Safety and Efficacy of Anti-Amyloid-β Immunotherapy in Alzheimer’s Disease: A Systematic Review and Meta-Analysis

Immunotherapeutics targeting amyloid-β (Aβ) have had mixed results in clinical trials. The present study aims to evaluate the safety and clinical efficacy of immunotherapeutic agents targeting Aβ in Alzheimer’s disease. Randomised controlled trials of at least two weeks duration were included in the review. Fourteen randomised controlled trials (n = 5554) were identified in a systematic search of eight electronic databases. Upon pooling of data, there was no increased risk of any adverse event, serious adverse events, or death with the exception of a near fivefold increase in amyloid-related imaging abnormalities (ARIA; OR 4.79, 95% CI 1.24–18.55; p = 0.02). Of the cognitive indicators, the Mini-Mental State Examination (MMSE) showed a small statistically significant improvement (diff in means =0.44; p = 0.02), while the others (ADAS-cog, ADCS-ADL, and CDR-sb) showed no change. Therefore, immunotherapeutic agents have been relatively well tolerated, with some promise for cognitive improvements if the occurrence of ARIA can be mitigated.     

Pathological changes induced by amyloid-β in Alzheimer's disease

The pathologic hallmarks of Alzheimer's disease (AD) include senile plaque, neurofibrillary tangles (NFTs), synaptic loss, and neurodegeneration. Senile plaque and NFTs are formed by accumulation of amyloid-β (Aβ) and hyperphosphorylated tau, respectively. Progressive synaptic dysfunction and loss closely correlate with cognitive deficits in AD. Based on studies of the genes responsible for familial AD and temporal patterns of pathologic changes in AD brains, the Aβ accumulation is thought to be a primary event that influences other AD pathologies in the developmental cascade of AD. However, the details of Aβ effects on the other AD pathologies remain poorly understood. In this review, we provide an overview of the effects of Aβ in AD brains, especially focusing on synaptic dysfunction and microglia. We have recently found abnormal accumulation of a key molecule for actin assembly in NFTs of AD brains, and it was revealed that the accumulation requires not only tau pathology but also an Aβ burden in a study using transgenic mouse models of AD. Synaptic integrity is morphologically maintained by the precise regulation of actin assembly. Therefore, the results suggest the possibility that Aβ may promote NFT maturation and induce synaptic dysfunction through the disturbance of actin assembly. Thus Aβ seems to be a promoting factor in brain aging. On the other hand, we have studied microglial phagocytic ability for a compensatory pathologic reaction to Aβ accumulation. Further studies on the Aβ-dependent AD pathologies may contribute to determining novel mechanisms of AD development and new therapeutic targets in AD.     

Mechanisms of Amyloid-β Peptide Clearance: Potential Therapeutic Targets for Alzheimer’s Disease

Amyloid-β peptide (Aβ) is still best known as a molecule to cause Alzheimer’s disease (AD) through accumulation and deposition within the frontal cortex and hippocampus in the brain. Thus, strategies on developing AD drugs have been focused on the reduc-tion of Aβ in the brain. Since accumulation of Aβ depends on the rate of its synthesis and clearance, the metabolic pathway of Aβ in the brain and the whole body should be carefully explored for AD research. Although the synthetic pathway of Aβ is equally important, we summarize primarily the clearance pathway in this paper because the former has been extensively reviewed in previous studies. The clearance of Aβ from the brain is accomplished by several mechanisms which include non-enzymatic and enzymatic pathways. Nonenzymatic pathway includes interstitial fluid drainage, uptake by microglial phagocytosis, and transport across the blood vessel walls into the circulation. Multiple Aβ-degrading enzymes (ADE) implicated in the clearance process have been identified, which include neprilysin, insulin-degrading enzyme, matrix metalloproteinase-9, glutamate carboxypeptidase II and others. A series of studies on Aβ clearance mechanism provide new insight into the pathogenesis of AD at the molecular level and suggest a new target for the development of novel therapeutics.     

