The Future of Anti-Amyloid Trials

Spatial extent as a sensitive amyloid-PET metric in preclinical Alzheimer's disease

INTRODUCTION

Spatial extent-based measures of how far amyloid beta (Aβ) has spread throughout the neocortex may be more sensitive than traditional Aβ-positron emission tomography (PET) measures of Aβ level for detecting early Aβ deposits in preclinical Alzheimer's disease (AD) and improve understanding of Aβ's association with tau proliferation and cognitive decline.

METHODS

Pittsburgh Compound-B (PIB)-PET scans from 261 cognitively unimpaired older adults from the Harvard Aging Brain Study were used to measure Aβ level (LVL; neocortical PIB DVR) and spatial extent (EXT), calculated as the proportion of the neocortex that is PIB+.

RESULTS

EXT enabled earlier detection of Aβ deposits longitudinally confirmed to reach a traditional LVL-based threshold for Aβ+ within 5 years. EXT improved prediction of cognitive decline (Preclinical Alzheimer Cognitive Composite) and tau proliferation (flortaucipir-PET) over LVL.

DISCUSSION

These findings indicate EXT may be more sensitive to Aβ's role in preclinical AD than level and improve targeting of individuals for AD prevention trials.

HIGHLIGHTS

Aβ spatial extent (EXT) was measured as the percentage of the neocortex with elevated Pittsburgh Compound-B. Aβ EXT improved detection of Aβ below traditional PET thresholds. Early regional Aβ deposits were spatially heterogeneous. Cognition and tau were more closely tied to Aβ EXT than Aβ level. Neocortical tau onset aligned with reaching widespread neocortical Aβ.

Advancements and Challenges in Antiamyloid Therapy for Alzheimer's Disease: A Comprehensive Review

Alzheimer's disease (AD) is a progressive neurodegenerative disorder caused by the accumulation of amyloid-beta (Aβ) proteins and neurofibrillary tangles in the brain. There have been recent advancements in antiamyloid therapy for AD. This narrative review explores the recent advancements and challenges in antiamyloid therapy. In addition, a summary of evidence from antiamyloid therapy trials is presented with a focus on lecanemab. Lecanemab is the most recently approved monoclonal antibody that targets Aβ protofibrils for the treatment of patients with early AD and mild cognitive impairment (MCI). Lecanemab was the first drug shown to slow cognitive decline in patients with MCI or early onset AD dementia when administered as an infusion once every two weeks. In the Clarity AD trial, lecanemab was associated with infusion-site reactions (26.4%) and amyloid-related imaging abnormalities (12.6%). The clinical relevance and long-term side effects of lecanemab require further longitudinal observation. However, several challenges must be addressed before the drug can be routinely used in clinical practice. The drug's route of administration, need for imaging and genetic testing, affordability, accessibility, infrastructure, and potential for serious side effects are some of these challenges. Lecanemab's approval has fueled interest in the potential of other antiamyloid therapies, such as donanemab. Future research must focus on developing strategies to prevent AD; identify easy-to-use validated plasma-based assays; and discover newer user-friendly, and cost-effective drugs that target multiple pathways in AD pathology.

Efficacy of anti-amyloid-ß monoclonal antibody therapy in early Alzheimer's disease: a systematic review and meta-analysis

BACKGROUND

Studies targeting amyloid-ß in patients with Alzheimer's disease (AD) have conflicting results and early initiation of therapy may yield better outcomes.

METHODS

We systematically searched PubMed, Embase, Cochrane Library, and Clinicaltrials.gov for randomized trials comparing monoclonal antibodies (mAbs) with placebo in MCI or mild dementia due to AD.

