[125I]IPC-Lecanemab: Synthesis and Evaluation of Aβ-Plaque-Binding Antibody and Comparison with Small-Molecule [18F]Flotaza and [125I]IBETA in Postmortem Human Alzheimer's Disease

Therapeutic antibodies for reducing Aβ plaque load in Alzheimer's disease (AD) is currently making rapid progress. The diagnostic imaging of Aβ plaque load in AD has been underway and is now used in clinical studies. Here, we report our preliminary findings on imaging a therapeutic antibody, Lecanemab, in a postmortem AD brain anterior cingulate. [125I]5-iodo-3-pyridinecarboxamido-Lecanemab ([125I]IPC-Lecanemab) was prepared by coupling N-succinimidyl-5-([125I]iodo)-3-pyridinecarboxylate with Lecanemab in modest yields. The distinct binding of [125I]IPC-Lecanemab to Aβ-rich regions in postmortem human AD brains was higher in grey matter (GM) containing Aβ plaques compared to white matter (WM) (GM/WM was 1.6). Anti-Aβ immunostaining was correlated with [125I]IPC-Lecanemab regional binding in the postmortem AD human brains. [125I]IPC-Lecanemab binding was consistent with the binding of Aβ small molecules, [18F]flotaza and [125I]IBETA, in the same subjects. [18F]Flotaza and [125I]IBETA, however, exhibited significantly higher GM/WM ratios (>20) compared to [125I]IPC-Lecanemab. Our results suggest that radiolabeled [125I]IPC-Lecanemab retains the ability to bind to Aβ in human AD and may therefore be useful as a PET imaging radiotracer when labeled as [124I]IPC-Lecanemab. The ability to directly visualize in vivo a promising therapeutic antibody for AD may be useful in treatment planning and dosing and could be complimentary to small-molecule diagnostic imaging to assess outcomes of therapeutic interventions.

How promising are the latest monoclonal antibodies targeting amyloid-β for the treatment of early Alzheimer's disease?

INTRODUCTION

Monoclonal antibodies targeting amyloid-β are the first disease-modifying treatments for Alzheimer disease to have received FDA-approval. There are three different drugs approved or pending FDA-approval: aducanumab, lecanemab, and donanemab. These three drugs are each in different stages of regulatory approval by the FDA.

AREAS COVERED

We discuss the development of these drugs, the data regarding their clinical efficacy, their dosing regimens, and side effects. In addition, we examine pragmatic issues with their potential implementation as common treatments to slow the rate of decline in Alzheimer disease, and what unanswered questions remain regarding this new class of drugs.

EXPERT OPINION

We conclude that these new monoclonal antibodies that target amyloid-β represent a genuine advance in the treatment of Alzheimer disease. However, questions remain regarding their clinical significance. Additionally, it is presently unclear which patients would most benefit from these expensive drugs given the risk of side effects and the logistical difficulties concerning administration and the determination of eligibility.

Comparative efficacy, tolerability and acceptability of donanemab, lecanemab, aducanumab and lithium on cognitive function in mild cognitive impairment and Alzheimer's disease: A systematic review and network meta-analysis

BACKGROUND

The comparative clinical utility of the disease-modifying treatments for mild cognitive impairment and Alzheimer's disease that are approved or under review by the Food and Drug Administration (i.e., donanemab, lecanemab and aducanumab), and lithium, which is a potential disease-modifying agent for this condition, remains elusive.

OBJECTIVE

We aimed to compare the efficacy on cognitive decline, tolerability and acceptability of these drugs in this condition.

METHODS

We systematically searched in MEDLINE, CENTRAL, CINHAL and ClinicalTrials,gov for randomized controlled trials from their inception to 7 November 2023, and then performed a random-effect network meta-analysis.

RESULTS

The analysis included 8 randomized placebo-controlled trials with 6547 participants. On the Mini-Mental State Examination, lithium significantly outperformed donanemab, aducanumab and placebo. On the Alzheimer's Disease Assessment Scale-cognitive subscale, the efficacy of all active drugs was significantly higher than placebo. In addition, in the Clinical Dementia Rating sum of boxes, the efficacy of donanemab and lecanemab was significantly higher than placebo. Compared to placebo, donanemab and lecanemab were significantly less acceptable and tolerable. Aducanumab was also less well tolerated compared to placebo. There were no significant differences in the other comparisons.

CONCLUSION

Although it is yet to be determined which is more effective between lithium or lecanemab or donanemab, lithium may be more effective than aducanumab. Aducanumab, lecanemab and donanemab do not appear to differ in their effectiveness on cognitive function. Low-dose lithium may be safer than aducanumab, lecanemab and donanemab.

Comparative Efficacy, Tolerability, and Acceptability of Donanemab, Lecanemab, Aducanumab, Melatonin, and Aerobic Exercise for a Short Time on Cognitive Function in Mild Cognitive Impairment and Mild Alzheimer's Disease: A Systematic Review and Network Meta-Analysis

Background

The Food and Drug Administration (FDA) has approved lecanemab and aducanumab and is reviewing donanemab, but they have questionable efficacy, serious side effects and are costly, whereas melatonin administration and aerobic exercise for a short time may overcome these problems.

Objective

We aim to compare the efficacy on cognitive function, tolerability and acceptability of melatonin administration and aerobic exercise for a short time with donanemab, lecanemab, and aducanumab in people with mild AD and MCI.

Methods

We systematically reviewed relevant randomized placebo-controlled trials (RCTs) in PubMed, the Cochrane Library, CINHAL, and ClinicalTrials.gov and performed network meta-analyses.

Results

The analysis included 10 randomized placebo-controlled trials with 4,599 patients. Although melatonin and aerobic exercise for a short time were significantly more effective than donanemab, lecanemab, aducanumab and placebo in the primary analysis, there was significant heterogeneity. In the sensitivity analysis excluding exercise, melatonin was significantly more effective than donanemab, lecanemab, aducanumab and placebo, with no significant heterogeneity. Aerobic exercise for a short time was significantly less acceptable than donanemab, aducanumab and placebo. Donanemab, lecanemab, and aducanumab were significantly less tolerable than placebo and donanemab and lecanemab were significantly less acceptable than placebo.

CONCLUSIONS

Melatonin may be a better potential disease-modifying treatment for cognitive decline in mild AD and MCI. Aerobic exercise for a short time might also be better than donanemab, lecanemab and aducanumab if continued, as it is well tolerated and more effective, although less valid due to heterogeneity. Another limitation is the small number of participants.

Once upon a time, the Amyloid Cascade Hypothesis

Recent trials with monoclonal antibodies targeting amyloid-β (Aβ) in Alzheimer's disease (AD) have sparked a renewed interest in disease-modifying therapies. Despite their promise, these trials leave the issue open and posit some doubts about the validity of the Amyloid Cascade Hypothesis (ACH). While some scores of neurocognitive tests improved upon treatment, real-world clinical benefits were minimal. This Viewpoint discusses additional, often overlooked findings from these trials. We also emphasize the multifactorial nature of AD and the need for a broader research perspective beyond the simplistic disease model provided by the ACH.

The FDA-approved anti-amyloid-β monoclonal antibodies for the treatment of Alzheimer's disease: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Alzheimer's disease (AD) is a worldwide public health problem and is difficult to cure. Drugs aimed at slowing the progression of the disease have been developed, with the Food and Drug Administration (FDA) granting accelerated approval for aducanumab on June 21, 2021 and a new accelerated approval for lecanemab on January 22, 2023. We performed this systematic review and meta-analysis to assess the efficacy and safety of FDA-approved anti-amyloid-β (anti-Aβ) monoclonal antibodies (mabs) for the treatment of AD.

METHOD

PubMed, Embase, and Cochrane Library were systematically searched to identify relevant studies published before May 2023. Efficacy outcomes included Aβ, neuroimaging, and biomarker outcomes. Safety outcomes included amyloid-related imaging abnormalities with edema or effusions (ARIA-E) and ARIA with cerebral microhemorrhages, cerebral macrohemorrhages, or superficial siderosis (ARIA-H). Review Manager 5.4 software was used to assess the data. The standard mean differences (SMDs) or odds ratio (OR) with 95% confidence interval (95% CI) were analyzed and calculated with a random effect model or a fixed effect model.

