancer chemotherapy: failure in drug response from ADME to P-gp

Cancer chemotherapy resistance (MDR) is the innate and/or acquired ability of cancer cells to evade the effects of chemotherapeutics and is one of the most pressing major dilemmas in cancer therapy. Chemotherapy resistance can arise due to several host or tumor-related factors. However, most current research is focused on tumor-specific factors and specifically genes that handle expression of pumps that efflux accumulated drugs inside malignantly transformed types of cells. In this work, we suggest a wider and alternative perspective that sets the stage for a future platform in modifying drug resistance with respect to the treatment of cancer.

5-Fluorouracil derivatives: a patent review (2012 - 2014)

INTRODUCTION

5-Fluorouracil (5-FU)-based chemotherapy is the most widely prescribed treatment for gastrointestinal solid tumors, but there are several drawbacks such as toxicities, lack of selectivity and effectiveness as well as the development of resistance that need to be overcome.

AREAS COVERED

In this review, the authors present the latest innovations in 5-FU derivatives or combinations with: i) other chemotherapeutic drugs; ii) novel targeted compounds; iii) radiotherapy; iv) mAbs; v) siRNA strategies; and vi) traditional Chinese medicine extracts. Moreover, advances to overcome or determine 5-FU adverse effects and effectiveness are described. Finally, the authors introduce the ongoing clinical trials and highlight the main challenges to be addressed in the future.

EXPERT OPINION

Although in the past few years there has been a great advancement in the antitumor effectiveness and selectivity of 5-FU-based therapies, it is envisaged that future approaches using 'omics' technologies that could determine the tumor heterogeneity may help in identifying additional candidate genes, microRNAs or cytokines involved in both the path mechanisms of 5-FU-related toxicity and its therapeutic efficacy. Moreover, the development of novel targeted 5-FU derivatives or 5-FU-based therapies tailored to individual patients opens up new possibilities in the improvement of the quality of life and survival for those suffering from this devastating disease.

Cyclodextrin-based targeting strategies for tumor treatment

The efficacy and applicability of anticancer drugs are greatly restricted by severe systemic toxicities and drug resistance. Targeting drug delivery strategies have been developed to prevent the shortcomings of chemotherapy. Among various approaches to specifically target drug-loaded carrier systems to the required pathological sites, ligand-attached cyclodextrin-based targeting complexes are a promising drug delivery system, which is achieved mainly through specific molecular interactions between the drugs and cell surface receptors. The principal targeting tactics include conjugation of cyclodextrin with targeting moieties or encapsulation drugs in cyclodextrins. The cyclodextrin-based supramolecules, polymers, or nanoparticles bearing bioactive substances such as folate, estrogens, carbohydrates, peptides, etc. have been reviewed.

Role of OATP-1B1 and/or OATP-1B3 in hepatic disposition of tyrosine kinase inhibitors

BACKGROUND

The metabolism of tyrosine kinase inhibitors (TKIs) is mainly mediated via hepatic route, but the mechanism responsible for their hepatocellular accumulation is still unknown. This study was designed to understand the contribution of organic anion transporting polypeptides (OATPs) in the hepatic uptake of selected TKIs - pazopanib, canertinib, erlotinib, vandetanib and nilotinib.

METHODS

Michaelis-Menten (MM) kinetic parameters for TKIs were determined by concentration-dependent cellular accumulation of selected TKIs using Chinese hamster ovary cells - wild type as well as transfected with humanized OATP-1B1 and OATP-1B3 transporter proteins.

RESULTS

The MM constant (Km) values of OATP-1B1 for nilotinib and vandetanib are 10.14±1.91 and 2.72±0.25 μM, respectively, and Vmax values of OATP-1B1 for nilotinib and vandetanib were 6.95±0.47 and 75.95±1.99 nmol/mg protein per minute, respectively. Likewise, Km values of OATP-1B3 for canertinib, nilotinib and vandetanib were 12.18±3.32, 7.84±1.43 and 4.37±0.79 μM, respectively, and Vmax values of OATP-1B3 for canertinib, nilotinib and vandetanib were 15.34±1.59, 6.75±0.42 and 194.64±10.58 nmol/mg protein per minute, respectively. Canertinib did not exhibit any substrate specificity toward OATP-1B1. Also, erlotinib and pazopanib did not exhibit any substrate specificity toward OATP-1B1 and -1B3.

CONCLUSIONS

Because selected TKIs are the substrates of OATP-1B1 and -1B3 expressed in hepatic tissue, these compounds can be regarded as molecular targets for transporter-mediated drug-drug interactions (DDIs). Any alteration in the function of these hepatic OATPs might account for the pharmacokinetic variability of TKIs.