Developing therapeutic antibodies for neurodegenerative disease

Modeling Pharmacokinetics and Pharmacodynamics of Therapeutic Antibodies: Progress, Challenges, and Future Directions

With more than 90 approved drugs by 2020, therapeutic antibodies have played a central role in shifting the treatment landscape of many diseases, including autoimmune disorders and cancers. While showing many therapeutic advantages such as long half-life and highly selective actions, therapeutic antibodies still face many outstanding issues associated with their pharmacokinetics (PK) and pharmacodynamics (PD), including high variabilities, low tissue distributions, poorly-defined PK/PD characteristics for novel antibody formats, and high rates of treatment resistance. We have witnessed many successful cases applying PK/PD modeling to answer critical questions in therapeutic antibodies’ development and regulations. These models have yielded substantial insights into antibody PK/PD properties. This review summarized the progress, challenges, and future directions in modeling antibody PK/PD and highlighted the potential of applying mechanistic models addressing the development questions.

Integrin-directed antibody-based immunotherapy: focus on VLA-4

One major finding of chronic inflammatory diseases of various origins is the establishment of inflammatory infiltrates, bearing different leukocyte subpopulations, including activated T lymphocytes. Integrins are among the large series of molecular interactions that have been implicated as players in both triggering and maintenance of leukocyte influx from the blood into a given organ parenchyme. Accordingly, blocking the interaction between VLA-6 integrin and laminin, experimentally abrogates heart graft rejection. Many reports have shown that VLA-4 is used by T cells to cross endothelial barriers, as well as to migrate within target tissues. In this respect, a humanized IgG4 anti-VLA-4 monoclonal antibody (specific to the α4-integrin chain of VLA-4) has been successfully applied to treat multiple sclerosis as well as inflammatory bowel disease. Anti-VLA-4 monoclonal antibody has also been applied to block transendothelial passage in other autoimmune diseases, such as rheumatoid arthritis. On this same vein is the action of such a reagent in impairing in vitro transendothial and fibronectin-driven migration of CD4⁺ and CD8⁺ T cells expressing high densities of VLA-4 from Duchenne muscular dystrophy patients, thus potentially enlarging the use of this strategy to other diseases. Yet, in a small number of patients, the use of Natalizumab has been correlated with the progressive multifocal leukoencephalopathy, a serious brain infection caused by the John Cunningham virus. This issue restricted the use of the reagent. In this respect, the development of smaller and more specific antibody reagents should be envisioned as a next-generation promising strategy.

APOE: The New Frontier in the Development of a Therapeutic Target towards Precision Medicine in Late-Onset Alzheimer's

Alzheimer's disease (AD) has a critical unmet medical need. The consensus around the amyloid cascade hypothesis has been guiding pre-clinical and clinical research to focus mainly on targeting beta-amyloid for treating AD. Nevertheless, the vast majority of the clinical trials have repeatedly failed, prompting the urgent need to refocus on other targets and shifting the paradigm of AD drug development towards precision medicine. One such emerging target is apolipoprotein E (APOE), identified nearly 30 years ago as one of the strongest and most reproduceable genetic risk factor for late-onset Alzheimer's disease (LOAD). An exploration of APOE as a new therapeutic culprit has produced some very encouraging results, proving that the protein holds promise in the context of LOAD therapies. Here, we review the strategies to target APOE based on state-of-the-art technologies such as antisense oligonucleotides, monoclonal antibodies, and gene/base editing. We discuss the potential of these initiatives in advancing the development of novel precision medicine therapies to LOAD.

Phase 1 trial of olaratumab monotherapy and in combination with chemotherapy in pediatric patients with relapsed/refractory solid and central nervous system tumors

Olaratumab is a monoclonal antibody that specifically binds to platelet-derived growth factor receptor alpha (PDGFRα) and blocks receptor activation. We conducted a phase 1 trial to evaluate the safety of olaratumab and determine a recommended dose in combination with three different chemotherapy regimens in children. Patients <18 years with relapsed/refractory solid or central nervous system tumors were enrolled to two dose levels of olaratumab. Patients received olaratumab monotherapy at 15 mg/kg (Part A) or 20 mg/kg (Part B) on Days 1 and 8 of the first 21-day cycle, followed by olaratumab combined with standard fixed doses of chemotherapy with doxorubicin, vincristine/irinotecan, or high-dose ifosfamide by investigator choice for subsequent 21-day cycles. In Part C, patients received olaratumab 20 mg/kg plus assigned chemotherapy for all cycles. Parts A-C enrolled 68 patients across three chemotherapy treatment arms; olaratumab in combination with doxorubicin (N = 16), vincristine/irinotecan (N = 26), or ifosfamide (N = 26). Three dose-limiting toxicities (DLTs) occurred during olaratumab monotherapy (at 15 mg/kg, grade [G] 4 alanine aminotransferase [ALT]; at 20 mg/kg, G3 lung infection and G3 gamma-glutamyl transferase). One DLT occurred during vincristine/irinotecan with olaratumab 20 mg/kg therapy (G3 ALT). Treatment-emergent adverse events ≥G3 in >25% of patients included neutropenia, anemia, leukopenia, lymphopenia, and thrombocytopenia. Pharmacokinetic profiles of olaratumab with chemotherapy were within the projected range based on adult data. There was one complete response (rhabdomyosarcoma [Part B vincristine/irinotecan arm]) and three partial responses (two rhabdomyosarcoma [Part A doxorubicin arm and Part C doxorubicin arm]; one pineoblastoma [Part B vincristine/irinotecan arm]). Olaratumab was tolerable and safely administered in combination with chemotherapy regimens commonly used in children and adolescents.

Nonclinical safety evaluation, pharmacokinetics, and target engagement of Lu AF82422, a monoclonal IgG1 antibody against alpha-synuclein in development for treatment of synucleinopathies

Alpha-synuclein is a 15 kDa protein associated with neurodegenerative diseases such as Parkinson disease and multiple-system atrophy where pathological forms of alpha-synuclein aggregate and become neurotoxic. Here we describe the nonclinical program to support a first-in-human (FIH) single ascending dose (SAD) study for Lu AF82422, a human recombinant, anti-alpha-synuclein monoclonal antibody (mAb) in development for treatment of synucleinopathies. Alpha-synuclein is primarily expressed in brain, peripheral nerves and in blood cells. A tissue cross-reactivity assessment showed that Lu AF82422 binding was generally restricted to nervous tissues. Flow cytometry analysis did not show extracellular surface binding of Lu AF82422 to human platelets, erythrocytes, granulocytes, or lymphocytes, but to a low fraction of monocytes, without any functional consequences on activation or phagocytic capacity. A single dose pharmacokinetic (PK) study in cynomolgus monkeys with dose levels of 1-30 mg/kg confirmed PK properties in the expected range for a mAb with a soluble target, and target engagement was shown as a decrease in free alpha-synuclein in plasma. Four-week repeat-dose toxicity studies were conducted in rats and cynomolgus monkeys at doses up to 600 mg/kg administered intravenously every 10 days. Results showed no treatment-related adverse findings and the no-observed-adverse-effect-level was the highest dose tested. Target engagement was shown in plasma and cerebrospinal fluid. Taken together, the nonclinical data indicated no safety signal of concern and provided adequate safety margins between observed safe doses in animals and the planned dose levels in the FIH SAD study.

