Local implantation of doxorubicin drug eluting beads in rat glioma

Frontiers in the treatment of glioblastoma: Past, present and emerging

Glioblastoma (GBM) is one of the most aggressive cancers of the brain. Despite extensive research over the last several decades, the survival rates for GBM have not improved and prognosis remains poor. To date, only a few therapies are approved for the treatment of GBM with the main reasons being: 1) significant tumour heterogeneity which promotes the selection of resistant subpopulations 2) GBM induced immunosuppression and 3) fortified location of the tumour in the brain which hinders the delivery of therapeutics. Existing therapies for GBM such as radiotherapy, surgery and chemotherapy have been unable to reach the clinical efficacy necessary to prolong patient survival more than a few months. This comprehensive review evaluates the current and emerging therapies including those in clinical trials that may potentially improve both targeted delivery of therapeutics directly to the tumour site and the development of agents that may specifically target GBM. Particular focus has also been given to emerging delivery technologies such as focused ultrasound, cellular delivery systems nanomedicines and immunotherapy. Finally, we discuss the importance of developing novel materials for improved delivery efficacy of nanoparticles and therapeutics to reduce the suffering of GBM patients.

The Extracellular Matrix and Biocompatible Materials in Glioblastoma Treatment

During cancer genesis, the extracellular matrix (ECM) in the human brain undergoes important transformations, starting to resemble embryonic brain cell milieu with a much denser structure. However, the stiffness of the tumor ECM does not preclude cancer cells from migration. The importance of the ECM role in normal brain tissue as well as in tumor homeostasis has engaged much effort in trials to implement ECM as a target and an instrument in the treatment of brain cancers. This review provides a detailed analysis of both experimental and applied approaches in combined therapy for gliomas in adults. In general, matrix materials for glioma treatment should have properties facilitating the simplest delivery into the body. Hence, to deliver an artificial implant directly into the operation cavity it should be packed into a gel form, while for bloodstream injections matrix needs to be in the form of polymer micelles, nanoparticles, etc. Furthermore, the delivered material should mimic biomechanical properties of the native tissue, support vital functions, and slow down or stop the proliferation of surrounding cells for a prolonged period. The authors propose a two-step approach aimed, on the one hand, at elimination of remaining cancer cells and on the other hand, at restoring normal brain tissue. Thereby, the first bioartificial matrix to be applied should have relatively low elastic modulus should be loaded with anticancer drugs, while the second material with a higher elastic modulus for neurite outgrowth support should contain specific factors stimulating neuroregeneration.

Vandetanib-eluting Radiopaque Beads: In vivo Pharmacokinetics, Safety and Toxicity Evaluation following Swine Liver Embolization

PURPOSE: To evaluate the plasma and tissue pharmacokinetics, safety and toxicity following intra-arterial hepatic artery administration of Vandetanib (VTB)-eluting Radiopaque Beads (VERB) in healthy swine.

MATERIALS AND METHODS: In a first phase, healthy swine were treated with hepatic intra-arterial administration of VERB at target dose loading strengths of 36 mg/mL (VERB36), 72 mg/mL (VERB72) and 120 mg/mL (VERB120). Blood and tissue samples were taken and analysed for VTB and metabolites to determine pharmacokinetic parameters for the different dose forms over 30 days. In a second phase, animals were treated with unloaded radiopaque beads or high dose VTB loaded beads (VERB100, 100 mg/mL). Tissue samples from embolized and non-embolized areas of the liver were evaluated at necropsy (30 and 90 days) for determination of VTB and metabolite levels and tissue pathology. Imaging was performed prior to sacrifice using multi-detector computed tomography (MDCT) and imaging findings correlated with pathological changes in the tissue and location of the radiopaque beads.

RESULTS: The peak plasma levels of VTB (C_max) released from the various doses of VERB ranged between 6.19-17.3 ng/mL indicating a low systemic burst release. The plasma profile of VTB was consistent with a distribution phase up to 6 h after administration followed by elimination with a half-life of 20-23 h. The AUC of VTB and its major metabolite N-desmethyl vandetanib (NDM VTB) was approximately linear with the dose strength of VERB. VTB plasma levels were at or below limits of detection two weeks after administration. In liver samples, VTB and NDM VTB were present in treated sections at 30 days after administration at levels above the in vitro IC₅₀ for biological effectiveness. At 90 days both analytes were still present in treated liver but were near or below the limit of quantification in untreated liver sections, demonstrating sustained release from the VERB. Comparison of the reduction of the liver lobe size and associated tissue changes suggested a more effective embolization with VERB compared to the beads without drug.

CONCLUSIONS: Hepatic intra-arterial administration of VERB results in a low systemic exposure and enables sustained delivery of VTB to target tissues following embolization. Changes in the liver tissue are consistent with an effective embolization and this study has demonstrated that VERB100 is well tolerated with no obvious systemic toxicity.

