Preclinical results of camptothecin-polymer conjugate (IT-101) in multiple human lymphoma xenograft models

Nanomedicine from amphiphilizedprodrugs: Concept and clinical translation

Nanomedicines generally consisting of carrier materials with small fractions of active pharmaceutical ingredients (API) have long been used to improve the pharmacokinetics and biodistributions, augment the therapeutic efficacies and mitigate the side effects. Amphiphilizing hydrophobic/hydrophilic drugs to prodrugs capable of self-assembly into well-defined nanostructures has emerged as a facile approach to fabricating nanomedicines because this amphiphilized prodrug (APD) strategy presents many advantages, including minimized use of inert carrier materials, well-characterized prodrug structures, fixed and high drug loading contents, 100% loading efficiency, and burst-free but controlled drug release. This review comprehensively summarizes recent advances in APDs and their nanomedicines, from the rationale and the stimuli-responsive linker chemistry for on-demand drug release to their progress to the clinics, clinical performance of APDs, as well as the challenges and perspective on future development.

Cancer nanotechnology: current status and perspectives

Modern medicine has been waging a war on cancer for nearly a century with no tangible end in sight. Cancer treatments have significantly progressed, but the need to increase specificity and decrease systemic toxicities remains. Early diagnosis holds a key to improving prognostic outlook and patient quality of life, and diagnostic tools are on the cusp of a technological revolution. Nanotechnology has steadily expanded into the reaches of cancer chemotherapy, radiotherapy, diagnostics, and imaging, demonstrating the capacity to augment each and advance patient care. Nanomaterials provide an abundance of versatility, functionality, and applications to engineer specifically targeted cancer medicine, accurate early-detection devices, robust imaging modalities, and enhanced radiotherapy adjuvants. This review provides insights into the current clinical and pre-clinical nanotechnological applications for cancer drug therapy, diagnostics, imaging, and radiation therapy.

Measurement of NLG207 (formerly CRLX101) nanoparticle-bound and released camptothecin in human plasma

Camptothecin (CPT), a potent inhibitor of topoisomerase I and HIF-1α, failed to demonstrate utility as an anti-cancer agent in early clinical trial investigations, primarily due to limited clinical activity and significant toxicity attributable to unfavorable physicochemical properties (e.g. low plasma solubility, pH-labile lactone ring). NLG207 (formerly CRLX101), a nanoparticle-drug conjugate (NDC) of CPT designed to optimize plasma pharmacokinetics and facilitate drug delivery to tumors, is included as part of combination treatment in two Phase II clinical trials ongoing at the National Cancer Institute (NCT02769962 and NCT03531827). To better understand the potential for drug-drug interactions and to correlate drug exposure to clinical outcomes and pharmacodynamic biomarkers, a robust analytical method was developed to measure CPT in human plasma. Two sample processing methods were developed to quantify both NDC-bound CPT and free CPT, primarily via alteration of pH conditions. A solid-phase extraction recovered >79 % of CPT prior to quantitative analysis by ultra HPLC-MS/MS. Dynamic calibration ranges of 10 to 10,000 ng/mL and 1 to 1000 ng/mL for total and free CPT, respectively were utilized to capture clinical ranges. NLG207 NDCs demonstrated significant rates of CPT release in human plasma at room temperature after 2 h but were shown to be stable at 4 °C for 24 h and through 4 freeze/thaw cycles. This assay was used to quantitate CPT plasma concentrations in clinical samples to confirm clinical utility following NLG207 treatment in subjects with advanced prostate cancer.

Host immune response to anti-cancer camptothecin conjugated cyclodextrin-based polymers

Introduction

Efficacy and safety are critical concerns when designing drug carriers. Nanoparticles are a particular type of carrier that has gained recent attention in cancer therapeutics.