RESULTS

Nineteen studies comprising 15,275 patients were included. In patients with early AD, mAbs reduced the rate of decline, in both the Clinical Dementia Rating Scale, the sum of boxes (CDR-SB; MD -0.30; 95% CI -0.42,-0.19; p < 0.01), and the Alzheimer's Disease Assessment Scale, cognitive subscore (ADAS-cog; SMD -0.80; 95% CI -10.25,-0.35; p < 0.01). The results were similar between clinical stages for CDR-SB (MCI, MD -0.19; 95% CI -0.35,-0.03; p = 0.02; mild dementia, MD -0.45; 95% CI -0.65,-0.25; p < 0.01; subgroup differences, p = 0.13), as well as for ADAS-Cog (MCI, SMD -0.83; 95% CI -1.49,-0.17; p = 0.01; mild dementia, SMD -0.69; 95% CI -1.32 to -0.05; p = 0.03; subgroup differences, p = 0.47). The risk of amyloid-related imaging abnormalities (ARIA) was significantly higher in patients taking mAbs, including ARIA-edema (RR 7.7; 95% CI 4.60 to 13.00; p < 0.01), ARIA-hemorrhage (RR 1.8; 95% CI 1.22 to 2.59; p < 0.01), and symptomatic or serious ARIA (RR 14.1; 95% CI 7.30 to 27.14; p < 0.01).

CONCLUSION

Anti-amyloid-ß mAbs attenuate cognitive and functional decline compared with placebo in early AD; whether the magnitude of this effect is clinically important remains uncertain, especially relative to the safety profile of these medications. Starting immunotherapy in patients with MCI was not significantly different than starting in the mild dementia stage.

PROSPERO REGISTRY

CRD42023430698.

Software compatibility analysis for quantitative measures of [18F]flutemetamol amyloid PET burden in mild cognitive impairment

RATIONALE

Amyloid-β (Aβ) pathology is one of the earliest detectable brain changes in Alzheimer's disease pathogenesis. In clinical practice, trained readers will visually categorise positron emission tomography (PET) scans as either Aβ positive or negative. However, adjunct quantitative analysis is becoming more widely available, where regulatory approved software can currently generate metrics such as standardised uptake value ratios (SUVr) and individual Z-scores. Therefore, it is of direct value to the imaging community to assess the compatibility of commercially available software packages. In this collaborative project, the compatibility of amyloid PET quantification was investigated across four regulatory approved software packages. In doing so, the intention is to increase visibility and understanding of clinically relevant quantitative methods.

METHODS

Composite SUVr using the pons as the reference region was generated from [¹⁸F]flutemetamol (GE Healthcare) PET in a retrospective cohort of 80 amnestic mild cognitive impairment (aMCI) patients (40 each male/female; mean age = 73 years, SD = 8.52). Based on previous autopsy validation work, an Aβ positivity threshold of ≥ 0.6 SUVr_pons was applied. Quantitative results from MIM Software's MIMneuro, Syntermed's NeuroQ, Hermes Medical Solutions' BRASS and GE Healthcare's CortexID were analysed using intraclass correlation coefficient (ICC), percentage agreement around the Aβ positivity threshold and kappa scores.

RESULTS

Using an Aβ positivity threshold of ≥ 0.6 SUVr_pons, 95% agreement was achieved across the four software packages. Two patients were narrowly classed as Aβ negative by one software package but positive by the others, and two patients vice versa. All kappa scores around the same Aβ positivity threshold, both combined (Fleiss') and individual software pairings (Cohen's), were ≥ 0.9 signifying "almost perfect" inter-rater reliability. Excellent reliability was found between composite SUVr measurements for all four software packages, with an average measure ICC of 0.97 and 95% confidence interval of 0.957-0.979. Correlation coefficient analysis between the two software packages reporting composite z-scores was strong (r² = 0.98).

CONCLUSION

Using an optimised cortical mask, regulatory approved software packages provided highly correlated and reliable quantification of [¹⁸F]flutemetamol amyloid PET with a ≥ 0.6 SUVr_pons positivity threshold. In particular, this work could be of interest to physicians performing routine clinical imaging rather than researchers performing more bespoke image analysis. Similar analysis is encouraged using other reference regions as well as the Centiloid scale, when it has been implemented by more software packages.

Ginkgo biloba Extract EGb 761 in the Treatment of Patients with Mild Neurocognitive Impairment: A Systematic Review

Background

Many clinical trials testing Ginkgo biloba extract EGb 761 in patients with mild forms of cognitive impairment were conducted before widely accepted terms and diagnostic criteria for such conditions were available. This makes it difficult to compare any results from earlier and more recent trials. The objective of this systematic review was to provide a descriptive overview of clinical trials of EGb 761 in patients who met the diagnostic criteria for mild neurocognitive disorder (mild NCD) according to the Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5).