Nanodelivery Systems Targeting Epidermal Growth Factor Receptors for Glioma Management

A paradigm shift in treating the most aggressive and malignant form of glioma is continuously evolving; however, these strategies do not provide a better life and survival index. Currently, neurosurgical debulking, radiotherapy, and chemotherapy are the treatment options available for glioma, but these are non-specific in action. Patients invariably develop resistance to these therapies, leading to recurrence and death. Receptor Tyrosine Kinases (RTKs) are among the most common cell surface proteins in glioma and play a significant role in malignant progression; thus, these are currently being explored as therapeutic targets. RTKs belong to the family of cell surface receptors that are activated by ligands which in turn activates two major downstream signaling pathways via Rapidly Accelerating Sarcoma/mitogen activated protein kinase/extracellular-signal-regulated kinase (Ras/MAPK/ERK) and phosphatidylinositol 3-kinase/a serine/threonine protein kinase/mammalian target of rapamycin (PI3K/AKT/mTOR). These pathways are critically involved in regulating cell proliferation, invasion, metabolism, autophagy, and apoptosis. Dysregulation in these pathways results in uncontrolled glioma cell proliferation, invasion, angiogenesis, and cancer progression. Thus, RTK pathways are considered a potential target in glioma management. This review summarizes the possible risk factors involved in the growth of glioblastoma (GBM). The role of RTKs inhibitors (TKIs) and the intracellular signaling pathways involved, small molecules under clinical trials, and the updates were discussed. We have also compiled information on the outcomes from the various endothelial growth factor receptor (EGFR)-TKIs-based nanoformulations from the preclinical and clinical points of view. Aided by an extensive literature search, we propose the challenges and potential opportunities for future research on EGFR-TKIs-based nanodelivery systems.

Tauopathies: Deciphering Disease Mechanisms to Develop Effective Therapies

Tauopathies are neurodegenerative diseases characterized by the pathological accumulation of microtubule-associated protein tau (MAPT) in the form of neurofibrillary tangles and paired helical filaments in neurons and glia, leading to brain cell death. These diseases include frontotemporal dementia (FTD) and Alzheimer's disease (AD) and can be sporadic or inherited when caused by mutations in the MAPT gene. Despite an incredibly high socio-economic burden worldwide, there are still no effective disease-modifying therapies, and few tau-focused experimental drugs have reached clinical trials. One major hindrance for therapeutic development is the knowledge gap in molecular mechanisms of tau-mediated neuronal toxicity and death. For the promise of precision medicine for brain disorders to be fulfilled, it is necessary to integrate known genetic causes of disease, i.e., MAPT mutations, with an understanding of the dysregulated molecular pathways that constitute potential therapeutic targets. Here, the growing understanding of known and proposed mechanisms of disease etiology will be reviewed, together with promising experimental tau-directed therapeutics, such as recently developed tau degraders. Current challenges faced by the fields of tau research and drug discovery will also be addressed.

The blood-brain barrier in health and disease: Important unanswered questions

The blood vessels vascularizing the central nervous system exhibit a series of distinct properties that tightly control the movement of ions, molecules, and cells between the blood and the parenchyma. This "blood-brain barrier" is initiated during angiogenesis via signals from the surrounding neural environment, and its integrity remains vital for homeostasis and neural protection throughout life. Blood-brain barrier dysfunction contributes to pathology in a range of neurological conditions including multiple sclerosis, stroke, and epilepsy, and has also been implicated in neurodegenerative diseases such as Alzheimer's disease. This review will discuss current knowledge and key unanswered questions regarding the blood-brain barrier in health and disease.

Immune Escape in Glioblastoma Multiforme and the Adaptation of Immunotherapies for Treatment

Glioblastoma multiforme (GBM) is the most frequently occurring primary brain tumor and has a very poor prognosis, with only around 5% of patients surviving for a period of 5 years or more after diagnosis. Despite aggressive multimodal therapy, consisting mostly of a combination of surgery, radiotherapy, and temozolomide chemotherapy, tumors nearly always recur close to the site of resection. For the past 15 years, very little progress has been made with regards to improving patient survival. Although immunotherapy represents an attractive therapy modality due to the promising pre-clinical results observed, many of these potential immunotherapeutic approaches fail during clinical trials, and to date no immunotherapeutic treatments for GBM have been approved. As for many other difficult to treat cancers, GBM combines a lack of immunogenicity with few mutations and a highly immunosuppressive tumor microenvironment (TME). Unfortunately, both tumor and immune cells have been shown to contribute towards this immunosuppressive phenotype. In addition, current therapeutics also exacerbate this immunosuppression which might explain the failure of immunotherapy-based clinical trials in the GBM setting. Understanding how these mechanisms interact with one another, as well as how one can increase the anti-tumor immune response by addressing local immunosuppression will lead to better clinical results for immune-based therapeutics. Improving therapeutic delivery across the blood brain barrier also presents a challenge for immunotherapy and future therapies will need to consider this. This review highlights the immunosuppressive mechanisms employed by GBM cancers and examines potential immunotherapeutic treatments that can overcome these significant immunosuppressive hurdles.

Antisense Oligonucleotide Therapies for Neurodegenerative Diseases

Antisense oligonucleotides represent a novel therapeutic platform for the discovery of medicines that have the potential to treat most neurodegenerative diseases. Antisense drugs are currently in development for the treatment of amyotrophic lateral sclerosis, Huntington's disease, and Alzheimer's disease, and multiple research programs are underway for additional neurodegenerative diseases. One antisense drug, nusinersen, has been approved for the treatment of spinal muscular atrophy. Importantly, nusinersen improves disease symptoms when administered to symptomatic patients rather than just slowing the progression of the disease. In addition to the benefit to spinal muscular atrophy patients, there are discoveries from nusinersen that can be applied to other neurological diseases, including method of delivery, doses, tolerability of intrathecally delivered antisense drugs, and the biodistribution of intrathecal dosed antisense drugs. Based in part on the early success of nusinersen, antisense drugs hold great promise as a therapeutic platform for the treatment of neurological diseases.

