Novel multivalent design of a monoclonal antibody improves binding strength to soluble aggregates of amyloid beta

Delineating the tryptophan-galactosylamine conjugate mediated structural distortions in Aβ42 protofibrils

Amyloid-β (Aβ) fibrillation into neurotoxic soluble oligomers and mature fibrils is mainly responsible for the etiology of Alzheimer's disease (AD). A recent study revealed 61% disaggregation of the pre-formed Aβ42 fibrils upon incubating with a highly soluble tryptophan-galactosylamine conjugate, WGalNAc. WGalNAc displayed no toxicity and increased the viability of SH-SY5Y cells up to 62.9 ± 2% with an EC50 value of 2.3 μM against Aβ42 pre-formed fibrils. However, the key interactions and disruptive mechanism of WGalNAc against Aβ fibrils remain elusive. Thus, mechanistic insights into the disruptive potential of WGalNAc against Aβ42 protofibrils (PDB: 5OQV) were examined using molecular dynamics (MD) simulations. The molecular docking depicted a favourable binding energy (-6.60 kcal mol-1) and interaction of WGalNAc with the central hydrophobic core (CHC) region of chain A of the 5OQV protofibril. The MD simulations depicted that WGalNAc disrupted the contacts among Ala2, Phe4, Leu34, and Val36 in the hydrophobic core 1 of the 5OQV protofibril responsible for maintaining the stability of the LS-shaped 5OQV protofibril. WGalNAc binds favourably to the 5OQV protofibril (ΔGbinding = -21.76 ± 2.40 kcal mol-1) with a significant contribution from the van der Waals interaction term. Notably, the binding affinity between the neighbouring chains of the 5OQV protofibril was significantly reduced from -134.31 ± 11.12 to -121.88 ± 1.95 kcal mol-1 upon the incorporation of WGalNAc, which is consistent with the ThT kinetic results that revealed disaggregation of the pre-formed Aβ42 fibrils upon incubating with WGalNAc. The in silico ADMET properties of WGalNAc showed its ability as a promising therapeutic candidate due to its blood-brain barrier (BBB) permeability, extended half-life, and non-toxic profile. The MD simulations illuminated the binding interactions of WGalNAc with the 5OQV protofibril and provided mechanistic insights into the WGalNAc-mediated structural distortions in the 5OQV protofibril.

Serotransferrin enhances transferrin receptor-mediated brain uptake of antibodies

The propensity of antibody-based therapies to systemically enter the brain interstitium and ameliorate pathology associated with numerous neurological maladies is precluded by the presence of the blood-brain barrier (BBB). Through distinct mechanisms, the BBB has evolved to regulate transport of essential ions, minerals, certain peptides and cells between the blood and the brain, but very restrictive otherwise. Hijacking receptor-mediated transport pathways of the BBB has proved fruitful in developing "Trojan Horse" therapeutic approaches to deliver antibody-based therapies to the brain milieu. The transferrin receptor (TfR)-mediated transcytosis pathway (RMT) is one such example where large recombinant molecules have been designed to bind to the TfR, which in turn activates the RMT pathway, resulting in delivery across the BBB into the brain milieu. Based on these findings, we here investigated whether the addition of serotransferrin could trigger the endogenous TfR-mediated RMT pathway and hence be used to enhance the uptake of TfR binding antibodies. By using an in vitro model of a mouse BBB we could test whether co-administration of mouse serotransferrin with mouse and human-based monoclonal antibodies enhanced brain uptake. In all cases tested, no matter if the monoclonal antibodies were designed to bind the TfR in a monovalent, partially monovalent/bivalent or entirely bivalent fashion, with high or low affinity or avidity, the addition of mouse serotransferrin significantly improved transport across the artificial BBB. This was also true for TfR binding antibodies that on their own passes the BBB poorly. These results were subsequently confirmed using a human in vitro BBB model, along with human serotransferrin and human TfR-binding antibody. To corroborate the in vitro results further, we conducted two pilot in vivo brain uptake study in wildtype mice, by intravenously co-administering a monoclonal TfR-binding antibody in the presence or absence of mouse serotransferrin as a proof-of-concept. In a similar outcome to the in vitro studies, we observed a significant almost two-fold increase in uptake of two different TfR binding antibodies in the brain when it was co-administered with mouse serotransferrin. These findings show for the first time that serotransferrin supplementation can significantly improve the ability of TfR-binding antibodies to traverse the BBB, which provides a realistic therapeutic opportunity for improving the delivery of therapeutic antibodies to the brain.

