The effect of AZD2171- or sTRAIL/Apo2L-loaded polylactic-co-glycolic acid microspheres on a subcutaneous glioblastoma model

New Drug Delivery Systems Developed for Brain Targeting

The blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (B_CSF) are two of the most complex and sophisticated concierges that defend the central nervous system (CNS) by numerous mechanisms. While they maintain the neuro-ecological homeostasis through the regulated entry of essential biomolecules, their conservative nature challenges the entry of most of the drugs intended for CNS delivery. Targeted delivery challenges for a diverse spectrum of therapeutic agents/drugs (non-small molecules, small molecules, gene-based therapeutics, protein and peptides, antibodies) are diverse and demand specialized delivery and disease-targeting strategies. This review aims to capture the trends that have shaped the current brain targeting research scenario. This review discusses the physiological, neuropharmacological, and etiological factors that participate in the transportation of various drug delivery cargoes across the BBB/B_CSF and influence their therapeutic intracranial concentrations. Recent research works spanning various invasive, minimally invasive, and non-invasive brain- targeting approaches are discussed. While the pre-clinical outcomes from many of these approaches seem promising, further research is warranted to overcome the translational glitches that prevent their clinical use. Non-invasive approaches like intranasal administration, P-glycoprotein (P-gp) inhibition, pro-drugs, and carrier/targeted nanocarrier-aided delivery systems (alone or often in combination) hold positive clinical prospects for brain targeting if explored further in the right direction.

Recent developments in drug delivery strategies for targeting DNA damage response in glioblastoma

Glioblastoma is the most frequent and malignant brain tumor. The median survival for this disease is approximately 15 months, and despite all the available treatment strategies employed, it remains an incurable disease. Preclinical and clinical research have shown that the resistance process related to DNA damage repair pathways, glioma stem cells, blood-brain barrier selectivity, and dose-limiting toxicity of systemic treatment leads to poor clinical outcomes. In this context, the advent of drug delivery systems associated with localized treatment seems to be a promising and versatile alternative to overcome the failure of the current treatment approaches. In order to bypass therapeutic tumor resistance mechanisms, more effective combinatorial therapies should be identified, such as the use of cytotoxic drugs combined with the inhibition of DNA damage response (DDR)-related targets. Additionally, critical reasoning about the delivery approach and administration route in brain tumors treatment innovation is essential. The outcomes of future experimental studies regarding the association of delivery systems, alternative treatment routes, and DDR targets are expected to lead to the development of refined therapeutic interventions. Novel therapeutic approaches could improve the life's quality of glioblastoma patients and increase their survival rate.

Therapeutic strtegies of glioblastoma (GBM): The current advances in the molecular targets and bioactive small molecule compounds

Glioblastoma (GBM) is the most common aggressive malignant tumor in brain neuroepithelial tumors and remains incurable. A variety of treatment options are currently being explored to improve patient survival, including small molecule inhibitors, viral therapies, cancer vaccines, and monoclonal antibodies. Among them, the unique advantages of small molecule inhibitors have made them a focus of attention in the drug discovery of glioblastoma. Currently, the most used chemotherapeutic agents are small molecule inhibitors that target key dysregulated signaling pathways in glioblastoma, including receptor tyrosine kinase, PI3K/AKT/mTOR pathway, DNA damage response, TP53 and cell cycle inhibitors. This review analyzes the therapeutic benefit and clinical development of novel small molecule inhibitors discovered as promising anti-glioblastoma agents by the related targets of these major pathways. Meanwhile, the recent advances in temozolomide resistance and drug combination are also reviewed. In the last part, due to the constant clinical failure of targeted therapies, this paper reviewed the research progress of other therapeutic methods for glioblastoma, to provide patients and readers with a more comprehensive understanding of the treatment landscape of glioblastoma.