Methods

MEDLINE, PubMed and EMBASE were searched for randomized, placebo-controlled double-blind trials of EGb 761 in mild impairment of cognitive functioning. All trials involving patients who met retrospectively applied diagnostic criteria for mild NCD were included. Trials of primary prevention of dementia and trials of combinations of medical treatments were excluded.

Results

Among 298 records found in databases and 76 further records related to EGb 761 in references of systematic reviews, 9 reports on clinical trials involving 946 patients met the pre-specified criteria for inclusion. Beneficial effects of EGb 761 were seen in neuropsychological tests (8 of 9 studies), scales for neuropsychiatric symptoms (3 of 3 studies), geriatric rating scales (1 of 2 studies) and global ratings of change (1 of 1 study). Significant effects were found in several domains of cognition (memory, speed of processing, attention and executive functioning). Among the neuropsychiatric symptoms, depression (2 of 3 studies) and anxiety (1 of 1 study) were significantly improved. No differences between EGb 761 treatment and placebo were seen with regard to the rates of adverse events.

Discussion

The included studies demonstrate treatment benefits of Ginkgo biloba extract EGb 761, mainly on cognitive deficits and neuropsychiatric symptoms, in patients with mild NCD. The drug was safe and well tolerated.

Clinical Data Interchange Standards in Clinical Trials on Alzheimer's Disease

OBJECTIVE

The Clinical Data Interchange Standards Consortium (CDISC) proposed outcome measures for clinical trials on Alzheimer's disease (AD) in the Therapeutic Area User Guide for AD (TAUG-AD). To investigate how well the clinical trials on AD registered in the ClinicalTrials.gov complied with the recommendations on outcome measures by the CDISC.

METHODS

We compared the outcome measures proposed in the TAUG-AD version 2.0.1 with those employed in the protocols of clinical trials on AD registered in ClinicalTrials.gov.

RESULTS

We analyzed 101 outcome measures from 305 protocols. The TAUG-AD listed ten scales for outcome measures of clinical trials on AD. The scales for cognition, activities of daily living, behavioral and psychological symptoms of dementia, and global severity listed in TAUG-AD were most frequently employed in the clinical trials on AD. However, TAUG-AD did not include any scale on quality of life. Also, several scales such as Montreal Cognitive Assessment, Alzheimer's Disease Cooperative Study-Activities of Daily Living, and Cohen- Mansfield Agitation Inventory not listed in the TAUG-AD were commonly employed in the clinical trials on AD and changed over time.

CONCLUSION

To properly standardize the data from clinical trials on AD, the gap between the TAUG-AD and the measures employed in real-world clinical trials should be filled.

Amyloid-Related Imaging Abnormalities with Emerging Alzheimer Disease Therapeutics: Detection and Reporting Recommendations for Clinical Practice

Monoclonal antibodies are emerging disease-modifying therapies for Alzheimer disease that require brain MR imaging for eligibility assessment as well as for monitoring for amyloid-related imaging abnormalities. Amyloid-related imaging abnormalities result from treatment-related loss of vascular integrity and may occur in 2 forms. Amyloid-related imaging abnormalities with edema or effusion are transient, treatment-induced edema or sulcal effusion, identified on T2-FLAIR. Amyloid-related imaging abnormalities with hemorrhage are treatment-induced microhemorrhages or superficial siderosis identified on T2* gradient recalled-echo. As monoclonal antibodies become more widely available, treatment screening and monitoring brain MR imaging examinations may greatly increase neuroradiology practice volumes. Radiologists must become familiar with the imaging appearance of amyloid-related imaging abnormalities, how to select an appropriate imaging protocol, and report findings in clinical practice. On the basis of clinical trial literature and expert experience from clinical trial imaging, we summarize imaging findings of amyloid-related imaging abnormalities, describe potential interpretation pitfalls, and provide recommendations for a standardized imaging protocol and an amyloid-related imaging abnormalities reporting template. Standardized imaging and reporting of these findings are important because an amyloid-related imaging abnormalities severity score, derived from the imaging findings, is used along with clinical status to determine patient management and eligibility for continued monoclonal antibody dosing.