Methods

In this study, we assess the safety profile of IT-101, a nanoparticle formed by self-assembly of camptothecin (CPT) conjugated cyclodextrin-based polymers. IT-101 delivers CPT to target cancer cells in animal models of numerous human cancers and in humans. Previous data from preclinical and clinical trials indicate that IT-101 has no notable immunological side effects. However, there have been no published studies focused on evaluating the effects of IT-101 on host immune systems.

Results

In this work, we demonstrate that IT-101 diminished initial host immune response following first injection of the nanopharmaceutical and induced NK cell activation and T cell proliferation upon further IT-101 exposure. Additionally, IT-101 could attenuate tumor growth more efficiently than CPT treatment only.

Conclusions

Drugs administration in whole-body circulation may lead to poorly bioavailable in central nervous system and often has toxic effects on peripheral tissues. Conjugated with cyclodextrin-based polymers not only reduce adverse effects but also modulate the immune responses to elevate drug efficacy. These immune responses may potentially facilitate actions of immune blockage, such as PD1/PDL1 in cancer treatment.

Cancer-targeted design of bioresponsive prodrug with enhanced cellular uptake to achieve precise cancer therapy

Chemical drug design based on the biochemical characteristics of cancer cells has become an important strategy for discovery of novel anticancer drugs to enhance the cancer targeting effects and biocompatibility, and decrease toxic side effects. Camptothecin (CPT) demonstrated strong anticancer activity in clinical trials but also notorious adverse effects. In this study, we presented a smart targeted delivery system (Biotin-ss-CPT) that consists of cancer-targeted moiety (biotin), a cleavable disulfide linker (S-S bond) and the active drug CPT. Biotin-ss-CPT was found to exhibit potent effects on the migration of cancer cells and induced apoptosis by induction of ROS-mediated mitochondrial dysfunction and perturbation of GSH/GPXs system, as well as activation of caspases. In vivo tumor suppression investigation including toxicity evaluation and pathology analysis, accompanied by MR images showed that Biotin-ss-CPT can be recognized specifically and selectively and taken up preferentially by cancers cells, followed by localization and accumulation effectively in tumor site, then released CPT by biological response to achieve high therapeutic effect and remarkably reduced the side effects that free CPT caused, such as liver damage, renal injury, and weight loss to realize precise cancer therapy. Taken together, our results suggest that biotinylation and bioresponsive functionalization of anticancer drugs could be a good way for the discovery of next-generation cancer therapeutics.

Preclinical effects of CRLX101, an investigational camptothecin-containing nanoparticle drug conjugate, on treating glioblastoma multiforme via apoptosis and antiangiogenesis

Malignant gliomas are difficult to treat in clinical practice. This study was aimed to investigate the preclinical efficacy of CRLX101, an investigational nanoparticle-drug conjugate developed by conjugating camptothecin (CPT) with cyclodextrin-polyethylene glycol, against gliomas. CPT fluorescence was detected across tight-junction barriers and in mouse plasma and brain. Following CRLX101 treatment, CPT was distributed in the cytoplasm of human U87 MG glioma cells. U87 MG cell viability was decreased by CRLX101 and CPT. Moreover, CRLX101 induced less cytotoxicity to human astrocytes compared to CPT. Exposure of U87 MG cells to CRLX101 induced G₂/M cell cycle arrest and apoptosis. Administration of CRLX101 induced apoptosis in mice brain tumor tissues and prolonged the survival rate of mice. In addition, CRLX101 inhibited hypoxia and angiogenesis by suppressing the expression of carbonic anhydrase IX, vascular endothelial growth factor, and CD31 in tumor sections. Taken together, this preclinical study showed that CRLX101 possesses antitumor abilities by inducing cell cycle arrest and apoptosis in glioma cells and inhibiting tumor angiogenesis, thereby prolonging the lifespan of mice bearing intracranial gliomas. These data support further research of CRLX101 in patients with brain tumors.

