Blood-Brain Barrier in Brain Tumors: Biology and Clinical Relevance.

The presence of barriers, such as the blood-brain barrier (BBB) and brain-tumor barrier (BTB), limits the penetration of antineoplastic drugs into the brain, resulting in poor response to treatments. Many techniques have been developed to overcome the presence of these barriers, including direct injections of substances by intranasal or intrathecal routes, chemical modification of drugs or constituents of BBB, inhibition of efflux pumps, physical disruption of BBB by radiofrequency electromagnetic radiation (EMP), laser-induced thermal therapy (LITT), focused ultrasounds (FUS) combined with microbubbles and convection enhanced delivery (CED). However, most of these strategies have been tested only in preclinical models or in phase 1-2 trials, and none of them have been approved for treatment of brain tumors yet. Concerning the treatment of brain metastases, many molecules have been developed in the last years with a better penetration across BBB (new generation tyrosine kinase inhibitors like osimertinib for non-small-cell lung carcinoma and neratinib/tucatinib for breast cancer), resulting in better progression-free survival and overall survival compared to older molecules. Promising studies concerning neural stem cells, CAR-T (chimeric antigen receptors) strategies and immunotherapy with checkpoint inhibitors are ongoing.

New therapeutic approaches for brainstem tumors: a comparison of delivery routes using nanoliposomal irinotecan in an animal model.

Despite the advances in imaging, surgery and radiotherapy, the majority of patients with brainstem gliomas die within 2 years after initial diagnosis. Factors that contribute to the dismal prognosis of these patients include the infiltrative nature and anatomic location in an eloquent area of the brain, which prevents total surgical resection and the presence of the blood-brain barrier (BBB), which reduces the distribution of systemically administered agents. The development of new therapeutic approaches which can circumvent the BBB is a potential path to improve outcomes for these children. Convection-enhanced delivery (CED) and intranasal delivery (IND) are strategies that permit direct drug delivery into the central nervous system and are an alternative to intravenous injection (IV). We treated rats bearing human brainstem tumor xenografts with nanoliposomal irinotecan (CPT-11) using CED, IND, and IV. A single treatment of CED irinotecan had a similar effect on overall survival as multiple treatments by IV route. IND CPT-11 showed significantly increased survival of animals with brainstem tumors, and demonstrated the promise of this non-invasive approach of drug delivery bypassing the BBB when combined with nanoliposomal chemotherapy. Our results indicated that using CED and IND of nanoliposomal therapy increase likelihood of practical therapeutic approach for the treatment of brainstem gliomas.

Convection-enhanced delivery of nanodiamond drug delivery platforms for intracranial tumor treatment.

This study examined a novel drug delivery system for treatment of malignant brain gliomas: DOX complexed with nanodiamonds (ND-Dox), and administered via convection-enhanced delivery (CED). Drug retention and toxicity were examined in glioma cell lines, and distribution, retention and toxicity were examined in normal rat parenchyma. Efficacy was assessed in a bioluminescence rodent tumor model. NDs markedly enhanced DOX uptake and retention in glioma cells. ND-Dox delivered via CED extended DOX retention and localized DOX toxicity in normal rodent parenchyma, and was significantly more efficient at killing tumor cells than uncomplexed DOX. Outcomes from this work suggest that CED of ND-Dox is a promising approach for brain tumor treatment. FROM THE CLINICAL EDITOR: In this paper, nanodiamonds were utilized to enhance delivery of DOX in a preclinical glioma model using a convection-enhanced delivery method, demonstrating remarkably enhanced efficacy.

Multi-Targeted Neutron Capture Therapy Combined with an 18 kDa Translocator Protein-Targeted Boron Compound Is an Effective Strategy in a Rat Brain Tumor Model.