"Current and emerging drug therapies in Alzheimer's disease: A pathophysiological Perspective"

The analytical and experimental investigation of several targets and biomarkers that help in explaining significant cognitive deficits, covering drug development and precision medicine aimed at different chronic neurodegenerative conditions such as Alzheimer's disease (AD), Parkinson's disease, synaptic dysfunction, brain damage from neuronal apoptosis, and other disease pathologies; this served as the foundation for all phase studies. The focus of current therapeutic approaches is on developing humanized antibodies, agonist and antagonist drugs, receptors, signaling molecules, major targeted drug-metabolizing enzymes, and other metabolites to treat neurodegeneration in the AD brain brought on by tau hyperphosphorylation, amyloid plagues, or other cholinergic effects. The five A's-amnesia, agnosia, aphasia, apraxia, and anomia-are the typical symptoms associated with AD. While the main goal of drug therapeutics studies is modified amino acids acting as pro-drugs, pharmacokinetics studies and trends in evaluating drug-drug interactions focus on interactions between drugs and antibodies, drugs and therapeutic biologics like metabolites, herbs, interleukin-based, and gene silencing mechanism-based. Studies on the biotransformation of xenobiotic compounds and the metabolism of exogenous and endogenous substances are conducted under Phase I, Phase II, and Phase III trials because the pivotal pharmacokinetic properties of drugs, such as absorption, distribution, metabolism, and excretion (ADME), aid in understanding variations in the crucial improvement of various target drugs. This review also highlights the developments in soon-to-be genetically created targeted medications that may serve as ground-breaking treatments for cholinergic illnesses in the brains of AD patients and other neurodegenerative conditions.

Lowering the affinity of single-chain monovalent BBB shuttle scFc-scFv8D3 prolongs its half-life and increases brain concentration

Monoclonal antibody therapeutics is a massively growing field. Progress in providing monoclonal antibody therapeutics to treat brain disorders is complicated, due to the impermeability of the blood-brain barrier (BBB) to large macromolecular structures. To date, the most successful approach for delivering antibody therapeutics to the brain is by targeting the transferrin receptor (TfR) using anti-TfR BBB shuttles, with the 8D3 antibody being one of the most extensively studied in the field. The strategy of fine-tuning TfR binding affinity has shown promise, with previous results showing an improved brain delivery of bivalent 8D3-BBB constructs. In the current study, a fine-tuning TfR affinity strategy has been employed to improve single-chain variable fragment (scFv) 8D3 (scFv8D3) affinity mutants. Initially, in silico protein-protein docking analysis was performed to identify amino acids (AAs) likely to contribute to 8D3s TfR binding affinity. Mutating the identified AAs resulted in decreased TfR binding affinity, increased blood half-life and increased brain concentration. As monovalent BBB shuttles are seemingly superior for delivering antibodies at therapeutically relevant doses, our findings and approach may be relevant for optimizing brain delivery.

Levetiracetam prevents Aβ42 production through SV2a-dependent modulation of App processing in Alzheimer's disease models

In Alzheimer's disease (AD), amyloid-beta (Aβ) peptides are produced by proteolytic cleavage of the amyloid precursor protein (APP), which can occur during synaptic vesicle (SV) cycling at presynapses. Precisely how amyloidogenic APP processing may impair presynaptic proteostasis and how to therapeutically target this process remains poorly understood. Using App knock-in mouse models of early Aβ pathology, we found proteins with hampered degradation accumulate at presynaptic sites. At this mild pathological stage, amyloidogenic processing leads to accumulation of Aβ42 inside SVs. To explore if targeting SVs modulates Aβ accumulation, we investigated levetiracetam (Lev), a SV-binding small molecule drug that has shown promise in mitigating AD-related pathologies despite its mechanism of action being unclear. We discovered Lev reduces Aβ42 levels by decreasing amyloidogenic processing of APP in a SV2a-dependent manner. Lev corrects SV protein levels and cycling, which results in increased surface localization of APP, where it favors processing via the non-amyloidogenic pathway. Using metabolic stable isotopes and mass spectrometry we confirmed that Lev prevents the production of Aβ42 in vivo. In transgenic mice with aggressive pathology, electrophysiological and immunofluorescent microscopy analyses revealed that Lev treatment reduces SV cycling and minimizes synapse loss. Finally, we found that human Down syndrome brains with early Aβ pathology, have elevated levels of presynaptic proteins, confirming a comparable presynaptic deficit in human brains. Taken together, we report a mechanism that highlights the therapeutic potential of Lev to modify the early stages of AD and represent a promising strategy to prevent Aβ42 pathology before irreversible damage occurs.

