Pharmacokinetic/pharmacodynamic modeling and simulation of neutropenia during phase I development of liposome-entrapped paclitaxel

DNA Nanobarrel-Based Drug Delivery for Paclitaxel and Doxorubicin

Co-delivery of anticancer drugs and target agents by endogenous materials is an inevitable approach towards targeted and synergistic therapy. Employing DNA base pair complementarities, DNA nanotechnology exploits a unique nanostructuring method and has demonstrated its capacity for nanoscale positioning and templated assembly. Moreover, the water solubility, biocompatibility, and modifiability render DNA structure suitable candidate for drug delivery applications. We here report single-stranded DNA tail conjugated antitumor drug paclitaxel (PTX), and the co-delivery of PTX, doxorubicin and targeting agent mucin 1 (MUC-1) aptamer on a DNA nanobarrel carrier. We investigated the effect of tail lengths on drug release efficiencies and dual drug codelivery-enabled cytotoxicity. Owing to the rapidly developing field of structural DNA nanotechnology, functional DNA-based drug delivery is promising to achieve clinical therapeutic applications.

Current development of cabazitaxel drug delivery systems

The second-generation taxane cabazitaxel has been clinically approved for the treatment of metastatic castration-resistant prostate cancer after docetaxel failure. Compared with the first-generation taxanes paclitaxel and docetaxel, cabazitaxel has potent anticancer activity and is less prone to drug resistance due to its lower affinity for the P-gp efflux pump. The relatively high hydrophobicity of cabazitaxel and the poor aqueous colloidal stability of the commercial formulation, following its preparation for injection, presents opportunities for new cabazitaxel formulations with improved features. This review provides an overview of cabazitaxel drug formulations and hydrophobic taxane drug delivery systems in general, and particularly focuses on emerging cabazitaxel delivery systems discovered in the past 5 years. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Liposomes and liposome-like nanoparticles: From anti-fungal infection to the COVID-19 pandemic treatment

The liposome is the first nanomedicine transformed into the market and applied to human patients. Since then, such phospholipid bilayer vesicles have undergone technological advancements in delivering small molecular-weight compounds and biological drugs. Numerous investigations about liposome uses were conducted in different treatment fields, including anti-tumor, anti-fungal, anti-bacterial, and clinical analgesia, owing to liposome's ability to reduce drug cytotoxicity and improve the therapeutic efficacy and combinatorial delivery. In particular, two liposomal vaccines were approved in 2021 to combat COVID-19. Herein, the clinically used liposomes are reviewed by introducing various liposomal preparations in detail that are currently proceeding in the clinic or on the market. Finally, we discuss the challenges of developing liposomes and cutting-edge liposomal delivery for biological drugs and combination therapy.

Construction of gastric cancer patient-derived organoids and their utilization in a comparative study of clinically used paclitaxel nanoformulations

Background

Gastric cancer (GC) is a highly heterogeneous disease with many different histological and molecular subtypes. Due to their reduced systemic adverse effects, nanoformulation agents have attracted increasing attention for use in the treatment of GC patients in the clinic. To improve therapeutic outcomes, it is vitally necessary to provide individual medication references and guidance for use of these nanoformulations, and patient-derived organoids (PDOs) are promising models through which to achieve this goal.

Results

Using an improved enzymatic digestion process, we succeeded in constructing GC PDOs from surgically resected tumor tissues and endoscopic biopsies from GC patients; these PDOs closely recapitulated the histopathological and genomic features of the corresponding primary tumors. Next, we chose two representative paclitaxel (PTX) nanoformulations for comparative study and found that liposomal PTX outperformed albumin-bound PTX in killing GC PDOs at both the transcriptome and cellular levels. Our results further showed that the different distributions of liposomal PTX and albumin-bound PTX in PDOs played an essential role in the distinct mechanisms through which they kill PDOs. Finally, we constructed patient-derived xenografts model in which we verified the above distinct therapeutic outcomes via an intratumoral administration route.

Conclusions

This study demonstrates that GC PDOs are reliable tools for predicting nanoformulation efficacy.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01431-8.

Paclitaxel Drug Delivery Systems: Focus on Nanocrystals' Surface Modifications

Paclitaxel (PTX) is a chemotherapeutic agent that belongs to the taxane family and which was approved to treat various kinds of cancers including breast cancer, ovarian cancer, advanced non-small-cell lung cancer, and acquired immunodeficiency syndrome (AIDS)-related Kaposi’s sarcoma. Several delivery systems for PTX have been developed to enhance its solubility and pharmacological properties involving liposomes, nanoparticles, microparticles, micelles, cosolvent methods, and the complexation with cyclodextrins and other materials that are summarized in this article. Specifically, this review discusses deeply the developed paclitaxel nanocrystal formulations. As PTX is a hydrophobic drug with inferior water solubility properties, which are improved a lot by nanocrystal formulation. Based on that, many studies employed nano-crystallization techniques not only to improve the oral delivery of PTX, but IV, intraperitoneal (IP), and local and intertumoral delivery systems were also developed. Additionally, superior and interesting properties of PTX NCs were achieved by performing additional modifications to the NCs, such as stabilization with surfactants and coating with polymers. This review summarizes these delivery systems by shedding light on their route of administration, the methods used in the preparation and modifications, the in vitro or in vivo models used, and the advantages obtained based on the developed formulations.