BACKGROUND: Boron neutron capture therapy (BNCT) has been adapted to high-grade gliomas (HG); however, some gliomas are refractory to BNCT using boronophenylalanine (BPA). In this study, the feasibility of BNCT targeting the 18 kDa translocator protein (TSPO) expressed in glioblastoma and surrounding environmental cells was investigated. METHODS: Three rat glioma cell lines, an F98 rat glioma bearing brain tumor model, DPA-BSTPG which is a boron-10 compound targeting TSPO, BPA, and sodium borocaptate (BSH) were used. TSPO expression was evaluated in the F98 rat glioma model. Boron uptake was assessed in three rat glioma cell lines and in the F98 rat glioma model. In vitro and in vivo neutron irradiation experiments were performed. RESULTS: DPA-BSTPG was efficiently taken up in vitro. The brain tumor has 16-fold higher TSPO expressions than its brain tissue. The compound biological effectiveness value of DPA-BSTPG was 8.43 to F98 rat glioma cells. The boron concentration in the tumor using DPA-BSTPG convection-enhanced delivery (CED) administration was approximately twice as high as using BPA intravenous administration. BNCT using DPA-BSTPG has significant efficacy over the untreated group. BNCT using a combination of BPA and DPA-BSTPG gained significantly longer survival times than using BPA alone. CONCLUSION: DPA-BSTPG in combination with BPA may provide the multi-targeted neutron capture therapy against HG.

Targeting the IL4 receptor with MDNA55 in patients with recurrent glioblastoma: Results of a phase IIb trial.

BACKGROUND: MDNA55 is an interleukin 4 receptor (IL4R)-targeting toxin in development for recurrent GBM, a universally fatal disease. IL4R is overexpressed in GBM as well as cells of the tumor microenvironment. High expression of IL4R is associated with poor clinical outcomes. METHODS: MDNA55-05 is an open-label, single-arm phase IIb study of MDNA55 in recurrent GBM (rGBM) patients with an aggressive form of GBM (de novo GBM, IDH wild-type, and nonresectable at recurrence) on their 1st or 2nd recurrence. MDNA55 was administered intratumorally as a single dose treatment (dose range of 18 to 240 ug) using convection-enhanced delivery (CED) with up to 4 stereo-tactically placed catheters. It was co-infused with a contrast agent (Gd-DTPA, Magnevist®) to assess distribution in and around the tumor margins. The flow rate of each catheter did not exceed 10µL/min to ensure that the infusion duration did not exceed 48 h. The primary endpoint was mOS, with secondary endpoints determining the effects of IL4R status on mOS and PFS. RESULTS: MDNA55 showed an acceptable safety profile at doses up to 240 µg. In all evaluable patients (n = 44) mOS was 11.64 months (80% one-sided CI 8.62, 15.02) and OS-12 was 46%. A subgroup (n = 32) consisting of IL4R High and IL4R Low patients treated with high-dose MDNA55 (>180 ug) showed the best benefit with mOS of 15 months, OS-12 of 55%. Based on mRANO criteria, tumor control was observed in 81% (26/32), including those patients who exhibited pseudo-progression (15/26). CONCLUSIONS: MDNA55 demonstrated tumor control and promising survival and may benefit rGBM patients when treated at high-dose irrespective of IL4R expression level.Trial Registration: Clinicaltrials.gov NCT02858895.

In-vitro and in-vivo performance studies of a porous infusion catheter designed for intraparenchymal delivery of therapeutic agents of varying size.

BACKGROUND: Limitations have previously existed for the use of brain infusion catheters with extended delivery port designs to achieve larger distribution volumes using convection-enhanced delivery (CED), due to poor transmittance of materials and uncontrolled backflow. The goal of this study was to evaluate a novel brain catheter that has been designed to allow for extended delivery and larger distribution volumes with limited backflow of fluid. It was characterized using a broad range of therapeutic pore sizes both for transmittance across the membranes to address possible occlusion and for distribution in short term infusion studies, both in-vitro in gels and in-vivo in canines. METHODS: Brain catheters with pore sizes of 10, 12, 15, 20 and 30 µm were evaluated using three infusates prepared in 0.9% sterile saline with diameters approximating 2, 5, and 30 nm, respectively. Magnevist™ was chosen as the small molecule infusate to mimic low-molecular weight therapeutics. Galbumin™ served as a surrogate for an assortment of proteins used for brain cancer and Parkinson's disease. Gadoluminate™ was used to assess the distribution of large therapeutics, such as adeno-associated viral particles and synthetic nanoparticles. The transmittance of the medium and large tracer particles through catheters of different pore size (15, 20 and 30 µm) was measured by MRI and compared with the measured concentration of the control. Infusions into 0.2% agarose gels were performed in order to evaluate differences in transmittance and distribution of the small, medium, and large tracer particles through catheters with different pore sizes (10, 12, 15, 20 and 30 µm). In-vivo infusions were performed in the canine in order to evaluate the ability of the catheter to infuse the small, medium, and large tracer particles into brain parenchyma at high flow rates through catheters with different pore sizes (10, 15, and 20 µm). Two catheters were stereotactically inserted into the brain for infusion, one per hemisphere, in each animal (N = 6). RESULTS: The transmittance of Galbumin and Gadoluminate across the catheter membrane surface was 100% to within the accuracy of the measurements. There was no evidence of any blockage or retardation of any of the infusates. Catheter pore size did not appear to significantly affect transmittance or distribution in gels of any of the molecule sizes in the range of catheter pore sizes tested. There were differences in the distributions between the different tracer molecules: Magnevist produced relatively large distributions, followed by Gadoluminate and Galbumin. We observed no instances of uncontrolled backflow in a total of 12 in-vivo infusions. In addition, several of the infusions resulted in substantial amounts remaining in tissue. We expect the in-tissue distributions to be substantially improved in the larger human brain. COMPARISON WITH EXISTING METHODS: The new porous brain catheter performed well in terms of both backflow and intraparenchymal infusion of molecules of varying size in the canine brain under CED flow conditions. CONCLUSIONS: Overall, the data presented in this report support that the novel porous brain catheter can deliver therapeutics of varying sizes at high infusion rates in the brain parenchyma, and resist backflow that can compromise the efficacy of CED therapy. Additional work is needed to further characterize the brain catheter, including animal toxicity studies of chronically implanted brain catheters to lay the foundation for its use in the clinic.