RESULT

Overall, 4471 patients from 6 randomized controlled trials (RCTs), with 2190 patients in the treatment group and 2281 patients in the placebo group meeting the inclusion criteria. FDA-approved anti-Aβ mabs showed statistically significant improvements in clinical outcomes, including CDR-SB (P = 0.01), ADCS-ADL-MCI (P = 0.00003), ADCOMS (P < 0.00001), ADAS-Cog (P < 0.00001). Moreover, FDA-approved anti-Aβ mabs increased cerebrospinal fluid (CSF) Aβ1-42 (P = 0.002) and plasma Aβ42/40 ratios (P = 0.0008). They also decreased CSF P-Tau (P < 0.00001), CSF T-Tau (P < 0.00001), and plasma p-tau181 (P < 0.00001). FDA-approved anti-Aβ mabs perform neuroimaging changes in amyloid Positron Emission Tomography Standardized Uptake Value ratio (PET SUVr) (P < 0.00001). However, compared with placebo, FDA-approved anti-Aβ mabs had higher risk of ARIA-E (P < 0.00001) and ARIA-H (P < 0001).

CONCLUSION

FDA-approved anti-Aβ mabs have a role in slowing disease progression in patients with AD, at the cost of an increased probability of side effects.

Efficacy and safety of anti-amyloid-β monoclonal antibodies in current Alzheimer's disease phase III clinical trials: A systematic review and interactive web app-based meta-analysis

The risk-benefit profile of anti-Aβ monoclonal antibodies (mAbs) in Alzheimer's disease (AD) remains unclear, especially concerning their safety and overall effects on AD progression and cognitive function. Here, we investigated cognitive, biomarker and side effects of anti-Aβ mAbs in large phase III randomized placebo-controlled clinical trials (RCTs) in sporadic AD. The search was performed on Google Scholar, PubMed and ClinicalTrials.gov by applying Jadad score to evaluate the methodological quality of the reports. Studies were excluded if they scored < 3 on Jadad scale or if they analyzed less than 200 sporadic AD patients. We followed PRISMA guidelines and DerSimonian-Laird random-effects model in R. Primary outcomes were cognitive: AD Assessment Scale-Cognitive Subscale (ADAS-Cog), Mini Mental State Examination (MMSE) and Clinical Dementia Rating Scale-sum of Boxes (CDR-SB). Secondary and tertiary outcomes included biomarkers of Aβ and tau pathology, adverse events, and performance on Alzheimer's Disease Cooperative Study - Activities of Daily Living Scale. The meta-analysis included 14,980 patients in 14 studies and four mAbs: Bapineuzumab, Aducanumab, Solanezumab and Lecanemab. The results of this study suggest that anti-Aβ mAbs statistically improved cognitive and biomarker outcomes, particularly Aducanumab and Lecanemab. However, while cognitive effects were of small effect sizes, these drugs considerably increased risk of side effects such as Amyloid Related Imaging Abnormalities (ARIA), especially in APOE-ε4 carriers. Meta-regression revealed that higher (better) baseline MMSE score was associated with improved ADAS Cog and CDR-SB. In order to improve reproducibility and update the analysis in the future, we developed AlzMeta.app, web-based application freely available at https://alzmetaapp.shinyapps.io/alzmeta/.

Cognitivism ageing: The Alzheimer conundrum as switched ontology & the potential for a new materialist dementia

Following recent regulatory approvals for anti-Alzheimer's monoclonal antibodies, this paper considers the contemporary role of cognitivism in defining the ontological commitments of dementia research, as well as movements away from cognitivism under the umbrella of 4E cognitive science. 4E cognitive theories, extending cognition into bodies, their environs, and active relations between the two, share potentially fruitful affinities with new materialisms which focus on the co-constitution of matter in intra-action. These semi-overlapping conceptual positions furnish some opportunity for an ontological alternative to longstanding cognitivist commitments, particularly to the isolated brain as a material catalyst for commercial interventions. After outlining mainstream cognitivism and its shortcomings, I explore 4E and new materialism as possibly transformative conceptual schemas for dementia research, a field for which cognitivist imaginings of cognitive decline in later life have profound and often regrettable ramifications. To realise this new materialist dementia, I sketch out a cognitive ontology based on Barad's agential realism. This facilitates a reassessment of the biggest conundrum in dementia research - the lack of neat correlation between (apparently material) neuropathology and (apparently immaterial) cognitive impairment - alongside the continued failure of efforts to develop effective interventions. It also gives social researchers working on cognitive decline in later life an opportunity to reappraise the nature of social science as a response to such phenomena. If cognition and cognitive ageing are reimagined as an emergent characteristic of intra-acting matter, then new materialist social science might be at least as conducive to salutogenic interventions as the neuropsychiatric technoscience that dominates the contemporary dementia research economy despite continual failures. I argue that a new materialist cognitive ontology could help us think beyond an ageing cognitivism and, by extension, beyond the Alzheimer conundrum.

Acute cholangitis following mRNA COVID-19 vaccine booster in a patient receiving an anti-amyloid antibody for Alzheimer's disease: A case report

A 77-year-old woman had 2 weeks of fever and flu-like symptoms starting several hours after receiving an mRNA booster for SARS-CoV-2 and the influenza vaccine, in separate shots. Laboratory tests showed cholangitis. Medical history included APOE-ε4 carrier genotype, mild Alzheimer's disease, participation in a clinical trial of aducanumab, and resolving polymyalgia rheumatica. The patient recovered with at-home supportive care. She had aducanumab-associated amyloid-related imaging abnormalities-edema (ARIA-E) both before and after the acute cholangitis. Two months following the vaccinations polymyalgia rheumatica recurred. This case raises questions about interactions among immune-mediated disease, complications of anti-amyloid monoclonal antibodies, and adverse events following SARS-CoV-2 mRNA vaccination.

Is Aducanumab treatment developed to prevent progression of Alzheimer's disease cost-effective in Turkey?

BACKGROUND

Alzheimer's Disease (AD), the most common type of dementia, is a chronic, progressive, and neurodegenerative brain discomfort that causes the be damage to brain cells. Although there is no definitive treatment for AD, various drug treatments are used to reduce and control the symptoms of the disease. Developed for the treatment of mild-stage Alzheimer's patients, Aducanumab is the only drug approved by the Food and Drug Administration (FDA) in the past two decades. However, the cost is very high and, in many countries, Aducanumab has not been approved due to insufficient clinical efficacy and lack of evidence yet. This study aims to analyze the cost-effectiveness of Aducanumab, which was developed for the treatment of mild-stage AD, from the patient's perspective.

METHODS

In the study, the Markov model was developed to determine the cost-effectiveness of Aducanumab compared to Standard of Care (SoC) therapy over a 5-year horizon. Cost and effectiveness data were taken from the literature. In the study, the discount rate was determined as 6%. The results were presented as the incremental cost-effectiveness ratio (ICER), which represents the cost per quality-adjusted life years (QALY). The results were retested with a one-way and probabilistic sensitivity analysis (PSA) due to possible uncertainties in the research parameters. The results were presented with the tornado diagram and the scatter plots.

RESULTS

With the Markov model, the total costs of Aducanumab and SoC treatments over a 5-year horizon were found to be 98.068 $ and 21.292 $, respectively. Aducanumab treatment had an incremental gain of 0.64 QALY and an incremental cost of 76.776 $ compared to the SoC treatment. The ICER value, which shows the additional cost per QALY of Aducanumab, was 119.408 $/QALY. As a result of the study, it was determined that Aducanumab was not cost-effective when compared to SoC treatment. Sensitivity analysis results showed stability against uncertainties. Aducanumab was confirmed not to be cost-effective with its current price and potential clinical benefit.

CONCLUSION

The result of the research is considered important in terms of providing evidence-based information on the cost-effectiveness of Aducanumab in Turkey. However, further, research is needed to evaluate Aducanumab's clinical efficacy and cost-effectiveness.

Aducanumab in Alzheimer's disease: A critical update

Alzheimer's disease (AD) is a complex neurological disorder that results in cognitive decline. The incidence rates of AD have been increasing, particularly among individuals 60 years of age or older. In June 2021, the US FDA approved aducanumab, the first humanized monoclonal antibody, as a potential therapeutic option for AD. Clinical trials have shown this drug to effectively target the accumulation of Aβ (beta-amyloid) plaques in the brain, and its effectiveness is dependent on the dosage and duration of treatment. Additionally, aducanumab has been associated with improvements in cognitive function. Biogen, the pharmaceutical company responsible for developing and marketing aducanumab, has positioned it as a potential breakthrough for treating cerebral damage in AD. However, the drug has raised concerns due to its high cost, limitations, and potential side effects. AD is a progressive neurological condition that affects memory, cognitive function, and behaviour. It significantly impacts the quality of life of patients and caregivers and strains healthcare systems. Ongoing research focuses on developing disease-modifying therapies that can halt or slow down AD progression. The pathogenesis of AD involves various molecular cascades and signaling pathways. However, the formation of extracellular amyloid plaques is considered a critical mechanism driving the development and progression of the disease. Aducanumab, as a monoclonal antibody, has shown promising results in inhibiting amyloid plaque formation, which is the primary pathological feature of AD. This review explores the signaling pathways and molecular mechanisms through which aducanumab effectively prevents disease pathogenesis in AD.

