Bidirectional pharmacodynamic interaction between pegylated liposomal CKD-602 (S-CKD602) and monocytes in patients with refractory solid tumors

Understanding nanoparticle-liver interactions in nanomedicine

INTRODUCTION

Understanding the interactions between administered nanoparticles and the liver is crucial for developing safe and effective nanomedicines. As the liver can sequester up to 99% of these particles due to its major phagocytic role, exploring these interactions is vital for clinical translation.

AREAS COVERED

This review highlights recent studies on nanoparticle-liver interactions, including the influence of nanoparticle physicochemical properties on delivery, strategies to enhance delivery efficiency by modulating liver Kupffer cells, and their potential for treating certain hepatic diseases. Additionally, it discusses how aging impacts the liver's phagocytic functions.

EXPERT OPINION

While liver accumulation can hinder nanomedicine effectiveness, it also presents opportunities for treating liver diseases, especially considering how aging affects liver phagocytic functions. A thorough understanding of these interactions is essential for advancing the clinical application of nanomedicines.

Liposomes - Human phagocytes interplay in whole blood: effect of liposome design

Nanomedicine holds immense potential for therapeutic manipulation of phagocytic immune cells. However, in vitro studies often fail to accurately translate to the complex in vivo environment. To address this gap, we employed an ex vivo human whole-blood assay to evaluate liposome interactions with immune cells. We systematically varied liposome size, PEG-surface densities and sphingomyelin and ganglioside content. We observed differential uptake patterns of the assessed liposomes by neutrophils and monocytes, emphasizing the importance of liposome design. Interestingly, our results aligned closely with published in vivo observations in mice and patients. Moreover, liposome exposure induced changes in cytokine release and cellular responses, highlighting the potential modulation of immune system. Our study highlights the utility of human whole-blood models in assessing nanoparticle-immune cell interactions and provides insights into liposome design for modulating immune responses.

PEGylated Liposomes Accumulate in the Areas Relevant to Skin Toxicities via Passive Extravasation across "Leaky" Endothelium

PEGylated liposome is the cornerstone platform for modern drug delivery. Unfortunately, as exemplified by PEGylated liposomal doxorubicin (aka Doxil), altered doxorubicin pharmacokinetics causes off-target accumulation in the skin, including the palms and feet, leading to severe dose-limiting toxicity. In addition to Doxil, other nanoparticles and PEGylated liposomes exhibit significant deposition in the skin, but mechanisms of accumulation are poorly understood. Using ex vivo imaging and ex vivo confocal microscopy, we show that PEGylated liposomes in mice accumulate predominantly in the areas subject to mechanical stress/pressure. Blood vessels in foot skin appear to be especially leaky, exhibiting burst-like extravasations. Using high-resolution confocal microscopy and liposomes labeled with different dyes in the membrane and/or interior, two modes of extravasation were observed: (1) as intact liposomes; (2) as separated liposomal components. On the other hand, stable cross-linked iron oxide nanoworms extravasated only as intact nanoparticles. There was no colocalization between liposomes and exosomal marker CD81, excluding the role of exocytosis. Also, in situ perfusion of formalin-fixed foot skin with labeled liposomes revealed that the extravasation is mediated by passive, energy-independent diffusion and not by leukocyte "hitchhiking". These findings improve our understanding of extravasation pathways of nanocarriers in the areas relevant to skin pathologies and could lead to strategies to prevent and treat liposome-induced skin toxicities.

Revisiting the outstanding questions in cancer nanomedicine with a future outlook

The field of cancer nanomedicine has been fueled by the expectation of mitigating the inefficiencies and life-threatening side effects of conventional chemotherapy. Nanomedicine proposes to utilize the unique nanoscale properties of nanoparticles to address the most pressing questions in cancer treatment and diagnosis. The approval of nano-based products in the 1990s inspired scientific explorations in this direction. However, despite significant progress in the understanding of nanoscale properties, there are only very few success stories in terms of substantial increase in clinical efficacy and overall patient survival. All existing paradigms such as the concept of enhanced permeability and retention (EPR), the stealth effect and immunocompatibility of nanomedicine have been questioned in recent times. In this review we critically examine impediments posed by biological factors to the clinical success of nanomedicine. We put forth current observations on critical outstanding questions in nanomedicine. We also provide the promising side of cancer nanomedicine as we move forward in nanomedicine research. This would provide a future direction for research in nanomedicine and inspire ongoing investigations.

Recent Advances in Tumor Targeting via EPR Effect for Cancer Treatment

Cancer causes the second-highest rate of death world-wide. A major shortcoming inherent in most of anticancer drugs is their lack of tumor selectivity. Nanodrugs for cancer therapy administered intravenously escape renal clearance, are unable to penetrate through tight endothelial junctions of normal blood vessels and remain at a high level in plasma. Over time, the concentration of nanodrugs builds up in tumors due to the EPR effect, reaching several times higher than that of plasma due to the lack of lymphatic drainage. This review will address in detail the progress and prospects of tumor-targeting via EPR effect for cancer therapy.