Medical Device Advances in the Treatment of Glioblastoma.

Despite decades of research and the growing emergence of new treatment modalities, Glioblastoma (GBM) frustratingly remains an incurable brain cancer with largely stagnant 5-year survival outcomes of around 5%. Historically, a significant challenge has been the effective delivery of anti-cancer treatment. This review aims to summarize key innovations in the field of medical devices, developed either to improve the delivery of existing treatments, for example that of chemo-radiotherapy, or provide novel treatments using devices, such as sonodynamic therapy, thermotherapy and electric field therapy. It will highlight current as well as emerging device technologies, non-invasive versus invasive approaches, and by doing so provide a detailed summary of evidence from clinical studies and trials undertaken to date. Potential limitations and current challenges are discussed whilst also highlighting the exciting potential of this developing field. It is hoped that this review will serve as a useful primer for clinicians, scientists, and engineers in the field, united by a shared goal to translate medical device innovations to help improve treatment outcomes for patients with this devastating disease.

PEAMOtecan, a novel chronotherapeutic polymeric drug for brain cancer.

Glioblastoma multiforme (GBM) is an aggressive and difficult to treat form of brain cancer. In this work, we report on a novel chronotherapeutic polymeric drug, PEAMOtecan, for GBM therapy. PEAMOtecan was synthesized by conjugating camptothecin, a topoisomerase I inhibitor, to our proprietary, 'clickable' and modular polyoxetane polymer platform consisting of acetylene-functionalized 3-ethyl-3-(hydroxymethyl)oxetane (EAMO) repeat units (Patent No.: US 9,421,276) via the linker 3,3'-dithiodipropionic acid (DDPA) with a disulfide bond (SS) extended by short-chain polyethylene glycol (PEG). We show that PEAMOtecan is a highly modular polymer nanoformulation that protects covalently bound CPT until slowly being released over extended periods of time dependent on the cleavage of the disulfide and ester linkages. PEAMOtecan kills glioma cells by mitotic catastrophe with p53 mutant/knockdown cells being more sensitive than matched wild type cells potentially providing cancer-specific targeting. To establish proof-of-principle therapeutic effects, we tested PEAMOtecan as monotherapy for efficacy in a mouse orthotopic glioma model. PEAMOtecan was administered by one-time, convection-enhanced delivery (CED) intra-tumorally to achieve superior distribution and extended drug release over time. In addition, the near-infrared (NIR) dye Cy5.5 was coupled to the polymer providing live-animal imaging capability to track tissue distribution and clearance of the injected polymer over time. We show that PEAMOtecan significantly improves the survival of mice harboring intra-cranial tumors (p = .0074 compared to untreated group). Altogether, these results support further development and testing of our nanoconjugate platform.

Convection Enhanced Delivery for Diffuse Intrinsic Pontine Glioma: Review of a Single Institution Experience.