Accelerated drug approval: Meeting the ethical yardstick

Drugs addressing unmet medical needs can change the lives of millions. Developing and validating new drugs can, however, take many years. To streamline the assessment of new drugs, regulatory agencies have long established shortened review pathways. Among these programs, Accelerated Approval (AA) has recently come under scrutiny due to the U.S. Food and Drug Administration's decision to authorize Aducanumab, the first Alzheimer's disease drug. This decision attracted fierce criticism due to the allegedly insufficient evidence about the safety and efficacy of the drug. While considerable scholarly attention has been devoted to this case, the ethical aspects of the AA regulatory pathway have so far remained relatively unexplored. In this paper, we set out to fill this gap. We illustrate six conditions that should be met for AA to be ethically acceptable: moral solicitude, evidence, risk mitigation, impartiality, sustainability, and transparency. We discuss such conditions and suggest practical steps to implement them in regulatory and oversight processes. Taken together, our six conditions represent a benchmark for assessing the ethical validity of AA processes and decisions.

Repurposing drugs against Alzheimer's disease: can the anti-multiple sclerosis drug fingolimod (FTY720) effectively tackle inflammation processes in AD?

Therapeutic approaches providing effective medication for Alzheimer's disease (AD) patients after disease onset are urgently needed. Previous studies in AD mouse models and in humans suggested that physical exercise or changed lifestyle can delay AD-related synaptic and memory dysfunctions when treatment started in juvenile animals or in elderly humans before onset of disease symptoms. However, a pharmacological treatment that can reverse memory deficits in AD patients was thus far not identified. Importantly, AD disease-related dysfunctions have increasingly been associated with neuro-inflammatory mechanisms and searching for anti-inflammatory medication to treat AD seems promising. Like for other diseases, repurposing of FDA-approved drugs for treatment of AD is an ideally suited strategy to reduce the time to bring such medication into clinical practice. Of note, the sphingosine-1-phosphate analogue fingolimod (FTY720) was FDA-approved in 2010 for treatment of multiple sclerosis patients. It binds to the five different isoforms of Sphingosine-1-phosphate receptors (S1PRs) that are widely distributed across human organs. Interestingly, recent studies in five different mouse models of AD suggest that FTY720 treatment, even when starting after onset of AD symptoms, can reverse synaptic deficits and memory dysfunction in these AD mouse models. Furthermore, a very recent multi-omics study identified mutations in the sphingosine/ceramide pathway as a risk factor for sporadic AD, suggesting S1PRs as promising drug target in AD patients. Therefore, progressing with FDA-approved S1PR modulators into human clinical trials might pave the way for these potential disease modifying anti-AD drugs.

Application of 89Zr-DFO*-immuno-PET to assess improved target engagement of a bispecific anti-amyloid-ß monoclonal antibody

PURPOSE

The recent conditional FDA approval of Aducanumab (Adu) for treating Alzheimer's disease (AD) and the continued discussions around that decision have increased interest in immunotherapy for AD and other brain diseases. Reliable techniques for brain imaging of antibodies may guide decision-making in the future but needs further development. In this study, we used ⁸⁹Zr-immuno-PET to evaluate the targeting and distribution of a bispecific brain-shuttle IgG based on Adu with transferrin receptor protein-1 (TfR1) shuttling mechanism, mAbAdu-scFab8D3, designated Adu-8D3, as a candidate theranostic for AD. We also validated the ⁸⁹Zr-immuno-PET platform as an enabling technology for developing new antibody-based theranostics for brain disorders.

METHODS

Adu, Adu-8D3, and the non-binding control construct B12-8D3 were modified with DFO*-NCS and radiolabeled with ⁸⁹Zr. APP/PS1 mice were injected with ⁸⁹Zr-labeled mAbs and imaged on days 3 and 7 by positron emission tomography (PET). Ex vivo biodistribution was performed on day 7, and ex vivo autoradiography and immunofluorescence staining were done on brain tissue to validate the PET imaging results and target engagement with amyloid-β plaques. Additionally, [⁸⁹Zr]Zr-DFO*-Adu-8D3 was evaluated in 3, 7, and 10-month-old APP/PS1 mice to test its potential in early stage disease.

RESULTS

A 7-fold higher brain uptake was observed for [⁸⁹Zr]Zr-DFO*-Adu-8D3 compared to [⁸⁹Zr]Zr-DFO*-Adu and a 2.7-fold higher uptake compared to [⁸⁹Zr]Zr-DFO*-B12-8D3 on day 7. Autoradiography and immunofluorescence of [⁸⁹Zr]Zr-DFO*-Adu-8D3 showed co-localization with amyloid plaques, which was not the case with the Adu and B12-8D3 conjugates. [⁸⁹Zr]Zr-DFO*-Adu-8D3 was able to detect low plaque load in 3-month-old APP/PS1 mice.

CONCLUSION

⁸⁹Zr-DFO*-immuno-PET revealed high and specific uptake of the bispecific Adu-8D3 in the brain and can be used for the early detection of Aβ plaque pathology. Here, we demonstrate that ⁸⁹Zr-DFO*-immuno-PET can be used to visualize and quantify brain uptake of mAbs and contribute to the evaluation of biological therapeutics for brain diseases.

Impacts of FDA approval and Medicare restriction on antiamyloid therapies for Alzheimer's disease: patient outcomes, healthcare costs, and drug development

In 2021, the US Food and Drug Administration (FDA) granted approval to aducanumab, an antiamyloid antibody for early-stage Alzheimer's disease, despite a lack of clear clinical evidence demonstrating the drug's cognitive benefits. The manufacturer initially priced the drug at a staggering $56,000 per year, a price that was later reduced to $28,200. Unfortunately, these costs do not include the additional expenses associated with monitoring the treatment. However, the Centers for Medicare and Medicaid Services (CMS) recently announced that they will only cover individuals enrolled in clinical trials and will limit coverage of future antiamyloid antibodies. This discrepancy between the FDA and CMS positions has caused confusion and concerns for patients who could potentially benefit from antiamyloid therapy. It is important to acknowledge the clinical and economic uncertainties surrounding aducanumab and its potential impacts on future antiamyloid drug development and approval processes. The FDA's approval, despite limited clinical evidence, raises questions about the integrity and rigor of the approval process. The drug's high cost also raises accessibility concerns, especially for those without insurance or sufficient financial resources. Given the CMS's limited coverage policy, it's critical to evaluate the long-term implications of this decision on future antiamyloid drug development. Without adequate support and coverage from insurance providers, the development and approval of future Alzheimer's treatments may be hindered. In summary, the approval and pricing of aducanumab, coupled with the CMS's limited coverage policy, has created a confusing and concerning landscape for Alzheimer's patients. It's important that stakeholders, including patients, clinicians, insurers, and regulatory bodies, work together to address these challenges and ensure that individuals with Alzheimer's have access to effective, affordable treatments.

Newer modalities in the management of Alzheimer's dementia along with the role of aducanumab and lecanemab in the treatment of its refractory cases

Alzheimer's disease (AD) is a common neurological condition characterized by a gradual and progressive decline in memory, language, emotion, and cognition. It mainly affects elderly people. Due to the effects of AD, pharmaceutical medications and anticholinesterases have been vigorously promoted and approved by the FDA as a form of AD therapy. However, it was progressively found that these drugs did not address the underlying causes of AD pathogenesis; rather, they focused on the symptoms in order to enhance patients' cognitive outcomes. Consequently, a hunt for superior disease-modifying options is launched. Designing new therapeutic agents requires a thorough understanding of the neuroprotective processes and varied functions carried out by certain genes, and antibodies. In this comprehensive review article, we give an overview of the history of Alzheimer's disease, the significance of the blood-brain barrier in determining the scope of treatment options, as well as the advantages and disadvantages of the current therapeutic treatment options for stem cell therapy, immunotherapy, regenerative therapy, and improved Alzheimer's disease care and diagnosis. We have also included a discussion on the potential role of aducanumab and Lecanemab as a cutting-edge therapy in refractory Alzheimer's disease patients. Lecanemab has been recently approved by the FDA for the treatment of Alzheimer's disease.