Investigating the Mechanisms of Antibody Binding to Alpha-Synuclein for the Treatment of Parkinson's Disease

Parkinson's disease (PD) is an idiopathic neurodegenerative disorder with the second-highest prevalence rate behind Alzheimer's disease. The pathophysiological hallmarks of PD are both degeneration of dopaminergic neurons in the substantia nigra pars compacta and the inclusion of misfolded α-synuclein (α-syn) aggregates known as Lewy bodies. Despite decades of research for potential PD treatments, none have been developed, and developing new therapeutic agents is a time-consuming and expensive process. Computational methods can be used to investigate the properties of drug candidates currently undergoing clinical trials to determine their theoretical efficiency at targeting α-syn. Monoclonal antibodies (mAbs) are biological drugs with high specificity, and Prasinezumab (PRX002) is an mAb currently in Phase II, which targets the C-terminus (AA 118-126) of α-syn. We utilized BioLuminate and PyMol for the structure prediction and preparation of the fragment antigen-binding (Fab) region of PRX002 and 34 different conformations of α-syn. Protein-protein docking simulations were performed using PIPER, and 3 of the docking poses were selected based on the best fit. Molecular dynamics simulations were conducted on the docked protein structures in triplicate for 1000 ns, and hydrogen bonds and electrostatic and hydrophobic interactions were analyzed using MDAnalysis to determine which residues were interacting and how often. Hydrogen bonds were shown to form frequently between the HCDR2 region of PRX002 and α-syn. Free energy was calculated to determine the binding affinity. The predicted binding affinity shows a strong antibody-antigen attraction between PRX002 and α-syn. RMSD was calculated to determine the conformational change of these regions throughout the simulation. The mAb's developability was determined using computational screening methods. Our results demonstrate the efficiency and developability of this therapeutic agent.

A charged tail on anti-α-Synuclein antibodies does not enhance their affinity to α-Synuclein fibrils

The aggregation of α-Synuclein (αSyn) is strongly linked to neuronal death in Parkinson's disease and other synucleinopathies. The spreading of aggregated αSyn between neurons is at least partly dependent on electrostatic interactions between positively charged stretches on αSyn fibrils and the negatively charged heparan sulphate proteoglycans on the cell surface. To date there is still no therapeutic option available that could halt the progression of Parkinson's disease and one of the major limitations is likely the relatively low proportion of αSyn aggregates accessible to drugs in the extracellular space. Here, we investigated whether a negatively charged peptide tail fused to the αSyn aggregate-specific antibodies SynO2 and 9E4 could enhance the antibodies' avidity to αSyn aggregates in order to improve their potential therapeutic effect through inhibiting cell-to-cell spreading and enhancing the clearance of extracellular aggregates. We performed ELISAs to test the avidity to αSyn aggregates of both monovalent and bivalent antibody formats with and without the peptide tail. Our results show that the addition of the negatively charged peptide tail decreased the binding strength of both antibodies to αSyn aggregates at physiological salt conditions, which can likely be explained by intermolecular repulsions between the tail and the negatively charged C-terminus of αSyn. Additionally, the tail might interact with the paratopes of the SynO2 antibody abolishing its binding to αSyn aggregates. Conclusively, our peptide tail did not fulfil the required characteristics to improve the antibodies' binding to αSyn aggregates. Fine-tuning the design of the peptide tail to avoid its interaction with the antibodies' CDR and to better mimic relevant characteristics of heparan sulphates for αSyn aggregate binding may help overcome the limitations observed in this study.

Multifunctional Liposomes Targeting Amyloid-β Oligomers for Early Diagnosis and Therapy of Alzheimer's Disease

Early detection and treatment are crucial for Alzheimer's disease (AD) management. Current diagnostic and therapeutic methods focus on late-stage amyloid fibrils and plaques, overlooking toxic soluble amyloid β oligomers (AβOs) accumulating early in AD. A multifunctional liposome-based platform is designed for early diagnosis and therapy of AD, leveraging a novel self-assembled cyclic d,l-α-peptide (CP-2) that selectively targets AβOs. Biocompatible CP-2 conjugated liposomes (CP-2-LPs) effectively disrupt Aβ aggregation and mitigate Aβ-mediated toxicity in human neuroblastoma cells. In transgenic Caenorhabditis elegans AD models, CP-2-LPs significantly outperformed free CP-2 by improving cognitive and behavioral functions, extending lifespan, and reducing toxic AβO levels. Intravenous injection of fluorescently labeled CP-2-LPs reveals effective blood-brain barrier penetration, with significantly higher brain fluorescence in transgenic mice than WT, enabling precise diagnosis. These findings underscore CP-2-LPs as a valuable tool for early detection and targeted therapy in AD.

