Adaptive, Dose-finding Phase 2 Trial Evaluating the Safety and Efficacy of ABT-089 in Mild to Moderate Alzheimer Disease

Review on anti-alzheimer drug development: approaches, challenges and perspectives

Alzheimer is an irreversible progressive neurodegenerative disease that causes failure of cerebral neurons and disability of the affected person to practice normal daily life activities. There is no concrete evidence to identify the exact reason behind the disease, so several relevant hypotheses emerged, highlighting many possible therapeutic targets, such as acetylcholinesterase, cholinergic receptors, N-methyl d-aspartate receptors, phosphodiesterase, amyloid β protein, protein phosphatase 2A, glycogen synthase kinase-3 beta, β-secretase, γ-secretase, α-secretase, serotonergic receptors, glutaminyl cyclase, tumor necrosis factor-α, γ-aminobutyric acid receptors, and mitochondria. All of these targets have been involved in the design of new potential drugs. An extensive number of these drugs have been studied in clinical trials. However, only galantamine, donepezil, and rivastigmine (ChEIs), memantine (NMDA antagonist), and aducanumab and lecanemab (selective anti-Aβ monoclonal antibodies) have been approved for AD treatment. Many drugs failed in the clinical trials to such an extent that questions have been posed about the significance of some of the aforementioned targets. On the contrary, the data of other drugs were promising and shed light on the significance of their targets for the development of new potent anti-alzheimer drugs.

A Systematic Review on Drugs Acting as Nicotinic Acetylcholine Receptor Agonists in the Treatment of Dementia

Acetylcholine signaling is attenuated in early Alzheimer's disease (AD) and other dementias. A significant reduction in the expression of nicotinic acetylcholine receptors (nAChRs) in the brain of AD patients has also been reported in several molecular biological and in situ labeling studies. The modulation of the functional deficit of the cholinergic system as a pharmacological target could therefore have a clinical benefit, which is not to be neglected. This systematic review was conducted to identify clinical trials, which evaluated the safety and efficacy of nicotinic acetylcholine receptor agonists using Clinicaltrial (CT) and EudraCT databases. Structured searches identified 39 trials, which used 15 different drugs designed to increase the function of the nAChRs. Most of the identified clinical trials were phase II trials, with some of them classified as ongoing for several years. The systematic screening of the literature led to the selection of 14 studies out of the 8261 bibliographic records retrieved. Six trials reported detailed data on adverse events associated with the intervention, while twelve trials reported data on efficacy measures, such as attention, behavior and cognition. Overall, smost of the physical side effects of cholinergic agonists were reported to be well tolerated. Some trials also reported improvements in attention. However, the efficacy of these drugs in other cognitive and behavioral outcomes remains highly controversial.

Advances in Alzheimer's disease's pharmacological treatment

Alzheimer's disease (AD) is the most common type of dementia in the elderly. Several hypotheses emerged from AD pathophysiological mechanisms. However, no neuronal protective or regenerative drug is available nowadays. Researchers still work in drug development and are finding new molecular targets to treat AD. Therefore, this study aimed to summarize main advances in AD pharmacological therapy. Clinical trials registered in the National Library of Medicine database were selected and analyzed accordingly to molecular targets, therapeutic effects, and safety profile. The most common outcome was the lack of efficacy. Only seven trials concluded that tested drugs were safe and induced any kind of therapeutic improvement. Three works showed therapeutic effects followed by toxicity. In addition to aducanumab recent FDA approval, antibodies against amyloid-β (Aβ) showed no noteworthy results. 5-HT6 antagonists, tau inhibitors and nicotinic agonists' data were discouraging. However, anti-Aβ vaccine, BACE inhibitor and anti-neuroinflammation drugs showed promising results.