Clinical application of nano-targeting for enhancing chemotherapeutic efficacy and safety in cancer management

Despite improvements in treatment, cancer remains a leading cause of death worldwide. While chemotherapy is effective, it also damages healthy tissue, leading to severe, dose-limiting side effects that can impair efficacy and even contribute to chemoresistance. Nano-based drug-delivery systems can potentially target the delivery of chemotherapy to improve efficacy and reduce adverse effects. A number of nanocarriers have been investigated for the delivery of chemotherapy, and many of the most promising agents have advanced to clinical trials. This review examines the safety and efficacy of nanoformulated chemotherapeutic agents in clinical trials, with particular emphasis on anthracyclines, taxanes and platinum compounds. It also briefly discusses the role nano-targeting might play in the prevention and treatment of chemoresistance.

Bioactive nanotherapeutic trends to combat triple negative breast cancer

The management of aggressive breast cancer, particularly, triple negative breast cancer (TNBC) remains a formidable challenge, despite treatment advancement. Although newer therapies such as atezolizumab, olaparib, and sacituzumab can tackle the breast cancer prognosis and/or progression, but achieved limited survival benefit(s). The current research efforts are aimed to develop and implement strategies for improved bioavailability, targetability, reduce systemic toxicity, and enhance therapeutic outcome of FDA-approved treatment regimen. This review presents various nanoparticle technology mediated delivery of chemotherapeutic agent(s) for breast cancer treatment. This article also documents novel strategies to employ cellular and cell membrane cloaked (biomimetic) nanoparticles for effective clinical translation. These technologies offer a safe and active targeting nanomedicine for effective management of breast cancer, especially TNBC.

Ribociclib Population Pharmacokinetics and Pharmacokinetic/Pharmacodynamic Analysis of Neutrophils in Cancer Patients

The population pharmacokinetics (popPK) of ribociclib and population pharmacokinetic/pharmacodynamic (PK/PD) relationship between ribociclib and absolute neutrophil count (ANC) were characterized in patients with cancer. PopPK and ANC PK/PD modeling were both conducted in 2 rounds per data availability. Initial models were developed based on data sets from early-phase trials and qualified using external data from the phase III MONALEESA-2 trial. The second round of analyses was performed using updated data sets that included 2 more phase III trials (MONALEESA-3 and -7). The popPK and ANC PK/PD models adequately described the data and demonstrated reasonable predictive ability. Covariate analysis showed that ribociclib PK were not affected by age, sex, race, baseline Eastern Cooperative Oncology Group (ECOG) status (grade 1), mild/moderate renal impairment, mild hepatic impairment, or concomitant use of combination partners, including aromatase inhibitors (letrozole, anastrozole) or fulvestrant, proton-pump inhibitors, or weak cytochrome P450 3A4/5 inhibitors. Body weight had no impact on ribociclib clearance to warrant dose adjustment. The ANC PK/PD relationship was not affected by age, weight, sex, race, baseline ECOG status (grade 1), or concomitant use of letrozole, anastrozole, or fulvestrant. The PK/PD analysis confirmed reversibility of ribociclib's effect on ANC; it also suggested that lowering the dose of ribociclib would mitigate ANC decrease and neutropenia risk. The popPK and ANC PK/PD analyses support the use of ribociclib in combination with an aromatase inhibitor or fulvestrant in patients with hormone receptor-positive, human epidermal growth factor receptor-2-negative advanced or metastatic breast cancer without dose adjustment in subpopulations, and the use of dose interruption/reduction to mitigate potential treatment-emergent neutropenia.

Recent Clinical Developments of Nanomediated Drug Delivery Systems of Taxanes for the Treatment of Cancer

Conventional taxanes are used as cornerstone of the chemotherapeutical treatment for a variety of malignancies. Nevertheless, a large proportion of patients do not benefit from their treatment while they do suffer from severe adverse events related to the solvent or to the active compound. Cremophor EL and polysorbate 80 free formulations, conjugates, oral formulations and different types of drug delivery systems are some examples of the several attempts to improve the treatment with taxanes. In this review article, we discuss recent clinical developments of nanomediated drug delivery systems of taxanes for the treatment of cancer. Targeting mechanisms of drug delivery systems and characteristics of the most commonly used taxane-containing drug delivery systems in the clinical setting will be discussed in this review.