Innate and adaptive immune responses toward nanomedicines

Since the commercialization of the first liposomes used for drug delivery, Doxil/Caelyx® and Myocet®, tremendous progress has been made in understanding interactions between nanomedicines and biological systems. Fundamental work at the interface of engineering and medicine has allowed nanomedicines to deliver therapeutic small molecules and nucleic acids more efficiently. While nanomedicines are used in oncology for immunotherapy or to deliver combinations of cytotoxics, the clinical successes of gene silencing approaches like patisiran lipid complexes (Onpattro®) have paved the way for a variety of therapies beyond cancer. In parallel, the global severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has highlighted the potential of mRNA vaccines to develop immunization strategies at unprecedented speed. To rationally design therapeutic and vaccines, chemists, materials scientists, and drug delivery experts need to better understand how nanotechnologies interact with the immune system. This review presents a comprehensive overview of the innate and adaptative immune systems and emphasizes the intricate mechanisms through which nanomedicines interact with these biological functions.

Considerations for designing preclinical cancer immune nanomedicine studies

Immunotherapy is known to be clinically beneficial for cancer patients and in many cases represents the new standard of care. Because of this success, the interest in integrating nanomedicine with cancer immunotherapy to further improve clinical response and toxicity profiles has grown. However, unlike conventional systemic therapies, which are directly cytotoxic to tumour cells, cancer immunotherapy relies on the host's immune system to generate tumouricidal effects. As such, proper design of cancer immune nanomedicine requires scrutiny of tumours' intrinsic and extrinsic factors that may impact host antitumour immunity. Here, we highlight key parameters that differentiate cancer immunotherapy from conventional cytotoxic agents, and we discuss their implications for designing preclinical cancer immune nanomedicine studies. We emphasize that these factors, including intratumoural genomic heterogeneity, commensal diversity, sexual dimorphism and biological ageing, which were largely ignored in traditional cancer nanomedicine experiments, should be carefully considered and incorporated into cancer immune nanomedicine investigations given their critical involvement in shaping the body's antitumour immune responses.

Controlled anti-cancer drug release through advanced nano-drug delivery systems: Static and dynamic targeting strategies

Advances in nanomedicine, including early cancer detection, targeted drug delivery, and personalized approaches to cancer treatment are on the rise. For example, targeted drug delivery systems can improve intracellular delivery because of their multifunctionality. Novel endogenous-based and exogenous-based stimulus-responsive drug delivery systems have been proposed to prevent the cancer progression with proper drug delivery. To control effective dose loading and sustained release, targeted permeability and individual variability can now be described in more-complex ways, such as by combining internal and external stimuli. Despite these advances in release control, certain challenges remain and are identified in this research, which emphasizes the control of drug release and applications of nanoparticle-based drug delivery systems. Using a multiscale and multidisciplinary approach, this study investigates and analyzes drug delivery and release strategies in the nanoparticle-based treatment of cancer, both mathematically and clinically.

Animal models for analysis of immunological responses to nanomaterials: Challenges and considerations

Nanotechnology provides many solutions to improve conventional drug delivery and has a unique niche in the areas related to the specific targeting of the immune system, such as immunotherapies and vaccines. Preclinical studies in this field rely heavily on the combination of in vitro and in vivo methods to assess the safety and efficacy of nanotechnology platforms, nanoparticle-formulated drugs, and vaccines. While certain types of toxicities can be evaluated in vitro and good in vitro-in vivo correlation has been demonstrated for such tests, animal studies are still needed to address complex biological questions and, therefore, provide a unique contribution to establishing nanoparticle safety and efficacy profiles. The genetic, metabolic, mechanistic, and phenotypic diversity of currently available animal models often complicates both the animal choice and the interpretation of the results. This review summarizes current knowledge about differences in the immune system function and immunological responses of animals commonly used in preclinical studies of nanomaterials. We discuss challenges, highlight current gaps, and propose recommendations for animal model selection to streamline preclinical analysis of nanotechnology formulations.

Nanoparticle uptake by circulating leukocytes: A major barrier to tumor delivery

Decades of research into improving drug delivery to tumors has documented uptake of particulate delivery systems by resident macrophages in the lung, liver, and spleen, and correlated short circulation times with reduced tumor accumulation. An implicit assumption in these studies is that nanoparticles present in the blood are available for distribution to the tumor. This study documents significant levels of lipoplex uptake by circulating leukocytes, and its effect on distribution to the tumor and other organs. In agreement with previous studies, PEGylation dramatically extends circulation times and enhances tumor delivery. However, our studies suggest that this relationship is not straightforward, and that particle sequestration by leukocytes can significantly alter biodistribution, especially with non-PEGylated nanoparticle formulations. We conclude that leukocyte uptake should be considered in biodistribution studies, and that delivery to these circulating cells may present opportunities for treating viral infections and leukemia.