Diffuse intrinsic pontine gliomas (DIPGs) are a pontine subtype of diffuse midline gliomas (DMGs), primary central nervous system (CNS) tumors of childhood that carry a terrible prognosis. Because of the highly infiltrative growth pattern and the anatomical position, cytoreductive surgery is not an option. An initial response to radiation therapy is invariably followed by recurrence; mortality occurs approximately 11 months after diagnosis. The development of novel therapeutics with great preclinical promise has been hindered by the tightly regulated blood-brain barrier (BBB), which segregates the tumor comportment from the systemic circulation. One possible solution to this obstacle is the use of convection enhanced delivery (CED), a local delivery strategy that bypasses the BBB by direct infusion into the tumor through a small caliber cannula. We have recently shown CED to be safe in children with DIPG (NCT01502917). In this review, we discuss our experience with CED, its advantages, and technical advancements that are occurring in the field. We also highlight hurdles that will likely need to be overcome in demonstrating clinical benefit with this therapeutic strategy.

Convection-Enhanced Delivery of a Virus-Like Nanotherapeutic Agent with Dual-Modal Imaging for Besiegement and Eradication of Brain Tumors.

Convection-enhanced delivery (CED) is a promising technique for infusing a therapeutic agent directly into the brain, bypassing the blood-brain barrier (BBB) with a pressure gradient to increase drug concentration specifically around the brain tumor, thereby enhancing tumor inhibition and limiting the systemic toxicity of chemotherapeutic agents. Herein, we developed a dual-imaging monitored virus-like nanotherapeutic agent as an ideal CED infusate, which can be delivered to specifically besiege and eradicate brain tumors. Methods: We report one-pot fabrication of green-fluorescence virus-like particles (gVLPs) in Escherichia coli (E. coli) for epirubicin (EPI) loading, cell-penetrating peptide (CPP) modification, and 68Ga-DOTA labeling to form a positron emission tomography (PET)-fluorescence dual-imaging monitored virus-like nanotherapeutic agent (68Ga-DOTA labeled EPI@CPP-gVLPs) combined with CED for brain tumor therapy and image tracking. The drug delivery, cytotoxicity, cell uptake, biodistribution, PET-fluorescence imaging and anti-tumor efficacy of the 68Ga-DOTA labeled EPI@CPP-gVLPs were investigated in vitro and in vivo by using U87-MG glioma cell line and U87-MG tumor model. Results: The 68Ga-DOTA-labeled EPI@CPP-gVLPs showed excellent serum stability as an ideal CED infusate (30-40 nm in size), and can be disassembled through proteolytic degradation of the coat protein shell to enable drug release and clearance to minimize long-term accumulation. The present results indicated that 68Ga-DOTA-labeled EPI@CPP-gVLPs can provide a sufficiently high drug payload (39.2 wt% for EPI) and excellent detectability through fluorescence and PET imaging to accurately represent drug distribution during CED infusion. In vivo delivery of the 68Ga-DOTA-labeled EPI@CPP-gVLPs through CED demonstrated that the median survival was prolonged to over 50 days when the mice received two administrations (once per week) compared with the control group (median survival: 26 days). Conclusion: The results clearly indicated that a combination of 68Ga-DOTA-labeled EPI@CPP-gVLPs and CED can serve as a flexible and powerful synergistic treatment in brain tumors without evidence of systemic toxicity.

Treatment Strategies in Diffuse Midline Gliomas With the H3K27M Mutation: The Role of Convection-Enhanced Delivery in Overcoming Anatomic Challenges.

Diffuse midline gliomas harboring the H3 K27M mutation-including the previously named diffuse intrinsic pontine glioma (DIPG)-are lethal high-grade pediatric brain tumors that are inoperable and without cure. Despite numerous clinical trials, the prognosis remains poor, with a median survival of ~1 year from diagnosis. Systemic administration of chemotherapeutic agents is often hindered by the blood brain barrier (BBB), and even drugs that successfully cross the barrier may suffer from unpredictable distributions. The challenge in treating this deadly disease relies on effective delivery of a therapeutic agent to the bulk tumor as well as infiltrating cells. Therefore, methods that can enhance drug delivery to the brain are of great interest. Convection-enhanced delivery (CED) is a strategy that bypasses the BBB entirely and enhances drug distribution by applying hydraulic pressure to deliver agents directly and evenly into a target region. This technique reliably distributes infusate homogenously through the interstitial space of the target region and achieves high local drug concentrations in the brain. Moreover, recent studies have also shown that continuous delivery of drug over an extended period of time is safe, feasible, and more efficacious than standard single session CED. Therefore, CED represents a promising technique for treating midline tumors with the H3K27M mutation.