Engineered Antibodies to Improve Efficacy against Neurodegenerative Disorders

Antibodies that can selectively remove rogue proteins in the brain are an obvious choice to treat neurodegenerative disorders (NDs), but after decades of efforts, only two antibodies to treat Alzheimer's disease are approved, dozens are in the testing phase, and one was withdrawn, and the other halted, likely due to efficacy issues. However, these outcomes should have been evident since these antibodies cannot enter the brain sufficiently due to the blood-brain barrier (BBB) protectant. However, all products can be rejuvenated by binding them with transferrin, preferably as smaller fragments. This model can be tested quickly and at a low cost and should be applied to bapineuzumab, solanezumab, crenezumab, gantenerumab, aducanumab, lecanemab, donanemab, cinpanemab, and gantenerumab, and their fragments. This paper demonstrates that conjugating with transferrin does not alter the binding to brain proteins such as amyloid-β (Aβ) and α-synuclein. We also present a selection of conjugate designs that will allow cleavage upon entering the brain to prevent their exocytosis while keeping the fragments connected to enable optimal binding to proteins. The identified products can be readily tested and returned to patients with the lowest regulatory cost and delays. These engineered antibodies can be manufactured by recombinant engineering, preferably by mRNA technology, as a more affordable solution to meet the dire need to treat neurodegenerative disorders effectively.

Native ion mobility-mass spectrometry reveals the binding mechanisms of anti-amyloid therapeutic antibodies

One of the most important attributes of anti-amyloid antibodies is their selective binding to oligomeric and amyloid aggregates. However, current methods of examining the binding specificities of anti-amyloid β (Aβ) antibodies have limited ability to differentiate between complexes that form between antibodies and monomeric or oligomeric Aβ species during the dynamic Aβ aggregation process. Here, we present a high-resolution native ion-mobility mass spectrometry (nIM-MS) method to investigate complexes formed between a variety of Aβ oligomers and three Aβ-specific IgGs, namely two antibodies with relatively high conformational specificity (aducanumab and A34) and one antibody with low conformational specificity (crenezumab). We found that crenezumab primarily binds Aβ monomers, while aducanumab preferentially binds Aβ monomers and dimers and A34 preferentially binds Aβ dimers, trimers, and tetrameters. Through collision induced unfolding (CIU) analysis, our data indicate that antibody stability is increased upon Aβ binding and, surprisingly, this stabilization involves the Fc region. Together, we conclude that nIM-MS and CIU enable the identification of Aβ antibody binding stoichiometries and provide important details regarding antibody binding mechanisms.

Chiral nanomaterial-based approaches for diagnosis and treatment of protein-aggregated neurodiseases: current status and future opportunities

Protein misfolding and its aggregation, known as amyloid aggregates (Aβ), are some of the major causes of more than 20 diseases such as Parkinson's disease, Alzheimer's disease, and type 2 diabetes. The process of Aβ formation involves an energy-driven oligomerization of Aβ monomers, leading to polymerization and eventual aggregation into fibrils. Aβ fibrils exhibit multilevel chirality arising from its amino acid residues and the arrangement of folded polypeptide chains; thus, a chirality-driven approach can be utilized for the detection and inhibition of Aβ fibrils. In this regard, chiral nanomaterials have recently opened new possibilities for various biomedical applications owing to their stereoselective interaction with biological systems. Leveraging this chirality-driven approach with chiral nanomaterials against protein-aggregated diseases could yield promising results, particularly in the early detection of Aβ forms and the inhibition of Aβ aggregate formation via specific and strong "chiral-chiral interaction." Despite the advantages, the development of advanced theranostic systems using chiral nanomaterials against protein-aggregated diseases has received limited attention so far because of considerably limited formulations for chiral nanomaterials and lack of information of their chiroptical behavior. This review aims to present the current status of chiral nanomaterials explored for detecting and inhibiting Aβ forms. This review covers the origin of chirality in amyloid fibrils and nanomaterials and different chiral detection methods; furthermore, different chiral nanosystems such as chiral plasmonic nanomaterials, chiral carbon-based nanomaterials, and chiral nanosurfaces, which have been used so far for different therapeutic applications against protein-aggregated diseases, are discussed in detail. The findings from this review may pave the way for the development of novel approaches using chiral nanomaterials to combat diseases resulting from protein misfolding and can further be extended to other disease forms.

Altered amyloid-β structure markedly reduces gliosis in the brain of mice harboring the Uppsala APP deletion

Deposition of amyloid beta (Aβ) into plaques is a major hallmark of Alzheimer's disease (AD). Different amyloid precursor protein (APP) mutations cause early-onset AD by altering the production or aggregation properties of Aβ. We recently identified the Uppsala APP mutation (APPUpp), which causes Aβ pathology by a triple mechanism: increased β-secretase and altered α-secretase APP cleavage, leading to increased formation of a unique Aβ conformer that rapidly aggregates and deposits in the brain. The aim of this study was to further explore the effects of APPUpp in a transgenic mouse model (tg-UppSwe), expressing human APP with the APPUpp mutation together with the APPSwe mutation. Aβ pathology was studied in tg-UppSwe brains at different ages, using ELISA and immunohistochemistry. In vivo PET imaging with three different PET radioligands was conducted in aged tg-UppSwe mice and two other mouse models; tg-ArcSwe and tg-Swe. Finally, glial responses to Aβ pathology were studied in cell culture models and mouse brain tissue, using ELISA and immunohistochemistry. Tg-UppSwe mice displayed increased β-secretase cleavage and suppressed α-secretase cleavage, resulting in AβUpp42 dominated diffuse plaque pathology appearing from the age of 5-6 months. The γ-secretase cleavage was not affected. Contrary to tg-ArcSwe and tg-Swe mice, tg-UppSwe mice were [11C]PiB-PET negative. Antibody-based PET with the 3D6 ligand visualized Aβ pathology in all models, whereas the Aβ protofibril selective mAb158 ligand did not give any signals in tg-UppSwe mice. Moreover, unlike the other two models, tg-UppSwe mice displayed a very faint glial response to the Aβ pathology. The tg-UppSwe mouse model thus recapitulates several pathological features of the Uppsala APP mutation carriers. The presumed unique structural features of AβUpp42 aggregates were found to affect their interaction with anti-Aβ antibodies and profoundly modify the Aβ-mediated glial response, which may be important aspects to consider for further development of AD therapies.

