Molecular architecture determines brain delivery of a transferrin-receptor targeted lysosomal enzyme (original) (raw)
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Journal of Controlled Release, 2016
An unmet need exists for therapeutic compounds to traverse the brain capillary endothelial cells that denote the blood-brain barrier (BBB) to deliver effective treatment to the diseased brain. The use of nanoparticle technology for targeted delivery to the brain implies that targeted liposomes encapsulating a drug of interest will undergo receptor-mediated uptake and transport through the BBB with a subsequent unfolding of the liposomal content inside the brain, hence revealing drug release to adjacent drug-demanding neurons. As transferrin receptors (TfRs) are present on brain capillary endothelial, but not on endothelial cells elsewhere in the body, the use of TfR-targeted liposomescolloidal particulates with a phospholipid bilayer membraneremains the most relevant strategy to obtain efficient drug delivery to the brain. However, many studies have failed to provide sufficient quantitative data to proof passage of the BBB and significant appearance of drugs inside the brain parenchyma. Here, we critically evaluate the current evidence on the use of TfR-targeted liposomes for brain drug delivery based on a thorough investigation of all available studies within this research field. We focus on issues with respect to experimental design and data analysis that may provide an explanation to conflicting reports, and we discuss possible explanations for the current lack of sufficient transcytosis across the BBB for implementation in the design of TfR-targeted liposomes. We finally provide a list of suggestions for strategies to obtain substantial uptake and transport of drug carriers at the BBB with a concomitant transport of therapeutics into the brain.
2018
The highly specialised brain capillary endothelial cells (BCEC) that constitute the blood brain barrier (BBB) exhibit high resilience to the penetration of xenobiotic and biologic therapeutics, making drug delivery to the central nervous system (CNS) a challenging feat. Endogenous BCEC receptors such as transferrin receptor (TfR) have been proposed as exploitable targets for therapeutic payload transport into the CNS, and have been successfully targeted using monoclonal antibodies to deliver therapeutic molecules into the brains of rodents and non-human primates via receptor mediated transcytosis (RMT). <br><br> The overall aim of this study was to develop a BCEC drug delivery system using alternative domains to antibodies e.g. peptides and ssDNA aptamers, as a means of exploiting endogenous receptor transport mechanisms to deliver macromolecular drugs into the CNS via RMT. <br><br> The expression of three receptor candidates, TfR, low-density lipoprotein rec...
Scientific reports, 2017
Drug delivery to the brain is hampered by the presence of the blood-brain barrier, which excludes most molecules from freely diffusing into the brain, and tightly regulates the active transport mechanisms that ensure sufficient delivery of nutrients to the brain parenchyma. Harnessing the possibility of delivering neuroactive drugs by way of receptors already present on the brain endothelium has been of interest for many years. The transferrin receptor is of special interest since its expression is limited to the endothelium of the brain as opposed to peripheral endothelium. Here, we investigate the possibility of delivering immunoliposomes and their encapsulated cargo to the brain via targeting of the transferrin receptor. We find that transferrin receptor-targeting increases the association between the immunoliposomes and primary endothelial cells in vitro, but that this does not correlate with increased cargo transcytosis. Furthermore, we show that the transferrin receptor-target...
In-vitro characterisation of targeting ligands for enhanced delivery across the blood-brain barrier
2018
The blood-brain barrier (BBB) is the most extensive and restrictive barrier to brain delivery for therapeutic agents. A low proportion of low molecular-weight agents can cross into the CNS. This decreases further as the molecular weight increases, meaning therapeutic antibodies, oligonucleotides and other supramolecular entities effectively cannot reach therapeutic levels within the CNS. Targeting ligands against receptors thought to undergo transcytosis across the brain microvascular endothelial cells (BMECs), can boost CNS delivery of therapeutics. Understanding these mechanisms, in an in-vitro setting, has proved challenging, due to the constraints of cell culture systems and the difficulty to replicate the in-vivo environment. With even the most extensively studied targeting receptor, transferrin receptor, not producing clear evidence to suggest the occurrence of transcytosis. To understand in-vitro trafficking of brain targeting ligands a pulse-chase assay, in combination with ...