PARP-1-Targeted Radiotherapy in Mouse Models of Glioblastoma.

The DNA repair enzyme poly(ADP-ribose) polymerase 1 (PARP-1) is overexpressed in glioblastoma, with overall low expression in healthy brain tissue. Paired with the availability of specific small molecule inhibitors, PARP-1 is a near-ideal target to develop novel radiotherapeutics to induce DNA damage and apoptosis in cancer cells, while sparing healthy brain tissue. Methods: We synthesized an 131I-labeled PARP-1 therapeutic and investigated its pharmacology in vitro and in vivo. A subcutaneous tumor model was used to quantify retention times and therapeutic efficacy. A potential clinical scenario, intratumoral convection-enhanced delivery, was mimicked using an orthotopic glioblastoma model combined with an implanted osmotic pump system to study local administration of 131I-PARPi (PARPi is PARP inhibitor). Results:131I-PARPi is a 1(2H)-phthalazinone, similar in structure to the Food and Drug Administration-approved PARP inhibitor AZD-2281. In vitro studies have shown that 131I-PARPi and AZD-2281 share similar pharmacologic profiles. 131I-PARPi delivered 134.1 cGy/MBq intratumoral injected activity. Doses to nontarget tissues, including liver and kidney, were significantly lower. Radiation damage and cell death in treated tumors were shown by p53 activation in U87-MG cells transfected with a p53-bioluminescent reporter. Treated mice showed significantly longer survival than mice receiving vehicle (29 vs. 22 d, P < 0.005) in a subcutaneous model. Convection-enhanced delivery demonstrated efficient retention of 131I-PARPi in orthotopic brain tumors, while quickly clearing from healthy brain tissue. Conclusion: Our results demonstrate 131I-PARPi's high potential as a therapeutic and highlight PARP's relevance as a target for radionuclide therapy. Radiation plays an integral role in brain tumor therapy, and radiolabeled PARP therapeutics could ultimately lead to improvements in the standard of care.

Insights from mathematical modeling for convection-enhanced intraputamenal delivery of GDNF.

Glial cell line-derived neurotrophic factor (GDNF) is a potential therapy for Parkinson's disease (PD) promoting survival and functional recovery of dopaminergic neurons when delivered to the degenerated striatum. To study the aspects of intraputamenal delivery of GDNF, a mathematical model of recombinant methionyl human GDNF (r-metHuGDNF) convection in the human putamen has been developed. The convection-enhanced delivery infusions of r-metHuGDNF were simulated at rates up to 5 µL/min. The high-rate infusions (≥1 µL/min) permit rapid and uniform distribution of drug with up to 75% of the distribution volume having a concentration within 5% of the infusate concentration. No relevant differences in distribution at infusion rates of 3 and 5 µL/min were found. The patterns of GDNF distribution were analyzed in relation to the anatomy of the posterior dorsal putamen, and a cylindrical shape was found to be preferable considering risks of target overflow. A magnetic resonance (MR) tracer Gd-DTPA (Magnevist®) was evaluated as a surrogate in clinical studies, and the most accurate prediction of GDNF distribution was calculated immediately after infusion. The clearance of GDNF from the striatum is confirmed to be slow, with a half-life of ca. 19 h.

Targeting Nanomedicine to Brain Tumors: Latest Progress and Achievements.

Targeting nanomedicine to brain tumors is hampered by the heterogeneity of brain tumors and the blood brain barrier. These represent the main reasons of unsuccessful treatments. Nanomedicine based approaches hold promise for improved brain tissue distribution of drugs and delivery of combination therapies. In this review, we describe the recent advancements and latest achievements in the use of nanocarriers, virus and cell-derived nanoparticles for targeted therapy of brain tumors. We provide successful examples of nanomedicine based approaches for direct targeting of receptors expressed in brain tumor cells or modulation of pathways involved in cell survival as well as approaches for indirect targeting of cells in the tumor stroma and immunotherapies. Although the field is at its infancy, clinical trials involving nanomedicine based approaches for brain tumors are ongoing and many others will start in the near future.

Chronic, intermittent convection-enhanced delivery devices.