Real-world effectiveness and tolerability of erenumab: A retrospective cohort study

BACKGROUND

We aimed to systematically assess the effectiveness and tolerability of erenumab in a clinical setting, specifically a tertiary headache center.

METHODS

This was a retrospective cohort study at the John Graham Headache Center of Brigham and Women's Hospital. All patients who received erenumab from a headache specialist at the Center from 17 May 2018 to 31 January 2019 were included. Patients were contacted and underwent a structured clinical interview including information about erenumab use, perceived benefit, adverse events (AEs), and a global assessment of benefit versus drawbacks. Chart review was performed for patients who could not be contacted.

RESULTS

Four hundred and forty-four patients were initially identified and 418 were eligible. Two hundred and ninety-five participants completed the structured clinical interview portion of the study (response rate 70.6%). Seventy-four patient charts were additionally reviewed. Two hundred and forty-one participants had used erenumab. One hundred and sixty nine (70%) of participants experienced at least one adverse event, with constipation (43%), injection site reaction (24%), fatigue (15%), worsening headache (12%), and dizziness (11%) the five most commonly reported AEs. One hundred and sixty-eight participants (69.7%) felt that the benefits of erenumab outweighed any drawbacks. One hundred and fifty-one participants (62.7%) planned to continue using erenumab. Cost of treatment was cited by 12% of participants as a reason for either not starting or for stopping erenumab. Of patients who had an increase in dose due to lack of or partial efficacy, 46.5% felt that the dose increase was helpful. We identified one case of unintended pregnancy in our study population.

CONCLUSIONS

This large "real-world" study validates the findings of benefit of erenumab observed in clinical trials. Although adverse events were far more common in this population than in clinical trials, the planned continuation rate was relatively high. The substantial discrepancy between adverse events seen in clinical practice compared with clinical trials suggests systematic differences between clinical trial participants and patients who receive the treatment in clinical practice, or may indicate suboptimal ascertainment of adverse events in the trials. Clinicians should continue to be vigilant for adverse events in clinical practice.

Physiological blood-brain transport is impaired with age by a shift in transcytosis

The vascular interface of the brain, known as the blood-brain barrier (BBB), is understood to maintain brain function in part via its low transcellular permeability^1-3. Yet, recent studies have demonstrated that brain ageing is sensitive to circulatory proteins^4,5. Thus, it is unclear whether permeability to individually injected exogenous tracers-as is standard in BBB studies-fully represents blood-to-brain transport. Here we label hundreds of proteins constituting the mouse blood plasma proteome, and upon their systemic administration, study the BBB with its physiological ligand. We find that plasma proteins readily permeate the healthy brain parenchyma, with transport maintained by BBB-specific transcriptional programmes. Unlike IgG antibody, plasma protein uptake diminishes in the aged brain, driven by an age-related shift in transport from ligand-specific receptor-mediated to non-specific caveolar transcytosis. This age-related shift occurs alongside a specific loss of pericyte coverage. Pharmacological inhibition of the age-upregulated phosphatase ALPL, a predicted negative regulator of transport, enhances brain uptake of therapeutically relevant transferrin, transferrin receptor antibody and plasma. These findings reveal the extent of physiological protein transcytosis to the healthy brain, a mechanism of widespread BBB dysfunction with age and a strategy for enhanced drug delivery.

Nanoparticle-Mediated Drug Delivery: Blood-Brain Barrier as the Main Obstacle to Treating Infectious Diseases in CNS

BACKGROUND

Parasitic infections affecting the central nervous system (CNS) present high morbidity and mortality rates and affect millions of people worldwide. The most important parasites affecting the CNS are protozoans (Plasmodium sp., Toxoplasma gondii, Trypanosoma brucei), cestodes (Taenia solium) and free-living amoebae (Acantamoeba spp., Balamuthia mandrillaris and Naegleria fowleri). Current therapeutic regimens include the use of traditional chemicals or natural compounds that have very limited access to the CNS, despite their elevated toxicity to the host. Improvements are needed in drug administration and formulations to treat these infections and to allow the drug to cross the blood-brain barrier (BBB).

METHODS

This work aims to elucidate the recent advancements in the use of nanoparticles as nanoscaled drug delivery systems (NDDS) for treating and controlling the parasitic infections that affect the CNS, addressing not only the nature and composition of the polymer chosen, but also the mechanisms by which these nanoparticles may cross the BBB and reach the infected tissue.

RESULTS

There is a strong evidence in the literature demonstrating the potential usefulness of polymeric nanoparticles as functional carriers of drugs to the CNS. Some of them demonstrated the mechanisms by which drugloaded nanoparticles access the CNS and control the infection by using in vivo models, while others only describe the pharmacological ability of these particles to be utilized in in vitro environments.

CONCLUSION

The scarcity of the studies trying to elucidate the compatibility as well as the exact mechanisms by which NDDS might be entering the CNS infected by parasites reveals new possibilities for further exploratory projects. There is an urgent need for new investments and motivations for applying nanotechnology to control parasitic infectious diseases worldwide.

An Affibody Molecule Is Actively Transported into the Cerebrospinal Fluid via Binding to the Transferrin Receptor

The use of biotherapeutics for the treatment of diseases of the central nervous system (CNS) is typically impeded by insufficient transport across the blood-brain barrier. Here, we investigate a strategy to potentially increase the uptake into the CNS of an affibody molecule (ZSYM73) via binding to the transferrin receptor (TfR). ZSYM73 binds monomeric amyloid beta, a peptide involved in Alzheimer's disease pathogenesis, with subnanomolar affinity. We generated a tri-specific fusion protein by genetically linking a single-chain variable fragment of the TfR-binding antibody 8D3 and an albumin-binding domain to the affibody molecule ZSYM73. Simultaneous tri-specific target engagement was confirmed in a biosensor experiment and the affinity for murine TfR was determined to 5 nM. Blockable binding to TfR on endothelial cells was demonstrated using flow cytometry and in a preclinical study we observed increased uptake of the tri-specific fusion protein into the cerebrospinal fluid 24 h after injection.

Antibody transcytosis across brain endothelial-like cells occurs nonspecifically and independent of FcRn

The blood-brain barrier (BBB) hinders the brain delivery of therapeutic immunoglobulin γ (IgG) antibodies. Evidence suggests that IgG-specific processing occurs within the endothelium of the BBB, but any influence on transcytosis remains unclear. Here, involvement of the neonatal Fc receptor (FcRn), which mediates IgG recycling and transcytosis in peripheral endothelium, was investigated by evaluating the transcytosis of IgGs with native or reduced FcRn engagement across human induced pluripotent stem cell-derived brain endothelial-like cells. Despite differential trafficking, the permeability of all tested IgGs were comparable and remained constant irrespective of concentration or competition with excess IgG, suggesting IgG transcytosis occurs nonspecifically and originates from fluid-phase endocytosis. Comparison with the receptor-enhanced permeability of transferrin indicates that the phenomena observed for IgG is ubiquitous for most macromolecules. However, increased permeability was observed for macromolecules with biophysical properties known to engage alternative endocytosis mechanisms, highlighting the importance of biophysical characterizations in assessing transcytosis mechanisms.