Camptothecin (CPT) and its derivatives are known to target topoisomerase I (Top1) as their mechanism of action: did we miss something in CPT analogue molecular targets for treating human disease such as cancer?

Camptothecin (CPT) was discovered from plant extracts more than 60 years ago. Since then, only two CPT analogues (irinotecan and topotecan) have been approved for cancer treatment, although several thousand CPT derivatives have been synthesized and many of them were actively studied in our research community over the past 6+ decades. In this review article, we briefly summarize: (1) the discovery and early development of CPTs, (2) the recognized CPT mechanism of action (MOA), (3) the synthesis of CPT and CPT analogues, and (4) the structure-activity relationship (SAR) of CPT and its analogues. Next, we provide evidence that certain CPT analogues can exert improved efficacy with low toxicity independently of topoisomerase I (Top1) inhibition; instead, these CPT analogues use novel MOAs by targeting important cancer survival-associated oncogenic proteins and/or by bypassing various treatment-resistant mechanisms. We then present a comprehensive review of the most advanced CPT analogues in clinical development, with the goal of resolving why no new CPTs have been FDA approved for cancer treatment, beyond irinotecan and topotecan. We argue that new CPT Top1 inhibitor drugs are unlikely being found to be significantly better than irinotecan and/or topotecan in terms of the overall antitumor activity and toxicity. The significance of CPT analogues that possess novel MOAs has not been sufficiently recognized so far. In our opinion, this is a research area with great potential to make a breakthrough for development of the next generation of CPT analogues that possess high efficacy (due to novel targets) and low toxicity (due to low inhibition of Top1 activity/function) for effective treatment of human disease, including cancer.

Cyclodextrin-based supramolecular nanoparticles for biomedical applications

Supramolecular host-guest interactions are ideal for engineering supramolecular nanoparticles (SNPs), because their modular character offers the possibility of using the same basic SNPs made of very similar building blocks in a variety of applications. The most widely used host is cyclodextrin (CD), therefore, this review will focus on SNPs involving CD as the host entity. In the first part, particle formation and size control are described, and the forces that induce the assembly between the different components and, therefore, result in the formation of stable and controllable nanoparticles. In the second part, the use of CD-based SNPs for diagnostics and therapeutics is described. Here, the emphasis is on how the therapeutic agent/imaging component is included in the system and how it is released at the target site. CD-based SNPs provide great possibilities for the formulation of nanoparticles for biomedical applications because of their high flexibility, stability, modular character, and biocompatibility.

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.

The chick chorioallantoic membrane as an in vivo xenograft model for Burkitt lymphoma

Background

Burkitt lymphoma (BL) is an aggressive malignancy that arises from B-cells and belongs to the group of Non-Hodgkin lymphomas (NHL). Due to the lack of appropriate in vivo models NHL research is mainly performed in vitro. Here, we studied the use of the chick chorioallantoic membrane (CAM) for the generation of human BL xenograft tumors, which we compared with known characteristics of the human disease.

Methods

In order to generate experimental BL tumors, we inoculated human BL2B95 and BL2-GFP cells on the CAM. BL2B95 xenograft-tumors were grown for seven days and subsequently analyzed with transmission electron and immunofluorescence microscopy, as well as histological staining approaches. BL2-GFP cells were studied at regular intervals up to seven days, and their metastatic behavior was visualized with intravital immunofluorescence techniques.

Results

Xenografted BL2B95 cells formed solid tumors in the CAM model with a Ki67-index greater than 90%, preservation of typical tumor markers (CD10, CD19, CD20), a ‘starry sky’ morphology, production of agyrophilic fibers in the stroma, formation of blood and lymphatic vessels and lymphogenic dissemination of BL2B95 to distant sites. We identified macrophages, lymphocytes and heterophilic granulocytes (chick homolog of neutrophils) as the most abundant immune cells in the experimental tumors. BL2-GFP cells could be traced in real-time during their distribution in the CAM, and the first signs for their dissemination were visible after 2-3 days.