Characterization of exposure-Clinical Dementia Rating-Sum of Boxes relationship in subjects with early Alzheimer's disease from the aducanumab Phase 3 trials

Clinical Dementia Rating-Sum of Boxes (CDR-SB) assessments from two Phase 3 studies (ENGAGE and EMERGE) of aducanumab in subjects with early Alzheimer's disease (AD) were pooled to develop an exposure-response (ER) model. A linear model in the logit-transformed scaled CDR-SB best characterized the time profile for placebo- and aducanumab-treated subjects, with concentration as the exposure metric. The model allowed delineation of slow (4%), typical (86%), and fast (10%) progressing subpopulations in the data. The estimated drug effect on the disease progression rate was significant, 2.05 L/(g·year), with a 95% confidence interval (1.60, 2.50) that did not include zero. Following an evaluation of a series of ER model forms including differential drug and null effects either between the studies or among the three progression classes, the final ER model with a common (pooled) estimate of the drug effect between the studies and among the three progression classes was considered parsimonious. The final model provides supportive evidence that the two studies demonstrate a common intrinsic pharmacology. None of the identified covariates (Mini-Mental State Examination-BL score and Asian race) were clinically meaningful. Finally, simulations demonstrated that the intrinsic pharmacology remained consistent between the two Phase 3 studies.

A Review of Scientific Ethics Issues Associated with the Recently Approved Drugs for Alzheimer's Disease

Alzheimer's disease (AD), the devastating and most prevailing underlying cause for age-associated dementia, has no effective disease-modifying treatment. The last approved drug for the relief of AD symptoms was in 2003. The recent approval of sodium oligomannate (GV-971, 2019) in China and the human antibody aducanumab in the USA (ADUHELM, 2021) therefore represent significant breakthroughs, albeit ones that are fraught with controversy. Here, we explore potential scientific ethics issues associated with GV-971 and aducanumab's development and approval. While these issues may be belied by socioeconomic and political complexities in the heady business of commercial drug development, they are of fundamental importance to scientific integrity and ultimately, welfare of patients. We posit that the push for approval of both AD drugs based on incomplete research and unconvincing marginal effectiveness is ethically unsound. Regardless of how both these drugs shall perform in the market for the years to come, the scientific ethics issues and potentially questionable research practices should therefore be duly noted and lessons learned.

Investigating Partially Discordant Results in Phase 3 Studies of Aducanumab

OBJECTIVES

Efficacy and safety results from the EMERGE (NCT02484547) and ENGAGE (NCT02477800) phase 3 studies of aducanumab in early Alzheimer's disease (AD) have been published. In EMERGE, but not in ENGAGE, high-dose aducanumab demonstrated significant treatment effects across primary and secondary endpoints. Low-dose aducanumab results were consistent across studies with non-significant differences versus placebo that were intermediate to the high-dose arm in EMERGE. The present investigation examined data from EMERGE and ENGAGE through post-hoc analyses to determine factors that contributed to discordant results between the high-dose arms of the two studies.

DESIGN

EMERGE and ENGAGE were 2 phase 3, randomized, double-blind, placebo-controlled, parallel-group studies.

SETTING

EMERGE and ENGAGE were 2 global multicenter studies involving 348 sites in 20 countries.

PARTICIPANTS

Participants in EMERGE and ENGAGE were aged 50 to 85 years and had mild cognitive impairment or mild AD dementia with confirmed amyloid pathology. The randomized and dosed population (all randomized patients who received at least one dose of study treatment) included 1638 patients in EMERGE and 1647 in ENGAGE.

INTERVENTION

In EMERGE and ENGAGE, participants were randomized to receive low- or high-dose aducanumab or placebo (1:1:1) once every 4 weeks.

MEASUREMENTS

In this paper, 4 areas were investigated through post-hoc analyses to understand the discordance in the high-dose arms of the EMERGE and ENGAGE studies: baseline characteristics, amyloid-related imaging abnormalities, non-normality of the data, and dosing/exposure to aducanumab.

RESULTS

Post-hoc analyses showed that outcomes in the ENGAGE high-dose group were affected by an imbalance in a small number of patients with extremely rapid progression and by lower exposure to the target dose of 10 mg/kg. These factors were confounded and present in early enrolled patients but were not present in later-enrolled patients who were randomized to the target dosing regimen of 10 mg/kg after titration. Neither baseline characteristics nor amyloid-related imaging abnormalities contributed to the difference in results between the high-dose arms.

CONCLUSIONS

Results were consistent across studies in later enrolled patients in which the incidence of rapidly progressing patients was balanced across treatment arms.

Lecanemab, Aducanumab, and Gantenerumab - Binding Profiles to Different Forms of Amyloid-Beta Might Explain Efficacy and Side Effects in Clinical Trials for Alzheimer's Disease

Immunotherapy against amyloid-beta (Aβ) is a promising option for the treatment of Alzheimer's disease (AD). Aβ exists as various species, including monomers, oligomers, protofibrils, and insoluble fibrils in plaques. Oligomers and protofibrils have been shown to be toxic, and removal of these aggregates might represent an effective treatment for AD. We have characterized the binding properties of lecanemab, aducanumab, and gantenerumab to different Aβ species with inhibition ELISA, immunodepletion, and surface plasmon resonance. All three antibodies bound monomers with low affinity. However, lecanemab and aducanumab had very weak binding to monomers, and gantenerumab somewhat stronger binding. Lecanemab was distinctive as it had tenfold stronger binding to protofibrils compared to fibrils. Aducanumab and gantenerumab preferred binding to fibrils over protofibrils. Our results show different binding profiles of lecanemab, aducanumab, and gantenerumab that may explain clinical results observed for these antibodies regarding both efficacy and side effects.

Enhanced delivery of a low dose of aducanumab via FUS in 5×FAD mice, an AD model

BACKGROUND

Aducanumab (Adu), which is a human IgG1 monoclonal antibody that targets oligomer and fibril forms of beta-amyloid, has been reported to reduce amyloid pathology and improve impaired cognition after administration of a high dose (10 mg/kg) of the drug in Alzheimer's disease (AD) clinical trials. The purpose of this study was to investigate the effects of a lower dose of Adu (3 mg/kg) with enhanced delivery via focused ultrasound (FUS) in an AD mouse model.

METHODS

The FUS with microbubbles opened the blood-brain barrier (BBB) of the hippocampus for the delivery of Adu. The combined therapy of FUS and Adu was performed three times in total and each treatment was performed biweekly. Y-maze test, Brdu labeling, and immunohistochemical experimental methods were employed in this study. In addition, RNA sequencing and ingenuity pathway analysis were employed to investigate gene expression profiles in the hippocampi of experimental animals.

RESULTS

The FUS-mediated BBB opening markedly increased the delivery of Adu into the brain by approximately 8.1 times in the brains. The combined treatment induced significantly less cognitive decline and decreased the level of amyloid plaques in the hippocampi of the 5×FAD mice compared with Adu or FUS alone. Combined treatment with FUS and Adu activated phagocytic microglia and increased the number of astrocytes associated with amyloid plaques in the hippocampi of 5×FAD mice. Furthermore, RNA sequencing identified that 4 enriched canonical pathways including phagosome formation, neuroinflammation signaling, CREB signaling and reelin signaling were altered in the hippocami of 5×FAD mice receiving the combined treatment.

CONCLUSION

In conclusion, the enhanced delivery of a low dose of Adu (3 mg/kg) via FUS decreases amyloid deposits and attenuates cognitive function deficits. FUS-mediated BBB opening increases adult hippocampal neurogenesis as well as drug delivery. We present an AD treatment strategy through the synergistic effect of the combined therapy of FUS and Adu.