Nanoparticle delivery systems to combat drug resistance in ovarian cancer

Due to the lack of early symptoms and difficulty of accurate diagnosis, ovarian cancer is the most lethal gynecological cancer faced by women. First-line therapy includes a combination of tumor resection surgery and chemotherapy regimen. However, treatment becomes more complex upon recurrence due to development of drug resistance. Drug resistance has been linked to many mechanisms, including efflux transporters, apoptosis dysregulation, autophagy, cancer stem cells, epigenetics, and the epithelial-mesenchymal transition. Thus, developing and choosing effective therapies is exceptionally complex. There is a need for increased specificity and efficacy in therapies for drug-resistant ovarian cancer, and research in targeted nanoparticle delivery systems aims to fulfill this challenge. Although recent research has focused on targeted nanoparticle-based therapies, few of these therapies have been clinically translated. In this review, non-viral nanoparticle delivery systems developed to overcome drug-resistance in ovarian cancer were analyzed, including their structural components, surface modifications, and drug-resistance targeted mechanisms.

Updates on the use of liposomes for active tumor targeting in cancer therapy

In the development of cancer chemotherapy, besides the discovery of new anticancer drugs, a variety of nanocarrier systems for the delivery of previously developed and new chemotherapeutic drugs have currently been explored. Liposome is one of the most studied nanocarrier systems because of its biodegradability, simple preparation method, high efficacy and low toxicity. To make the best use of this vehicle, a number of multifunctionalized liposomal formulations have been investigated. The objective of this review is to summarize the current development of novel active targeting liposomal formulations, and to give insight into the challenges and future direction of the field. The recent studies in active targeting liposomes suggest the great potential of precise targeted anticancer drug delivery in cancer therapeutics.

Pharmacokinetic and Pharmacodynamic Properties of Drug Delivery Systems

The use of drug delivery systems (DDS) is an attractive approach to facilitate uptake of therapeutic agents at the desired site of action, particularly when free drug has poor pharmacokinetics/biodistribution (PK/BD) or significant off-site toxicities. Successful translation of DDS into the clinic is dependent on a thorough understanding of the in vivo behavior of the carrier, which has, for the most part, been an elusive goal. This is, at least in part, due to significant differences in the mechanisms controlling pharmacokinetics for classic drugs and DDSs. In this review, we summarize the key physiologic mechanisms controlling the in vivo behavior of DDS, compare and contrast this with classic drugs, and describe engineering strategies designed to improve DDS PK/BD. In addition, we describe quantitative approaches that could be useful for describing PK/BD of DDS, as well as critical steps between tissue uptake and pharmacologic effect.

Assessing drug response in engineered brain microenvironments

Tissue engineered systems are important models for the testing and discovery of therapeutics against a number of diseases. The use of these models in vitro can expand both our understanding of the mechanisms behind disease and allow for higher throughput and personalized modeling of therapeutic response. Over the past decade there has been an explosion of models of neurological disorders that can be used in vitro to study new therapies against devastating neurodegenerative, neurodevelopmental, and neuro-oncological disease. These models span several types of engineered microenvironments which are produced using microfluidic devices, microtissue technology and/or the incorporation of biomaterial scaffolds to model neurological conditions such as; Alzheimer's disease, idiopathic autism, Parkinson's disease, Zika-induced microcephaly and neoplasms. Using engineered brain microenvironments, therapeutics can be tested in more physiologically relevant ways leading to new knowledge of the underlying causes and interactions occurring at the tissue level. However, much is still left to learn and model within these systems to make them truly valuable in the discovery and testing of novel therapies. Here we review the current state of the art of engineered brain microenvironments being used specifically to screen and test new therapeutic strategies and discuss the current benefits and limitations that still exist.

Liposomal paclitaxel induces fewer hematopoietic and cardiovascular complications than bioequivalent doses of Taxol

Paclitaxel (PTX) exhibits potent antineoplastic activity against various human malignancies; however, clinical application must overcome the inherent hydrophobicity of this molecule. The commercialized Taxol formulation utilizes Cremophor EL (CrEL)/ethanol as a solvent to stabilize and dispense PTX in an aqueous solution. However, adverse CrEL-induced hypersensitivity reactions have been reported in ~30% of recipients, and 40% of patients receiving premedication may also experience this adverse effect. Therefore, the development of a CrEL-free delivery system is crucial, in order to fully exploit the therapeutic efficacy of PTX. In the present study, a novel liposomal PTX (lipo-PTX) formulation was optimized with regards to encapsulation rate and long-term stability, arriving at a molar constituent ratio of soybean phosp hatidylcholine:cholesterol:N-(carbonyl-methoxy-poly-ethylene glycol 2000)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine, sodium salt:PTX at 95:2:1:2. Comparable doses of lipo-PTX and Taxol were bioequivalent in terms of therapeutic efficacy in xenograft tumor models. However, the systemic side effects, including hematopoietic toxicity, acute hypersensitivity reactions and cardiac irregularities, were significantly reduced in lipo-PTX-treated mice compared with those infused with reference formulations of PTX. In conclusion, the present study reported that lipo-PTX exhibited a higher therapeutic index than clinical PTX formulations.