Engineering Antibody and Protein Therapeutics to Cross the Blood–Brain Barrier
Antibody Therapeutics
Diseases in the central nervous system (CNS) are often difficult to treat. Antibody and protein-based therapeutics hold huge promises in CNS disease treatment. However, proteins are restricted from entering the CNS by the blood–brain barrier (BBB). To achieve enhanced BBB crossing, antibody-based carriers have been developed by utilizing the endogenous macromolecule transportation pathway known as receptor-mediated transcytosis (RMT). In this report, we first provided an overall review on key CNS diseases and the most promising antibody or protein-based therapeutics approved or in clinical trials. The CNS diseases covered include glioblastoma (GBM), Alzheimer’s disease (AD), Parkinson’s disease (PD), and Lysosomal storage diseases (LSDs). We then reviewed the platforms that are being explored to increase macromolecule brain entry to combat CNS diseases. Highlights include targeting the transferrin receptor (TfR) and insulin receptor (InsR) for enhancing macromolecule therapeutics br...
EMBO Molecular Medicine, 2013
Mucopolysaccharidoses type IIIA (MPS-IIIA) is a neurodegenerative lysosomal storage disorder (LSD) caused by inherited defects of the sulphamidase gene. Here, we used a systemic gene transfer approach to demonstrate the therapeutic efficacy of a chimeric sulphamidase, which was engineered by adding the signal peptide (sp) from the highly secreted iduronate-2-sulphatase (IDS) and the bloodbrain barrier (BBB)-binding domain (BD) from the Apolipoprotein B (ApoB-BD). A single intravascular administration of AAV2/8 carrying the modified sulphamidase was performed in adult MPS-IIIA mice in order to target the liver and convert it to a factory organ for sustained systemic release of the modified sulphamidase. We showed that while the IDS sp replacement results in increased enzyme secretion, the addition of the ApoB-BD allows efficient BBB transcytosis and restoration of sulphamidase activity in the brain of treated mice. This, in turn, resulted in an overall improvement of brain pathology and recovery of a normal behavioural phenotype. Our results provide a novel feasible strategy to develop minimally invasive therapies for the treatment of brain pathology in MPS-IIIA and other neurodegenerative LSDs.
Blood-Brain Barrier Transport of Transferrin-Receptor Targeted Nanoparticles
The blood-brain barrier (BBB), built by brain endothelial cells (BECs), is impermeable to biologics. Liposomes and other nanoparticles are good candidates for delivery of biologics across the BECs, as they can encapsulate numerous molecules of interest in an omnipotent manner. The liposomes need attachment of a targeting molecule, as BECs unfortunately are virtually incapable of uptake of non-targeted liposomes from the circulation. Experiments of independent research groups have qualified antibodies targeting the transferrin receptor as superior for targeted delivery of nanoparticles to BECs. Functionalization of nanoparticles via conjugation with anti-transferrin receptor antibodies leads to nanoparticle uptake by endothelial cells of both brain capillaries and post-capillary venules. Reducing the density of transferrin receptor-targeted antibodies conjugated to liposomes limits uptake in BECs. Opposing the transport of nanoparticles conjugated to high-affine anti-transferrin rece...
Neuron, 2014
Although biotherapeutics have vast potential for treating brain disorders, their use has been limited due to low exposure across the blood-brain barrier (BBB). We report that by manipulating the binding mode of an antibody fragment to the transferrin receptor (TfR), we have developed a Brain Shuttle module, which can be engineered into a standard therapeutic antibody for successful BBB transcytosis. Brain Shuttle version of an anti-Ab antibody, which uses a monovalent binding mode to the TfR, increases b-Amyloid target engagement in a mouse model of Alzheimer's disease by 55-fold compared to the parent antibody. We provide in vitro and in vivo evidence that the monovalent binding mode facilitates transcellular transport, whereas a bivalent binding mode leads to lysosome sorting. Enhanced target engagement of the Brain Shuttle module translates into a significant improvement in amyloid reduction. These findings have major implications for the development of biologics-based treatment of brain disorders.