High-clearance anti-amyloid immunotherapies in Alzheimer's disease. Part 1: Meta-analysis and review of efficacy and safety data, and medico-economical aspects

In 2021, aducanumab, an immunotherapy targeting amyloid-β, was approved for Alzheimer's disease (AD) by the US Food and Drug Administration thanks to positive results on a putative biological surrogate marker. This approval has raised an unprecedented controversy. It was followed by a refusal of the European Medicine Agency, which does not allow the marketing of drugs solely on biological arguments and raised safety issues, and important US coverage limitations by the Centers for Medicare & Medicaid Services. Two other anti-amyloid immunotherapies showed significant results regarding a clinical outcome in phase 2 trials, and five drugs are being studied in phase 3 trials. Compared to those tested in previous trials of the 2010s, the common feature and novelty of these anti-amyloid immunotherapies is their ability to induce a high clearance of amyloid load, as measured with positron emission tomography, in the brain of early-stage biomarker-proven AD patients. Here, we review the available evidence regarding efficacy and safety data and medico-economical aspects for high-clearance anti-amyloid immunotherapies. We also perform frequentist and Bayesian meta-analyses of the clinical efficacy and safety of the highest dose groups from the two aducanumab phase 3 trials and the donanemab and lecanemab phase 2 trials. When pooled together, the data from high-clearance anti-amyloid immunotherapies trials confirm a statistically significant clinical effect of these drugs on cognitive decline after 18 months (difference in cognitive decline measured with CDR-SB after 18 months between the high dose immunotherapy groups vs. placebo = -0.24 points; P=0.04, frequentist random-effect model), with results on ADAS-Cog being the most statistically robust. However, this effect remains below the previously established minimal clinically relevant values. In parallel, the drugs significantly increased the occurrence of amyloid-related imaging abnormalities-edema (ARIA-E: risk ratio=13.39; P<0.0001), ARIA-hemorrhage (risk ratio=2.78; P=0.0002), and symptomatic and serious ARIA (7/1321=0.53% in the high dose groups versus 0/1446 in the placebo groups; risk ratio=6.44; P=0.04). The risk/benefit ratio of high-clearance immunotherapies in early AD is so far questionable after 18 months. Identifying subgroups of better responders, the perspective of combination therapies, and a longer follow-up may help improve their clinical relevance. Finally, the preliminary evidence from medico-economical analyses seems to indicate that the current cost of aducanumab in the US is not in reasonable alignment with its clinical benefits.

High-clearance anti-amyloid immunotherapies in Alzheimer's disease. Part 2: putative scenarios and timeline in case of approval, recommendations for use, implementation, and ethical considerations in France

In 2021, aducanumab, an immunotherapy targeting amyloid-β, was approved for Alzheimer's disease (AD) by the US Food and Drug Administration thanks to positive results on a putative biological surrogate marker. This approval has raised an unprecedented controversy. It was followed by a refusal of the European Medicine Agency, which does not allow the marketing of drugs solely on biological arguments and raised safety issues, and important US coverage limitations by the Centers for Medicare & Medicaid Services. Two other anti-amyloid immunotherapies showed significant results regarding a clinical outcome in phase II trials, and five drugs are being studied in phase III trials. Lecanemab is currently under examination for an 'Accelerated Approval' in the US, with an expected decision in January 2023. The common feature and novelty of these anti-amyloid immunotherapies, compared to those tested in previous trials of the 2010s, is their ability to induce a high clearance of amyloid load, as measured with positron emission tomography, in the brain of early-stage biomarker-proven AD patients. In the first part of this review, we underlined through a meta-analysis that the pooled data from high-clearance anti-amyloid immunotherapies trials demonstrated a significant but slight clinical effect after 18 months. Still, safety remains an issue with serious and symptomatic amyloid-related imaging abnormalities, which are seldom (∼1 per 200 treated patients) but occur beyond chance. In the second part of this review, we hypothesized that there is a high probability that some phase III trials of high-clearance anti-amyloid immunotherapies in early AD will finally be unarguably positive on clinical outcomes in the next five years with acceptable safety data. This may, in turn, lead to approval by the European Medicine Agency if the risk-benefit profile is deemed favorable. Such approval would be a game-changer in managing AD patients and for the organization of memory clinics in France. We review the possible timeline and scenarios for putative approval in France and make propositions regarding putative use in clinical practice, putative implementation in a real-life setting, and ethical considerations.

Comparative efficacy of lithium and aducanumab for cognitive decline in patients with mild cognitive impairment or Alzheimer's disease: A systematic review and network meta-analysis

BACKGROUND

In 2021, the US Food and Drug Administration granted an accelerated approval to aducanumab for patients with mild cognitive impairment (MCI) and mild dementia caused by Alzheimer's disease (AD); however, the cost of aducanumab is high, at approximately $28,000 for one year per person. On the other hand, lithium is much cheaper at $40 a year, and has been reported to be effective for the cognitive decline observed in both patients with MCI and AD. In contrast to acetylcholinesterase inhibitors and N-methyl D-aspartate receptor antagonists, aducanumab and lithium may be disease-modifying drugs. Therefore, we focused on aducanumab and lithium and compared the effects of these drugs on the cognitive decline in MCI and AD patients using a network meta-analysis.

METHODS

PubMed, the Cochrane Library, CINHAL, and ClinicalTrials.gov were searched for randomized controlled trials testing lithium or aducanumab for the treatment of cognitive decline in patients with MCI or AD, up to January 31, 2022. A frequentist fixed-effect network meta-analysis was performed to estimate direct and indirect effects. The primary outcome was change scores in cognitive decline measured by Mini-Mental State Examination. This study has been registered with PROSPERO (number CRD42022304807).

RESULTS

Network meta-analysis demonstrated that lithium was significantly more effective than aducanumab in the primary outcome.

CONCLUSION

Although there were various limitations in this study, lithium may be a more cost-effective treatment than aducanumab for MCI and AD.

Vascular Considerations for Amyloid Immunotherapy

PURPOSE OF REVIEW

Amyloid beta (Aβ) plaque accumulation is a hallmark pathology contributing to Alzheimer's disease (AD) and is widely hypothesized to lead to cognitive decline. Decades of research into anti-Aβ immunotherapies provide evidence for increased Aβ clearance from the brain; however, this is frequently accompanied by complicated vascular deficits. This article reviews the history of anti-Aβ immunotherapies and clinical findings and provides recommendations moving forward.

RECENT FINDINGS

In 20 years of both animal and human studies, anti-Aβ immunotherapies have been a prevalent avenue of reducing hallmark Aβ plaques. In both models and with different anti-Aβ antibody designs, amyloid-related imaging abnormalities (ARIA) indicating severe cerebrovascular compromise have been common and concerning occurrence. ARIA caused by anti-Aβ immunotherapy has been noted since the early 2000s, and the mechanisms driving it are still unknown. Recent approval of aducanumab comes with renewed urgency to consider vascular deficits caused by anti-Aβ immunotherapy.

Advancing 89Zr-immuno-PET in neuroscience with a bispecific anti-amyloid-beta monoclonal antibody - The choice of chelator is essential

The accelerated approval of the monoclonal antibody (mAb) aducanumab as a treatment option for Alzheimer's Disease and the continued discussions about its efficacy have shown that a better understanding of immunotherapy for the treatment of neurodegenerative diseases is needed. ⁸⁹Zr-immuno-PET could be a suitable tool to open new avenues for the diagnosis of CNS disorders, monitoring disease progression, and assessment of novel therapeutics. Herein, three different ⁸⁹Zr-labeling strategies and direct radioiodination with ¹²⁵I of a bispecific anti-amyloid-beta aducanumab derivate, consisting of aducanumab with a C-terminal fused anti-transferrin receptor binding single chain Fab fragment derived from 8D3 (Adu-8D3), were compared ex vivo and in vivo with regard to brain uptake and target engagement in an APP/PS1 Alzheimer's disease mouse model and wild type animals.

Methods: Adu-8D3 and a negative control antibody, based on the HIV specific B12 antibody also carrying C-terminal fused 8D3 scFab (B12-8D3), were each conjugated with NCS-DFO, NCS-DFO*, or TFP-N-suc-DFO-Fe-ester, followed by radiolabeling with ⁸⁹Zr. ¹²⁵I was used as a substitute for ¹²⁴I for labeling of both antibodies. 30 µg of radiolabeled mAb, corresponding to approximately 6 MBq ⁸⁹Zr or 2.5 MBq ¹²⁵I, were injected per mouse. PET imaging was performed 1, 3 and 7 days post injection (p.i.). All mice were sacrificed on day 7 p.i. and subjected to ex vivo biodistribution and brain autoradiography. Immunostaining on brain tissue was performed after autoradiography for further validation.