Preclinical development of drug delivery systems for paclitaxel-based cancer chemotherapy

Paclitaxel (PTX) is one of the most successful drugs ever used in cancer chemotherapy, acting against a variety of cancer types. Formulating PTX with Cremophor EL and ethanol (Taxol®) realized its clinical potential, but the formulation falls short of expectations due to side effects such as peripheral neuropathy, hypotension, and hypersensitivity. Abraxane®, the albumin bound PTX, represents a superior replacement of Taxol® that mitigates the side effects associated with Cremophor EL. While Abraxane® is now considered a gold standard in chemotherapy, its 21% response rate leaves much room for further improvement. The quest for safer and more effective cancer treatments has led to the development of a plethora of innovative PTX formulations, many of which are currently undergoing clinical trials. In this context, we review recent development of PTX drug delivery systems and analyze the design principles underpinning each delivery strategy. We chose several representative examples to highlight the opportunities and challenges of polymeric systems, lipid-based formulations, as well as prodrug strategies.

The battle of "nano" paclitaxel

Paclitaxel (PTX) is one of the three most widely used chemotherapeutic agents, together with doxorubicin and cisplatin, and is first or second line treatment for several types of cancers. In 2000, Taxol, the conventional formulation of PTX, became the best-selling cancer drug of all time with annual sales of 1.6 billion. In 2005, the introduction of the albumin-based formulation of PTX, known as Abraxane, ended Taxol's monopoly of the PTX market. Abraxane's ability to push the Taxol innovator and generic formulations aside attracted fierce competition amongst competitors worldwide to develop their own unique, new and improved formulation of PTX. At this time there are at least 18 companies focused on pre-clinical and/or clinical development of nano-formulations of PTX. These pharmaceutical companies are investing substantial capital to capture a share of the lucrative global PTX market. It is hoped that any formulation that dominates the market will result in tangible benefits to patients in terms of both survival and quality of life. Given all of this activity, here we address the question: Who is going to win the battle of "nano" paclitaxel?

Liposome encapsulated luteolin showed enhanced antitumor efficacy to colorectal carcinoma

Luteolin is a falconoid compound that is present in various types of plants and possesses remarkable potential as a chemopreventive agent. However, the poor aqueous solubility of luteolin limits its clinical application. In the present study, an approach towards chemoprevention was explored using liposomes to deliver luteolin, and the antitumor efficacy was investigated in colorectal carcinoma. The present findings demonstrated that luteolin was efficiently encapsulated into liposomes with an encapsulation efficiency as high as 90%. The particle size of the liposomal luteolin (Lipo-Lut) and ζ-potential were optimized. In vitro studies demonstrated that, Lipo-Lut had a significant inhibitory effect on the growth on the CT26 colorectal carcinoma cell line compared with free luteolin (Free-Lut). The in vivo study indicated that Lipo-Lut could achieve superior antitumor effects against CT26 tumor compared with luteolin alone. The present results suggested that liposome delivery of luteolin improved solubility, bioavailability and may have potential applications in chemoprevention in clinical settings.

Investigational nanomedicines in 2016: a review of nanotherapeutics currently undergoing clinical trials

Nanomedicine is a relatively new field that is rapidly evolving. Formulation of drugs on the nanoscale imparts many physical and biological advantages. Such advantages can in turn translate into improved therapeutic efficacy and reduced toxicity. While approximately 50 nanotherapeutics have already entered clinical practice, a greater number of drugs are undergoing clinical investigation for a variety of indications. This review aims to examine all the nanoformulations that are currently undergoing clinical investigation and their outlook for ultimate clinical translation. WIREs Nanomed Nanobiotechnol 2017, 9:e1416. doi: 10.1002/wnan.1416 For further resources related to this article, please visit the WIREs website.

Bringing Model-Based Prediction to Oncology Clinical Practice: A Review of Pharmacometrics Principles and Applications

Despite much investment and progress, oncology is still an area with significant unmet medical needs, with new therapies and more effective use of current therapies needed. The emergent field of pharmacometrics combines principles from pharmacology (pharmacokinetics [PK] and pharmacodynamics [PD]), statistics, and computational modeling to support drug development and optimize the use of already marketed drugs. Although it has gained a role within drug development, its use in clinical practice remains scarce. The aim of the present study was to review the principal pharmacometric concepts and provide some examples of its use in oncology. Integrated population PK/PD/disease progression models as part of the pharmacometrics platform provide a powerful tool to predict outcomes so that the right dose can be given to the right patient to maximize drug efficacy and reduce drug toxicity. Population models often can be developed with routinely collected medical record data; therefore, we encourage the application of such models in the clinical setting by generating close collaborations between physicians and pharmacometricians.