Navigating the Alzheimer's Treatment Landscape: Unraveling Amyloid-beta Complexities and Pioneering Precision Medicine Approaches

A variety of cutting-edge methods and good knowledge of the illness's complex causes are causing a sea change in the field of Alzheimer's Disease (A.D.) research and treatment. Precision medicine is at the vanguard of this change, where individualized treatment plans based on genetic and biomarker profiles give a ray of hope for customized therapeutics. Combination therapies are becoming increasingly popular as a way to address the multifaceted pathology of Alzheimer's by simultaneously attacking Aβ plaques, tau tangles, neuroinflammation, and other factors. The article covers several therapeutic design efforts, including BACE inhibitors, gamma- secretase modulators, monoclonal antibodies (e.g., Aducanumab and Lecanemab), and anti- Aβ vaccinations. While these techniques appear promising, clinical development faces safety concerns and uneven efficacy. To address the complicated Aβ pathology in Alzheimer's disease, a multimodal approach is necessary. The statement emphasizes the continued importance of clinical trials in addressing safety and efficacy concerns. Looking ahead, it suggests that future treatments may take into account genetic and biomarker traits in order to provide more personalized care. Therapies targeting Aβ, tau tangles, neuroinflammation, and novel drug delivery modalities are planned. Nanoparticles and gene therapies are only two examples of novel drug delivery methods that have the potential to deliver treatments more effectively, with fewer side effects, and with better therapeutic results. In addition, medicines that target tau proteins in addition to Aβ are in the works. Early intervention, based on precise biomarkers, is a linchpin of Alzheimer's care, emphasizing the critical need for detecting the disease at its earliest stages. Lifestyle interventions, encompassing diet, exercise, cognitive training, and social engagement, are emerging as key components in the fight against cognitive decline. Data analytics and art are gaining prominence as strategies to mitigate the brain's inflammatory responses. To pool knowledge and resources in the fight against Alzheimer's, international cooperation between scientists, doctors, and pharmaceutical companies is still essential. In essence, a complex, individualized, and collaborative strategy will characterize Alzheimer's research and therapy in the future. Despite obstacles, these encouraging possibilities show the ongoing commitment of the scientific and medical communities to combat A.D. head-on, providing a glimmer of hope to the countless people and families touched by this savage sickness.

Polyvalency: an emerging trend in the development of clinical antibodies

Medicine has benefited greatly from the development of monoclonal antibody (mAb) technology. First-generation mAbs have seen significant success in the treatment of major diseases, such as autoimmune, inflammation, cancer, infectious, and cardiovascular diseases. Developing next-generation antibodies with improved potency, safety, and non-natural characteristics is a booming field of mAb research. In this review, we discuss the significance of polyvalency and polyvalent antibodies, as well as important findings from preclinical studies and clinical trials involving polyvalent antibodies. We then review the role of tumor necrosis factor-alpha (TNF-α) in inflammatory diseases and the need for polyvalent anti-TNF-α antibodies.

Amyloid fibril proteomics of AD brains reveals modifiers of aggregation and toxicity

BACKGROUND

The accumulation of amyloid beta (Aβ) peptides in fibrils is prerequisite for Alzheimer's disease (AD). Our understanding of the proteins that promote Aβ fibril formation and mediate neurotoxicity has been limited due to technical challenges in isolating pure amyloid fibrils from brain extracts.

METHODS

To investigate how amyloid fibrils form and cause neurotoxicity in AD brain, we developed a robust biochemical strategy. We benchmarked the success of our purifications using electron microscopy, amyloid dyes, and a large panel of Aβ immunoassays. Tandem mass-spectrometry based proteomic analysis workflows provided quantitative measures of the amyloid fibril proteome. These methods allowed us to compare amyloid fibril composition from human AD brains, three amyloid mouse models, transgenic Aβ42 flies, and Aβ42 seeded cultured neurons.