Results:Ex vivo biodistribution revealed that the brain uptake of [⁸⁹Zr]Zr-DFO*-NCS-Adu-8D3 (2.19 ±0.12 %ID/g) was as high as for its ¹²⁵I-analog (2.21 ±0.15 %ID/g). [⁸⁹Zr]Zr-DFO-NCS-Adu-8D3 and [⁸⁹Zr]Zr-DFO-N-suc-Adu-8D3 showed significantly lower uptake (< 0.65 %ID/g), being in the same range as for the ⁸⁹Zr-labeled controls (B12-8D3). Autoradiography of [⁸⁹Zr]Zr-DFO*-NCS-Adu-8D3 and [¹²⁵I]I-Adu-8D3 showed an amyloid-beta related granular uptake pattern of radioactivity. In contrast, the [⁸⁹Zr]Zr-DFO-conjugates and the control antibody groups did not show any amyloid-beta related uptake pattern, indicating that DFO is inferior for ⁸⁹Zr-immuno-PET imaging of the brain in comparison to DFO* for Adu-8D3. This was confirmed by day 7 PET images showing only amyloid-beta related brain uptake for [⁸⁹Zr]Zr-DFO*-NCS-Adu-8D3. In wild type animals, such an uptake was not observed. Immunostaining showed a co-localization of all administered Adu-8D3 conjugates with amyloid-beta plaques.

Conclusion: We successfully demonstrated that ⁸⁹Zr-immuno-PET is suitable for imaging and quantifying amyloid-beta specific brain uptake using a bispecific aducanumab brain shuttling antibody, Adu-8D3, but only when using the novel chelator DFO*, and not DFO, for labeling with ⁸⁹Zr.

Potential eligibility for Aducanumab therapy in an Irish specialist cognitive service-Utilising cerebrospinal fluid biomarkers and appropriate use criteria

OBJECTIVES

Aducanumab is a monoclonal antibody which has recently been licenced for use by the food and drug administration for treatment of patients with mild cognitive impairment due to Alzheimer's disease (AD) or mild AD dementia. Appropriate use criteria (AUC) for Aducanumab in clinical practice are available. We look to review patients in our specialist interdisciplinary cognitive service with positive cerebrospinal fluid (CSF) biomarkers for AD for their hypothetical eligibility for Aducanumab, or a similar anti-amyloid agent.

METHODS

Retrospective analysis was undertaken of patients with positive AD-biomarker CSF analysis. Data available at time of CSF analysis was reviewed to determine hypothetical eligibility for Aducanumab.

RESULTS

Seventy patients had positive AD-CSF biomarkers. Forty nine of these were seen in the Gerontology-led service, with 21 in the neurology cohort. Average patient age was 70 years old. Forty patients (57%) met eligibility criteria for Aducanumab therapy by AUC guidelines.

CONCLUSION

We highlight the patients within our service who would be appropriate for Aducanumab or similar anti-amyloid agents should licencing be granted in the European Union, and the need to develop the resources and capacity to deliver this or other emerging disease modifying AD therapies.

CLINICAL TRIAL REGISTRATION

All patients in the combined cognitive clinic provide consent re willingness to be contacted re research.

Under-Represented Populations Left Out of Alzheimer's Disease Treatment with Aducanumab: Commentary on Ethics

Despite controversy about the efficacy and safety of aducanumab, the FDA's fast-tracking of this medicine is truly historic. However, structural problems leading to socioeconomic disparities and systemic racism in science, healthcare, and society have left out under-represented populations. This perspective outlines the racial and socioeconomic health disparities in aducanumab treatment: 1) Disparities in the risk of Alzheimer's disease (AD), 2) Limited participation from under-represented groups in AD trials raising concerns about the generalizability of the results, 3) Questionable applicability of the amyloid hypothesis in groups under-represented in AD research, and 4) Aducanumab's initial sticker price that unfairly singled out those with lower socioeconomic backgrounds. Potential solutions are discussed.

The new therapy for Alzheimer's disease: from a hope for a few to a false hope?

Since the late ninety, research on Alzheimer's disease has been focused on the search of drugs able to modify the disease course. Patients and caregivers waiting for news on this topic, received enthusiastically the advice of the approval of Aducanumab-anti-amyloid β monoclonal antibody-by the FDA, and that of its rejection by the EMA with even greater disappointment. To estimate the number of patients that we would be able to treat-hypothesizing a possible future approval by EMA- in the memory clinic of the IRCCS S. Giovanni di Dio FBF of Brescia, we analyzed 1561 patients undergone a first geriatric visit in January 1st to December 31st 2019. Applying the EMERGE and ENGAGE studies criteria, only 15 of them (1%) could be eligible for Aducanumab. The communication of scientific news should be transparent, more balanced and less sensationalistic, to avoid the rise of false hopes and consequent disillusionment.

Two Randomized Phase 3 Studies of Aducanumab in Early Alzheimer's Disease

BACKGROUND

Alzheimer's disease is a progressive, irreversible, and fatal disease for which accumulation of amyloid beta is thought to play a key role in pathogenesis. Aducanumab is a human monoclonal antibody directed against aggregated soluble and insoluble forms of amyloid beta.

OBJECTIVES

We evaluated the efficacy and safety of aducanumab in early Alzheimer's disease.

DESIGN

EMERGE and ENGAGE were two randomized, double-blind, placebo-controlled, global, phase 3 studies of aducanumab in patients with early Alzheimer's disease.

SETTING

These studies involved 348 sites in 20 countries.

PARTICIPANTS

Participants included 1638 (EMERGE) and 1647 (ENGAGE) patients (aged 50-85 years, confirmed amyloid pathology) who met clinical criteria for mild cognitive impairment due to Alzheimer's disease or mild Alzheimer's disease dementia, of which 1812 (55.2%) completed the study.

INTERVENTION

Participants were randomly assigned 1:1:1 to receive aducanumab low dose (3 or 6 mg/kg target dose), high dose (10 mg/kg target dose), or placebo via IV infusion once every 4 weeks over 76 weeks.

MEASUREMENTS

The primary outcome measure was change from baseline to week 78 on the Clinical Dementia Rating Sum of Boxes (CDR-SB), an integrated scale that assesses both function and cognition. Other measures included safety assessments; secondary and tertiary clinical outcomes that assessed cognition, function, and behavior; and biomarker endpoints.

RESULTS

EMERGE and ENGAGE were halted based on futility analysis of data pooled from the first approximately 50% of enrolled patients; subsequent efficacy analyses included data from a larger data set collected up to futility declaration and followed prespecified statistical analyses. The primary endpoint was met in EMERGE (difference of -0.39 for high-dose aducanumab vs placebo [95% CI, -0.69 to -0.09; P=.012; 22% decrease]) but not in ENGAGE (difference of 0.03, [95% CI, -0.26 to 0.33; P=.833; 2% increase]). Results of biomarker substudies confirmed target engagement and dose-dependent reduction in markers of Alzheimer's disease pathophysiology. The most common adverse event was amyloid-related imaging abnormalities-edema.

CONCLUSIONS

Data from EMERGE demonstrated a statistically significant change across all four primary and secondary clinical endpoints. ENGAGE did not meet its primary or secondary endpoints. A dose- and time-dependent reduction in pathophysiological markers of Alzheimer's disease was observed in both trials.

"Aducanumab" making a comeback in Alzheimer's disease: An old wine in a new bottle

Despite presence of substantial evidence suggesting the pivotal role of amyloid (Aβ) in Alzheimer's disease (AD), very few therapeutic agents have been able to ameliorate the disease. This paved the way for the discovery of antibody-based immunotherapy to ace Aβ clearance and curb neuronal toxicity, resulting in revival of aducanumab, which following its entry into the brain, interacts with the parenchymal amyloid and decreases Aβ concentration, in a dose-dependent manner. However, the surprising approval from the FDA has created a controversy among healthcare professionals, due to Alzheimer's related imaging abnormality (ARIA) and hypersensitivity, serving as backlogs in its acceptance. Therefore, aducanumab is recognised as being "risen from the grave", accompanied with contrasting statements within the healthcare paradigm. The manuscript provides a collection of data, aiming to elucidate, both the commendable and critical faces, simultaneously intending to gain the attention of the global researchers towards the possibility of disease-modifying therapy in AD. The manuscript discusses the failure of anti-amyloid therapies in AD, that have accelerated the need to find a suitable therapeutic approach, followed by the discussion of timeline and impact of aducanumab in AD models, alongside the controversial judgement raising significant question. Besides, the authors throw some light on the onco-therapeutic implications of the drug approval, which is identified as a significant consequence of the event. The text provides a holistic picture of the drug action, and enlists the considerations for the future, that might be beneficial to both the acceptance of the drug, and the treatment of the disease.