Pharmacokinetics variability: Why nanoparticles are not just magic-bullets in oncology

Developing nanoparticles to improve the specificity of anticancer agents towards tumor tissue and to better control drug delivery is a rising strategy in oncology. An increasing number of forms (e.g., conjugated nanoparticles, liposomes, immunoliposomes…) are now available on the shelves and numerous other scaffolds (e.g., dendrimeres, nanospheres, squalenes …) are currently at various stages of development. However, as of today most nanoparticles made available remain lipidic carriers. Pharmacokinetic variability is a major, yet largely underestimated issue with liposomal nanoparticles. A wide variety of causes (e.g., tumor type and disease staging, comorbidities, patient's immune system) can explain this variability, which can in return negatively impact pharmacodynamic endpoints such as poor efficacy or severe toxicities. This review aims to cover the main causes for erratic pharmacokinetics observed with most nanoparticles, especially liposomes used in oncology. Should the main causes of such variability be identified, specific studies in non-clinical or clinical development stages could be undertaken using dedicated models (i.e., mechanistic or semi-mechanistic mathematical models such as PBPK approaches) to better describe nanoparticles pharmacokinetics and decipher PK/PD relationships. In addition, identifying relevant biomarkers or parameters likely to impact nanoparticles pharmacokinetics would allow for either the modification of their characteristics to reduce the influence of the expected variability during development phases or the development of biomarker-based adaptive dosing strategies to maintain an optimal efficacy/toxicity balance. Broadly, we call for the development of comprehensive distribution studies and state-of-the-art modeling support to better understand and anticipate nanoparticle pharmacokinetics in oncology.

Complex effects of tumor microenvironment on the tumor disposition of carrier-mediated agents

Major advances in carrier-mediated agents, including nanoparticle, conjugates and antibody-drug conjugates, have created revolutionary drug delivery systems in cancer over the past two decades. While these agents provide several advantages, such as greater duration of exposure and solubility, compared with their small-molecule counterparts, there is substantial variability in delivery of these agents to tissues and especially tumors. This review provides an overview of tumor microenvironment factors that affect the pharmacokinetics and pharmacodynamics of carrier-mediated agents observed in preclinical models and patients.

Complement proteins bind to nanoparticle protein corona and undergo dynamic exchange in vivo

When nanoparticles are intravenously injected into the body, complement proteins deposit on the surface of nanoparticles in a process called opsonization. These proteins prime the particle for removal by immune cells and may contribute toward infusion-related adverse effects such as allergic responses. The ways complement proteins assemble on nanoparticles have remained unclear. Here, we show that dextran-coated superparamagnetic iron oxide core-shell nanoworms incubated in human serum and plasma are rapidly opsonized with the third complement component (C3) via the alternative pathway. Serum and plasma proteins bound to the nanoworms are mostly intercalated into the nanoworm shell. We show that C3 covalently binds to these absorbed proteins rather than the dextran shell and the protein-bound C3 undergoes dynamic exchange in vitro. Surface-bound proteins accelerate the assembly of the complement components of the alternative pathway on the nanoworm surface. When nanoworms pre-coated with human plasma were injected into mice, C3 and other adsorbed proteins undergo rapid loss. Our results provide important insight into dynamics of protein adsorption and complement opsonization of nanomedicines.

Physiologically Based Pharmacokinetic (PBPK) Modeling of Pharmaceutical Nanoparticles

With the great interests in the discovery and development of drug products containing nanoparticles, there is a great demand of quantitative tools for assessing quality, safety, and efficacy of these products. Physiologically based pharmacokinetic (PBPK) modeling and simulation approaches provide excellent tools for describing and predicting in vivo absorption, distribution, metabolism, and excretion (ADME) of nanoparticles administered through various routes. PBPK modeling of nanoparticles is an emerging field, and more than 20 PBPK models of nanoparticles used in pharmaceutical products have been published in the past decade. This review provides an overview of the ADME characteristics of nanoparticles and how these ADME processes are described in PBPK models. Recent advances in PBPK modeling of pharmaceutical nanoparticles are summarized. The major challenges in model development and validation and possible solutions are also discussed.

Profiling the relationship between tumor-associated macrophages and pharmacokinetics of liposomal agents in preclinical murine models

The mononuclear phagocyte system (MPS) has previously been shown to significantly affect the clearance, tumor delivery, and efficacy of nanoparticles (NPs). This study profiled MPS cell infiltration in murine preclinical tumor models and evaluated how these differences may affect tumor disposition of PEGylated liposomal doxorubicin (PLD) in models sensitive and resistant to PLD. Significant differences in MPS presence existed between tumor types (e.g. ovarian versus endometrial), cell lines within the same tumor type, and location of tumor implantation (i.e. flank versus orthotopic xenografts). Further, the differences in MPS presence of SKOV-3 ovarian and HEC1A endometrial orthotopic cancer models may account for the 2.6-fold greater PLD tumor exposure in SKOV-3, despite similar plasma, liver and spleen exposures. These findings suggest that profiling the presence of MPS cells within and between tumor types is important in tumor model selection and in tumor types and patients likely to respond to NP treatment.