Quantification of amyloid PET for future clinical use: a state-of-the-art review

Amyloid-β (Aβ) pathology is one of the earliest detectable brain changes in Alzheimer's disease (AD) pathogenesis. The overall load and spatial distribution of brain Aβ can be determined in vivo using positron emission tomography (PET), for which three fluorine-18 labelled radiotracers have been approved for clinical use. In clinical practice, trained readers will categorise scans as either Aβ positive or negative, based on visual inspection. Diagnostic decisions are often based on these reads and patient selection for clinical trials is increasingly guided by amyloid status. However, tracer deposition in the grey matter as a function of amyloid load is an inherently continuous process, which is not sufficiently appreciated through binary cut-offs alone. State-of-the-art methods for amyloid PET quantification can generate tracer-independent measures of Aβ burden. Recent research has shown the ability of these quantitative measures to highlight pathological changes at the earliest stages of the AD continuum and generate more sensitive thresholds, as well as improving diagnostic confidence around established binary cut-offs. With the recent FDA approval of aducanumab and more candidate drugs on the horizon, early identification of amyloid burden using quantitative measures is critical for enrolling appropriate subjects to help establish the optimal window for therapeutic intervention and secondary prevention. In addition, quantitative amyloid measurements are used for treatment response monitoring in clinical trials. In clinical settings, large multi-centre studies have shown that amyloid PET results change both diagnosis and patient management and that quantification can accurately predict rates of cognitive decline. Whether these changes in management reflect an improvement in clinical outcomes is yet to be determined and further validation work is required to establish the utility of quantification for supporting treatment endpoint decisions. In this state-of-the-art review, several tools and measures available for amyloid PET quantification are summarised and discussed. Use of these methods is growing both clinically and in the research domain. Concurrently, there is a duty of care to the wider dementia community to increase visibility and understanding of these methods.

Amyloid-Related Imaging Abnormalities With Anti-amyloid Antibodies for the Treatment of Dementia Due to Alzheimer's Disease

Second-generation anti-amyloid monoclonal antibodies are emerging as a viable therapeutic option for individuals with prodromal and mild dementia due to Alzheimer's disease (AD). Passive immunotherapy with aducanumab (Aduhelm), lecanemab, donanemab, and gantenerumab all lower CNS amyloid (Aβ) burden but come with a significant risk of amyloid-related imaging abnormality (ARIA)—the most common side effect of this class of drugs. While usually asymptomatic and detected only on brain MRI, ARIA may lead to new signs and symptoms including headache, worsening confusion, dizziness, visual disturbances, nausea, and seizures. In addition, one fatality related to ARIA-E (edema) with aducanumab and one fatality due to ARIA-H (hemorrhage) with donanemab are reported to date. ARIA-E may be associated with excessive neuroinflammation and saturation of perivascular clearance pathways, while ARIA-H may be related to vascular amyloid clearance with weakening and rupture of small blood vessels. The risk of ARIA-E is higher at treatment initiation, in ApoE4 carriers, with higher dosage, and with >4 of microhemorrhages on a baseline MRI. The risk of ARIA-H increases with age and cerebrovascular disease. Dose titration mitigates the risk of ARIA, and contraindications include individuals with >4 microhemorrhages and those prescribed anti-platelet or anti-coagulant drugs. A brain MRI is required before aducanumab is initiated, before each scheduled dose escalation, and with any new neurologic sign or symptom. Management of ARIA ranges from continued antibody treatment with monthly MRI monitoring for asymptomatic individuals to temporary or permanent suspension for symptomatic individuals or those with moderate to severe ARIA on MRI. Controlled studies regarding prevention and treatment of ARIA are lacking, but anecdotal evidence suggests that a pulse of intravenous corticosteroids may be of benefit, as well as a course of anticonvulsant for seizures.

Extensive frontal focused ultrasound mediated blood-brain barrier opening for the treatment of Alzheimer's disease: a proof-of-concept study

BACKGROUND

Focused ultrasound (FUS)-mediated blood-brain barrier (BBB) opening has shown efficacy in removal of amyloid plaque and improvement of cognitive functions in preclinical studies, but this is rarely reported in clinical studies. This study was conducted to evaluate the safety, feasibility and potential benefits of repeated extensive BBB opening.