Conclusions

We show that xenografted BL2B95 cells generate tumors in the CAM with a high degree of cellular, molecular and proliferative concord with the human disease, supporting the application of the CAM model for NHL research with a focus on tumor-stroma interactions. Additionally we report that BL2-GFP cells, grafted on the CAM of ex ovo cultured chick embryos, provide a powerful tool to study lymphogenic dissemination in real-time.

Pharmacodynamic and pharmacogenomic study of the nanoparticle conjugate of camptothecin CRLX101 for the treatment of cancer

CRLX101 is a nanopharmaceutical consisting of cyclodextrin-based polymer molecule and camptothecin. The CRLX101 nanoparticle is designed to concentrate and slowly release camptothecin in tumors over an extended period of time. Tumor biopsy and blood samples collected from patients with advanced solid malignancies before and after CRLX101 treatment are subjected to immunohistochemistry and pharmacogenomics. The expression of Topoisomerase-1, Ki-67, CaIX, CD31 and VEGF decreased after CRLX101 treatment. The expressions of these proteins are inversely proportional with survival duration of the patients. The Drug Metabolism Enzymes and Transporters (DMET) array shows an allele frequency in patients similar to global populations with none of the SNPs associated with toxicity. The results suggest that the observed lower toxicity is not likely to be due to different genotypes in SNPs. CRLX101 demonstrates a promising anti-tumor activity in heavily pre-treated or treatment-refractory solid tumor malignancies presumably by inhibition of proliferation and angiogenesis correlating with tumor growth inhibition. From the clinical editor: In this cancer treatment study clinical samples collected from patients were subjected to immunohistochemistry and pharmacogenomics. The expressions of key proteins that are inversely proportional with survival duration of the patients decreased after treatment with CRLX101, a camptothecin slow-release nanoparticle conjugate. This anti-tumor activity in heavily pre-treated and treatment resistant solid tumors, promises a novel therapeutic approach.

Polymeric nanotherapeutics: clinical development and advances in stealth functionalization strategies

Long-circulating polymeric nanotherapeutics have garnered increasing interest in research and in the clinic owing to their ability to improve the solubility and pharmacokinetics of therapeutic cargoes. Modulation of carrier properties promises more effective drug localization at the disease sites and can lead to enhanced drug safety and efficacy. In the present review, we highlight the current development of polymeric nanotherapeutics in the clinic. In light of the importance of stealth properties in therapeutic nanoparticles, we also review the advances in stealth functionalization strategies and examine the performance of different stealth polymers in the literature. In addition, we discuss the recent development of biologically inspired "self" nanoparticles, which present a differing stealth concept from conventional approaches.

Correlating preclinical animal studies and human clinical trials of a multifunctional, polymeric nanoparticle

Nanoparticles are currently being investigated in a number of human clinical trials. As information on how nanoparticles function in humans is difficult to obtain, animal studies that can be correlative to human behavior are needed to provide guidance for human clinical trials. Here, we report correlative studies on animals and humans for CRLX101, a 20- to 30-nm-diameter, multifunctional, polymeric nanoparticle containing camptothecin (CPT). CRLX101 is currently in phase 2 clinical trials, and human data from several of the clinical investigations are compared with results from multispecies animal studies. The pharmacokinetics of polymer-conjugated CPT (indicative of the CRLX101 nanoparticles) in mice, rats, dogs, and humans reveal that the area under the curve scales linearly with milligrams of CPT per square meter for all species. Plasma concentrations of unconjugated CPT released from CRLX101 in animals and humans are consistent with each other after accounting for differences in serum albumin binding of CPT. Urinary excretion of polymer-conjugated CPT occurs primarily within the initial 24 h after dosing in animals and humans. The urinary excretion dynamics of polymer-conjugated and unconjugated CPT appear similar between animals and humans. CRLX101 accumulates into solid tumors and releases CPT over a period of several days to give inhibition of its target in animal xenograft models of cancer and in the tumors of humans. Taken in total, the evidence provided from animal models on the CRLX101 mechanism of action suggests that the behavior of CRLX101 in animals is translatable to humans.