Challenges in preclinical to clinical translation for anticancer carrier-mediated agents

Major advances in carrier-mediated agents (CMAs), which include nanoparticles and conjugates, have revolutionized drug delivery capabilities over the past decade. While providing numerous advantages over their small-molecule counterparts, there is substantial variability in how individual CMA formulations and patient characteristics affect the pharmacology, pharmacokinetics (PK), and pharmacodynamics (PD) (efficacy and toxicity) of these agents. Development or selection of animal models is used to predict the effects within a particular human disease. A breadth of studies have begun to emphasize the importance of preclinical animal models in understanding and evaluating the interaction between CMAs and the immune system and tumor matrix, which ultimately influences CMA PK (clearance and distribution) and PD (efficacy and toxicity). It is fundamental to study representative preclinical tumor models that recapitulate patients with diseases (e.g., cancer) and evaluate the interplay between CMAs and the immune system, including the mononuclear phagocyte system (MPS), chemokines, hormones, and other immune modulators. Furthermore, standard allometric scaling using body weight does not accurately predict drug clearance in humans. Future studies are warranted to better understand the complex pharmacology and interaction of CMA carriers within individual preclinical models and their biological systems, such as the MPS and tumor microenvironment, and their application to allometric scaling across species. WIREs Nanomed Nanobiotechnol 2016, 8:642-653. doi: 10.1002/wnan.1394 For further resources related to this article, please visit the WIREs website.

Technetium Tc 99m sulfur colloid phenotypic probe for the pharmacokinetics and pharmacodynamics of PEGylated liposomal doxorubicin in women with ovarian cancer

PURPOSE

Significant variability in the pharmacokinetics and pharmacodynamics of PEGylated liposomal doxorubicin (PLD) exists. PLD undergoes clearance via the mononuclear phagocyte system (MPS). Technetium Tc 99m sulfur colloid (TSC) is approved for imaging MPS cells. We investigated TSC as a phenotypic probe of PLD pharmacokinetics and pharmacodynamics in women with epithelial ovarian cancer.

METHODS

TSC 10 mCi IVP was administered and followed by dynamic planar and SPECT/CT imaging and blood pharmacokinetics sampling. PLD 30-40 mg/m(2) IV was administered with or without carboplatin, followed by plasma pharmacokinetics sampling.

RESULTS

There was a linear relationship between TSC clearance and encapsulated doxorubicin clearance (R(2) = 0.61, p = 0.02), particularly in patients receiving PLD alone (R(2) = 0.81, p = 0.04). There was a positive relationship (ρ = 0.81, p = 0.01) between maximum grade palmar-plantar erythrodysesthesia toxicity developed and estimated encapsulated doxorubicin concentration in hands.

CONCLUSIONS

TSC is a phenotypic probe for PLD pharmacokinetics and pharmacodynamics and may be used to individualize PLD therapy in ovarian cancer and for other nanoparticles in development.

Modulatory Role of Surface Coating of Superparamagnetic Iron Oxide Nanoworms in Complement Opsonization and Leukocyte Uptake

Notwithstanding rapid advances of nanotechnology in diagnostic imaging and drug delivery, the engineered nanocarriers still exhibit substantial lack of hemocompatibility. Thus, when injected systemically, nanoparticles are avidly recognized by blood leukocytes and platelets, but the mechanisms of immune recognition are not well understood and strategies to mitigate these phenomena remain underexplored. Using superparamagnetic dextran iron oxide (SPIO) nanoworms (NWs) we demonstrate an efficient and predominantly complement-dependent uptake by mouse lymphocytes, neutrophils and monocytes from normal and tumor bearing mice in vitro. Following intravenous injection into wild type mice, blood leukocytes as well as platelets became magnetically labeled, while the labeling was decreased by 95% in complement C3-deficient mice. Using blood cells from healthy and cancer patient donors, we demonstrated that neutrophils, monocytes, lymphocytes and eosinophils took up SPIO NWs, and the uptake was prevented by EDTA (a general complement inhibitor) and by antiproperdin antibody (an inhibitor of the alternative pathway of the complement system). Cross-linking and hydrogelation of SPIO NWs surface by epichlorohydrin decreased C3 opsonization in mouse serum, and consequently reduced the uptake by mouse leukocytes by more than 70% in vivo. Remarkably, the cross-linked particles did not show a decrease in C3 opsonization in human serum, but showed a significant decrease (over 60%) of the uptake by human leukocytes. The residual uptake of cross-linked nanoparticles was completely blocked by EDTA. These findings demonstrate species differences in complement-mediated nanoparticle recognition and uptake by leukocytes, and further show that human hemocompatibility could be improved by inhibitors of complement alternative pathway and by nanoparticle surface coating. These results provide important insights into the mechanisms of hemocompatibility of nanomedicines.