IMPLICATIONS FOR PRACTICE

The present review details how the emerging field of pharmacometrics can integrate medical record data with predictive pharmacological and statistical models of drug response to optimize and individualize therapies. In order to make this routine practice in the clinic, greater awareness of the potential benefits of the field is required among clinicians, together with closer collaboration between pharmacometricians and clinicians to ensure the requisite data are collected in a suitable format for pharmacometrics analysis.

Advances and Challenges of Liposome Assisted Drug Delivery

The application of liposomes to assist drug delivery has already had a major impact on many biomedical areas. They have been shown to be beneficial for stabilizing therapeutic compounds, overcoming obstacles to cellular and tissue uptake, and improving biodistribution of compounds to target sites in vivo. This enables effective delivery of encapsulated compounds to target sites while minimizing systemic toxicity. Liposomes present as an attractive delivery system due to their flexible physicochemical and biophysical properties, which allow easy manipulation to address different delivery considerations. Despite considerable research in the last 50 years and the plethora of positive results in preclinical studies, the clinical translation of liposome assisted drug delivery platforms has progressed incrementally. In this review, we will discuss the advances in liposome assisted drug delivery, biological challenges that still remain, and current clinical and experimental use of liposomes for biomedical applications. The translational obstacles of liposomal technology will also be presented.

Semimechanistic cell-cycle type-based pharmacokinetic/pharmacodynamic model of chemotherapy-induced neutropenic effects of diflomotecan under different dosing schedules

The current work integrates cell-cycle dynamics occurring in the bone marrow compartment as a key element in the structure of a semimechanistic pharmacokinetic/pharmacodynamic model for neutropenic effects, aiming to describe, with the same set of system- and drug-related parameters, longitudinal data of neutropenia gathered after the administration of the anticancer drug diflomotecan (9,10-difluoro-homocamptothecin) under different dosing schedules to patients (n = 111) with advanced solid tumors. To achieve such an objective, the general framework of the neutropenia models was expanded, including one additional physiologic process resembling cell cycle dynamics. The main assumptions of the proposed model are as follows: within the stem cell compartment, proliferative and quiescent cells coexist, and only cells in the proliferative condition are sensitive to drug effects and capable of following the maturation chain. Cell cycle dynamics were characterized by two new parameters, FProl (the fraction of proliferative [Prol] cells that enters into the maturation chain) and kcycle (first-order rate constant governing cell cycle dynamics within the stem cell compartment). Both model parameters were identifiable as indicated by the results from a bootstrap analysis, and their estimates were supported by date from the literature. The estimates of FProl and kcycle were 0.58 and 1.94 day(-1), respectively. The new model could properly describe the neutropenic effects of diflomotecan after very different dosing scenarios, and can be used to explore the potential impact of dosing schedule dependencies on neutropenia prediction.

Computational nanomedicine: modeling of nanoparticle-mediated hyperthermal cancer therapy

Nanoparticle-mediated hyperthermia for cancer therapy is a growing area of cancer nanomedicine because of the potential for localized and targeted destruction of cancer cells. Localized hyperthermal effects are dependent on many factors, including nanoparticle size and shape, excitation wavelength and power, and tissue properties. Computational modeling is an important tool for investigating and optimizing these parameters. In this review, we focus on computational modeling of magnetic and gold nanoparticle-mediated hyperthermia, followed by a discussion of new opportunities and challenges.

Population pharmacokinetic–pharmacodynamic modelling and simulation of neutropenia induced by TP300, a novel topoisomerase I inhibitor

Objectives

TP300 is a novel topoisomerase I inhibitor with neutropenia as a significant toxicity. We developed and evaluated a pharmacokinetic–pharmacodynamic (PK-PD) model, using data from Phase I and II trials to predict neutrophil decrease in patients treated with TP300.

Methods

Plasma drug concentrations of TP300, its active form TP3076 and active metabolite TP3011 and absolute neutrophil counts (ANCs) from a Phase I trial were analysed as a training dataset. A two-plus-two-compartment model was applied to the pharmacokinetics of TP3076 and TP3011. A semi-mechanistic model was used to describe the PK-PD relationship between the plasma concentration of TP3076 and TP3011, and changes in ANC.

Key findings

 The model fitted well to plasma concentrations of TP3076 and TP3011. Model appropriateness was confirmed in a Phase II trial validation dataset. Body weight and liver biochemistry values were identified as covariates. A semi-mechanistic PK-PD model was applied and the longitudinal decrease in ANC was simulated. Neutrophil counts reached their nadir approximately 2 weeks after administration of TP300, and the proportion of subjects affected increased with dose.