New Insights into the Susceptibility of Immunocompetent Mice to Usutu Virus

Usutu virus (USUV) is a mosquito-borne flavivirus that shares many similarities with the closely related West Nile virus (WNV) in terms of ecology and clinical manifestations. Initially distributed in Africa, USUV emerged in Italy in 1996 and managed to co-circulate with WNV in many European countries in a similar mosquito-bird life cycle. The rapid geographic spread of USUV, the seasonal mass mortalities it causes in the European avifauna, and the increasing number of infections with neurological disease both in healthy and immunocompromised humans has stimulated interest in infection studies to delineate USUV pathogenesis. Here, we assessed the pathogenicity of two USUV isolates from a recent Belgian outbreak in immunocompetent mice. The intradermal injection of USUV gave rise to disorientation and paraplegia and was associated with neuronal death in the brain and spinal cord in a single mouse. Intranasal inoculation of USUV could also establish the infection; viral RNA was detected in the brain 15 days post-infection. Overall, this pilot study probes the suitability of this murine model for the study of USUV neuroinvasiveness and the possibility of direct transmission in mammals.

Drugena: A Fully Automated Immunoinformatics Platform for the Design of Antibody-Drug Conjugates Against Neurodegenerative Diseases

Antibodies are proteins that are the first line of defense in the adaptive immune response of vertebrates. Thereby, they are involved in a multitude of biochemical mechanisms and clinical manifestations with significant medical interest, such as autoimmunity, the regulation of infection, and cancer. An emerging field in antibody science that is of huge medicinal interest is the development of novel antibody-interacting drugs. Such entities are the antibody-drug conjugates (ADCs), which are a new type of targeted therapy, which consist of an antibody linked to a payload drug. Overall, the underlying principle of ADCs is the discerning delivery of a drug to a target, hoping to increase the potency of the original drug. Drugena suite is a pioneering platform that employs state-of-the-art computational biology methods in the fight against neurodegenerative diseases using ADCs. Drugena encompasses an up-to-date structural database of specialized antibodies for neurological disorders and the NCI database with over 96 million entities for the in silico development of ADCs. The pipeline of the Drugena suite has been divided into several steps and modules that are closely related with a synergistic fashion under a user-friendly graphical user interface.

Anti-Phospho-Tau Gene Therapy for Chronic Traumatic Encephalopathy

Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative disorder caused by repetitive trauma to the central nervous system (CNS) suffered by soldiers, contact sport athletes, and civilians following accident-related trauma. CTE is a CNS tauopathy, with trauma-induced inflammation leading to accumulation of hyperphosphorylated forms of the microtubule-binding protein Tau (pTau), resulting in neurofibrillary tangles and progressive loss of neurons. At present, there are no therapies to treat CTE. We hypothesized that direct CNS administration of an adeno-associated virus (AAV) vector coding for an anti-pTau antibody would generate sufficient levels of anti-pTau in the CNS to suppress pTau accumulation thus interrupting the pathogenic process. Using a serotype AAVrh.10 gene transfer vector coding for a monoclonal antibody directed against pTau, we demonstrate the feasibility of this strategy in a murine CTE model in which pTau accumulation was elicited by repeated traumatic brain injury (TBI) using a closed cortical impact procedure over 5 days. Direct delivery of AAVrh.10 expression vectors coding for either of the two different anti-pTau antibodies to the hippocampus of these TBI mice significantly reduced pTau levels across the CNS. Using doses that can be safely scaled to humans, the data demonstrate that CNS administration of AAVrh.10anti-pTau is effective, providing a new strategy to interrupt the CTE consequences of TBI.

Antibody Therapy Targeting RAN Proteins Rescues C9 ALS/FTD Phenotypes in C9orf72 Mouse Model

The intronic C9orf72 G4C2 expansion, the most common genetic cause of ALS and FTD, produces sense- and antisense-expansion RNAs and six dipeptide repeat-associated, non-ATG (RAN) proteins, but their roles in disease are unclear. We generated high-affinity human antibodies targeting GA or GP RAN proteins. These antibodies cross the blood-brain barrier and co-localize with intracellular RAN aggregates in C9-ALS/FTD BAC mice. In cells, α-GA₁ interacts with TRIM21, and α-GA₁ treatment reduced GA levels, increased GA turnover, and decreased RAN toxicity and co-aggregation of proteasome and autophagy proteins to GA aggregates. In C9-BAC mice, α-GA₁ reduced GA as well as GP and GR proteins, improved behavioral deficits, decreased neuroinflammation and neurodegeneration, and increased survival. Glycosylation of the Fc region of α-GA₁ is important for cell entry and efficacy. These data demonstrate that RAN proteins drive C9-ALS/FTD in C9-BAC transgenic mice and establish a novel therapeutic approach for C9orf72 ALS/FTD and other RAN-protein diseases.

CSF1R Ligands IL-34 and CSF1 Are Differentially Required for Microglia Development and Maintenance in White and Gray Matter Brain Regions

Microglia are specialized brain macrophages that play numerous roles in tissue homeostasis and response to injury. Colony stimulating factor 1 receptor (CSF1R) is a receptor tyrosine kinase required for the development, maintenance, and proliferation of microglia. Here we show that in adult mice peripheral dosing of function-blocking antibodies to the two known ligands of CSF1R, CSF1, and IL-34, can deplete microglia differentially in white and gray matter regions of the brain, respectively. The regional patterns of depletion correspond to the differential expression of CSF1 and IL-34. In addition, we show that while CSF1 is required to establish microglia in the developing embryo, both CSF1 and IL-34 are required beginning in early postnatal development. These results not only clarify the roles of CSF1 and IL-34 in microglia maintenance, but also suggest that signaling through these two ligands might support distinct sub-populations of microglia, an insight that may impact drug development for neurodegenerative and other diseases.

A new era for migraine: Pharmacokinetic and pharmacodynamic insights into monoclonal antibodies with a focus on galcanezumab, an anti-CGRP antibody

PURPOSE

To review pharmacokinetic and pharmacodynamic characteristics of antibodies that bind to soluble ligands within the framework of calcitonin gene-related peptide antibodies.