The effects of nanoparticle drug loading on the pharmacokinetics of anticancer agents

Major advances in carrier-mediated agents, which include nanoparticles, nanosomes and conjugates, have revolutionized drug delivery capabilities over the past decade. While providing numerous advantages, such as greater solubility, duration of exposure and delivery to the site of action over their small-molecule counterparts, there is substantial variability in systemic clearance and distribution, tumor delivery and pharmacologic effects (efficacy and toxicity) of these agents. This review provides an overview of factors that affect the pharmacokinetics and pharmacodynamics of carrier-mediated agents in preclinical models and patients.

Formulation and physiologic factors affecting the pharmacology of carrier-mediated anticancer agents

INTRODUCTION

Major advances in carrier-mediated agents (CMAs), which include nanoparticles and conjugates, have revolutionized drug delivery capabilities over the past decade. While providing numerous advantages such as increased exposure duration, greater solubility and delivery to tumor sites over their small molecule counterparts, there is substantial variability in how individual CMA formulations affect the pharmacology, pharmacokinetics and pharmacodynamics (efficacy and toxicity) of these agents.

AREAS COVERED

CMA formulations are complex in nature compared to their small molecule counterparts and consist of multiple components and variables that can affect the pharmacological profile. This review provides an overview of factors that affect the pharmacologic profiles observed in CMA-formulated chemotherapy, primarily in liposomal formulations, that are currently in preclinical or early clinical development.

EXPERT OPINION

Despite the numerous advantages that CMA formulations provide, their clinical use is still in its infancy. It is critical that we understand the mechanisms and effects of CMAs in navigating biological barriers and how these factors affect their biodistribution and delivery to tumors. Future studies are warranted to better understand the complex pharmacology and interaction between CMA carriers and biological systems, such as the mononuclear phagocyte system and tumor microenvironment.

Factors affecting the pharmacokinetics and pharmacodynamics of PEGylated liposomal irinotecan (IHL-305) in patients with advanced solid tumors

IHL-305 is a PEGylated liposomal formulation of irinotecan (CPT-11). The objective of this study was to evaluate the factors associated with interpatient variability in the pharmacokinetics and pharmacodynamics of IHL-305 in patients with advanced solid tumors. IHL-305 was administered intravenously once every 4 weeks as part of a Phase I study. Pharmacokinetic studies of the liposomal sum total CPT-11, released CPT-11, SN-38, SN-38G, 7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidino]-carbonyloxycamptothecin, and 7-ethyl-10-[4-amino-1-piperidino]-carbonyloxycamptothecin in plasma were performed. Noncompartmental and compartmental pharmacokinetic analyses were conducted using pharmacokinetic data for sum total CPT-11. The pharmacokinetic variability of IHL-305 is associated with linear and nonlinear clearance. Patients whose age and body composition (ratio of total body weight to ideal body weight [TBW/IBW]) were greater than the median age and TBW/IBW of the study had a 1.7-fold to 2.6-fold higher ratio of released CPT-11 area under the concentration versus time curve (AUC) to sum total CPT-11 AUC. Patients aged <60 years had a 1.3-fold higher ratio of percent decrease in monocytes at nadir to percent decrease in absolute neutrophil count at nadir as compared with patients aged ≥60 years. There was an inverse relationship between patient age and percent decrease in monocytes at nadir, ie, younger patients have a higher percent decrease in monocytes. Patients with a higher percent decrease in monocytes at nadir have a decreased plasma exposure of sum total CPT-11. The pharmacokinetics and pharmacodynamics of IHL-305 are consistent with those of other PEGylated liposomal carriers. Interpatient variability in the pharmacokinetics and pharmacodynamics of IHL-305 was associated with age, body composition, and monocytes.

Summary report of PQRI Workshop on Nanomaterial in Drug Products: current experience and management of potential risks

At the Product Quality Research Institute (PQRI) Workshop held last January 14-15, 2014, participants from academia, industry, and governmental agencies involved in the development and regulation of nanomedicines discussed the current state of characterization, formulation development, manufacturing, and nonclinical safety evaluation of nanomaterial-containing drug products for human use. The workshop discussions identified areas where additional understanding of material attributes, absorption, biodistribution, cellular and tissue uptake, and disposition of nanosized particles would continue to inform their safe use in drug products. Analytical techniques and methods used for in vitro characterization and stability testing of formulations containing nanomaterials were discussed, along with their advantages and limitations. Areas where additional regulatory guidance and material characterization standards would help in the development and approval of nanomedicines were explored. Representatives from the US Food and Drug Administration (USFDA), Health Canada, and European Medicines Agency (EMA) presented information about the diversity of nanomaterials in approved and newly developed drug products. USFDA, Health Canada, and EMA regulators discussed the applicability of current regulatory policies in presentations and open discussion. Information contained in several of the recent EMA reflection papers was discussed in detail, along with their scope and intent to enhance scientific understanding about disposition, efficacy, and safety of nanomaterials introduced in vivo and regulatory requirements for testing and market authorization. Opportunities for interaction with regulatory agencies during the lifecycle of nanomedicines were also addressed at the meeting. This is a summary of the workshop presentations and discussions, including considerations for future regulatory guidance on drug products containing nanomaterials.