METHODS

In this open-label, prospective study, six patients with Alzheimer's disease (AD) were enrolled at Severance Hospital in Korea between August 2020 and September 2020. Five of them completed the study. FUS-mediated BBB opening, targeting the bilateral frontal lobe regions over 20 cm3, was performed twice at three-month intervals. Magnetic resonance imaging, 18F-Florbetaben (FBB) positron emission tomography, Caregiver-Administered Neuropsychiatric Inventory (CGA-NPI) and comprehensive neuropsychological tests were performed before and after the procedures.

RESULTS

FUS targeted a mean volume of 21.1 ± 2.7 cm3 and BBB opening was confirmed at 95.7% ± 9.4% of the targeted volume. The frontal-to-other cortical region FBB standardized uptake value ratio at 3 months after the procedure showed a slight decrease, which was statistically significant, compared to the pre-procedure value (- 1.6%, 0.986 vs1.002, P = 0.043). The CGA-NPI score at 2 weeks after the second procedure significantly decreased compared to baseline (2.2 ± 3.0 vs 8.6 ± 6.0, P = 0.042), but recovered after 3 months (5.2 ± 5.8 vs 8.6 ± 6.0, P = 0.89). No adverse effects were observed.

CONCLUSIONS

The repeated and extensive BBB opening in the frontal lobe is safe and feasible for patients with AD. In addition, the BBB opening is potentially beneficial for amyloid removal in AD patients.

Spontaneous ARIA-like Events in Cerebral Amyloid Angiopathy-Related Inflammation: A Multicenter Prospective Longitudinal Cohort Study

BACKGROUND AND OBJECTIVES

The goal of this work was to investigate the natural history and outcomes after treatment for spontaneous amyloid-related imaging abnormalities (ARIA)-like in cerebral amyloid angiopathy-related inflammation (CAA-ri).

METHODS

This was a multicenter, hospital-based, longitudinal, prospective observational study of inpatients meeting CAA-ri diagnostic criteria recruited through the Inflammatory Cerebral Amyloid Angiopathy and Alzheimer's Disease βiomarkers International Network from January 2013 to March 2017. A protocol for systematic data collection at first-ever presentation and at subsequent in-person visits, including T1-weighted, gradient recalled echo-T2*, fluid-suppressed T2-weighted (fluid-attenuated inversion recovery), and T1 postgadolinium contrast-enhanced images acquired on 1.5T MRI, was used at the 3-, 6-, 12-, and 24-month follow-up. Centralized reads of MRIs were performed by investigators blinded to clinical, therapeutic, and time-point information. Main outcomes were survival, clinical and radiologic recovery, intracerebral hemorrhage (ICH), and recurrence of CAA-ri.

RESULTS

The study enrolled 113 participants (10.6% definite, 71.7% probable, and 17.7% possible CAA-ri). Their mean age was 72.9 years; 43.4% were female; 37.1% were APOEε4 carriers; 36.3% had a history of Alzheimer disease; and 33.6% had a history of ICH. A history of ICH and the occurrence of new ICH at follow-up were more common in patients with cortical superficial siderosis at baseline (52.6% vs 14.3%, p < 0.0001 and 19.3% vs 3.6%, p < 0.009, respectively). After the first-ever presentation of CAA-ri, 70.3% (95% confidence interval [CI] 61.6%-78.5%) and 84.1% (95% CI 76.2%-90.6%) clinically recovered within 3 and 12 months, followed by radiologic recovery in 45.1% (95% CI 36.4%-54.8%) and 77.4% (95% CI 67.7%-85.9%), respectively. After clinicoradiologic resolution of the first-ever episode, 38.3% (95% CI 22.9%-59.2%) had at least 1 recurrence within the following 24 months. Recurrence was more likely if IV high-dose corticosteroid pulse therapy was suddenly stopped compared to slow oral tapering off (hazard ratio 4.68, 95% CI 1.57-13.93; p = 0.006).

DISCUSSION

These results from the largest longitudinal cohort registry of patients with CAA-ri support the transient and potentially relapsing inflammatory nature of the clinical-radiologic acute manifestations of the disease and the effectiveness of slow oral tapering off after IV corticosteroid pulse therapy in preventing recurrences. Our results highlight the importance of differential diagnosis for spontaneous ARIA-like events in β-amyloid-driven diseases, including treatment-related ARIA in patients with Alzheimer disease exposed to immunotherapy drugs.