BACKGROUND: Intraparenchymal convection-enhanced delivery (CED) of therapeutics directly into the brain has long been endorsed as a medium through which meaningful concentrations of drug can be administered to patients, bypassing the blood brain barrier. The translation of the technology to clinic has been hindered by poor distribution not previously observed in smaller pre-clinical models. In part this was due to the larger volumes of target structures found in humans but principally the poor outcome was linked to reflux (backflow) of infusate proximally along the catheter track. Over the past 10 years, improvements have been made to the technology in the field which has led to a small number of commercially available devices containing reflux inhibiting features. NEW METHOD: While these devices are currently suitable for acute or short term use, several indications would benefit from longer term repeated, intermittent administration of therapeutics (Parkinson's, Alzheimer's, Amyotrophic lateral sclerosis, Brain tumours such as Glioblastoma Multiforme (GBM) and Diffuse intrinsic Pontine Glioma (DIPG), etc.). RESULTS: Despite the need for a chronically accessible platform for such indications, limited experience exists in this part of the field. COMPARISON WITH EXISTING METHOD(S): At the time of writing no commercially available clinical platform, indicated for chronic, intermittent or continuous delivery to the brain exists. CONCLUSIONS: Here we review the improvements that have been made to CED devices over recent years and current state of the art for chronic infusion systems.

Distribution of polymer nanoparticles by convection-enhanced delivery to brain tumors.

Glioblastoma multiforme (GBM) is a fatal brain tumor characterized by infiltration beyond the margins of the main tumor mass and local recurrence after surgery. The blood-brain barrier (BBB) poses the most significant hurdle to brain tumor treatment. Convection-enhanced delivery (CED) allows for local administration of agents, overcoming the restrictions of the BBB. Recently, polymer nanoparticles have been demonstrated to penetrate readily through the healthy brain when delivered by CED, and size has been shown to be a critical factor for nanoparticle penetration. Because these brain-penetrating nanoparticles (BPNPs) have high potential for treatment of intracranial tumors since they offer the potential for cell targeting and controlled drug release after administration, here we investigated the intratumoral CED infusions of PLGA BPNPs in animals bearing either U87 or RG2 intracranial tumors. We demonstrate that the overall volume of distribution of these BPNPs was similar to that observed in healthy brains; however, the presence of tumors resulted in asymmetric and heterogeneous distribution patterns, with substantial leakage into the peritumoral tissue. Together, our results suggest that CED of BPNPs should be optimized by accounting for tumor geometry, in terms of location, size and presence of necrotic regions, to determine the ideal infusion site and parameters for individual tumors.

Convection-enhanced delivery for the treatment of glioblastoma.

Effective treatment of glioblastoma (GBM) remains a formidable challenge. Survival rates remain poor despite decades of clinical trials of conventional and novel, biologically targeted therapeutics. There is considerable evidence that most of these therapeutics do not reach their targets in the brain when administered via conventional routes (intravenous or oral). Hence, direct delivery of therapeutics to the brain and to brain tumors is an active area of investigation. One of these techniques, convection-enhanced delivery (CED), involves the implantation of catheters through which conventional and novel therapeutic formulations can be delivered using continuous, low-positive-pressure bulk flow. Investigation in preclinical and clinical settings has demonstrated that CED can produce effective delivery of therapeutics to substantial volumes of brain and brain tumor. However, limitations in catheter technology and imaging of delivery have prevented this technique from being reliable and reproducible, and the only completed phase III study in GBM did not show a survival benefit for patients treated with an investigational therapeutic delivered via CED. Further development of CED is ongoing, with novel catheter designs and imaging approaches that may allow CED to become a more effective therapeutic delivery technique.

Targeted therapy of glioblastoma stem-like cells and tumor non-stem cells using cetuximab-conjugated iron-oxide nanoparticles.

Malignant gliomas remain aggressive and lethal primary brain tumors in adults. The epidermal growth factor receptor (EGFR) is frequently overexpressed in the most common malignant glioma, glioblastoma (GBM), and represents an important therapeutic target. GBM stem-like cells (GSCs) present in tumors are felt to be highly tumorigenic and responsible for tumor recurrence. Multifunctional magnetic iron-oxide nanoparticles (IONPs) can be directly imaged by magnetic resonance imaging (MRI) and designed to therapeutically target cancer cells. The targeting effects of IONPs conjugated to the EGFR inhibitor, cetuximab (cetuximab-IONPs), were determined with EGFR- and EGFRvIII-expressing human GBM neurospheres and GSCs. Transmission electron microscopy revealed cetuximab-IONP GBM cell binding and internalization. Fluorescence microscopy and Prussian blue staining showed increased uptake of cetuximab-IONPs by EGFR- as well as EGFRvIII-expressing GSCs and neurospheres in comparison to cetuximab or free IONPs. Treatment with cetuximab-IONPs resulted in a significant antitumor effect that was greater than with cetuximab alone due to more efficient, CD133-independent cellular targeting and uptake, EGFR signaling alterations, EGFR internalization, and apoptosis induction in EGFR-expressing GSCs and neurospheres. A significant increase in survival was found after cetuximab-IONP convection-enhanced delivery treatment of 3 intracranial rodent GBM models employing human EGFR-expressing GBM xenografts.