Effects of tumor microenvironment heterogeneity on nanoparticle disposition and efficacy in breast cancer tumor models

PURPOSE

Tumor cells are surrounded by a complex microenvironment. The purpose of our study was to evaluate the role of heterogeneity of the tumor microenvironment in the variability of nanoparticle (NP) delivery and efficacy.

EXPERIMENTAL DESIGNS

C3(1)-T-Antigen genetically engineered mouse model (C3-TAg) and T11/TP53(Null) orthotopic syngeneic murine transplant model (T11) representing human breast tumor subtypes basal-like and claudin-low, respectively, were evaluated. For the pharmacokinetic studies, non-liposomal doxorubicin (NL-doxo) or polyethylene glycol tagged (PEGylated) liposomal doxorubicin (PLD) was administered at 6 mg/kg i.v. x1. Area under the concentration versus time curve (AUC) of doxorubicin was calculated. Macrophages, collagen, and the amount of vasculature were assessed by IHC. Chemokines and cytokines were measured by multiplex immunochemistry. NL-doxo or PLD was administered at 6 mg/kg i.v. weekly x6 in efficacy studies. Analyses of intermediary tumor response and overall survival were performed.

RESULTS

Plasma AUC of NL-doxo and PLD encapsulated and released doxorubicin was similar between two models. However, tumor sum total AUC of PLD was 2-fold greater in C3-TAg compared with T11 (P < 0.05). T11 tumors showed significantly higher expression of CC chemokine ligand (CCL) 2 and VEGF-a, greater vascular quantity, and decreased expression of VEGF-c compared with C3-TAg (P < 0.05). PLD was more efficacious compared with NL-doxo in both models.

CONCLUSION

The tumor microenvironment and/or tumor cell features of breast cancer affected NP tumor delivery and efficacy, but not the small-molecule drug. Our findings reveal the role of the tumor microenvironment in variability of NP delivery and therapeutic outcomes.

Cancer nanotechnology: the impact of passive and active targeting in the era of modern cancer biology

Cancer nanotherapeutics are progressing at a steady rate; research and development in the field has experienced an exponential growth since early 2000's. The path to the commercialization of oncology drugs is long and carries significant risk; however, there is considerable excitement that nanoparticle technologies may contribute to the success of cancer drug development. The pace at which pharmaceutical companies have formed partnerships to use proprietary nanoparticle technologies has considerably accelerated. It is now recognized that by enhancing the efficacy and/or tolerability of new drug candidates, nanotechnology can meaningfully contribute to create differentiated products and improve clinical outcome. This review describes the lessons learned since the commercialization of the first-generation nanomedicines including DOXIL® and Abraxane®. It explores our current understanding of targeted and non-targeted nanoparticles that are under various stages of development, including BIND-014 and MM-398. It highlights the opportunities and challenges faced by nanomedicines in contemporary oncology, where personalized medicine is increasingly the mainstay of cancer therapy. We revisit the fundamental concepts of enhanced permeability and retention effect (EPR) and explore the mechanisms proposed to enhance preferential "retention" in the tumor, whether using active targeting of nanoparticles, binding of drugs to their tumoral targets or the presence of tumor associated macrophages. The overall objective of this review is to enhance our understanding in the design and development of therapeutic nanoparticles for treatment of cancers.

From immunotoxicity to nanotherapy: the effects of nanomaterials on the immune system

The potential for human exposure to the diverse and ever-changing world of nanoscale materials has raised concerns about their influence on health and disease. The novel physical and chemical properties of these materials, which are associated with their small size, complicate toxicological evaluations. Further, these properties may make engineered nanomaterials (ENMs) a prime target for interaction with the immune system following uptake by phagocytes. Undesired effects on antigen-presenting cells and other phagocytic cells are of concern due to the high likelihood of ENM uptake by these cells. In addition, ENM interactions with lymphocytes and other cell types can contribute to a varied spectrum of possible effects, including inflammation, hypersensitivity, and immunomodulation. Furthermore, the mast cell (a type of immune cell traditionally associated with allergy) appears to contribute to certain inflammatory and toxic effects associated with some ENMs. Although incidental exposure may be undesirable, nanomedicines engineered for various clinical applications provide opportunities to develop therapies that may or may not intentionally target the immune system. The interaction between ENMs and the immune system and the resulting pharmacokinetic and phenotypic responses are critical factors that dictate the balance between toxicity and clinical efficacy of nanotherapeutics.

Translational studies of phenotypic probes for the mononuclear phagocyte system and liposomal pharmacology

As nanoparticles (NPs) are cleared via phagocytes of the mononuclear phagocyte system (MPS), we hypothesized that the function of circulating monocytes and dendritic cells (MO/DC) in blood can predict NP clearance (CL). We measured MO/DC phagocytosis and reactive oxygen species (ROS) production in mice, rats, dogs, and patients with refractory solid tumors. Pharmacokinetic studies of polyethylene glycol (PEG)-encapsulated liposomal doxorubicin (PEGylated liposomal doxirubicin [PLD]), CKD-602 (S-CKD602), and cisplatin (SPI-077) were performed at the maximum tolerated dose. MO/DC function was also evaluated in patients with recurrent epithelial ovarian cancer (EOC) administered PLD. Across species, a positive association was observed between cell function and CL of PEGylated liposomes. In patients with EOC, associations were observed between PLD CL and phagocytosis (R(2) = 0.43, P = 0.04) and ROS production (R(2) = 0.61, P = 0.008) in blood MO/DC. These findings suggest that probes of MPS function may help predict PEGylated liposome CL across species and PLD CL in patients with EOC.