Novel aβ isoforms in Alzheimer's disease - their role in diagnosis and treatment

The last decades have witnessed an explosion in studies of the role of amyloid-β (Aβ) in the progress of the neurodegenerative disorder Alzheimer's disease (AD) and it is now widely accepted that Aβ is related to the pathogenesis of AD. For example, studies have shown that Aβ is neurotoxic and that the neurotoxicity of Aβ is related to its aggregation state. The concentration of the 42 amino acid form of Aβ (Aβ1-42) is reduced in the cerebrospinal fluid (CSF) from AD patients, which is believed to reflect the AD pathology with plaques in the brain acting as sinks. Less well investigated, however, is the ability of other Aβ isoforms to distinguish AD patients from controls and to identify treatment effects in clinical trials. Recently, novel C-truncated forms of Aβ (Aβ1-14, Aβ1-15, and Aβ1-16) were identified in human CSF. The presence of these small peptides is consistent with a catabolic amyloid precursor protein cleavage pathway by β- followed by α-secretase. It has been shown that Aβ1-14, Aβ1-15, and Aβ1-16 increase dose-dependently in response to γ-secretase inhibitor treatment while Aβ1-42 levels are unchanged. Here, we review the many aspects of Aβ and its isoforms with special focus on their potential role as diagnostic and theragnostic markers.     

The Effect of HIV Protease Inhibitors on Amyloid-β Peptide Degradation and Synthesis in Human Cells and Alzheimer’s Disease Animal Model

Combined antiretroviral therapy (ART) tremendously improved the lifespan and symptoms associated with AIDS-defining illness in affected individuals. However, chronic ART-treated patients frequently develop age-dependent complications, including dementia, diabetes, and hyperlipidemia: all risk factors of Alzheimer??s disease. Importantly, the effect of ART compounds on amyloid generation and clearance has never been systematically examined. Nine prescribed HIV protease inhibitors were tested for their effect on amyloid-?? peptide (A??) clearance in primary cultured human monocyte-derived macrophages. Atazanavir, ritonavir, and saquinavir modestly inhibited of A?? degradation, while lopinavir, nelfinavir, and ritonavir enhanced secretion of undigested A?? after phagocytosis. Lopinavir, nelfinavir, ritonavir, and saquinavir inhibited endogenous A??40 production from primary cultured human cortical neurons, which were associated with reduction in Beta-site APP Converting Enzyme 1 (BACE1) and ??-secretase enzyme activities. However, ART compounds showed little inhibition of purified BACE1 activity in vitro, suggesting the indirect effect of ART compounds on BACE1 activity in neurons. Finally, nefinavir or lopinavir/ritonavir (Kaletra) were orally administered for 30?days into APP SCID mice expressing a double mutant form of APP 695 (KM670/671NL + V717F) in homozygosity for the scid allele of Prkdc. There was no difference in beta-amyloidosis by ART drug administration as determined by both immunohistochemistry and ELISA measurements although the therapeutic doses of the ART compounds was present in the brain. These data demonstrated that ART drugs can inhibit A?? clearance in macrophages and A?? production in neurons, but these effects did not significantly alter A?? accumulation in the mouse brain.     

Increased Amyloid-β Peptide-Induced Memory Deficits in Phospholipid Transfer Protein (PLTP) Gene Knockout Mice

Oxidative stress is recognized as one of the earliest and most intense pathological processes in Alzheimer''s disease (AD), and the antioxidant vitamin E has been shown to efficiently prevent amyloid plaque formation and neurodegeneration. Plasma phospholipid transfer protein (PLTP) has a major role in vitamin E transfers in vivo, and PLTP deficiency in mice is associated with reduced brain vitamin E levels. To determine the impact of PLTP on amyloid pathology in vivo, we analyzed the vulnerability of PLTP-deficient (PLTP-KO) mice to the toxic effects induced by intracerebroventricular injection of oligomeric amyloid-β_25–35 (Aβ_25–35) peptide, a non-transgenic model of AD. Under basal conditions, PLTP-KO mice showed increased cerebral oxidative stress, increased brain Aβ_1–42 levels, and a lower expression of the synaptic function marker synaptophysin, as compared with wild-type mice. This PLTP-KO phenotype was associated with increased memory impairment 1 week after Aβ_25–35 peptide injection. Restoration of brain vitamin E levels in PLTP-KO mice through a chronic dietary supplementation prevented Aβ_25–35-induced memory deficits and reduced cerebral oxidative stress and toxicity. We conclude that PLTP, through its ability to deliver vitamin E to the brain, constitutes an endogenous neuroprotective agent. Increasing PLTP activity may offer a new way to develop neuroprotective therapies.     