Effects of monoclonal antibodies against amyloid-β on clinical and biomarker outcomes and adverse event risks: A systematic review and meta-analysis of phase III RCTs in Alzheimer's disease

OBJECTIVE

To investigate the effects of monoclonal antibodies against Aβ on cognition, function, amyloid PET and other biomarkers, as well as risk for amyloid-related imaging abnormalities (ARIA) and other adverse events, in Alzheimer's disease (AD).

METHODS

Pubmed, Web of Science, ClinicalTrials.gov and gray literature were searched for phase III RCTs and random-effects meta-analyses were performed.

RESULTS

Seventeen studies (12,585 patients) were included. Antibodies statistically improved the cognitive outcomes ADAS-Cog {SMD = -0.06 [95 % CI (-0.10; -0.02), I2 = 0%]} and MMSE {SMD = 0.05 [95 % CI (0.01; 0.09), I2 = 0%]} by small effect sizes, but did not improve the cognitive/functional measure CDR-SOB {SMD = -0.03 [95 % CI (-0.07; 0.01), I2 = 18 %]}. Moreover, antibodies decreased amyloid PET SUVR {SMD = -1.02 [95 % CI (-1.70; -0.34), I2 = 95 %]} and CSF p181-tau {SMD = -0.87 [95 % CI (-1.32; -0.43), I2 = 89 %]} by large effect sizes. They also increased risk for ARIA {RR = 4.30 [95 % CI (2.39; 7.77), I2 = 86 %]} by a large effect size. Antibody effects on reducing amyloid PET SUVR were correlated with their effects on improving ADAS-Cog (r = +0.68, p = 0.02). In subgroup analyses by individual drug, Aducanumab improved ADAS-Cog, CDR-SOB, ADCS-ADL by small effect sizes and decreased amyloid PET SUVR and CSF p181-tau by large effect sizes. Solanezumab improved ADAS-Cog and MMSE by small effect sizes, and increased (improved) CSF Aβ1-40 levels by a moderate effect size. Bapineuzumab, Gantenerumab and Crenezumab did not improve any clinical outcomes. Bapineuzumab and Gantenerumab decreased CSF p181-tau by a small and large effect size, respectively. All drugs except Solanezumab increased ARIA risk.

CONCLUSIONS

In this meta-analysis of phase III trials in AD, we found that monoclonal antibodies against Aβ induced clinical improvements of small effect sizes, biomarker improvements of large effect sizes, and increases in risk for the hallmark adverse event, ARIA, by a large effect size, when all drugs were pooled together. Among individual drugs, Aducanumab produced the most favorable effects followed by Solanezumab. These findings provide moderate support for the continuous development of anti-Aβ monoclonal antibodies as a treatment for AD.

Alzheimer's protection effect of A673T mutation may be driven by lower Aβ oligomer binding affinity

Several mutations conferring protection against Alzheimer's disease (AD) have been described, none as profound as the A673T mutation, where carriers are four times less likely to get AD compared to noncarriers. This mutation results in reduced amyloid beta (Aβ) protein production in vitro and lower lifetime Aβ concentration in carriers. Better understanding of the protective mechanisms of the mutation may provide important insights into AD pathophysiology and identify productive therapeutic intervention strategies for disease modification. Aβ(1-42) protein forms oligomers that bind saturably to a single receptor site on neuronal synapses, initiating the downstream toxicities observed in AD. Decreased formation, toxicity, or stability of soluble Aβ oligomers, or reduction of synaptic binding of these oligomers, may combine with overall lower Aβ concentration to underlie A673T's disease protecting mechanism. To investigate these possibilities, we compared the formation rate of soluble oligomers made from Icelandic A673T mutant and wild type (wt) Aβ(1-42) synthetic protein, the amount and intensity of oligomer bound to mature primary rat hippocampal/cortical neuronal synapses, and the potency of bound oligomers to impact trafficking rate in neurons in vitro using a physiologically relevant oligomer preparation method. At equal protein concentrations, mutant protein forms approximately 50% or fewer oligomers of high molecular weight (>50 kDa) compared to wt protein. Mutant oligomers are twice as potent at altering the cellular vesicle trafficking rate as wt at equivalent concentrations, however, mutant oligomers have a >4-fold lower binding affinity to synaptic receptors (Kd  = 1,950 vs. 442 nM). The net effect of these differences is a lower overall toxicity at a given concentration. This study demonstrates for the first time that mutant A673T Aβ oligomers prepared with this method have fundamentally different assembly characteristics and biological impact from wt protein and indicates that its disease protecting mechanism may result primarily from the mutant protein's much lower binding affinity to synaptic receptors. This suggests that therapeutics that effectively reduce oligomer binding to synapses in the brain may be beneficial in AD.