Conclusions

This PK-PD model to predict neutropenia following treatment with TP300 fitted well the decrease in ANC with total concentration of TP3076 and TP3011.

A novel PEGylated liposome-encapsulated SANT75 suppresses tumor growth through inhibiting hedgehog signaling pathway

The Hedgehog (Hh) pathway inhibitors have shown great promise in cancer therapeutics. SANT75, a novel compound we previously designed to specially inhibit the Smoothened (SMO) protein in the Hh pathway, has greater inhibitory potency than many of commonly used Hh inhibitors. However, preclinical studies of SANT75 revealed water insolubility and acute toxicity. To overcome these limitations, we developed a liposomal formulation of SANT75 and investigated its antitumor efficacy in vitro and in vivo. We encapsulated SANT75 into PEGylated liposome and the mean particle size distribution and zeta-potential (ZP) of liposomes were optimized. Using the Shh-light2 cell and Gli-GFP or Flk-GFP transgenic reporter zebrafish, we confirmed that liposome-encapsulated SANT75 inhibited Hh activity with similar potency as the original SANT75. SANT75 encapsulated into liposome exerted strong tumor growth-inhibiting effects in vitro and in vivo. In addition, the liposomal SANT75 therapy efficiently improved the survival time of tumor-bearing mice without obvious systemic toxicity. The pathological morphology and immunohistochemistry staining revealed that liposomal SANT75 induced tumor cell apoptosis, inhibited tumor angiogenesis as assessed by CD31 and down-regulated the expression of Hh target protein Gli-1 in tumor tissues. Our findings suggest that liposomal formulated SANT75 has improved solubility and bioavailability and should be further developed as a drug candidate for treating tumors with abnormally high Hh activity.

Mechanism-based model characterizing bidirectional interaction between PEGylated liposomal CKD-602 (S-CKD602) and monocytes in cancer patients

S-CKD602 is a PEGylated liposomal formulation of CKD-602, a potent topoisomerase I inhibitor. The objective of this study was to characterize the bidirectional pharmacokinetic-pharmacodynamic (PK-PD) interaction between S-CKD602 and monocytes. Plasma concentrations of encapsulated CKD-602 and monocytes counts from 45 patients with solid tumors were collected following intravenous administration of S-CKD602 in the phase I study. The PK-PD models were developed and fit simultaneously to the PK-PD data, using NONMEM(®). The monocytopenia after administration of S-CKD602 was described by direct toxicity to monocytes in a mechanism-based model, and by direct toxicity to progenitor cells in bone marrow in a myelosuppression-based model. The nonlinear PK disposition of S-CKD602 was described by linear degradation and irreversible binding to monocytes in the mechanism-based model, and Michaelis-Menten kinetics in the myelosuppression-based model. The mechanism-based PK-PD model characterized the nonlinear PK disposition, and the bidirectional PK-PD interaction between S-CKD602 and monocytes.

Liposomal paclitaxel formulations

Over the past three decades, taxanes represent one of the most important new classes of drugs approved in oncology. Paclitaxel (PTX), the prototype of this class, is an anti-cancer drug approved for the treatment of breast and ovarian cancer. However, notwithstanding a suitable premedication, present-day chemotherapy employing a commercial preparation of PTX (Taxol®) is associated with serious side effects and hypersensitivity reactions. Liposomes represent advanced and versatile delivery systems for drugs. Generally, both in vivo mice tumor models and human clinical trials demonstrated that liposomal PTX formulations significantly increase a maximum tolerated dose (MTD) of PTX which outperform that for Taxol®. Liposomal PTX formulations are in various stages of clinical trials. LEP-ETU (NeoPharm) and EndoTAG®-1 (Medigene) have reached the phase II of the clinical trials; Lipusu® (Luye Pharma Group) has already been commercialized. Present achievements in the preparation of various liposomal formulations of PTX, the development of targeted liposomal PTX systems and the progress in clinical testing of liposomal PTX are discussed in this review summarizing about 30 years of liposomal PTX development.