Intratumoral heterogeneity in glioblastoma: don't forget the peritumoral brain zone

Glioblastoma (GB) is the most frequent and aggressive primary tumor of the central nervous system. Prognosis remains poor despite ongoing progress. In cases where the gadolinium-enhanced portion of the GB is completely resected, 90% of recurrences occur at the margin of surgical resection in the macroscopically normal peritumoral brain zone (PBZ). Intratumoral heterogeneity in GB is currently a hot topic in neuro-oncology, and the GB PBZ may be involved in this phenomenon. Indeed, this region, which possesses specific properties, has been less studied than the core of the GB tumor. The high rate of local recurrence in the PBZ and the limited success of targeted therapies against GB demonstrate the need for a better understanding of the PBZ. We present here a review of the literature on the GB PBZ, focusing on its radiological, cellular, and molecular characteristics. We discuss how intraoperative analysis of the PBZ is important for the optimization of surgical resection and the development of targeted therapies against GB.

Treatment of intermediate stage hepatocellular carcinoma: a review of intrahepatic doxorubicin drug-delivery systems

The biopharmaceutical properties of doxorubicin delivered via two drug-delivery systems (DDSs) for the palliative treatment of unresectable hepatocellular carcinoma were reviewed with relation to the associated liver and tumor (patho)physiology. These two DDSs, doxorubicin emulsified with Lipiodol® and doxorubicin loaded into DC Bead® are different regarding tumor delivery, release rate, local bioavailability, if and how they can be given repeatedly, biodegradability, length of embolization and safety profile. There have been few direct head-to-head comparisons of these DDSs, and in-depth investigations into their in vitro and in vivo performance is warranted.

Locoregional drug delivery using image-guided intra-arterial drug eluting bead therapy

Lipiodol-based transarterial chemoembolization (TACE) has been performed for over 3 decades for the treatment of solid tumors and describes the infusion of chemotherapeutic agents followed by embolization with particles. TACE is an effective treatment for inoperable hepatic tumors, especially hypervascular tumors such as hepatocellular carcinoma. Recently, drug eluting beads (DEBs), in which a uniform embolic material is loaded with a drug and delivered in a single image-guided step, have been developed to reduce the variability in a TACE procedure. DEB-TACE results in localization of drug to targeted tumors while minimizing systemic exposure to chemotherapeutics. Once localized in the tissue, drug is eluted from the DEB in a controlled manner and penetrates hundreds of microns of tissue from the DEB surface. Necrosis is evident surrounding a DEB in tissue days to months after therapy; however, the contribution of drug and ischemia is currently unknown. Future advances in DEB technology may include image-ability, DEB size tailored to tumor anatomy and drug combinations.

Development of a combination drug-eluting bead: towards enhanced efficacy for locoregional tumour therapies

Drug-eluting beads (DEBs) are becoming a mainstay locoregional therapy for hepatic malignancies but are currently loaded with single drugs alone. Here, we wished to prepare DEB containing different drug combinations, to screen their efficacy using an in-vitro cell culture assay and to include any promising combinations that demonstrate additive efficacy in an in-vivo model of locoregional tumour treatment. A modified in-vitro assay was used based upon the use of 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS) with either HepG2 liver cancer or PSN1 pancreatic cancer cell lines. The comparative cytotoxicity of DEB combinations prepared containing doxorubicin, irinotecan, topotecan and rapamycin was evaluated. Those combinations that demonstrated an additive cytotoxicity effect were investigated in vivo using a nude mouse xenograft model of pancreatic cancer. Although many of the DEB combinations showed either no effect or a slight antagonistic effect, the combination of doxorubicin and rapamycin DEBs demonstrated synergistic activity. On the basis of these findings, a method was developed to prepare a doxorubicin/rapamycin dual-loaded DEB, which was shown to possess the same drug-loading capacities, drug elution properties and HepG2 cell cytotoxicity synergy as the single drug-loaded DEB combination. Evaluation of this dual-loaded combination DEB versus the respective single drug-loaded DEBs in a mouse xenograft model of pancreatic cancer showed an equivalent tumour volume reduction as the doxorubicin DEB, but with less toxicity than the rapamycin DEB. The doxorubicin/rapamycin combination DEB offers great potential for enhanced efficacy in the locoregional treatment of malignant tumours.