Strategies for Treatment of Disease-Associated Dementia Beyond Alzheimer's Disease: An Update

Memory, cognition, dementia, and neurodegeneration are complexly interlinked processes with various mechanistic pathways, leading to a range of clinical outcomes. They are strongly associated with pathological conditions like Alzheimer's disease, Parkinson's disease, schizophrenia, and stroke and are a growing concern for their timely diagnosis and management. Several cognitionenhancing interventions for management include non-pharmacological interventions like diet, exercise, and physical activity, while pharmacological interventions include medicinal agents, herbal agents, and nutritional supplements. This review critically analyzed and discussed the currently available agents under different drug development phases designed to target the molecular targets, including cholinergic receptor, glutamatergic system, GABAergic targets, glycine site, serotonergic targets, histamine receptors, etc. Understanding memory formation and pathways involved therein aids in opening the new gateways to treating cognitive disorders. However, clinical studies suggest that there is still a dearth of knowledge about the pathological mechanism involved in neurological conditions, making the dropouts of agents from the initial phases of the clinical trial. Hence, a better understanding of the disease biology, mode of drug action, and interlinked mechanistic pathways at a molecular level is required.

The Development of Pharmacological Therapies for Alzheimer's Disease

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that currently has no cure. The aged population is growing globally, creating an urgent need for more promising therapies for this debilitating disease. Much effort has been made in recent decades, and the field is highly dynamic, with numerous trials. The main focus of these trials includes disease modification and symptomatic treatment. Some have shown beneficial outcomes, while others have shown no significant benefits. Here, we cover the outcome of recently published AD clinical trials, as well as the mechanism of action of these therapeutical agents, to re-think drug development strategies and directions for future studies.

Proportion of Women and Reporting of Outcomes by Sex in Clinical Trials for Alzheimer Disease: A Systematic Review and Meta-analysis

IMPORTANCE

Women represent two-thirds of patients with Alzheimer disease (AD), and sex differences might affect results of randomized clinical trials (RCTs). However, little information exists on differences in sex as reported in RCTs for AD.

OBJECTIVE

To assess the ratio of females to males and the reporting of sex-stratified data in large pharmaceutical RCTs for AD.

DATA SOURCES

A search for pharmaceutical RCTs for AD was conducted on September 4, 2019, using ClinicalTrials.gov with the key word Alzheimer disease, and articles related to those trials were identified using the PubMed, Scopus, and Google Scholar databases. Searches were conducted between September 4 and October 31, 2019, and between April 15 and May 31, 2020.

STUDY SELECTION

Controlled RCTs that had more than 100 participants and tested the efficacy of drugs or herbal extracts were included. Of 1047 RCTs identified, 409 were published and therefore screened. A total of 77 articles were included in the final analysis, including 56 primary articles on AD, 13 secondary articles on AD, and 8 articles on mild cognitive impairment.

DATA EXTRACTION AND SYNTHESIS

The location and date of publication; number, sex, and age of patients enrolled; disease severity; experimental or approved status of the drug; and whether the study included a sex-stratified analysis in the protocol, methods, or results were extracted by 1 reviewer for each article, and the meta-analysis followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline. Data were analyzed using a mixed-effects model.

MAIN OUTCOMES AND MEASURES

The mean proportion of women enrolled in the trials and the associations between prespecified variables were analyzed. The proportion of articles that included sex-stratified results and the temporal trends in the reporting of these results were also studied.

RESULTS

In this review of 56 RCTs for AD involving 39 575 participants, 23 348 women (59.0%) were included. The mean (SD) proportion of women in RCTs of approved drugs was 67.3% (6.9%), and in RCTs of experimental drugs was 57.9% (5.9%). The proportion of women in RCTs of experimental drugs was significantly lower than the proportion of women in the general population with AD in the US (62.1%; difference, -4.56% [95% CI, -6.29% to -2.87%]; P < .001) and Europe (68.2%; difference, -10.67% [95% CI, -12.39% to -8.97%]; P < .001). Trials of approved drugs had a higher probability of including women than trials of experimental drugs (odds ratio [OR], 1.26; 95% CI, 1.05-1.52; P = .02). Both the severity of AD at baseline and the trial location were associated with the probability of women being enrolled in trials (severity: OR, 0.98; 95% CI, 0.97-1.00; P = .02; location in Europe: OR, 1.26; 95% CI, 1.05-1.52; P = .01; location in North America: OR, 0.81; 95% CI, 0.71-0.93; P = .002). Only 7 articles (12.5%) reported sex-stratified results, with an increasing temporal trend (R, 0.30; 95% CI, 0.05-0.59; P = .03).

CONCLUSIONS AND RELEVANCE

In this systematic review and meta-analysis, the proportion of women in RCTs for AD, although higher than the proportion of men, was significantly lower than that in the general population. Only a small proportion of trials reported sex-stratified results. These findings support strategies to improve diversity in enrollment and data reporting in RCTs for AD.