Pretreating Mesenchymal Stem Cells with Cancer Conditioned-Media or Proinflammatory Cytokines Changes the Tumor and Immune Targeting by Nanoghosts Derived from these Cells

Nanoghosts (NGs) are nanovesicles reconstructed from the cytoplasmic membranes of mesenchymal stem cells (MSCs). By retaining MSC membranes, the NGs retain the ability of these cells to home in on multiple tumors, laying the foundations, thereby, for the development of a targeted drug delivery platform. The susceptibility of MSCs to functional changes, following their exposure to cytokines or cancer-derived conditioned-media (CM), presents the opportunity to modify the NGs by conditioning their source cells. This opportunity is investigated by comparing the membrane protein composition and the tumor uptake of NGs derived from naïve MSCs (N-NG) against conditioned NGs made from MSCs pre-treated with conditioned-media (CM-NG) or with a mix of the proinflammatory cytokines TNF-α and IL-1β (Cyto-NG). CM-NGs are found to be more targeted towards immune cells than Cyto- or N-NGs, while Cyto-NGs are the most tumor-targeted ones, with similar immune-targeting capacity as N-NGs but with a higher affinity towards endothelial cells. Proteomic variations were wider in the CM-NGs, with exceptionally higher levels of ICAM-1 compared to N- and Cyto-NGs. From a translational point of view, the data show that the tumor-targeting ability of the NGs, and possibly that of other MSC-derived extracellular vesicles, can be enhanced by simple conditioning of their source cells.

Crossing the Blood-Brain Barrier: Recent Advances in Drug Delivery to the Brain

CNS disorders are on the rise despite advancements in our understanding of their pathophysiological mechanisms. A major hurdle to the treatment of these disorders is the blood-brain barrier (BBB), which serves as an arduous janitor to protect the brain. Many drugs are being discovered for CNS disorders, which, however fail to enter the market because of their inability to cross the BBB. This is a pronounced challenge for the pharmaceutical fraternity. Hence, in addition to the discovery of novel entities and drug candidates, scientists are also developing new formulations of existing drugs for brain targeting. Several approaches have been investigated to allow therapeutics to cross the BBB. As the molecular structure of the BBB is better elucidated, several key approaches for brain targeting include physiological transport mechanisms such as adsorptive-mediated transcytosis, inhibition of active efflux pumps, receptor-mediated transport, cell-mediated endocytosis, and the use of peptide vectors. Drug-delivery approaches comprise delivery from microspheres, biodegradable wafers, and colloidal drug-carrier systems (e.g., liposomes, nanoparticles, nanogels, dendrimers, micelles, nanoemulsions, polymersomes, exosomes, and quantum dots). The current review discusses the latest advancements in these approaches, with a major focus on articles published in 2015 and 2016. In addition, we also cover the alternative delivery routes, such as intranasal and convection-enhanced diffusion methods, and disruption of the BBB for brain targeting.

PLGA-Listeriolysin O microspheres: Opening the gate for cytosolic delivery of cancer antigens

Strategies for cancer protein vaccination largely aim to activate the cellular arm of the immune system against cancer cells. This approach, however, is limited since protein vaccines mostly activate the system's humoral arm instead. One way to overcome this problem is to enhance the cross-presentation of such proteins by antigen-presenting cells, which may consequently lead to intense cellular response. Here we examined the ability of listeriolysin O (LLO) incorporated into poly-lactic-co-glycolic acid (PLGA) microspheres to modify the cytosolic delivery of low molecular weight peptides and enhance their cross-presentation. PLGA microspheres were produced in a size suitable for uptake by phagocytic cells. The peptide encapsulation and release kinetics were improved by adding NaCl to the preparation. PLGA microspheres loaded with the antigenic peptide and incorporated with LLO were readily up-taken by phagocytic cells, which exhibited an increase in the expression of peptide-MHC-CI complexes on the cell surface. Furthermore, this system enhanced the activation of a specific T hybridoma cell line, thus simulating cytotoxic T cells. These results establish, for the first time, a proof of concept for the use of PLGA microspheres incorporated with a pore-forming agent and the antigen peptide of choice as a unique cancer protein vaccination delivery platform.