Population pharmacokinetics of PEGylated liposomal CPT-11 (IHL-305) in patients with advanced solid tumors

PURPOSE

To investigate pharmacokinetics (PK) of encapsulated CPT-11, released CPT-11 and the active metabolite SN-38 following administration of IHL-305 and to identify factors that may influence IHL-305 PK.

METHODS

Plasma samples from 39 patients with solid tumors were collected in a phase I study. IHL-305 was administered as a 1 h IV infusion with doses ranging from 3.5 to 210 mg/m(2). Plasma concentrations of encapsulated CPT-11, released CPT-11 and SN-38 were used to develop a population PK model using NONMEM®.

RESULTS

PK of encapsulated CPT-11 was described by 1-compartment model with nonlinear clearance and PK of released CPT-11 was described by a 1-compartment model with linear clearance for all patients. PK of the active metabolite SN-38 was described by a 2-compartment model with linear clearance for all patients. Covariate analysis revealed that gender was a significant covariate for volume of distribution of encapsulated CPT-11. Vencap in male patients is 1.5-fold higher compared with female patients.

CONCLUSIONS

The developed population PK modeling approach is useful to predict PK exposures of encapsulated and released drug and can be applied to the more than 300 other nanoparticle formulations of anticancer agents that are currently in development. The effect of gender on PK of IHL-305 needs to be further evaluated.

Pharmacokinetics and efficacy of PEGylated liposomal doxorubicin in an intracranial model of breast cancer

Introduction

Breast cancer brain metastases (BCBM) are a challenging consequence of advanced BC. Nanoparticle agents, including liposomes, have shown enhanced delivery to solid tumors and brain. We compared pharmacokinetics (PK) and efficacy of PEGylated liposomal doxorubicin (PLD) with non-liposomal doxorubicin (NonL-doxo) in an intracranial model of BC.

Methods

Athymic mice were inoculated intracerebrally with MDA-MB-231-BR-luciferase-expressing cells. Tumor-bearing mice were administered PLD or NonL-doxo at 6mg/kg IV×1 and were euthanized prior to and 0.083, 1, 3, 6, 24, 72 and 96 h post-treatment. Samples were processed to measure sum total doxorubicin via HPLC. PLD and NonL-doxo were administered IV weekly as single agents (6 mg/kg) or in combination (4.5 mg/kg) with the PARP inhibitor, ABT-888, PO 25 mg/kg/day. Efficacy was assessed by survival and bioluminescence.

Results

Treatment with PLD resulted in approximately 1,500-fold higher plasma and 20-fold higher intracranial tumor sum total doxorubicin AUC compared with NonL-doxo. PLD was detected at 96 h; NonL-doxo was undetectable after 24 h in plasma and tumor. Median survival of PLD-treated animals was 32 days (d, [CI] 31–38), which was significantly longer than controls (26d [CI 25–28]; p = 0.0012) or NonL-doxo treatment (23.5d [CI 18–28], p = 0.0002). Combination treatment with PLD/ABT-888 yielded improved survival compared to NonL-doxo/ABT-888 (35d [CI 31–38] versus 29.5d [CI 25–34]; p = 0.006).

Conclusions

PLD provides both PK and efficacy advantage over NonL-doxo in the treatment of an in vivo model of BCBM. The results provide preclinical rationale to translate findings into early phase trials of PLD, with or without ABT-888, for patients with BCBM.

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.

Best practices in cancer nanotechnology: perspective from NCI nanotechnology alliance

Historically, treatment of patients with cancer using chemotherapeutic agents has been associated with debilitating and systemic toxicities, poor bioavailability, and unfavorable pharmacokinetics. Nanotechnology-based drug delivery systems, on the other hand, can specifically target cancer cells while avoiding their healthy neighbors, avoid rapid clearance from the body, and be administered without toxic solvents. They hold immense potential in addressing all of these issues, which has hampered further development of chemotherapeutics. Furthermore, such drug delivery systems will lead to cancer therapeutic modalities that are not only less toxic to the patient but also significantly more efficacious. In addition to established therapeutic modes of action, nanomaterials are opening up entirely new modalities of cancer therapy, such as photodynamic and hyperthermia treatments. Furthermore, nanoparticle carriers are also capable of addressing several drug delivery problems that could not be effectively solved in the past and include overcoming formulation issues, multidrug-resistance phenomenon, and penetrating cellular barriers that may limit device accessibility to intended targets, such as the blood-brain barrier. The challenges in optimizing design of nanoparticles tailored to specific tumor indications still remain; however, it is clear that nanoscale devices carry a significant promise toward new ways of diagnosing and treating cancer. This review focuses on future prospects of using nanotechnology in cancer applications and discusses practices and methodologies used in the development and translation of nanotechnology-based therapeutics.