Phase II (NAVIGATE-AD study) Results of LY3202626 Effects on Patients with Mild Alzheimer's Disease Dementia

Background:

LY3202626 is a small molecule inhibitor of β-site amyloid precursor protein cleaving enzyme (BACE)1 shown to reduce amyloid-β (Aβ)_1–40 and Aβ_1–42 concentrations in plasma and cerebrospinal fluid developed for the treatment of Alzheimer’s disease (AD).

Objective:

To assess the change from baseline in flortaucipir positron emission tomography (PET) after treatment with LY3202626 compared with placebo in patients with mild AD dementia.

Methods:

Patients received daily 3 mg or 12 mg doses of LY3202626 or placebo for 52 weeks. The primary outcome was assessment of cerebral neurofibrillary tangle load by flortaucipir PET. The study was terminated early following an interim analysis due to a low probability of identifying a statistically significant slowing of cognitive and/or functional decline.

Results:

A total of 316 patients were randomized and 47 completed the study. There was no statistically significant difference between placebo and either dose of LY3202626 from baseline to 52 weeks, or in annualized change for flortaucipir PET. There was no clinically meaningful difference between placebo and LY3202626 doses on efficacy measures of cognition and function. No deaths or serious adverse events considered related to LY3202626 were reported. A statistically significant increase in treatment-emergent adverse events in the psychiatric disorders system organ class was reported for both LY3202626 doses compared to placebo.

Conclusion:

LY3202626 tested at doses generating 70–90% BACE inhibition was generally well tolerated in this study. LY3202626 treatment did not result in a clinically significant change in cerebral tau burden as measured by flortaucipir nor in change of functional or cognitive decline compared to placebo.

Aβ Influx into the Blood Evoked by Different Blood Aβ Removal Systems: A Potential Therapy for Alzheimer's Disease

PURPOSE

Amyloid-β (Aβ) is a brain protein that causes Alzheimer's disease. We have revealed that extracorporeal blood Aβ-removal systems evoked a large Aβ influx into the blood. This study investigated the system that is more effective in evoking Aβ influx.

METHODS

Aβ removal activities were compared between hexadecyl-alkylated cellulose beads (HexDC) and fragments of polysulfone hollow fibers (PSf-HFs) in mini-columns to eliminate the filtration effect. Then, adsorptive filtration systems were adapted for PSf hemodialyzers to enhance Aβ adsorption on micropores in the wall of hollow fibers. Plasma Aβ concentrations of patients with renal failure were analyzed during treatment with PSf hemodialyzers alone for 8 h or tandemly connected HexDC and PSf hemodialyzers for 4 h.

RESULTS

In the in vitro study, Aβ removal efficiency for HexDC was approximately 100% during the 60 min treatment, whereas the removal efficiency for PSf-HF fragments gradually decreased. However, PSf hemodialyzer in adsorptive filtration systems removed Aβs comparably or more than HexDC. Aβ influx into the blood increases time-dependently. Concomitant use of HexDC and PSf hemodialyzer evoked a larger Aβ_1-40 influx than that of PSf hemodialyzer alone. However, Aβ_1-42 influx by PSf hemodialyzer alone was similar to or a little larger than influx by the combined system. Both systems evoked almost doubled Aβ influx than estimated Aβs existing in the normal brain during the 4 h treatment.

CONCLUSION

PSf hemodialyzer alone for a longer period and concomitant use of HexDC and PSf hemodialyzer for a shorter time effectively evoked a larger Aβ influx. To evoke Aβ_1-42 influx, PSf hemodialyzer alone was effective enough. These findings of devices and treatment time may lead to optimal clinical settings for therapy and prevention of Alzheimer's disease.