Clinical Trials in Japan-New GCP

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PP1 inhibition by Aβ peptide as a potential pathological mechanism in Alzheimer's disease

Abnormal protein phosphorylation has been associated with several neurodegenerative disorders, including Alzheimer's disease (AD). Aβ is the toxic peptide that results from proteolytic cleavage of the Alzheimer's amyloid precursor protein, a process where protein phosphatases are known to impact. The data presented here demonstrates that protein phosphatase 1 (PP1), an abundant neuronal serine/threonine-specific phosphatase highly enriched in dendritic spines, is specifically inhibited by Aβ peptides both in vitro and ex vivo. Indeed, the pathologically relevant Aβ_1–40 and Aβ_1–42 peptides, as well as Aβ_25–35, specifically inhibit PP1 with low micromolar potency, as compared to inactive controls and other disease related peptides (e.g. the prion related Pr_118–135 and Pr_106–126). Interestingly, PP1 inhibition is increased by Aβ aggregation, indicating a possible direct neurotoxic effect of the aggregated peptide. PP1 involvement in processes like long-term depression, memory and learning, and synaptic plasticity, prompt us to suggest that PP1 may constitute an important physiological target for Aβ and, therefore, increased Aβ production and/or aggregation may lead to abnormal PP1 activity and likely contribute to the progressive neuropsychiatric AD condition. Thus, PP1 activity and levels constitute potential biomolecular candidates for diagnostics and therapeutics.     

Curcumin mediates presenilin-1 activity to reduce β-amyloid production in a model of Alzheimer's Disease

Curcumin has been reported to inhibit the generation of Aβ, but the underlying mechanisms by which this occurs remain unknown. Aβ is thought to play an important role in the pathogenesis of Alzheimer's disease (AD). The amyloid hypothesis argues that aggregates of Aβ trigger a complex pathological cascade that leads to neurodegeneration. Aβ is generated by the processing of APP (amyloid precursor protein) by β- and γ-secretases. Presenilin 1 (PS1) is central to γ-secretase activity and is a substrate for GSK-3β, both of which are implicated in the pathogenesis of AD. The present study aimed to investigate the effects of curcumin on the generation of Aβ in cultured neuroblastoma cells and on the in vitro expression of PS1 and GSK-3β. To stimulate Aβ production, a plasmid expressing APP was transfected into human SH-SY5Y neuroblastoma cells. The transfected cells were then treated with curcumin at 0-20 μM for 24 h or with 5 μM curcumin for 0-48 h, and the extracellular levels of Aβ(40/42) were determined by ELISA. The levels of PS1 and GSK-3β mRNA were measured by RT-PCR, and the expression of the PS1 and GSK-3β proteins (including the phosphorylated form of GSK-3β, p-GSK-3β-Ser9) were evaluated by western blotting. Curcumin treatment was found to markedly reduce the production of Aβ(40/42). Treatment with curcumin also decreased both PS1 and GSK-3β mRNA and protein levels in a dose- and time-dependent manner. Furthermore, curcumin increased the inhibitory phosphorylation of GSK-3β protein at Ser9. Therefore, we propose that curcumin decreases Aβ production by inhibiting GSK-3β-mediated PS1 activation.     