OVERVIEW

Calcitonin gene-related peptide has been implicated in the pathophysiology of migraine. Galcanezumab is an antibody that binds to the ligand calcitonin gene-related peptide. Other antibodies that target calcitonin gene-related peptide include eptinezumab and fremanezumab. To understand how antibodies can affect the extent and duration of free ligand concentrations, it is important to consider the dose and pharmacokinetics of an antibody, and the kinetics of the ligand and antibody-ligand complex. Insights regarding the pharmacokinetic/pharmacodynamic properties of galcanezumab as a probe antibody drug and calcitonin gene-related peptide as its binding ligand regarding its clinical outcomes are provided.

DISCUSSION

Antibodies are administered parenterally because oral absorption is limited by gastrointestinal degradation and inefficient diffusion through the epithelium. The systemic absorption of antibodies following intramuscular or subcutaneous administration most likely occurs via convective transport through lymphatic vessels into blood. The majority of antibody elimination occurs via intracellular catabolism into peptides and amino acids following endocytosis. Binding of ligand to an antibody reduces the free ligand that is available to interact with the receptor and efficacy is driven by the magnitude and duration of the reduction in free ligand concentration. A galcanezumab pharmacokinetic/pharmacodynamic model shows that galcanezumab decreases free calcitonin gene-related peptide concentrations in a dose- and time-dependent manner and continues to suppress free calcitonin gene-related peptide with repeated dosing. The model provides evidence for a mechanistic linkage to galcanezumab therapeutic effects for the preventive treatment of migraine.

Development and Cell Biology of the Blood-Brain Barrier

The vertebrate vasculature displays high organotypic specialization, with the structure and function of blood vessels catering to the specific needs of each tissue. A unique feature of the central nervous system (CNS) vasculature is the blood-brain barrier (BBB). The BBB regulates substance influx and efflux to maintain a homeostatic environment for proper brain function. Here, we review the development and cell biology of the BBB, focusing on the cellular and molecular regulation of barrier formation and the maintenance of the BBB through adulthood. We summarize unique features of CNS endothelial cells and highlight recent progress in and general principles of barrier regulation. Finally, we illustrate why a mechanistic understanding of the development and maintenance of the BBB could provide novel therapeutic opportunities for CNS drug delivery.

Qß Virus-like particle-based vaccine induces robust immunity and protects against tauopathy

Tauopathies, including frontotemporal dementia (FTD) and Alzheimer’s disease (AD) are progressive neurodegenerative diseases clinically characterized by cognitive decline and could be caused by the aggregation of hyperphosphorylated pathological tau (pTau) as neurofibrillary tangles (NFTs) inside neurons. There is currently no FDA-approved treatment that cures, slows or prevents tauopathies. Current immunotherapy strategies targeting pTau have generated encouraging data but may pose concerns about scalability, affordability, and efficacy. Here, we engineered a virus-like particle (VLP)-based vaccine in which tau peptide, phosphorylated at threonine 181, was linked at high valency to Qß bacteriophage VLPs (pT181-Qß). We demonstrate that vaccination with pT181-Qß is sufficient to induce a robust and long-lived anti-pT181 antibody response in the sera and the brains of both Non-Tg and rTg4510 mice. Only sera from pT181-Qß vaccinated mice are reactive to classical somatodendritic pTau in human FTD and AD post-mortem brain sections. Finally, we demonstrate that pT181-Qß vaccination reduces both soluble and insoluble species of hyperphosphorylated pTau in the hippocampus and cortex, avoids a Th1-mediated pro-inflammatory cell response, prevents hippocampal and corpus callosum atrophy and rescues cognitive dysfunction in a 4-month-old rTg4510 mouse model of FTD. These studies provide a valid scientific premise for the development of VLP-based immunotherapy to target pTau and potentially prevent Alzheimer’s diseases and related tauopathies.

Tauopathies such as fronto-temporal dementia or Alzheimer’s disease are characterized by the accumulation of phosphorylated Tau (pTau) protein into pathogenic neurofibrillary tangles (NFT). Kiran Bhaskar and colleagues at the University of New Mexico investigate the efficacy of an active vaccine approach in the treatment of rTg4510 mice—an aggressive model of tauopathy. Mice receive 3 intramuscular doses of a disease-relevant pTau peptide (pT181) multivalently conjugated to an immunostimulatory bacteriophage virus-like particle (pT181-Qß). Vaccination induces high titers of anti-pTau—stable to at least 20 weeks—that is also able to bind human disease samples, but importantly does not react to unphosphorylated physiological Tau protein. Antibody can enter the brain and bind both soluble and intraneuronal pTau. Vaccination of mice reduces brain NFT, pathology, indicators of neuroinflammation and improves cognitive function in two different models of memory.

Tau immunotherapies for Alzheimer's disease

INTRODUCTION

Alzheimer's dementia (AD) is the most common form of dementia in the World. Pathologically, it is characterized by extracellular β-amyloid plaques and intraneuronal neurofibrillary tangles (NFTs). The latter is composed of irregular, pathological forms of the tau protein. Currently, FDA-approved symptomatic treatments are limited to the targeting of cholinergic deficits and glutamatergic dysfunctions. However, as understanding of β-amyloid plaques and NFTs expands, these dysfunctional proteins represent potential therapeutic interventions. The present review article evaluates active and passive immunotherapies in clinical development for AD to date and their potential to significantly improve the treatment of AD going forward.

AREAS COVERED

All clinical trials that have targeted β-amyloid to date have produced somewhat disappointing results, leading to a shift in intervention focus to targeting tau protein. A key component in understanding the value of targeting tau in therapeutic paradigms has come from the conceptualization of prion-like pathological spread of tau isoforms from neuron to neuron, and referred to as 'tauons'. Immunotherapies currently under investigation include approaches aiming at preventing pathological tau aggregation, stabilizing microtubules, and blocking of tauons.

EXPERT OPINION

A multi-targeted approach that would use biologics targeting tau offers great promise to the development of effective AD therapeutic interventions.

The potential roles of aquaporin 4 in amyotrophic lateral sclerosis

Aquaporin 4 (AQP4) is a primary water channel found on astrocytes in the central nervous system (CNS). Besides its function in water and ion homeostasis, AQP4 has also been documented to be involved in a myriad of acute and chronic cerebral pathologies, including autoimmune neurodegenerative diseases. AQP4 has been postulated to be associated with the incidence of a progressive neurodegenerative disorder known as amyotrophic lateral sclerosis (ALS), a disease that targets the motor neurons, causing muscle weakness and eventually paralysis. Raised AQP4 levels were noted in association with vessels surrounded with swollen astrocytic processes as well as in the brainstem, cortex, and gray matter in patients with terminal ALS. AQP4 depolarization may lead to motor neuron degeneration in ALS via GLT-1. Besides, alterations in AQP4 expression in ALS may result in the loss of blood-brain barrier (BBB) integrity. Changes in AQP4 function may also disrupt K⁺ homeostasis and cause connexin dysregulation, the latter of which is associated to ALS disease progression. Furthermore, AQP4 suppression augments recovery in motor function in ALS, a phenomenon thought to be associated to NGF. No therapeutic drug targeting AQP4 has been developed to date. Nevertheless, the plethora of suggestive experimental results underscores the significance of further exploration into this area.