Alzheimer's Disease: Related Targets, Synthesis of Available Drugs, Bioactive Compounds Under Development and Promising Results Obtained from Multi-target Approaches

We describe herein the therapeutic targets involved in Alzheimer's disease as well as the available drugs and their synthetic routes. Bioactive compounds under development are also exploited to illustrate some recent research advances on the medicinal chemistry of Alzheimer's disease, including structure-activity relationships for some targets. The importance of multi-target approaches, including some examples from our research projects, guides new perspectives in search of more effective drug candidates. This review comprises the period between 2001 and early 2020.

Innovative Therapeutic Development Programme for the Treatment of Early Alzheimer's Disease: Lecanemab (BAN2401)

Collapse

Genome-wide association study of rate of cognitive decline in Alzheimer's disease patients identifies novel genes and pathways

INTRODUCTION

Variability exists in the disease trajectories of Alzheimer's disease (AD) patients. We performed a genome-wide association study to examine rate of cognitive decline (ROD) in patients with AD.

METHODS

We tested for interactions between genetic variants and time since diagnosis to predict the ROD of a composite cognitive score in 3946 AD cases and performed pathway analysis on the top genes.

RESULTS

Suggestive associations (P < 1.0 × 10-6 ) were observed on chromosome 15 in DNA polymerase-γ (rs3176205, P = 1.11 × 10-7 ), chromosome 7 (rs60465337,P = 4.06 × 10-7 ) in contactin-associated protein-2, in RP11-384F7.1 on chromosome 3 (rs28853947, P = 5.93 × 10-7 ), family with sequence similarity 214 member-A on chromosome 15 (rs2899492, P = 5.94 × 10-7 ), and intergenic regions on chromosomes 16 (rs4949142, P = 4.02 × 10-7 ) and 4 (rs1304013, P = 7.73 × 10-7 ). Significant pathways involving neuronal development and function, apoptosis, memory, and inflammation were identified.

DISCUSSION

Pathways related to AD, intelligence, and neurological function determine AD progression, while previously identified AD risk variants, including the apolipoprotein (APOE) ε4 and ε2 variants, do not have a major impact.

Nicotinic Acetylcholine Receptor Agonists for the Treatment of Alzheimer's Dementia: An Update

A significant portion of the clinical phenotype observed in Alzheimer's disease (AD) occurs through nicotinic acetylcholine receptors (nAChRs). Degeneration of cholinergic neurons, combined with aberrant nAChR expression and activation partially through amyloid-beta peptide (Aβ)-nAChR leads to upregulation of pro-inflammatory pathways and subsequently the progressive cognitive decline of AD. Interestingly, the cholinergic anti-inflammatory pathway is also mediated through nAChR particularly α7 nAChR. Thus, agonists of these receptors will likely exert pro-cognitive benefits through multiple mechanisms including stimulating the cholinergic pathway, modulating inflammation, and buffering the effects of amyloid. Despite this promising theoretical use, trials thus far have been complicated by adverse effects or minimal improvement. This review will provide an update on several pharmacological nAChR agonists tested in clinical trials and reasons that further investigation of nAChR agonists is merited.

IMPLICATIONS

nAChRs have consistently presented a promising theoretical use in the treatment of AD; however, trials thus far have been complicated by adverse effects or minimal improvement. This review will provide an update on several pharmacological nAChR agonists trialed and reasons that further investigation of nAChR agonists is merited.

Alzheimer's disease drug development pipeline: 2019

Introduction

Alzheimer's disease (AD) has few available treatments, and there is a high rate of failure in AD drug development programs. Study of the AD drug development pipeline can provide insight into the evolution of drug development and how best to optimize development practices.

Methods

We reviewed clinicaltrials.gov and identified all pharmacologic AD trials of all agents currently being developed for treatment of AD.