Comparisons of Serum Infliximab and Antibodies-to-Infliximab Tests Used in Inflammatory Bowel Disease Clinical Trials of Remicade®

Monitoring infliximab (IFX) concentrations and antibodies-to-IFX (ATI) titers during inflammatory bowel disease treatment may allow more informed decisions in assessing exposure/response and determining appropriate dosing. To aid in interpreting results from different commercial tests in the context of Janssen’s published Remicade® results, the reliability of Janssen’s IFX and ATI assays was compared with commercial assays from KU Leuven, Sanquin, Dynacare, and LabCorp. Test results were independently reported to Janssen. All assays were tested for specificity, selectivity, and precision. ATI assays were evaluated for sensitivity, drug interference, and potential interference of tumor necrosis factor-alpha (TNF-α). IFX assays were specific, accurate, and reproducible. Intra-class correlation of Janssen IFX assay results with those from KU Leuven, Sanquin, Dynacare, and LabCorp were 0.960, 0.895, 0.931, and 0.971, respectively. ATI titers >10 interfered with IFX assessment in all IFX assays, whereas TNF-α (≤50 ng/mL) did not interfere with IFX detection in any assay. ATI assays specifically and reproducibly detected ATI. Janssen, Sanquin, and LabCorp ATI methods were more resistant to IFX interference than Dynacare and KU Leuven, which were affected by IFX concentrations at ≥2 μg/mL. TNF-α (<5 ng/mL) did not interfere with ATI detection. Strong agreement was observed between Janssen’s IFX and ATI assays and the diagnostic service provider assays. Our study results indicate that all four commercially available assays are suitable for therapeutic drug monitoring of IFX. The substantial agreement reported here between the comparator assays and the Janssen drug-tolerant assay provides support to clinicians in their use of these commercial assays, and for understanding their patients’ IFX and ATI results relative to published data from clinical studies of Remicade.     

Brain Clearance of Alzheimer's Amyloid-β40 in the Squirrel Monkey: A SPECT Study in a Primate Model of Cerebral Amyloid Angiopathy

Squirrel monkey is a valuable model to study pathogenesis of cerebrovascular amyloid angiopathy (CAA). Previous studies suggested that circulating amyloid- β 40 peptide (A β 40) crosses the blood-brain barrier (BBB) and may therefore enhance cerebrovascular amyloidosis in aged squirrel monkeys. In the present study, we used single photon emission computed tomography (SPECT) to determine elimination of 123 I-A β 40 and 99m Tc-DTPA, an extracellular marker, from the brain in squirrel monkeys at different age. Following intracerebral microinfusions, the time-activity brain clearance curves indicated bi-exponential removal of 123 I-A β 40 with an initial rapid washout (1.1 ≤ t 1/2 ≤ 2.7 h). This, plus the observed appearance of 123 I-radioactivity in plasma suggest significant brain-to-blood transport. In contrast, 99m Tc-DTPA was removed slowly by brain interstitial fluid bulk flow (monoexponential decay with 6.8 ≤ t 1/2 ≤ 16.8 h) . A comparison of three middle aged (11-16 years old) vs. two old (22 yrs old) monkeys was consistent with an age-related decline in the BBB capacity to remove 123 I-A β from the brain. This correlated with an age-dependent increase in A β 40/42 cerebrovascular immunoreactivity and amyloid deposition. Thus, vascular clearance plays an important role in reducing A β levels in the squirrel monkey brain and impaired A β 40 elimination across the BBB may contribute to the development of CAA.     

Immunotherapy of tumors with recombinant adenovirus encoding macrophage inflammatory protein 3β induces tumor-specific immune response in immunocompetent tumor-bearing mice

Aim： Tumor immunotherapy aims at activating the body＇s own immune system to fight an existing tumor. Effective antitumor responses require tumor antigens to be presented to lymphocytes. We aimed to test the hypothesis that intratumoral administration of recombinant adenovirus encoding MIP3β would induce antitumor immunity by attracting and facilitating the interaction between lymphocytes and dendritic cells.
Methods： A recombinant adenovirus encoding microphage inflammatory protein 3β （AdMIPβ） was constructed. The antitumor activity of AdMIP3β in BALB/c and C57BL/6 mice bearing CT26 colon adenocarcinoma and Lewis lung cancer was evaluated.
Results： Immunotherapy with AdMIP3β resulted in significant inhibition of tumor growth and prolonged survival of tumor-bearing mice. Tumor-specific immune responses elicited by AdMIP3β include MHC class I-dependent CD8^＋ CTL- mediated immune response and IFN-γ response. Immunohistochemical staining demonstrated numerous CD11c^＋ cells and CD3^＋ T lymphocytes within tumor tissues of AdMIP3β-treated mice. These findings suggest that the mechanism of specific antitumor immunity induced by AdMIP3β may be involved in the chemoattraction of both T lymphocytes and DCs to the tumor site and thus facilitate the process of antigen capture and mature DC to prime naive T cells.
Conclusion： The present study may be important in the exploration of the potential application of AdMIP3β in the treatment of a broad spectrum of tumors.     