A new technology for increasing therapeutic protein levels in the brain over extended periods

Effective delivery of protein therapeutics into the brain remains challenging because of difficulties associated with crossing the blood-brain barrier (BBB). To overcome this problem, many researchers have focused on antibodies binding the transferrin receptor (TfR), which is expressed in endothelial cells, including those of the BBB, and is involved in receptor-mediated transcytosis (RMT). RMT and anti-TfR antibodies provide a useful means of delivering therapeutics into the brain, but the anti-TfR antibody has a short half-life in blood because of its broad expression throughout the body. As a result, anti-TfR antibodies are only maintained at high concentrations in the brain for a short time. To overcome this problem, we developed a different approach which slows down the export of therapeutic antibodies from the brain by binding them to a brain-specific antigen. Here we report a new technology, named AccumuBrain, that achieves both high antibody concentration in the brain and a long half-life in blood by binding to myelin oligodendrocyte glycoprotein (MOG), which is specifically expressed in oligodendrocytes. We report that, using our technology, anti-MOG antibody levels in the brains of mice (Mus musculus) and rats (Rattus norvegicus) were increased several tens of times for a period of one month. The mechanism of this technology is different from that of RMT technologies like TfR and would constitute a breakthrough for central nervous system disease therapeutics.

David vs. Goliath: The Structure, Function, and Clinical Prospects of Antibody Fragments

Since the licensing of the first monoclonal antibody therapy in 1986, monoclonal antibodies have become the largest class of biopharmaceuticals with over 80 antibodies currently approved for a variety of disease indications. The development of smaller, antigen binding antibody fragments, derived from conventional antibodies or produced recombinantly, has been growing at a fast pace. Antibody fragments can be used on their own or linked to other molecules to generate numerous possibilities for bispecific, multi-specific, multimeric, or multifunctional molecules, and to achieve a variety of biological effects. They offer several advantages over full-length monoclonal antibodies, particularly a lower cost of goods, and because of their small size they can penetrate tissues, access challenging epitopes, and have potentially reduced immunogenicity. In this review, we will discuss the structure, production, and mechanism of action of EMA/FDA-approved fragments and of those in clinical and pre-clinical development. We will also discuss current topics of interest surrounding the potential use of antibody fragments for intracellular targeting and blood-brain barrier (BBB) penetration.

Mechanisms for lesion localization in neuromyelitis optica spectrum disorders

Purpose of review

Neuromyelitis optica spectrum disorders (NMOSD) are severe inflammatory diseases of the central nervous system (CNS), with the presence of aquaporin 4 (AQP4)-specific serum antibodies in the vast majority of patients, and with the presence of myelin oligodendrocyte glycoprotein (MOG)-specific antibodies in approximately 40% of all AQP4-antibody negative NMOSD patients. Despite differences in antigen recognition, the preferred sites of lesions are similar in both groups of patients: They localize to the spinal cord and to the anterior visual pathway including retina, optic nerves, chiasm, and optic tracts, and – to lesser extent – also to certain predilection sites in the brain.

Recent findings

The involvement of T cells in the formation of NMOSD lesions has been challenged for quite some time. However, several recent findings demonstrate the key role of T cells for lesion formation and localization. Studies on the evolution of lesions in the spinal cord of NMOSD patients revealed a striking similarity of early NMOSD lesions with those observed in corresponding T-cell-induced animal models, both in lesion formation and in lesion localization. Studies on retinal abnormalities in NMOSD patients and corresponding animals revealed the importance of T cells for the very early stages of retinal lesions which eventually culminate in damage to Müller cells and to the retinal nerve fiber layer. Finally, a study on cerebrospinal fluid (CSF) barrier pathology demonstrated that NMOSD immunopathology extends beyond perivascular astrocytic foot processes to include the pia, the ependyma, and the choroid plexus, and that diffusion of antibodies from the CSF could further influence lesion formation in NMOSD patients.

Summary

The pathological changes observed in AQP4-antibody positive and MOG-antibody positive NMOSD patients are strikingly similar to those found in corresponding animal models, and many mechanisms which determine lesion localization in experimental animals seem to closely reflect the human situation.

Human pluripotent stem cell-derived brain pericyte-like cells induce blood-brain barrier properties

Brain pericytes play important roles in the formation and maintenance of the neurovascular unit (NVU), and their dysfunction has been implicated in central nervous system disorders. While human pluripotent stem cells (hPSCs) have been used to model other NVU cell types, including brain microvascular endothelial cells (BMECs), astrocytes, and neurons, hPSC-derived brain pericyte-like cells have not been integrated into these models. In this study, we generated neural crest stem cells (NCSCs), the embryonic precursor to forebrain pericytes, from hPSCs and subsequently differentiated NCSCs to brain pericyte-like cells. These cells closely resembled primary human brain pericytes and self-assembled with endothelial cells. The brain pericyte-like cells induced blood-brain barrier properties in BMECs, including barrier enhancement and reduced transcytosis. Last, brain pericyte-like cells were incorporated with iPSC-derived BMECs, astrocytes, and neurons to form an isogenic human model that should prove useful for the study of the NVU.

Circulating AQP4-specific auto-antibodies alone can induce neuromyelitis optica spectrum disorder in the rat

It is well established that the binding of pathogenic aquaporin-4 (AQP4)-specific autoantibodies to astrocytes may initiate a cascade of events culminating in the destruction of these cells and in the formation of large tissue-destructive lesions typical for patients with neuromyelitis optica spectrum disorders (NMOSD). To date, not a single experimental study has shown that the systemic presence of the antibody alone can induce any damage to the central nervous system (CNS), while pathological studies on brains of NMOSD patients suggested that there might be ways for antibody entry and subsequent tissue damage. Here, we systemically applied a highly pathogenic, monoclonal antibody with high affinity to AQP4 over prolonged period of time to rats, and show that AQP4-abs can enter the CNS on their own, via circumventricular organs and meningeal or parenchymal blood vessels, that these antibodies initiate the formation of radically different lesions with AQP4 loss, depending on their mode and site of entry, and that lesion formation is much more efficient in the presence of encephalitogenic T-cell responses. We further demonstrate that the established tissue-destructive lesions trigger the formation of additional lesions by short and far reaching effects on blood vessels and their branches, and that AQP4-abs have profound effects on the AQP4 expression in peripheral tissues which counter-act possible titer loss by antibody absorption outside the CNS. Cumulatively, these data indicate that directly induced pathological changes caused by AQP4-abs inside and outside the CNS are efficient drivers of disease evolution in seropositive organisms.