Results

There are 132 agents in clinical trials for the treatment of AD. Twenty-eight agents are in 42 phase 3 trials; 74 agents are in 83 phase 2 trials; and 30 agents are in 31 phase 1 trials. There is an increase in the number of agents in each phase compared with that in the 2018 pipeline. Nineteen agents in trials target cognitive enhancement, and 14 are intended to treat neuropsychiatric and behavioral symptoms. There are 96 agents in disease modification trials; of these, 38 (40%) have amyloid as the primary target or as one of several effects. Eighteen of the antiamyloid agents are small molecules, and 20 are monoclonal antibodies or biological therapies. Seven small molecules and ten biologics have tau as a primary or combination target (18%). Amyloid is the most common specific target in phase 3 and phase 2 disease modification trials. Novel biomarkers (e.g., neurofilament light), new outcomes (e.g., AD Composite Score [ADCOMS]), enrollment of earlier populations, and innovative trial designs (e.g., Bayesian adaptive designs) are new features in recent clinical trials.

Discussion

Drug development continues robustly at all phases despite setbacks in several programs in the recent past. Continuing unmet needs require a commitment to growing and accelerating the pipeline.

Rate of β-amyloid accumulation varies with baseline amyloid burden: Implications for anti-amyloid drug trials

INTRODUCTION

This study examined a longitudinal trajectory of β-amyloid (Aβ) accumulation at the predementia stage of Alzheimer's disease in the context of clinical trials.

METHODS

Analyzed were baseline (BL) and 2 years' follow-up 18F-florbetapir positron emission tomography data of 246 Aβ-positive subjects with normal cognition and mild cognitive impairment. We studied the relationship between annual accumulation rates of 18F-florbetapir and BL standard uptake value ratios in whole gray matter (SUVR_GM).

RESULTS

Subjects with BL SUVR_GM of 0.56 to 0.92 (n = 134) appeared to accumulate Aβ approximately 1.5 times faster than remaining subjects. In subjects with SUVR_GM above 0.95, most regions with the highest annual accumulation rate were outside the established set of Alzheimer's disease typical regions.

CONCLUSION

There are global and regional variations in annual accumulation rate at the predementia stage of Alzheimer's disease. When taken into account, the sample size in anti-amyloid trials can be substantially reduced. Critically, treated and placebo groups should be matched for BL SUVR_GM.

Statistical advances in clinical trials and clinical research

Introduction

New treatments for neurodegenerative disease are urgently needed, and clinical trial methods are an essential component of new drug development. Although a parallel-group study design for neurological disorder clinical trials is commonly used to test the effectiveness of a new treatment as compared to placebo, it does not efficiently use information from the on-going study to increase the success rate of a trial or to stop a trial earlier when the new treatment is indeed ineffective.

Methods

We review some recent advances in designs for clinical trials, including futility designs and adaptive designs.

Results

Futility designs and noninferiority designs are used to test the nonsuperiority and the noninferiority of a new treatment, respectively. We provide some guidance on using these two designs and analyzing data from these studies properly. Adaptive designs are increasingly used in clinical trials to improve the flexibility and efficiency of trials with the potential to reduce resources, time, and costs. We review some typical adaptive designs and new statistical methods to handle the statistical challenges from adaptive designs.

Discussion

Statistical advances in clinical trial designs may be helpful to shorten study length and benefit more patients being treated with a better treatment during the discovery of new therapies for neurological disorders. Advancing statistical underpinnings of neuroscience research is a critical aspect of the core activities supported by the Center of Biomedical Research Excellence award supporting the Center for Neurodegeneration and Translational Neuroscience.

Clinical trial design for progressive MS trials

The design of clinical trials is a key aspect to maximizing the possibility to detect a treatment effect. This fact is particularly challenging in progressive multiple sclerosis (PMS) studies due to the uncertainty about the right target and/or outcome in phase-2 studies. The aim of this review is to evaluate the current challenges facing the design of clinical trials for PMS. The selection of patients, the instrumental and clinical outcomes that can be used in PMS trials, and issues in their design will be covered in this report.

Prediction of Conversion to Alzheimer's Disease with Longitudinal Measures and Time-To-Event Data

BACKGROUND

Identifying predictors of conversion to Alzheimer's disease (AD) is critically important for AD prevention and targeted treatment.

OBJECTIVE

To compare various clinical and biomarker trajectories for tracking progression and predicting conversion from amnestic mild cognitive impairment to probable AD.

METHODS

Participants were from the ADNI-1 study. We assessed the ability of 33 longitudinal biomarkers to predict time to AD conversion, accounting for demographic and genetic factors. We used joint modelling of longitudinal and survival data to examine the association between changes of measures and disease progression. We also employed time-dependent receiver operating characteristic method to assess the discriminating capability of the measures.