RESULTS

Amyloid fibrils are primarily composed by Aβ42 and unexpectedly harbor Aβ38 but generally lack Aβ40 peptides. Multidimensional quantitative proteomics allowed us to redefine the fibril proteome by identifying 20 new amyloid-associated proteins. Notably, we confirmed 57 previously reported plaque-associated proteins. We validated a panel of these proteins as bona fide amyloid-interacting proteins using antibodies and orthogonal proteomic analysis. One metal-binding chaperone metallothionein-3 is tightly associated with amyloid fibrils and modulates fibril formation in vitro. Lastly, we used a transgenic Aβ42 fly model to test if knock down or over-expression of fibril-interacting gene homologues modifies neurotoxicity. Here, we could functionally validate 20 genes as modifiers of Aβ42 toxicity in vivo.

CONCLUSIONS

These discoveries and subsequent confirmation indicate that fibril-associated proteins play a key role in amyloid formation and AD pathology.

Commentaries: Lecanemab: pioneering the way as the first approved drug for Alzheimer's disease treatment

Alzheimer's disease (AD) is a progressive neurodegenerative disorder marked by cognitive decline and neuronal abnormalities. Current therapies address symptoms without altering disease progression. Lecanemab, an anti-amyloid antibody, binds to amyloid-beta (Aβ) protofibrils. Phase II trials revealed dose-dependent amyloid clearance and reduced clinical decline. Phase III trials demonstrated cognitive benefits with potential adverse events. Full FDA approval was granted for lecanemab due to its ability to eliminate toxic brain amyloids. However, longer trials are needed to assess its efficacy and safety. While lecanemab marks a significant advancement, further breakthroughs are essential for effective AD treatment.

Are fibrinaloid microclots a cause of autoimmunity in Long Covid and other post-infection diseases?

It is now well established that the blood-clotting protein fibrinogen can polymerise into an anomalous form of fibrin that is amyloid in character; the resultant clots and microclots entrap many other molecules, stain with fluorogenic amyloid stains, are rather resistant to fibrinolysis, can block up microcapillaries, are implicated in a variety of diseases including Long COVID, and have been referred to as fibrinaloids. A necessary corollary of this anomalous polymerisation is the generation of novel epitopes in proteins that would normally be seen as 'self', and otherwise immunologically silent. The precise conformation of the resulting fibrinaloid clots (that, as with prions and classical amyloid proteins, can adopt multiple, stable conformations) must depend on the existing small molecules and metal ions that the fibrinogen may (and is some cases is known to) have bound before polymerisation. Any such novel epitopes, however, are likely to lead to the generation of autoantibodies. A convergent phenomenology, including distinct conformations and seeding of the anomalous form for initiation and propagation, is emerging to link knowledge in prions, prionoids, amyloids and now fibrinaloids. We here summarise the evidence for the above reasoning, which has substantial implications for our understanding of the genesis of autoimmunity (and the possible prevention thereof) based on the primary process of fibrinaloid formation.

Anti-Amyloid Monoclonal Antibodies are Transformative Treatments that Redefine Alzheimer's Disease Therapeutics

Two anti-amyloid monoclonal antibodies (MABs)-lecanemab (Leqembi®) and aducanumab (Aduhelm®)-have been approved in the USA for the treatment of Alzheimer's disease (AD). Anti-amyloid monoclonal antibodies are the first disease-modifying therapies for AD that achieve slowing of clinical decline by intervening in the basic biological processes of the disease. These are breakthrough agents that can slow the inevitable progression of AD into more severe cognitive impairment. The results of trials of anti-amyloid MABs support the amyloid hypothesis and amyloid as a target for AD drug development. The success of MABs reflects a relentless application of neuroscience knowledge to solving major challenges facing humankind. The success of these transformative agents will foster the development of more anti-amyloid MABs, other types of anti-amyloid therapies, treatments of other targets of AD biology, and new approaches to therapies for an array of neurodegenerative disorders. Monoclonal antibodies have side effects and, during the period of treatment initiation, patients must be closely monitored for the occurrence of amyloid-related imaging abnormalities (ARIA) and infusion reactions. A successful first step in the development of disease-modifying therapy for AD defines desirable features for the next phase of therapeutic development including less frequent ARIA, more convenient administration, and greater efficacy. Unprecedented agents make new demands on patients and care partners, clinicians, payers, and health care systems. Collaboration among stakeholders is essential to take advantage of the therapeutic benefits offered by these agents and to make them widely available. Monoclonal antibodies usher in a new era in AD therapy and define a new landscape of what is possible for therapeutic development for neurodegenerative disorders.