Disulfide cross-linked phosphorylcholine micelles for triggered release of camptothecin

A series of block copolymers based on 2-methacryloyloxyethyl phosphorylcholine (MPC) were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. Incorporation of dihydrolipoic acid (DHLA) into the hydrophobic block led to formation of block copolymer micelles in water. The micelles were between 15 and 30 nm in diameter, as characterized by dynamic light scattering (DLS), with some size control achieved by adjusting the hydrophobic/hydrophilic balance. Cross-linked micelles were prepared by disulfide formation, and observed to be stable in solution for weeks. The micelles proved amenable to disassembly when treated with a reducing agent, such as dithiothreitol (DTT), and represent a potential delivery platform for chemotherapeutic agents. As a proof-of-concept, camptothecin (CPT) was conjugated to the polymer scaffold through a disulfide linkage, and release of the drug from the micelle was monitored by fluorescence spectroscopy. These CPT-loaded prodrug micelles showed a reduction in release rate compared to physically encapsulated CPT. The use of disulfide conjugation facilitated drug release under reducing conditions, with a half-life (t1/2) of 5.5 h in the presence of 3 mM DTT, compared to 28 h in PBS. The toxicity of the micellar prodrugs was evaluated in cell culture against human breast (MCF7) and colorectal (COLO205) cancer cell lines.

Serial diffusion MRI to monitor and model treatment response of the targeted nanotherapy CRLX101

PURPOSE

Targeted nanotherapies are being developed to improve tumor drug delivery and enhance therapeutic response. Techniques that can predict response will facilitate clinical translation and may help define optimal treatment strategies. We evaluated the efficacy of diffusion-weighted magnetic resonance imaging to monitor early response to CRLX101 (a cyclodextrin-based polymer particle containing the DNA topoisomerase I inhibitor camptothecin) nanotherapy (formerly IT-101), and explored its potential as a therapeutic response predictor using a mechanistic model of tumor cell proliferation.

EXPERIMENTAL DESIGN

Diffusion MRI was serially conducted following CRLX101 administration in a mouse lymphoma model. Apparent diffusion coefficients (ADCs) extracted from the data were used as treatment response biomarkers. Animals treated with irinotecan (CPT-11) and saline were imaged for comparison. ADC data were also input into a mathematical model of tumor growth. Histological analysis using cleaved-caspase 3, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling, Ki-67, and hematoxylin and eosin (H&E) were conducted on tumor samples for correlation with imaging results.

RESULTS

CRLX101-treated tumors at day 2, 4, and 7 posttreatment exhibited changes in mean ADC = 16 ± 9%, 24 ± 10%, 49 ± 17%, and size (TV) = -5 ± 3%, -30 ± 4%, and -45 ± 13%, respectively. Both parameters were statistically greater than controls [p(ADC) ≤ 0.02, and p(TV) ≤ 0.01 at day 4 and 7], and noticeably greater than CPT-11-treated tumors (ADC = 5 ± 5%, 14 ± 7%, and 18 ± 6%; TV = -15 ± 5%, -22 ± 13%, and -26 ± 8%). Model-derived parameters for cell proliferation obtained using ADC data distinguished CRLX101-treated tumors from controls (P = 0.02).

CONCLUSIONS

Temporal changes in ADC specified early CRLX101 treatment response and could be used to model image-derived cell proliferation rates following treatment. Comparisons of targeted and nontargeted treatments highlight the utility of noninvasive imaging and modeling to evaluate, monitor, and predict responses to targeted nanotherapeutics.