[Causal treatment of Alzheimer's disease: amyloid antibodies]

BACKGROUND

Alzheimer's disease (AD) is the most common cause of dementia. The number of people affected will increase dramatically in the coming decades due to the demographic change. Causal pharmacological approaches have not been available to date. The monoclonal anti-amyloid beta antibody aducanumab was recently approved for the treatment of AD in the USA but was rejected in Europe in December 2021 by the European Medicines Agency (EMA).

OBJECTIVE

This review presents the background and rationale for amyloid beta-directed treatment approaches in AD. The focus is on passive immunization with monoclonal anti-amyloid beta antibodies.

DATA SITUATION

There are four monoclonal anti-amyloid beta antibodies in an advanced stage of clinical development. Evidence of a clear and significant reduction of the cerebral amyloid load was found for all of them. In the case of aducanumab this has already led to approval by the U.S. Food and Drug Administration (FDA). In the USA donanemab, gantenerumab and lecanemab have received the status of a so-called breakthrough therapy and are expected to go through an accelerated approval process by the FDA in the next 1-2 years.

CONCLUSION

Anti-amyloid antibodies represent the first cause-based, disease-modifying therapy for AD approved in the USA. Compared to the near-complete removal of cerebral amyloid plaques, the magnitude of the clinical effect is smaller and the benefit for patients is currently subject to controversial discussions. Nonetheless, the new treatment option represents an important step in the development of effective treatment. Future strategies for the treatment of AD will likely aim at a multimodal concept with different molecular targets. A prerequisite for all effective disease-modifying therapies will be an early biomarker-based diagnosis prior to the onset of a dementia-type syndrome.

Aducanumab and Adenoviral COVID-19 Vaccines: Increased Cerebral Hemorrhage Risk?

The abstract was removed and reincorporated into the main body of the text. (Since Editorial articles within the expert collection journals no longer include abstracts.).

Effect of Aducanumab Approval on Willingness to Participate in Preclinical Alzheimer's Disease Trials

BACKGROUND

Clinical trials now test promising therapies in the preclinical stages of Alzheimer's disease (AD). Participant willingness to enroll in different types of preclinical AD trials is understudied and whether the FDA approval of aducanumab affected these attitudes is unknown.

OBJECTIVE

To evaluate preferences toward three preclinical AD trial scenarios and whether the FDA approval of aducanumab changed willingness to participate among potential trial participants.

METHODS

Through an electronic survey, we asked enrollees in a recruitment registry age 50-79 to rate their willingness (using a 6-point Likert scale) to enroll in three hypothetical preclinical AD trial scenarios: an in-clinic infused monoclonal antibody intervention, a home-infused monoclonal antibody intervention, and an oral BACE inhibitor intervention. We administered the survey before and after the FDA approval of aducanumab. We used a generalized estimating equation model to assess group differences in preference for the trial scenarios. We used a paired t-test to determine if willingness to participate (using total willingness across three scenarios as the outcome) changed after the FDA decision.

RESULTS

At baseline, the mean participant willingness was highest in the in-clinic infusion scenario. There was no significant change in willingness to participate, overall, after the FDA decision. Participants who were independently aware of the FDA's decision (prior to the second survey) demonstrated reduced willingness to participate; participants unaware of the FDA decision demonstrated no change.

CONCLUSION

Willingness to participate in preclinical AD trials may have been negatively affected by the FDA's decision to approve aducanumab among those aware of the decision.

Comparative Analysis of Aducanumab, Zagotenemab and Pioglitazone as Targeted Treatment Strategies for Alzheimer's Disease

Alzheimer’s disease (AD) is the leading cause of dementia that has remained a major medical, sociocultural and economical challenge globally. Previously developed treatments like anticholinesterase inhibitors (AChEIs) and N-methyl-D-aspartate receptor (NMDAR) antagonists only provide short-term symptomatic improvement and do not prevent progression. Repeated setbacks and failures over the past 25 years in AD clinical trials have hindered efforts to develop effective AD treatments. Fortunately, Aducanumab, a specific anti-amyloid β antibody, has shown promising clinical results and was recently approved by the Food and Drug Administration (FDA) through an accelerated approval pathway. This has raised hopes for AD patients; however post-approval trials are necessary to estimate the true scope of its clinical benefits. We have reviewed several AD clinical studies and summarized the experience to date with Aducanumab and two other potential AD drugs including Zagotenemab (an anti-tau antibody) and Pioglitazone (nuclear Peroxisome-Proliferator Activated Receptor γ (PPARγ) agonist). These have shown mixed results so far and the next few years will be critical to elucidate and interpret their broad long-term protective effects. A concerted effort is required to understand and strengthen the translation of pre-clinical findings from these drugs to routine clinical practice.

Predicted Lifetime Health Outcomes for Aducanumab in Patients with Early Alzheimer's Disease

INTRODUCTION

Alzheimer's disease (AD) is a chronic and progressive neurodegenerative disease that places a substantial burden on patients and caregivers. Aducanumab is the first AD therapy approved by the US Food and Drug Administration to reduce a defining pathophysiological feature of the disease, brain amyloid plaques. In the phase 3 clinical trial EMERGE (NCT02484547), aducanumab reduced clinical decline in patients with mild cognitive impairment (MCI) due to AD and mild AD dementia and confirmed amyloid pathology.

METHODS

We used a Markov modeling approach to predict the long-term clinical benefits of aducanumab for patients with early AD based on EMERGE efficacy data. In the model, patients could transition between AD severity levels (MCI due to AD; mild, moderate, and severe AD dementia) and care settings (community vs. institution) or transition to death. The intervention was aducanumab added to standard of care (SOC), and the comparator was SOC alone. Data sources for base-case and scenario analyses included EMERGE, published National Alzheimer's Coordinating Center analyses, and other published literature.

RESULTS

Per patient over a lifetime horizon, aducanumab treatment corresponded to 0.65 incremental patient quality-adjusted life-years (QALYs) and 0.09 fewer caregiver QALYs lost compared with patients treated with SOC. Aducanumab treatment translated to a lower lifetime probability of transitioning to AD dementia, a lower lifetime probability of transitioning to institutionalization (25.2% vs. 29.4%), delays in the median time to transition to AD dementia (7.50 vs. 4.92 years from MCI to moderate AD dementia or worse), and an incremental median time in the community of 1.32 years compared with SOC.

CONCLUSION

The model predicted long-term benefits of aducanumab treatment in patients with MCI due to AD and mild AD dementia and their caregivers. The predicted outcomes provide a foundation for healthcare decision-makers and policymakers to understand the potential clinical and socioeconomic value of aducanumab.

Aducanumab (Marketed as Aduhelm) Approval Is Likely Based on Misinterpretation of PET Imaging Data

According to the FDA, aducanumab (Aduhelm), the recently approved anti-Alzheimer drug, reduces the level of cerebral amyloid plaques-a hallmark finding in patients with Alzheimer's disease-and this will result in a reduction in clinical decline. The authors of this article are not convinced that amyloid deposits are a hallmark of Alzheimer's disease and are of the opinion that the apparent reduction in amyloid accumulation following aducanumab treatment is likely instead a result of continued and advanced cerebral cell death and, thus, not a sign of improvement but of an even more advanced disease.

A Primer on the Evolution of Aducanumab: The First Antibody Approved for Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia with global burden projected to triple by 2050. It incurs significant biopsychosocial burden worldwide with limited treatment options. Aducanumab is the first monoclonal antibody recently approved by the US-FDA for mild AD through the accelerated approval pathway. It is the first molecule to be approved for AD since 2003 and carries with it a therapeutic promise for the future. As the definition of AD has evolved from a pathological entity to a Clinico-biological construct over the years, the amyloid-β (Aβ) pathway has been increasingly implicated in its pathogenesis. The approval of Aducanumab is based on reduction of the Aβ load in the brain, which forms a surrogate marker for this pathway. The research populace has, however, been globally divided by skepticism and hope regarding this approval. Failure to meet clinical endpoints in the trials, alleged transparency issues, cost-effectiveness, potential adverse effects, need for regular monitoring, and critique of 'amyloid cascade hypothesis' itself are the main caveats concerning the antibody. With this controversy in background, this paper critically looks at antibody research in AD therapeutics, evidence, and evolution of Aducanumab as a drug and the potential clinical implications of its use in future. While the efficacy of this monoclonal antibody in AD stands as a test of time, based on the growing evidence it is vital to rethink and explore alternate pathways of pathogenesis (oxidative stress, neuroinflammation, cholesterol metabolism, vascular factors, etc.) as possible therapeutic targets that may help elucidate the enigma of this complex yet progressive and debilitating neurodegenerative disorder.