Drug delivery strategies for the treatment of malignant gliomas

As primary brain tumors, malignant gliomas are known to be one of the most insidious types of brain cancer afflicting the humans. The current standard strategy for the treatment of malignant gliomas includes the surgical resection of the tumor when possible, followed by a combination of radiotherapy and/or a certain chemotherapeutic protocol. However, due to the short mean survival, frequent recurrences, and poor prognosis associated with the tumors, new therapeutic strategies are investigated consecutively. These novel drug delivery approaches can be subdivided as systemic and local drug administration. This review focuses on localized drug delivery strategies for the treatment of malignant gliomas, including the injections, infusions, trans-nasal delivery systems, convection enhanced delivery (CED) systems, and various types of polymeric implants. Furthermore, systemic strategies to increase the drug penetration into the brain, such as temporary disruption of the blood brain barrier (BBB), chemical modification of the available therapeutic substances, and utilization of endogenous transport systems will be briefly discussed.

Doxorubicin loading and eluting characteristics of bioresorbable hydrogel microspheres: in vitro study

Non-bioresorbable drug eluting microspheres are being increasingly used for the treatment of unresectable liver tumors, whereas bioresorbable microspheres have not received much attention. In this study, bioresorbable microspheres prepared from chitosan and carboxymethyl cellulose were loaded with doxorubicin (Doxo) via ion-exchange interactions with carboxylic groups in the microspheres. With a 25-40% decrease in the microsphere size depending on their size ranges, the microspheres could load a maximum of 0.3-0.7 mg Doxo/mg dry spheres. As confirmed by confocal microscopy, Doxo was mainly concentrated in the outer 20±5 μm surface layer of the microspheres. The loaded microspheres were stable in aqueous dispersions without aggregation for a prolonged period of time but degradable in a lysozyme solution. Furthermore, the loaded microspheres exhibited a noticeable pH-sensitive behavior with accelerated release of Doxo in acidic environment due to the protonation of carboxylic groups in the microspheres. Compared to commercial non-resorbable drug eluting beads, the loaded bioresorbable microspheres showed a sustained release manner in phosphate buffered saline (PBS). The release data were fitted to an empirical relationship, which reveals a non-Fickian transport mechanism (n=0.55-0.59). These results demonstrate that the bioresorbable microspheres are promising as attractive carriers for Doxo.

DC Bead embolic drug-eluting bead: clinical application in the locoregional treatment of tumours

INTRODUCTION

DC Bead is an embolic drug-eluting bead designed to be loaded with chemotherapeutic agents (such as doxorubicin and irinotecan), delivered intra-arterially into tumor blood vessels to block nutrient flow and then to deliver the drug locally in a sustained fashion. This product is finding increasing use in the treatment of patients with both primary and secondary liver cancers.

AREAS COVERED

This review positions DC Bead in the field of targeted embolic drug delivery and with respect to other competitive technologies in the treatment of liver cancer. An overview of the studies that demonstrate the product's performance, safety and efficacy is presented. The clinical application of the doxorubicin loaded DC Bead is firstly reviewed, in the context of treatment of patients with various stages of hepatocellular carcinoma. Its combination with other therapies is also discussed, together with consideration of the treatment of other liver tumors. Secondly, the use of irinotecan loaded DC Bead, primarily for the treatment of colorectal cancer metastases to the liver, but also some additional rare metastases, is summarized.

EXPERT OPINION

An opinion is proffered as to how this technology and its application is evolving, illustrating a move towards synergistic combination therapies and into other cancer indications.

Studying protein degradation pathways in vivo using a cranial window-based approach

Understanding how specific proteins are degraded by neurons in living animals is a fundamental question with relevance to many neurodegenerative diseases. Dysfunction in the ubiquitin-proteasome system (UPS) specifically has been implicated in several important neurodegenerative diseases including Alzheimer's Disease, Parkinson's Disease, and amyotrophic lateral sclerosis. Research in this area has been limited by the fact that many inhibitors of the UPS given systemically do not cross the blood-brain barrier (BBB) in appreciable levels. This limits the ability to easily test in vivo specific hypotheses generated in reduced systems, like brain slice or dissociated cell culture, about whether the UPS may degrade a particular protein of interest. Although several techniques including intracerebral application via direct syringe injection, catheter-pump systems and drug-eluting beads are available to introduce BBB-impermeant drugs into brain they each have certain limitations and new approaches could provide further insights into this problem. In order to test the role of the UPS in protein degradation in vivo we have developed a strategy to treat mouse cortex with the UPS inhibitor clasto-lactacystin beta-lactone (CLBL) via a "cranial window" and recover the treated tissue for immunoblot analysis. This approach can be used in several different cranial window configurations including single window and double hemi-window arrangements that are tailored for different applications. We have also developed two different strategies for recovering treated cortical tissue including a vibratome/laser capture microscopy (LCM)-based and a vibratome only-based approach, each with its own specific advantages. We have documented UPS inhibition >600μm deep into the cortex with this strategy. This set of techniques in the living mammalian brain is complementary to previously developed approaches and extends the repertoire of tools that can be used to the study protein degradation pathways relevant to neurodegenerative disease.