Passive Immunotherapies for Central Nervous System Disorders: Current Delivery Challenges and New Approaches

Passive immunotherapy, i.e., the administration of exogenous antibodies that recognize a specific target antigen, has gained significant momentum as a potential treatment strategy for several central nervous system (CNS) disorders, including Alzheimer's disease, Parkinson's disease, Huntington's disease, and brain cancer, among others. Advances in antibody engineering to create therapeutic antibody fragments or antibody conjugates have introduced new strategies that may also be applied to treat CNS disorders. However, drug delivery to the CNS for antibodies and other macromolecules has thus far proven challenging, due in large part to the blood-brain barrier and blood-cerebrospinal fluid barriers that greatly restrict transport of peripherally administered molecules from the systemic circulation into the CNS. Here, we summarize the various passive immunotherapy approaches under study for the treatment of CNS disorders, with a primary focus on disease-specific and target site-specific challenges to drug delivery and new, cutting edge methods.

Biologically-derived nanomaterials for targeted therapeutic delivery to the brain

Delivery of imaging agents and pharmaceutical payloads to the central nervous system (CNS) is essential for efficient diagnosis and treatment of brain diseases. However, therapeutic delivery is often restricted by the blood-brain barrier (BBB), which prevents transport of clinical compounds to their region of interest. This review discusses the methods that have been used to avoid or overcome this barrier, presenting the use of biologically-derived nanomaterial systems as an efficient strategy for the diagnosis and treatment of CNS diseases. Biological nanomaterials have many advantages over synthetic systems, including being biodegradable, biocompatible, easily surface functionalised for conjugation of targeting moieties, and are often able to self-assemble. These abilities are discussed in relation to various systems, including liposomes, dendrimers, and viral nanoparticles.

Notch3ECD immunotherapy improves cerebrovascular responses in CADASIL mice

OBJECTIVE

CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy), caused by dominant mutations in the NOTCH3 receptor, is the most aggressive small vessel disease of the brain. A key feature of its pathogenesis is accumulation of the extracellular domain of NOTCH3 receptor (Notch3^ECD ) in small vessels, with formation of characteristic extracellular deposits termed granular osmiophilic material (GOM). Here, we investigated the therapeutic potential of a mouse monoclonal antibody (5E1) that specifically recognizes Notch3^ECD .

METHODS

The binding affinity of 5E1 toward purified NOTCH3 was assessed using Octet analysis. The ability of 5E1 to bind Notch3^ECD deposits in brain vessels and its effects on disease-related phenotypes were evaluated in the CADASIL mouse model, which overexpresses a mutant rat NOTCH3. Notch3^ECD and GOM deposition, white matter lesions, and cerebral blood flow deficits were assessed at treatment initiation (10 weeks) and study completion (30 weeks) using quantitative immunohistochemistry, electron microscopy, and laser-Doppler flowmetry.

RESULTS

5E1 antibody bound recombinant rat NOTCH3 with an average affinity of 317nM. A single peripheral injection of 5E1 robustly decorated Notch3^ECD deposits in the brain vasculature. Chronic administration of 5E1 did not attenuate Notch3^ECD or GOM deposition and was not associated with perivascular microglial activation. It also failed to halt the development of white matter lesions. Despite this, 5E1 treatment markedly protected against impaired cerebral blood flow responses to neural activity and topical application of vasodilators and normalized myogenic responses of cerebral arteries.

INTERPRETATION

This study establishes immunotherapy targeting Notch3^ECD as a new avenue for disease-modifying treatment in CADASIL that warrants further development. Ann Neurol 2018;84:246-259.

Blood-brain barrier shuttle peptides enhance AAV transduction in the brain after systemic administration

The adeno-associated virus (AAV) vector has been used in preclinical and clinical trials of gene therapy for central nervous system (CNS) diseases. One of the biggest challenges of effectively delivering AAV to the brain is to surmount the blood-brain barrier (BBB). Herein, we identified several potential BBB shuttle peptides that significantly enhanced AAV8 transduction in the brain after a systemic administration, the best of which was the THR peptide. The enhancement of AAV8 brain transduction by THR is dose-dependent, and neurons are the primary THR targets. Mechanism studies revealed that THR directly bound to the AAV8 virion, increasing its ability to cross the endothelial cell barrier. Further experiments showed that binding of THR to the AAV virion did not interfere with AAV8 infection biology, and that THR competitively blocked transferrin from binding to AAV8. Taken together, our results demonstrate, for the first time, that BBB shuttle peptides are able to directly interact with AAV and increase the ability of the AAV vectors to cross the BBB for transduction enhancement in the brain. These results will shed important light on the potential applications of BBB shuttle peptides for enhancing brain transduction with systemic administration of AAV vectors.

Glucose-regulated protein 78 autoantibody associates with blood-brain barrier disruption in neuromyelitis optica

Neuromyelitis optica (NMO) is an inflammatory disorder mediated by antibodies to aquaporin-4 (AQP4) with prominent blood-brain barrier (BBB) breakdown in the acute phase of the disease. Anti-AQP4 antibodies are produced mainly in the periphery, yet they target the astrocyte perivascular end feet behind the BBB. We reasoned that an endothelial cell-targeted autoantibody might promote BBB transit of AQP4 antibodies and facilitate NMO attacks. Using monoclonal recombinant antibodies (rAbs) from patients with NMO, we identified two that strongly bound to the brain microvascular endothelial cells (BMECs). Exposure of BMECs to these rAbs resulted in nuclear translocation of nuclear factor κB p65, decreased claudin-5 protein expression, and enhanced transit of macromolecules. Unbiased membrane proteomics identified glucose-regulated protein 78 (GRP78) as the rAb target. Using immobilized GRP78 to deplete GRP78 antibodies from pooled total immunoglobulin G (IgG) of 50 NMO patients (NMO-IgG) reduced the biological effect of NMO-IgG on BMECs. GRP78 was expressed on the surface of murine BMECs in vivo, and repeated administration of a GRP78-specific rAb caused extravasation of serum albumin, IgG, and fibrinogen into mouse brains. Our results identify GRP78 antibodies as a potential component of NMO pathogenesis and GRP78 as a candidate target for promoting central nervous system transit of therapeutic antibodies.