Aducanumab for Alzheimer's disease: A regulatory perspective

On June 7th 2021, the Food and Drug Administration (FDA) granted approval for Aduhelm (aducanumab) for the treatment of Alzheimer's disease under its accelerated approval program. Aducanumab is the first putative disease-modifying therapy (DMT) approved for the treatment of AD with a great potential for clinical benefit over current symptomatic therapies. The scientific community has been largely confounded by this historical decision since this has been based on the reduction of a surrogate marker (amyloid beta) and not on data showing clinical efficacy. Here we provide a regulatory perspective on the topic and discuss potential similarities and differences between the FDA's and EMA's evaluative processes.

Lessons Learnt from the Second Generation of Anti-Amyloid Monoclonal Antibodies Clinical Trials

BACKGROUND

Alzheimer disease (AD) is a chronic neurodegenerative disorder with complex pathophysiology that affects over 50 million people worldwide. Most drug therapies, to date, have focused on targeting the amyloid-beta (Aβ) pathway, but clinical outcomes of anti-Aβ antibodies have been unsuccessful and unable to meet their primary endpoints. Similar trends have also been observed in treatments that target the tau pathway.

SUMMARY

This paper reviews recent anti-Aβ passive monotherapies, since Bapineuzumab, that have progressed to phase 3 clinical trials. Specifically, we discuss the 4 clinical trial programs of Solanezumab (targets Aβ monomers), Aducanumab (targets Aβ oligomers and plaques), Crenezumab (targets Aβ oligomers), and Gantenerumab (targets Aβ fibrils) which are all exogenous monoclonal antibodies. We conclude with potential reasons for why they have not met their primary endpoints and discuss lessons learnt from these trials. Key Message: Future disease-modifying trials (DMTs) for AD should be conducted in asymptomatic, Aβ-positive individuals. Moreover, potential additive and/or synergistic benefits focusing on anti-Aβ and anti-tau drug combinations merit further investigation.

Galantamine-Memantine combination in the treatment of Alzheimer's disease and beyond

Alzheimer's disease (AD) is the most prevalent form of dementia in the elderly population worldwide. Despite the major unmet clinical need, no new medications for the treatment of AD have been approved since 2003. Galantamine is an acetylcholinesterase inhibitor that is also a positive allosteric modulator at the α4β2 and α7nACh receptors. Memantine is an N-methyl-d-aspartate receptor modulator/agonist. Both galantamine and memantine are FDA-approved medications for the treatment of AD. The objective of this review is to highlight the potential of the galantamine-memantine combination to conduct randomized controlled trials (RCTs) in AD. Several studies have shown the combination to be effective. Neurodegenerative diseases involve multiple pathologies; therefore, combination treatment appears to be a rational approach. Although underutilized, the galantamine-memantine combination is the standard of care in the treatment of AD. Positive RCTs with the combination with concurrent improvement in symptoms and biomarkers may lead to FDA approval, which may lead to greater utilization of this combination in clinical practice.

Aducanumab, gantenerumab, BAN2401, and ALZ-801-the first wave of amyloid-targeting drugs for Alzheimer's disease with potential for near term approval

The body of evidence suggesting a causative, initiating role of beta amyloid (Aβ) in the pathogenesis of Alzheimer’s disease (AD) is substantial. Yet, only a few anti-amyloid agents have shown meaningful efficacy in clinical trials. We evaluated the unifying characteristics of anti-amyloid agents with positive clinical or biomarker effects in long-duration trials and analyzed how pharmacological characteristics determine their clinical product profiles. Four agents with the potential for near term approval fulfill these criteria: the injectable antibodies, aducanumab, gantenerumab, and BAN2401, and a small molecule oral agent, ALZ-801. Aducanumab and BAN2401 showed significant efficacy on both clinical and biomarker outcomes; gantenerumab showed significant biomarker effects, with no clinical efficacy reported to date; and ALZ-801 showed significant clinical effects in the high-risk population of patients homozygous for the ε4 allele of apolipoprotein E gene (APOE4) and a dose-dependent preservation of hippocampal volume. We explored how the pharmacological properties of these agents, namely selectivity for Aβ oligomers, plasma half-life, brain penetration, and time to peak brain exposure, determine their clinical profiles. A crucial characteristic shared by these agents is their ability to engage neurotoxic soluble Aβ oligomers, albeit to various degrees. Aducanumab and gantenerumab partially target oligomers, while mostly clearing insoluble amyloid plaques; BAN2401 preferentially targets soluble protofibrils (large oligomers) over plaques; and ALZ-801 blocks the formation of oligomers without binding to plaques. The degree of selectivity for Aβ oligomers and brain exposure drive the magnitude and onset of clinical efficacy, while the clearance of plaques is associated with vasogenic brain edema. Only the highest doses of aducanumab and BAN2401 show modest efficacy, and higher dosing is limited by increased risk of vasogenic edema, especially in APOE4 carriers. These limitations can be avoided, and efficacy improved by small molecule agents that selectively inhibit the formation or block the toxicity of Aβ oligomers without clearing amyloid plaques. The most advanced selective anti-oligomer agent is ALZ-801, an optimized oral prodrug of tramiprosate, which demonstrated efficacy in homozygous APOE4/4 AD subjects. ALZ-801 selectively and fully inhibits the formation of Aβ42 oligomers at the clinical dose, without evidence of vasogenic edema, and will be evaluated in a phase 3 trial in homozygous APOE4/4 patients with early AD. In addition to clinical measures, the phase 3 trial will include cerebrospinal fluid, plasma, and imaging biomarkers to gain further insights into the role of soluble Aβ oligomers in the pathogenesis of AD and their impact on disease progression.

From monomer to fibril: Abeta-amyloid binding to Aducanumab antibody studied by molecular dynamics simulation

Alzheimer's disease is one of the most common causes of dementia. It is believed that the aggregation of short Aβ-peptides to form oligomeric and protofibrillar amyloid assemblies plays a central role for disease-relevant neurotoxicity. In recent years, passive immunotherapy has been introduced as a potential treatment strategy with anti-amyloid antibodies binding to Aβ-amyloids and inducing their subsequent degradation by the immune system. Although so far mostly unsuccessful in clinical studies, the high-dosed application of the monoclonal antibody Aducanumab has shown therapeutic potential that might be attributed to its much greater affinity to Aβ-aggregates vs monomeric Aβ-peptides. In order to better understand how Aducanumab interacts with aggregated Aβ-forms compared to monomers, we have generated structural model complexes based on the known structure of Aducanumab in complex with an Aβ_2 - 7 -eptitope. Structural models of Aducanumab bound to full-sequence Aβ_1 - 40 -monomers, oligomers, protofilaments and mature fibrils were generated and investigated using extensive molecular dynamics simulations to characterize the flexibility and possible additional interactions. Indeed, an aggregate-specific N-terminal binding motif was found in case of Aducanumab binding to oligomers, protofilaments and fibrils that is located next to but not overlapping with the epitope binding site found in the crystal structure with Aβ_2 - 7 . Analysis of binding energetics indicates that this motif binds weaker than the epitope but likely contributes to Aducanumab's preference for aggregated Aβ-species. The predicted aggregate-specific binding motif could potentially serve as a basis to reengineer Aducanumab for further enhanced preference to bind Aβ-aggregates vs monomers.

The path forward in Alzheimer's disease therapeutics: Reevaluating the amyloid cascade hypothesis

Development of disease-modifying treatments for Alzheimer's disease (AD) has been challenging, with no drugs approved to date. The failures of several amyloid-targeted programs have led many to dismiss the amyloid beta (Aβ) hypothesis of AD. An antiamyloid antibody aducanumab recently showed modest but significant efficacy in a phase 3 trial, providing important validation of amyloid as a therapeutic target. However, the inconsistent results observed with aducanumab may be explained by the limited brain penetration and lack of selectivity for the soluble Aβ oligomers, which are implicated as upstream drivers of neurodegeneration by multiple studies. Development of agents that can effectively inhibit Aβ oligomer formation or block their toxicity is therefore warranted. An ideal drug would cross the blood-brain barrier efficiently and achieve sustained brain levels that can continuously prevent oligomer formation or inhibit their toxicity. A late-stage candidate with these attributes is ALZ-801, an oral drug with a favorable safety profile and high brain penetration that can robustly inhibit Aβ oligomer formation. An upcoming phase 3 trial with ALZ-801 in APOE4/4 homozygous patients with early AD will effectively test this amyloid oligomer hypothesis.