First-in-human phase 1/2a trial of CRLX101, a cyclodextrin-containing polymer-camptothecin nanopharmaceutical in patients with advanced solid tumor malignancies

Patients with advanced solid malignancies were enrolled to an open-label, single-arm, dose-escalation study, in which CRLX101 was administered intravenously over 60 min among two dosing schedules, initially weekly at 6, 12, and 18 mg/m(2) and later bi-weekly at 12, 15, and 18 mg/m(2). The maximum tolerated dose (MTD) was determined at 15 mg/m(2) bi-weekly, and an expansion phase 2a study was completed. Patient samples were obtained for pharmacokinetic (PK) and pharmacodynamic (PD) assessments. Response was evaluated per RECIST criteria v1.0 every 8 weeks. Sixty-two patients (31 male; median age 63 years, range 39-79) received treatment. Bi-weekly dosing was generally well tolerated with myelosuppression being the dose-limiting toxicity. Among all phase 1/2a patients receiving the MTD (n = 44), most common grade 3/4 adverse events were neutropenia and fatigue. Evidence of systemic plasma exposure to both the polymer-conjugated and unconjugated CPT was observed in all treated patients. Mean elimination unconjugated CPT Tmax values ranged from 17.7 to 24.5 h, and maximum plasma concentrations and areas under the curve were generally proportional to dose for both polymer-conjugated and unconjugated CPT. Best overall response was stable disease in 28 patients (64 %) treated at the MTD and 16 (73 %) of a subset of NSCLC patients. Median progression-free survival (PFS) for patients treated at the MTD was 3.7 months and for the subset of NSCLC patients was 4.4 months. These combined phase 1/2a data demonstrate encouraging safety, pharmacokinetic, and efficacy results. Multinational phase 2 clinical development of CRLX101 across multiple tumor types is ongoing.

Cyclodextrin-containing polymers: versatile platforms of drug delivery materials

Nanoparticles are being widely explored as potential therapeutics for numerous applications in medicine and have been shown to significantly improve the circulation, biodistribution, efficacy, and safety profiles of multiple classes of drugs. One leading class of nanoparticles involves the use of linear, cyclodextrin-containing polymers (CDPs). As is discussed in this paper, CDPs can incorporate therapeutic payloads into nanoparticles via covalent attachment of prodrug/drug molecules to the polymer (the basis of the Cyclosert platform) or by noncovalent inclusion of cationic CDPs to anionic, nucleic acid payloads (the basis of the RONDEL platform). For each of these two approaches, we review the relevant molecular architecture and its rationale, discuss the physicochemical and biological properties of these nanoparticles, and detail the progress of leading drug candidates for each that have achieved clinical evaluation. Finally, we look ahead to potential future directions of investigation and product candidates based upon this technology.

Epratuzumab-SN-38: a new antibody-drug conjugate for the therapy of hematologic malignancies

We previously found that slowly internalizing antibodies conjugated with SN-38 could be used successfully when prepared with a linker that allows approximately 50% of the IgG-bound SN-38 to dissociate in serum every 24 hours. In this study, the efficacy of SN-38 conjugates prepared with epratuzumab (rapidly internalizing) and veltuzumab (slowly internalizing), humanized anti-CD22 and anti-CD20 IgG, respectively, was examined for the treatment of B-cell malignancies. Both antibody-drug conjugates had similar nanomolar activity against a variety of human lymphoma/leukemia cell lines, but slow release of SN-38 compromised potency discrimination in vitro even against an irrelevant conjugate. When SN-38 was stably linked to the anti-CD22 conjugate, its potency was reduced 40- to 55-fold. Therefore, further studies were conducted only with the less stable, slowly dissociating linker. In vivo, similar antitumor activity was found between CD22 and CD20 antibody-drug conjugate in mice-bearing Ramos xenografts, even though Ramos expressed 15-fold more CD20 than CD22, suggesting that the internalization of the epratuzumab-SN-38 conjugate (Emab-SN-38) enhanced its activity. Emab-SN-38 was more efficacious than a nonbinding, irrelevant IgG-SN-38 conjugate in vivo, eliminating a majority of well-established Ramos xenografts at nontoxic doses. In vitro and in vivo studies showed that Emab-SN-38 could be combined with unconjugated veltuzumab for a more effective treatment. Thus, Emab-SN-38 is active in lymphoma and leukemia at doses well below toxic levels and therefore represents a new promising agent with therapeutic potential alone or combined with anti-CD20 antibody therapy.