Multivalent design of the monoclonal SynO2 antibody improves binding strength to soluble α-Synuclein aggregates

Soluble aggregates are reported to be the most neurotoxic species of α-Synuclein (αSyn) in Parkinson's disease (PD) and hence are a promising target for diagnosis and treatment of PD. However, the predominantly intracellular location of αSyn limits its accessibility, especially for antibody-based molecules and prompts the need for exceptionally strong soluble αSyn aggregate binders to enhance their sensitivity and efficacy for targeting the extracellular αSyn pool. In this study, we have created the multivalent antibodies TetraSynO2 and HexaSynO2, derived from the αSyn oligomer-specific antibody SynO2, to increase avidity binding to soluble αSyn aggregate species through more binding sites in close proximity. The multivalency was achieved through recombinant fusion of single-chain variable fragments of SynO2 to the antibodies' original N-termini. Our ELISA results indicated a 20-fold increased binding strength of the multivalent formats to αSyn aggregates, while binding to αSyn monomers and unspecific binding to amyloid β protofibrils remained low. Kinetic analysis using LigandTracer revealed that only 80% of SynO2 bound bivalently to soluble αSyn aggregates, whereas the proportion of TetraSynO2 and HexaSynO2 binding bi- or multivalently to soluble αSyn aggregates was increased to ~ 95% and 100%, respectively. The overall improved binding strength of TetraSynO2 and HexaSynO2 implies great potential for immunotherapeutic and diagnostic applications with targets of limited accessibility, like extracellular αSyn aggregates. The ability of the multivalent antibodies to bind a wider range of αSyn aggregate species, which are not targetable by conventional bivalent antibodies, thus could allow for an earlier and more effective intervention in the progression of PD.

Aβ42 oligomer-specific antibody ALZ-201 reduces the neurotoxicity of Alzheimer's disease brain extracts

BACKGROUND

In Alzheimer's disease (AD), amyloid-β 1-42 (Aβ42) neurotoxicity stems mostly from its soluble oligomeric aggregates. Studies of such aggregates have been hampered by the lack of oligomer-specific research tools and their intrinsic instability and heterogeneity. Here, we developed a monoclonal antibody with a unique oligomer-specific binding profile (ALZ-201) using oligomer-stabilising technology. Subsequently, we assessed the etiological relevance of the Aβ targeted by ALZ-201 on physiologically derived, toxic Aβ using extracts from post-mortem brains of AD patients and controls in primary mouse neuron cultures.

METHODS

Mice were immunised with stable oligomers derived from the Aβ42 peptide with A21C/A30C mutations (AβCC), and ALZ-201 was developed using hybridoma technology. Specificity for the oligomeric form of the Aβ42CC antigen and Aβ42 was confirmed using ELISA, and non-reactivity against plaques by immunohistochemistry (IHC). The antibody's potential for cross-protective activity against pathological Aβ was evaluated in brain tissue samples from 10 individuals confirmed as AD (n=7) and non-AD (n=3) with IHC staining for Aβ and phosphorylated tau (p-Tau) aggregates. Brain extracts were prepared and immunodepleted using the positive control 4G8 antibody, ALZ-201 or an isotype control to ALZ-201. Fractions were biochemically characterised, and toxicity assays were performed in primary mouse neuronal cultures using automated high-content microscopy.

RESULTS

AD brain extracts proved to be more toxic than controls as demonstrated by neuronal loss and morphological determinants (e.g. synapse density and measures of neurite complexity). Immunodepletion using 4G8 reduced Aβ levels in both AD and control samples compared to ALZ-201 or the isotype control, which showed no significant difference. Importantly, despite the differential effect on the total Aβ content, the neuroprotective effects of 4G8 and ALZ-201 immunodepletion were similar, whereas the isotype control showed no effect.

CONCLUSIONS

ALZ-201 depletes a toxic species in post-mortem AD brain extracts causing a positive physiological and protective impact on the integrity and morphology of mouse neurons. Its unique specificity indicates that a low-abundant, soluble Aβ42 oligomer may account for much of the neurotoxicity in AD. This critical attribute identifies the potential of ALZ-201 as a novel drug candidate for achieving a true, clinical therapeutic effect in AD.

Introducing or removing heparan sulfate binding sites does not alter brain uptake of the blood-brain barrier shuttle scFv8D3

The blood-brain barrier (BBB) greatly limits the delivery of protein-based drugs into the brain and is a major obstacle for the treatment of brain disorders. Targeting the transferrin receptor (TfR) is a strategy for transporting protein-based drugs into the brain, which can be utilized by using TfR-binding BBB transporters, such as the TfR-binding antibody 8D3. In this current study, we investigated if binding to heparan sulfate (HS) contributes to the brain uptake of a single chain fragment variable of 8D3 (scFv8D3). We designed and produced a scFv8D3 mutant, engineered with additional HS binding sites, HS(+)scFv8D3, to assess whether increased HS binding would improve brain uptake. Additionally, a mutant with a reduced number of HS binding sites, HS(-)scFv8D3, was also engineered to see if reducing the HS binding sites could also affect brain uptake. Heparin column chromatography showed that only the HS(+)scFv8D3 mutant bound HS in the experimental conditions. Ex vivo results showed that the brain uptake was unaffected by the introduction or removal of HS binding sites, which indicates that scFv8D3 is not dependent on the HS binding sites for brain uptake. Conversely, introducing HS binding sites to scFv8D3 decreased its renal excretion while removing them had the opposite effect.