Interpatient pharmacokinetic and pharmacodynamic variability of carrier-mediated anticancer agents

Major advances in the field of carrier-mediated agents (CMAs) have revolutionized drug delivery capabilities over the past decade. While providing numerous advantages over their small-molecule counterparts (solubility,duration of exposure, and delivery to the site of action are higher), these agents display substantial variability in systemic clearance (CL) and distribution, tumor delivery, and pharmacologic effects. This review provides an overview of factors that affect the pharmacokinetics (PK) and pharmacodynamics (PD) of CMAs in preclinical models and patients.

Tumor-targeted drug delivery using MR-contrasted docetaxel - carboxymethylcellulose nanoparticles

A carboxymethylcellulose-based polymer conjugate with nanoparticle forming properties (Cellax) has been shown to enhance the pharmacokinetics, specificity of biodistribution, anti-tumor efficacy and safety of docetaxel (DTX) in comparison to the Taxotere™ formulation. We examined Cellax and Taxotere efficacy in four tumor models (EMT-6, B16F10, PC3, and MDA-MB-231), and observed variances in efficacy. To explore whether differences in tumor uptake of Cellax were responsible for these effects, we incorporated superparamagnetic iron oxide nanoparticles (SPIONs) into Cellax particles to enable magnetic resonance (MR) imaging (Cellax-MR). In the EMT-6 tumor model, Cellax-MR nanoparticles exhibited peak tumor accumulation 3-24 h post intravenous injection, and 3 days post-treatment, significant MR contrast was still detected. The amount of Cellax-MR deposited in the EMT-6 tumors was quantifiable as a hypointense volume fraction, a value positively correlated with drug content as determined by LC/MS analysis (R(2) = 0.97). In the four tumor models, Cellax-MR uptake was linearly associated with anti-tumor efficacy (R(2) > 0.9), and was correlated with blood vessel density (R(2) > 0.9). We have affirmed that nanoparticle uptake is variable in tumor physiology, and that this efficacy-predictive parameter can be non-invasively estimated in real-time using a theranostic variant of Cellax.

Factors affecting the pharmacokinetics and pharmacodynamics of liposomal drugs

Various attempts to increase the therapeutic index of the drug while minimizing side effects have been made in drug delivery systems. Among several promising strategies, liposomes represent an advanced technology to target active molecules to the site of action. Rapid clearance of circulating liposomal drugs administered intravenously has been a critical issue because circulation time in the blood affects drug exposure at the target site. The clinical use of liposomal drugs is complicated by large intra- and interindividual variability in their pharmacokinetics (PK) and pharmacodynamics (PD). Thus, it is important to understand the factors affecting the PK/PD of the liposomal formulation of drugs and to elucidate the mechanisms underlying the variability in the PK/PD of liposomal drugs. In this review article, we describe the characteristics of liposome formulations and discuss the effects of various factors, including liposome-associated factors, host-associated factors, and treatment on the PK/PD of liposomal agents.

Allometric scaling of pegylated liposomal anticancer drugs

Pegylated liposomal formulations contain lipid conjugated to polyethylene glycol. The disposition of encapsulated drug is dictated by the composition of the liposome, thus altering the pharmacokinetic (PK) profile of the drug. Allometric scaling is based on a power-log relationship between body weight (W) and drug clearance (CL) among mammals and has been used to compare the disposition of nonliposomal drugs across species. The objectives of this study were to use allometric scaling to: (1) compare the disposition of pegylated liposomal drugs across speciesand determine the best scaling model and (2) predict PK parameters of pegylated liposomal drugs in humans. The PK of pegylated liposomal CKD-602 (S-CKD602), doxorubicin (Doxil®), and cisplatin (SPI-077) were compared. PK studies ofS-CKD602, Doxil®, and SPI-077 were performed at the maximum tolerated dose (MTD) in male and female mice, rats, dogs and patients with refractory solid tumors. The allometric equation used to evaluate the relationship between W and CL in each species was CL = a(W)(m) (a = empirical coefficient; m = allometric exponent). Substitution of physiological variables other than body weight, such as factors representative of the mononuclear phagocyte system (MPS) were evaluated. Dedrick Plots and Maximum Life-Span Potential (MLP) were used to determine scaling feasibility. Standard allometry demonstrated a relationship between clearance of S-CKD602, Doxil®, and SPI-077 and body, spleen, liver, and kidney weights, total monocyte count, and spleen and liver blood flow. However, using scaling to predict CL of these agents in humans often resulted in differences >30%. Despite a strong correlation between body weight and MPS-associated variables with CL among preclinical species, the use of the equations did not predict CL. Thus, new methods of allometric scaling and measures of MPS function need to be developed.