Conatumumab (AMG 655) coated nanoparticles for targeted pro-apoptotic drug delivery

Colloidal nanoparticle drug delivery systems have attracted much interest for their ability to enable effective formulation and delivery of therapeutic agents. The selective delivery of these nanoparticles to the disease site can be enhanced by coating the surface of the nanoparticles with targeting moieties, such as antibodies. In this current work, we demonstrate that antibodies on the surface of the particles can also elicit key biological effects. Specifically, we demonstrate the induction of apoptosis in colorectal HCT116 cancer cells using PLGA nanoparticles coated with Conatumumab (AMG 655) death receptor 5-specific antibodies (DR5-NP). We show that DR5-NP preferentially target DR5-expressing cells and present a sufficient density of antibody paratopes to induce apoptosis via DR5, unlike free AMG 655 or non-targeted control nanoparticles. We also demonstrate that DR5-targeted nanoparticles encapsulating the cytotoxic drug camptothecin are effectively targeted to the tumour cells, thereby producing enhanced cytotoxic effects through simultaneous drug delivery and apoptosis induction. These results demonstrate that antibodies on nanoparticulate surfaces can be exploited for dual modes of action to enhance the therapeutic utility of the modality.

Surface-modified silica nanoparticles for tumor-targeted delivery of camptothecin and its biological evaluation

Here we report the design, synthesis and biological evaluation of surface-modified silica nanoparticles (SNP) for the delivery of camptothecin (CPT). Drug has been covalently linked to the nanoparticle through an ester bond with the 20-hydroxy moiety, in order to stabilize its lactone ring and to avoid unspecific release of the drug. The obtained material is highly stable in plasma, with low release of the cargo at physiological pH. Cell internalization and in vitro efficacy assays demonstrated that nanoparticles carrying CPT (SNP-CPT) entered cells via endocytosis and the intracellular release of the cargo induced cell death with half maximal inhibitory concentration (IC₅₀) values and cell cycle distribution profiles similar to those observed for the naked drug. Further, in vivo biodistribution, therapeutic efficacy and biocompatibility of the SNP-CPT were evaluated in human colorectal cancer xenografts using in vivo fluorescence or bioluminescence optical imaging. In vivo tumor-accumulation and whole-body tissue distribution were carried out based on the acquisition of fluorescence emission of a fluorophore (Cy5.5) conjugated to the SNP-CPT, as well as by HPLC quantification of tissue CPT levels. The results showed that, although SNP-CPT tended to accumulate in organs of the reticulo-endothelial system, nanoparticles boost CPT concentration in tumor vs administration of the free drug. Accordingly, SNP-CPT treatment delayed the growth of subcutaneous tumors while significantly reducing the systemic toxicity associated with CPT administration. These results indicate that the SNP-CPT could be used as a robust drug delivery system for antitumoral treatments based on CPT.

CRLX101 (formerly IT-101)-A Novel Nanopharmaceutical of Camptothecin in Clinical Development

CRLX101 (formerly IT-101) is a first-in-class nanopharmaceutical, currently in Phase 2a development, which has been developed by covalently conjugating camptothecin (CPT) to a linear, cyclodextrin-polyethylene glycol (CD-PEG) co-polymer that self-assembles into nanoparticles. As a nanometer-scale drug carrier system, the cyclodextrin polymeric nanoparticle technology, referred to as “CDP”, has unique design features and capabilities. Specifically, CRLX101 preclinical and clinical data confirm that CDP can address not only solubility, formulation, toxicity, and pharmacokinetic challenges associated with administration of CPT, but more importantly, can impart unique biological properties that enhance CPT pharmacodynamics and efficacy.