Neutrophil dynamics after chemotherapy and G-CSF: the role of pharmacokinetics in shaping the response

Chemotherapy has profound effects on the hematopoietic system, most notably leading to neutropenia. Granulocyte colony stimulating factor (G-CSF) is often used to deal with this neutropenia, but the response is highly variable. In this paper we examine the role of pharmacokinetics and delivery protocols in shaping the neutrophil responses to chemotherapy and G-CSF. Neutrophil responses to different protocols of chemotherapy administration with varying dosages, infusion times, and schedules are studied through a mathematical model. We find that a single dose of chemotherapy produces a damped oscillation in neutrophil levels, and short-term applications of chemotherapy can induce permanent oscillations in neutrophil level if there is a bistability in the system. In addition, we confirm previous findings [Zhuge et al., J. Theor. Biol., 293(2012), 111-120] that when periodic chemotherapy is given, there is a significant period of delivery that induces resonance in the system and exacerbates the corresponding neutropenia. The width of this resonant period peak increases with the recovery rate after a single chemotherapy, which is given by the real part of the dominant eigenvalue pair at the steady state, and both are determined by a single cooperativity coefficient in the feedback function for the neutrophils. Our numerical studies show that the neutropenia caused by chemotherapy can be overcome if G-CSF is given early after chemotherapy but can actually be worsened if G-CSF is given later, consistent with results reported in Zhuge et al. (2012). The nadir in neutrophil level is found to be more sensitive to the dosage of chemotherapy than that of the G-CSF. Furthermore, dependence of our results with changes in key pharmacokinetic parameters as well as initial functions are studied. Thus, this study illuminates the potential for destructive resonance leading to neutropenia in response to periodic chemotherapy, and explores and explains why the timing of G-CSF is so crucial for successful reversal of chemotherapy induced neutropenia.

Meta-analysis of nanoparticulate paclitaxel delivery system pharmacokinetics and model prediction of associated neutropenia

PURPOSE

Nanoparticulate paclitaxel carriers have entered clinical evaluation as alternatives to the Cremophor-based standard Taxol(®) (Cre-pac). Their pharmacokinetics (PK) is complex, and factors influencing their pharmacodynamics (PD) are poorly understood. We aimed to develop a unified quantitative model for 4 paclitaxel carriers that captures systems-level PK, predicts micro-scale PK processes, and permits correlations between carrier properties and observed PD.

METHODS

Data consisting of 54 PK profiles and 574 observations were extracted from 20 clinical studies investigating Cre-pac, albumin-(A-pac), liposome-(L-pac), and tocopherol-(T-pac) nanocarriers. A population-PK approach was used for data analysis. All datasets were simultaneously fitted to produce a unified model. Model-based simulations explored relationships between predicted PK and myelosuppression for each formulation.

RESULTS

The final model employed nonlinear drug-binding mechanisms to describe Cre-pac and a delayed-release model for A-pac, L-pac, and T-pac. Estimated drug-release rate constants (h(-1)): Cre-pac (5.19), L-pac (1.26), A-pac (0.72), T-pac (0.74). Simulations of equivalent dosing schemes ranked neutropenia severity (highest to lowest): T-pac~Cre-pac>L-pac~A-pac and predicted remarkably well the clinically-observed relationships between neutropenia and free drug exposure relative to a threshold concentration.

CONCLUSIONS

Paclitaxel disposition was well-described for all formulations. The derived model predicts toxicodynamics of diverse paclitaxel carriers.

The antitumour activities induced by pegylated liposomal cytochalasin D in murine models

Cytochalasin D targets actin and is ubiquitous in eukaryotic cells. When cytochalasin D is used as a cytotoxic agent in cancer therapy, it causes significant side effects. To prevent this, cytochalasin D can be encapsulated in polyethylene liposomes. In this study, high-performance liquid chromatography observation of the biodistribution of pegylated liposomal cytochalasin D in tumour-bearing mice showed that liposomal cytochalasin D could be conveniently dissolved in water for i.v. injection and that it specifically accumulated in tumour tissues, more than natural cytochalasin D did. The half-time of liposomal cytochalasin D in the plasma was also significantly longer than that of natural cytochalasin D (4h versus 10 min). MTT 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed that liposomal cytochalasin D treatment could cause significant inhibition of cell proliferation in vitro in a manner similar to that of natural cytochalasin D. The antitumour activities of liposomal cytochalasin D were investigated in B16 melanoma, CT26 colorectal carcinoma and H22 hepatoma models, and the results indicated that liposomal cytochalasin D could significantly inhibit tumour growth and prolong survival in a manner similar to that of cisplatin. TUNEL-based apoptosis assays showed that liposomal cytochalasin D induced significant tumour cell apoptosis. Significant inhibition of tumour angiogenesis was observed in mice treated with liposomal cytochalasin D. In addition, no significant side effects were observed in mice treated with liposomal cytochalasin D. Our results show that liposomal cytochalasin D increases solubility and bioavailability, a lower incidence of side effects and improves antitumour effects, indicating its potential as a chemical agent for cancer therapy.

Clinical development of liposome-based drugs: formulation, characterization, and therapeutic efficacy

Research on liposome formulations has progressed from that on conventional vesicles to new generation liposomes, such as cationic liposomes, temperature sensitive liposomes, and virosomes, by modulating the formulation techniques and lipid composition. Many research papers focus on the correlation of blood circulation time and drug accumulation in target tissues with physicochemical properties of liposomal formulations, including particle size, membrane lamellarity, surface charge, permeability, encapsulation volume, shelf time, and release rate. This review is mainly to compare the therapeutic effect of current clinically approved liposome-based drugs with free drugs, and to also determine the clinical effect via liposomal variations in lipid composition. Furthermore, the major preclinical and clinical data related to the principal liposomal formulations are also summarized.