NeuroDefend,a novel Chinese medicine,attenuates amyloid-β and tau pathology in experimental Alzheimer's disease models

Alzheimer's disease (AD) is the most common age-related neurodegenerative disorder. Amyloid-β (Aβ) and hyper-phosphorylated tau accumulation are accountable for the progressive neuronal loss and cognitive impairments usually observed in AD. Currently, medications for AD offer moderate symptomatic relief but fail to cure the disease; hence development of effective and safe drugs is urgently needed for AD treatment. In this study, we investigated a Chinese medicine (CM) formulation named NeuroDefend (ND), for reducing amyloid β (Aβ) and tau pathology in transgenic AD mice models. Regular oral administration of ND improved cognitive function and memory in 3XTg-AD and 5XFAD mice. In addition, ND reduced beta-amyloid precursor protein (APP), APP C-terminal fragments (CTF-β/α), Aβ and 4G8 positive Aβ burden in 3XTg-AD and 5XFAD mice. Furthermore, ND efficiently reduced the levels of insoluble phospho-tau protein aggregates and AT8 positive phospho tau neuron load in 3XTg-AD mice. Hence, ND could be a promising candidate for the treatment of AD in humans.     

Clinical Trials in Peking Union Medical College Hospital

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Tau-Directed Immunotherapy: A Promising Strategy for Treating Alzheimer’s Disease and Other Tauopathies

Immunotherapy directed against tau is a promising treatment strategy for Alzheimer’s Disease (AD) and tauopathies. We review initial studies on tau-directed immunotherapy, and present data from our laboratory testing antibodies using the rTg4510 mouse model, which deposits tau in forebrain neurons. Numerous antibodies have been tested for their efficacy in treating both pathology and cognitive function, in different mouse models, by different routes of administration, and at different ages or durations. We report, here, that the conformation-specific antibody MC-1 produces some degree of improvement to both cognition and pathology in rTg4510. Pathological improvements as measured by Gallyas staining for fully formed tangles and phosphorylated tau appeared 4 days after intracranial injection into the hippocampus. We also examined markers for microglial activation, which did not appear impacted from treatment. Behavioral effects were noted after continuous infusion of antibodies into the lateral ventricle for approximately 2 weeks. We examined basic motor skills, which were not impacted by treatment, but did note cognitive improvements with both novel object and radial arm water maze testing. Our results support earlier reports in the initial review presented here, and collectively show promise for this strategy of treatment. The general absence of extracellular tau deposits may avoid the opsonization and phagocytosis mechanisms activated by antibodies against amyloid, and make anti tau approaches a safer method of immunotherapy for Alzheimer’s disease.     

Biomarkers in oncology drug development: rescuers or troublemakers?

Oncology is considered as the pioneer indication for the clinical application of molecular biomarkers. Newly developed targeted anticancer therapies call for the implementation of molecular biomarker strategies but even novel cytotoxic treatments use biomarkers for the assessment of efficacy and toxicity. Biomarkers may play several roles in the progression of a drug from research to personalised medicine. In particular biomarkers are used to understand the mechanism of action of a drug, monitor the modulation of the intended target, assess efficacy and safety, adapt dosing and schedule, select patients and prognosticate the clinical outcome. Nowadays, the use of biomarkers in oncology is still challenged as only a limited number of oncology drugs on the market have a companion biomarker test to be mandatorily performed before treatment. This is in contradiction with the current major investment the pharmaceutical sector is devoting to biomarker identification and development. What are the measurable milestones and outcomes of these investments? How does biomarker development contribute to reaching the ultimate goal of finding the right molecules for the right targets at the right doses and schedules for the right patients? This review provides a critical overview of recent salient achievements in the identification and development of biomarkers.