Multifunctional receptor-targeted nanocomplexes for the delivery of therapeutic nucleic acids to the brain.

Convection enhanced delivery (CED) is a method of direct injection to the brain that can achieve widespread dispersal of therapeutics, including gene therapies, from a single dose. Non-viral, nanocomplexes are of interest as vectors for gene therapy in the brain, but it is essential that administration should achieve maximal dispersal to minimise the number of injections required. We hypothesised that anionic nanocomplexes administered by CED should disperse more widely in rat brains than cationics of similar size, which bind electrostatically to cell-surface anionic moieties such as proteoglycans, limiting their spread. Anionic, receptor-targeted nanocomplexes (RTN) containing a neurotensin-targeting peptide were prepared with plasmid DNA and compared with cationic RTNs for dispersal and transfection efficiency. Both RTNs were labelled with gadolinium for localisation in the brain by MRI and in brain sections by LA-ICP-MS, as well as with rhodamine fluorophore for detection by fluorescence microscopy. MRI distribution studies confirmed that the anionic RTNs dispersed more widely than cationic RTNs, particularly in the corpus callosum. Gene expression levels from anionic formulations were similar to those of cationic RTNs. Thus, anionic RTN formulations can achieve both widespread dispersal and effective gene expression in brains after administration of a single dose by CED.

Convection Enhanced Delivery: A Comparison of infusion characteristics in ex vivo and in vivo non-human primate brain tissue.

BACKGROUND: Convection enhanced delivery (CED) is emerging as a promising infusion toolto facilitate delivery of therapeutic agents into the brain via mechanically controlled pumps. Infusion protocols and catheter design have an important impact on delivery. CED is a valid alternative for systemic administration of agents in clinical trials for cell and gene therapies. Where gel and ex vivo models are not sufficient in modeling the disease, in vivo models allow researchers to better understand the underlying mechanisms of neuron degeneration, which is helpful in finding novel approaches to control the process or reverse the progression. Determining the risks, benefits, and efficacy of new gene therapies introduced via CED will pave a way to enter human clinical trial. PURPOSE: The objective of this study is to compare volume distribution (Vd)/ volume infused (Vi) ratios and backflow measurements following CED infusions in ex vivo versus in vivo non-human primate brain tissue, based on infusion protocols developed in vitro. METHODS: In ex vivo infusions, the first brain received 2 infusions using a balloon catheter at rates of 1 µL/min and 2 µL/min for 30 minutes. The second and third brains received infusions using a valve-tip (VT) catheter at 1 µL/min for 30 minutes. The fourth brain received a total of 45 µL infused at a rate of 1 µL/min for 15 minutes followed by 2 µL/min for 15 minutes. Imaging was performed (SPGR FA34) every 3 minutes. In the in vivo group, 4 subjects received a total of 8 infusions of 50 µL. Subjects 1 and 2 received infusions at 1.0 µL/min using a VT catheter in the left hemisphere and a smart-flow (SF) catheter in the right hemisphere. Subjects 3 and 4 each received 1 infusion in the left and right hemisphere at 1.0 µL/min. RESULTS: MRI calculations of Vd/Vi did not significantly differ from those obtained on post-mortem pathology. The mean measured Vd/Vi of in vivo (5.23 + /-1.67) compared to ex vivo (2.17 + /-1.39) demonstrated a significantly larger Vd/Vi for in vivo by 2.4 times (p = 0.0017). CONCLUSION: We detected higher ratios in the in vivo subjects than in ex vivo. This difference could be explained by the extra cellular space volume fraction. Studies evaluating backflow and morphology use in vivo tissue as a medium are recommended. Further investigation is warranted to evaluate the role blood pressure and heart rate may play in human CED clinical trials.