Quantitative Algorithm-Based Paired Imaging Measurement for Antibody-Triggered Endocytosis in Cultured Cells

Antibody-triggered endocytosis (ATE) is a biological mechanism on which many therapeutic strategies are grounded, such as delivery of antibody-drug conjugates (ADCs). Current methods monitoring ATE include confocal Z-stack analysis, acid wash, antibody quenching, and pH-sensitive dye labeling. However, those generate less quantifiable results with low throughput. Here we report a new method referred to as "paired imaging measurement" to analyze ATE using a quantitative algorithm in conjunction with high-content imaging. With two sequential measurements of cell surface antibody employing live cell staining and total antibody by immunostaining before and after cell permeabilization, intracellular antibody undergoing endocytosis can be quantified indirectly. Antibodies against CD98 and transferrin receptor were tested on hCMEC/D3 and hiPSC-derived endothelial cells. The maximal response and potency of endocytosed antibodies were generated with good assay robustness (Z' > 0.6) and >5-fold signal/background ratio. Antibody endocytosis response ranking is consistent between batches ( R² > 0.9). The obtained results were confirmed by other traditional methods. In conclusion, we have developed a novel method using a quantitative imaging algorithm in conjunction with live cell staining for high-throughput investigation of ATE.

A Blood-Brain-Barrier-Penetrating Anti-human Transferrin Receptor Antibody Fusion Protein for Neuronopathic Mucopolysaccharidosis II

Mucopolysaccharidosis II (MPS II) is an X-linked recessive lysosomal storage disease caused by mutations in the iduronate-2-sulfatase (IDS) gene. Since IDS catalyzes the degradation of glycosaminoglycans (GAGs), deficiency in this enzyme leads to accumulation of GAGs in most cells in all tissues and organs, resulting in severe somatic and neurological disorders. Although enzyme replacement therapy with human IDS (hIDS) has been used for the treatment of MPS II, this therapy is not effective for defects in the CNS mainly because the enzyme cannot cross the blood-brain barrier (BBB). Here, we developed a BBB-penetrating fusion protein, JR-141, which consists of an anti-human transferrin receptor (hTfR) antibody and intact hIDS. The TfR-mediated incorporation of JR-141 was confirmed by using human fibroblasts in vitro. When administrated intravenously to hTfR knockin mice or monkeys, JR-141, but not naked hIDS, was detected in the brain. In addition, the intravenous administration of JR-141 reduced the accumulation of GAGs both in the peripheral tissues and in the brain of hTfR knockin mice lacking Ids, an animal model of MPS II. These data provide a proof of concept for the translation of JR-141 to clinical study for the treatment of patients with MPS II with CNS disorders.

Prospects for strain-specific immunotherapy in Alzheimer's disease and tauopathies

With increasing age, as the incidence of Alzheimer's disease is increasing, finding a therapeutic intervention is becoming critically important to either prevent or slow down the progression of the disease. Passive immunotherapy has been demonstrated as a successful way of reducing large aggregates and improving cognition in animal models of both tauopathies and Alzheimer's disease. However, with all the continuous attempts and significant success of immunotherapy in preclinical studies, finding a successful clinical therapy has been a great challenge, possibly indicating a lack of accuracy in targeting the toxic species. Both active and passive immunotherapy approaches in transgenic animals have been demonstrated to have pros and cons. Passive immunotherapy has been favored and many mechanisms have been shown to clear toxic amyloid and tau aggregates and improve memory. These mechanisms may differ depending on the antibodie's' target and administration route. In this regard, deciding on affinity vs. specificity of the antibodies plays a significant role in terms of avoiding the clearance of the physiological forms of the targeted proteins and reducing adverse side effects. In addition, knowing that a single protein can exist in different conformational states, termed as strains, with varying degrees of neurotoxicity and seeding properties, presents an additional level of complexity. Therefore, immunotherapy targeting specifically the toxic strains will aid in developing potential strategies for intervention. Moreover, an approach of combinatorial immunotherapies against different amyloidogenic proteins, at distinct levels of the disease progression, might offer an effective therapy in many neurodegenerative diseases.

Causative Genes in Amyotrophic Lateral Sclerosis and Protein Degradation Pathways: a Link to Neurodegeneration

Amyotrophic lateral sclerosis (ALS) is a disease caused by the degeneration of motor neurons (MNs) leading to progressive muscle weakness and atrophy. Several molecular pathways have been implicated, such as glutamate-mediated excitotoxicity, defects in cytoskeletal dynamics and axonal transport, disruption of RNA metabolism, and impairments in proteostasis. ALS is associated with protein accumulation in the cytoplasm of cells undergoing neurodegeneration, which is a hallmark of the disease. In this review, we focus on mechanisms of proteostasis, particularly protein degradation, and discuss how they are related to the genetics of ALS. Indeed, the genetic bases of the disease with the implication of more than 30 genes associated with familial ALS to date, together with the important increase in understanding of endoplasmic reticulum (ER) stress, proteasomal degradation, and autophagy, allow researchers to better understand the mechanisms underlying the selective death of motor neurons in ALS. It is clear that defects in proteostasis are involved in this type of cellular degeneration, but whether or not these mechanisms are primary causes or merely consequential remains to be clearly demonstrated. Novel cellular and animal models allowing chronic expression of mutant proteins, for example, are required. Further studies linking genetic discoveries in ALS to mechanisms of protein clearance will certainly be crucial in order to accelerate translational and clinical research towards new therapeutic targets and strategies.

Live Imaging of Pathological Tau Protein and Tau Antibodies in a Neuron-Like Cellular Model

Several tau antibody therapies are now in clinical trials and numerous other tau antibodies are in various stages of preclinical development to treat Alzheimer's disease and related tauopathies. This involves long-term studies in mouse models that are necessary but time consuming and typically provide only a limited mechanistic understanding of how the antibodies work and why some are not effective. Live cellular imaging with fluorescently tagged pathological tau proteins and tau antibodies provides a valuable insight into their dynamic interaction outside or within the cell. Furthermore, this acute technique may have predictive validity to assess the potential efficacy of different tau antibodies in neutralizing and/or clearing tau aggregates, and can likely be applied to other amyloid diseases. Overall, it should facilitate identifying candidate antibodies for more detailed long-term validation. Due to the human origin of the model, it may be particularly useful to characterize humanized antibodies that utilize receptor-mediated uptake to reach their intracellular target.

Discovery of an Orally Bioavailable Benzofuran Analogue That Serves as a β-Amyloid Aggregation Inhibitor for the Potential Treatment of Alzheimer's Disease

We developed an orally active and blood-brain-barrier-permeable benzofuran analogue (8, MDR-1339) with potent antiaggregation activity. Compound 8 restored cellular viability from Aβ-induced cytotoxicity but also improved the learning and memory function of AD model mice by reducing the Aβ aggregates in the brains. Given the high bioavailability and brain permeability demonstrated in our pharmacokinetic studies, 8 will provide a novel scaffold for an Aβ-aggregation inhibitor that may offer an alternative treatment for AD.