Nanotechnology and human health: risks and benefits

Nanotechnology is expected to be promising in many fields of medical applications, mainly in cancer treatment. While a large number of very attractive exploitations open up for the clinics, regulatory agencies are very careful in admitting new nanomaterials for human use because of their potential toxicity. The very active research on new nanomaterials that are potentially useful in medicine has not been counterbalanced by an adequate knowledge of their pharmacokinetics and toxicity. The different nanocarriers used to transport and release the active molecules to the target tissues should be treated as additives, with potential side effects of themselves or by virtue of their dissolution or aggregation inside the body. Only recently has a systematic classification of nanomaterials been proposed, posing the basis for dedicated modeling at the nanoscale level. The use of in silico methods, such as nano-QSAR and PSAR, while highly desirable to expedite and rationalize the following stages of toxicological research, are not an alternative, but an introduction to mandatory experimental work.

The pharmacokinetic/pharmacodynamic pipeline: translating anticancer drug pharmacology to the clinic

Progress in an understanding of the genetic basis of cancer coupled to molecular pharmacology of potential new anticancer drugs calls for new approaches that are able to address key issues in the drug development process, including pharmacokinetic (PK) and pharmacodynamic (PD) relationships. The incorporation of predictive preclinical PK/PD models into rationally designed early-stage clinical trials offers a promising way to relieve a significant bottleneck in the drug discovery pipeline. The aim of the current review is to discuss some considerations for how quantitative PK and PD analyses for anticancer drugs may be conducted and integrated into a global translational effort, and the importance of examining drug disposition and dynamics in target tissues to support the development of preclinical PK/PD models that can be subsequently extrapolated to predict pharmacologic characteristics in patients. In this article, we describe three different physiologically based (PB) PK modeling approaches, i.e., the whole-body PBPK model, the hybrid PBPK model, and the two-pore model for macromolecules, as well as their applications. General conclusions are that greater effort should be made to generate more clinical data that could validate scaled preclinical PB-PK/PD tumor-based models and, thus, stimulate a framework for preclinical to clinical translation. Finally, given the innovative techniques to measure tissue drug concentrations and associated biomarkers of drug responses, development of predictive PK/PD models will become a standard approach for drug discovery and development.

Prediction of neutropenia-related effects of a new combination therapy with the anticancer drugs BI 2536 (a Plk1 inhibitor) and pemetrexed

This study investigated the feasibility of predicting the neutropenia-related effects of a therapy that combines the investigational drug BI 2536 (inhibitor of Polo-like kinase 1) and pemetrexed, an approved anticancer drug. Predictions were arrived at using the pharmacokinetic/pharmacodynamic (PK/PD) parameters of each of the drugs obtained from monotherapy studies and assuming that the neutropenic effect is additive when the drugs are administered as a combination therapy. Subsequently, a PK/PD model was developed to determine whether this assumption of additive effect was reasonable in relation to these two drugs. All analyses and simulations were performed using the population approach in NONMEM, version VI.

Predictive ability of a semi-mechanistic model for neutropenia in the development of novel anti-cancer agents: two case studies

In cancer chemotherapy neutropenia is a common dose-limiting toxicity. An ability to predict the neutropenic effects of cytotoxic agents based on proposed trial designs and models conditioned on previous studies would be valuable. The aim of this study was to evaluate the ability of a semi-mechanistic pharmacokinetic/pharmacodynamic (PK/PD) model for myelosuppression to predict the neutropenia observed in Phase I clinical studies, based on parameter estimates obtained from prior trials. Pharmacokinetic and neutropenia data from 5 clinical trials for diflomotecan and from 4 clinical trials for indisulam were used. Data were analyzed and simulations were performed using the population approach with NONMEM VI. Parameter sets were estimated under the following scenarios: (a) data from each trial independently, (b) pooled data from all clinical trials and (c) pooled data from trials performed before the tested trial. Model performance in each of the scenarios was evaluated by means of predictive (visual and numerical) checks. The semi-mechanistic PK/PD model for neutropenia showed adequate predictive ability for both anti-cancer agents. For diflomotecan, similar predictions were obtained for the three scenarios. For indisulam predictions were better when based on data from the specific study, however when the model parameters were conditioned on data from trials performed prior to a specific study, similar predictions of the drug related-neutropenia profiles and descriptors were obtained as when all data were used. This work provides further indication that modeling and simulation tools can be applied in the early stages of drug development to optimize future trials.