Clinical developments in nanotechnology for cancer therapy

Nanoparticle approaches to drug delivery for cancer offer exciting and potentially "game-changing" ways to improve patient care and quality of life in numerous ways, such as reducing off-target toxicities by more selectively directing drug molecules to intracellular targets of cancer cells. Here, we focus on technologies being investigated clinically and discuss numerous types of therapeutic molecules that have been incorporated within nanostructured entities such as nanoparticles. The impacts of nanostructured therapeutics on efficacy and safety, including parameters like pharmacokinetics and biodistribution, are described for several drug molecules. Additionally, we discuss recent advances in the understanding of ligand-based targeting of nanoparticles, such as on receptor avidity and selectivity.

Host-guest interaction mediated polymeric assemblies: multifunctional nanoparticles for drug and gene delivery

Novel core-shell structured nanoassemblies are assembled by a beta-cyclodextrin containing a positively charged host polymer and a hydrophobic guest polymer. The hydrophobic core of these types of assemblies serves as a nanocontainer to load and release the hydrophobic drugs, while the positively charged hydrophilic shell is able to condense the plasmid DNA and achieve its transfection/expression in osteoblast cells. These assemblies may be used as a new generation of multifunctional nanocarriers for simultaneous drug delivery and gene therapy.

Design and development of IT-101, a cyclodextrin-containing polymer conjugate of camptothecin

IT-101 (Insert Therapeutics-101) is a linear, cyclodextrin-containing polymer conjugate of camptothecin (CPT). When formulated properly, the polymer conjugate self-assembles into nanoparticles of ca. 30 nm diameter and near neutral zeta potential. The nanoparticles show long circulation half-lives in animals and humans and localize in tumors. The nanoparticles enter the tumor cells and slowly release the CPT causing them to disassemble into individual polymer chains that are sufficiently small to be cleared renally. IT-101 is currently being investigated in human clinical trials. Here, the design and development of IT-101 is described with emphasis on features distinguishing it from other polymer-containing therapeutics.

Pharmacokinetics and tumor dynamics of the nanoparticle IT-101 from PET imaging and tumor histological measurements

IT-101, a cyclodextrin polymer-based nanoparticle containing camptothecin, is in clinical development for the treatment of cancer. Multiorgan pharmacokinetics and accumulation in tumor tissue of IT-101 is investigated by using PET. IT-101 is modified through the attachment of a 1,4,7,10-tetraazacyclododecane-1,4,7-Tris-acetic acid ligand to bind (64)Cu(2+). This modification does not affect the particle size and minimally affects the surface charge of the resulting nanoparticles. PET data from (64)Cu-labeled IT-101 are used to quantify the in vivo biodistribution in mice bearing Neuro2A s.c. tumors. The (64)Cu-labeled IT-101 displays a biphasic plasma elimination. Approximately 8% of the injected dose is rapidly cleared as a low-molecular-weight fraction through the kidneys. The remaining material circulates in plasma with a terminal half-life of 13.3 h. Steadily increasing concentrations, up to 11% injected dose per cm(3), are observed in the tumor over 24 h, higher than any other tissue at that time. A 3-compartment model is used to determine vascular permeability and nanoparticle retention in tumors, and is able to accurately represent the experimental data. The calculated tumor vascular permeability indicates that the majority of nanoparticles stay intact in circulation and do not disassemble into individual polymer strands. A key assumption to modeling the tumor dynamics is that there is a "sink" for the nanoparticles within the tumor. Histological measurements using confocal microscopy show that IT-101 localizes within tumor cells and provides the sink in the tumor for the nanoparticles.