Pharmacophore Modeling and 3D-QSAR Study of Indole and Isatin Derivatives as Antiamyloidogenic Agents Targeting Alzheimer's Disease

Thirty-six novel indole-containing compounds, mainly 3-(2-phenylhydrazono) isatins and structurally related 1H-indole-3-carbaldehyde derivatives, were synthesized and assayed as inhibitors of beta amyloid (Aβ) aggregation, a hallmark of pathophysiology of Alzheimer's disease. The newly synthesized molecules spanned their IC50 values from sub- to two-digit micromolar range, bearing further information into structure-activity relationships. Some of the new compounds showed interesting multitarget activity, by inhibiting monoamine oxidases A and B. A cell-based assay in tau overexpressing bacterial cells disclosed a promising additional activity of some derivatives against tau aggregation. The accumulated data of either about ninety published and thirty-six newly synthesized molecules were used to generate a pharmacophore hypothesis of antiamyloidogenic activity exerted in a wide range of potencies, satisfactorily discriminating the 'active' compounds from the 'inactive' (poorly active) ones. An atom-based 3D-QSAR model was also derived for about 80% of 'active' compounds, i.e., those achieving finite IC50 values lower than 100 μM. The 3D-QSAR model (encompassing 4 PLS factors), featuring acceptable predictive statistics either in the training set (n = 45, q2 = 0.596) and in the external test set (n = 14, r2ext = 0.695), usefully complemented the pharmacophore model by identifying the physicochemical features mainly correlated with the Aβ anti-aggregating potency of the indole and isatin derivatives studied herein.

Alzheimer's disease beyond amyloid: strategies for future therapeutic interventions

Jiong Shi and colleagues discuss recent evidence of clinical trials for Alzheimer’s disease and new development strategies

The Role of HDL and HDL Mimetic Peptides as Potential Therapeutics for Alzheimer's Disease

The role of high-density lipoproteins (HDL) in the cardiovascular system has been extensively studied and the cardioprotective effects of HDL are well established. As HDL particles are formed both in the systemic circulation and in the central nervous system, the role of HDL and its associated apolipoproteins in the brain has attracted much research interest in recent years. Alzheimer’s disease (AD) is the most prevalent neurodegenerative disorder and the leading cause of dementia worldwide, for which there currently exists no approved disease modifying treatment. Multiple lines of evidence, including a number of large-scale human clinical studies, have shown a robust connection between HDL levels and AD. Low levels of HDL are associated with increased risk and severity of AD, whereas high levels of HDL are correlated with superior cognitive function. Although the mechanisms underlying the protective effects of HDL in the brain are not fully understood, many of the functions of HDL, including reverse lipid/cholesterol transport, anti-inflammation/immune modulation, anti-oxidation, microvessel endothelial protection, and proteopathy modification, are thought to be critical for its beneficial effects. This review describes the current evidence for the role of HDL in AD and the potential of using small peptides mimicking HDL or its associated apolipoproteins (HDL-mimetic peptides) as therapeutics to treat AD.

Rationally Designed Antibodies as Research Tools to Study the Structure-Toxicity Relationship of Amyloid-β Oligomers

Alzheimer's disease is associated with the aggregation of the amyloid-β peptide (Aβ), resulting in the deposition of amyloid plaques in brain tissue. Recent scrutiny of the mechanisms by which Aβ aggregates induce neuronal dysfunction has highlighted the importance of the Aβ oligomers of this protein fragment. Because of the transient and heterogeneous nature of these oligomers, however, it has been challenging to investigate the detailed mechanisms by which these species exert cytotoxicity. To address this problem, we demonstrate here the use of rationally designed single-domain antibodies (DesAbs) to characterize the structure-toxicity relationship of Aβ oligomers. For this purpose, we use Zn2+-stabilized oligomers of the 40-residue form of Aβ (Aβ40) as models of brain Aβ oligomers and two single-domain antibodies (DesAb18-24 and DesAb34-40), designed to bind to epitopes at residues 18-24 and 34-40 of Aβ40, respectively. We found that the DesAbs induce a change in structure of the Zn2+-stabilized Aβ40 oligomers, generating a simultaneous increase in their size and solvent-exposed hydrophobicity. We then observed that these increments in both the size and hydrophobicity of the oligomers neutralize each other in terms of their effects on cytotoxicity, as predicted by a recently proposed general structure-toxicity relationship, and observed experimentally. These results illustrate the use of the DesAbs as research tools to investigate the biophysical and cytotoxicity properties of Aβ oligomers.