Blood-brain barrier penetrating neprilysin degrades monomeric amyloid-beta in a mouse model of Alzheimer's disease

BACKGROUND

Aggregation of the amyloid-β (Aβ) peptide in the brain is one of the key pathological events in Alzheimer's disease (AD). Reducing Aβ levels in the brain by enhancing its degradation is one possible strategy to develop new therapies for AD. Neprilysin (NEP) is a membrane-bound metallopeptidase and one of the major Aβ-degrading enzymes. The secreted soluble form of NEP (sNEP) has been previously suggested as a potential protein-therapy degrading Aβ in AD. However, similar to other large molecules, peripherally administered sNEP is unable to reach the brain due to the presence of the blood-brain barrier (BBB).

METHODS

To provide transcytosis across the BBB, we recombinantly fused the TfR binding moiety (scFv8D3) to either sNEP or a previously described variant of NEP (muNEP) suggested to have higher degradation efficiency of Aβ compared to other NEP substrates, but not per se to degrade Aβ more efficiently. To provide long blood half-life, an Fc-based antibody fragment (scFc) was added to the designs, forming sNEP-scFc-scFv8D3 and muNEP-scFc-scFv8D3. The ability of the mentioned recombinant proteins to degrade Aβ was first evaluated in vitro using synthetic Aβ peptides followed by sandwich ELISA. For the in vivo studies, a single injection of 125-iodine-labelled sNEP-scFc-scFv8D3 and muNEP-scFc-scFv8D3 was intravenously administered to a tg-ArcSwe mouse model of AD, using scFc-scFv8D3 protein that lacks NEP as a negative control. Different ELISA setups were applied to quantify Aβ concentration of different conformations, both in brain tissues and blood samples.

RESULTS

When tested in vitro, sNEP-scFc-scFv8D3 retained sNEP enzymatic activity in degrading Aβ and both constructs efficiently degraded arctic Aβ. When intravenously injected, sNEP-scFc-scFv8D3 demonstrated 20 times higher brain uptake compared to sNEP. Both scFv8D3-fused NEP proteins significantly reduced aggregated Aβ levels in the blood of tg-ArcSwe mice, a transgenic mouse model of AD, following a single intravenous injection. In the brain, monomeric and oligomeric Aβ were significantly reduced. Both scFv8D3-fused NEP proteins displayed a fast clearance from the brain.

CONCLUSION

A one-time injection of a BBB-penetrating NEP shows the potential to reduce, the likely most toxic, Aβ oligomers in the brain in addition to monomers. Also, Aβ aggregates in the blood were reduced.

A Brain-Targeting Bispecific-Multivalent Antibody Clears Soluble Amyloid-Beta Aggregates in Alzheimer's Disease Mice

Amyloid-β (Aβ) oligomers and protofibrils are suggested to be the most neurotoxic Aβ species in Alzheimer's disease (AD). Hence, antibodies with strong and selective binding to these soluble Aβ aggregates are of therapeutic potential. We have recently introduced HexaRmAb158, a multivalent antibody with additional Aβ-binding sites in the form of single-chain fragment variables (scFv) on the N-terminal ends of Aβ protofibril selective antibody (RmAb158). Due to the additional binding sites and the short distance between them, HexaRmAb158 displayed a slow dissociation from protofibrils and strong binding to oligomers in vitro. In the current study, we aimed at investigating the therapeutic potential of this antibody format in vivo using mouse models of AD. To enhance BBB delivery, the transferrin receptor (TfR) binding moiety (scFv8D3) was added, forming the bispecific-multivalent antibody (HexaRmAb158-scFv8D3). The new antibody displayed a weaker TfR binding compared to the previously developed RmAb158-scFv8D3 and was less efficiently transcytosed in a cell-based BBB model. HexaRmAb158 detected soluble Aβ aggregates derived from brains of tg-ArcSwe and AppNL-G-F mice more efficiently compared to RmAb158. When intravenously injected, HexaRmAb158-scFv8D3 was actively transported over the BBB into the brain in vivo. Brain uptake was marginally lower than that of RmAb158-scFv8D3, but significantly higher than observed for conventional IgG antibodies. Both antibody formats displayed similar brain retention (72 h post injection) and equal capacity in clearing soluble Aβ aggregates in tg-ArcSwe mice. In conclusion, we demonstrate a bispecific-multivalent antibody format capable of passing the BBB and targeting a wide-range of sizes of soluble Aβ aggregates.