RESULTS

23 of 33 longitudinal clinical and imaging measures are significant predictors of AD conversion beyond demographic and genetic factors. The strong phenotypic and biological predictors are in the cognitive domain (ADAS-Cog; RAVLT), functional domain (FAQ), and neuroimaging domain (middle temporal gyrus and hippocampal volume). The strongest predictor is ADAS-Cog 13 with an increase of one SD in ADAS-Cog 13 increased the risk of AD conversion by 2.92 times.

CONCLUSION

Prediction of AD conversion can be improved by incorporating longitudinal change information, in addition to baseline characteristics. Cognitive measures are consistently significant and generally stronger predictors than imaging measures.

Old and new acetylcholinesterase inhibitors for Alzheimer's disease

INTRODUCTION

To date, pharmacological treatment of Alzheimer's disease (AD) includes Acetylcholinesterase Inhibitors (AChEIs) for mild-to-moderate AD, and memantine for moderate-to-severe AD. AChEIs reversibly inhibit acetylcholinesterase (AChE), thus increasing the availability of acetylcholine in cholinergic synapses, enhancing cholinergic transmission. These drugs provide symptomatic short-term benefits, without clearly counteracting the progression of the disease.

AREAS COVERED

On the wake of successful clinical trials which lead to the marketing of AChEIs donepezil, rivastigmine and galantamine, many compounds with AChEI properties have been developed and tested mainly in Phase I-II clinical trials in the last twenty years. Here, we review clinical trials initiated and interrupted, and those ongoing so far.

EXPERT OPINION

Despite many clinical trials with novel AChEIs have been carried out after the registration of those currently used to treat mild to moderate AD, none so far has been successful in a Phase III trial and marketed. Alzheimer's disease is a complex multifactorial disorder, therefore therapy should likely address not only the cholinergic system but also additional neurotransmitters. Moreover, such treatments should be started in very mild phases of the disease, and preventive strategies addressed in elderly people.

Re-Engineering Alzheimer Clinical Trials: Global Alzheimer's Platform Network

Alzheimer's disease (AD) drug development is costly, time-consuming, and inefficient. Trial site functions, trial design, and patient recruitment for trials all require improvement. The Global Alzheimer Platform (GAP) was initiated in response to these challenges. Four GAP work streams evolved in the US to address different trial challenges: 1) registry-to-cohort web-based recruitment; 2) clinical trial site activation and site network construction (GAP-NET); 3) adaptive proof-of-concept clinical trial design; and 4) finance and fund raising. GAP-NET proposes to establish a standardized network of continuously funded trial sites that are highly qualified to perform trials (with established clinical, biomarker, imaging capability; certified raters; sophisticated management system. GAP-NET will conduct trials for academic and biopharma industry partners using standardized instrument versions and administration. Collaboration with the Innovative Medicines Initiative (IMI) European Prevention of Alzheimer's Disease (EPAD) program, the Canadian Consortium on Neurodegeneration in Aging (CCNA) and other similar international initiatives will allow conduct of global trials. GAP-NET aims to increase trial efficiency and quality, decrease trial redundancy, accelerate cohort development and trial recruitment, and decrease trial costs. The value proposition for sites includes stable funding and uniform training and trial execution; the value to trial sponsors is decreased trial costs, reduced time to execute trials, and enhanced data quality. The value for patients and society is the more rapid availability of new treatments for AD.

Nicotinic ligands as multifunctional agents for the treatment of neuropsychiatric disorders

The challenges associated with developing more effective treatments for neurologic and psychiatric illness such as Alzheimer's disease and schizophrenia are considerable. Both the symptoms and the pathophysiology of these conditions are complex and poorly understood and the clinical presentations across different patients can be very heterogeneous. Moreover, it has become apparent that the reductionist approach to drug discovery for these illnesses that has dominated the field for decades (i.e., the development of highly selective compounds or other treatment modalities focused on a very specific pathophysiologic target) has not been widely successful. Accordingly, a variety of new strategies have emerged including the development of "multitarget-directed ligands" (MTDLs), the development and/or identification of compounds that exhibit "multifunctional" activity (e.g., pro-cognitive plus neuroprotective, pro-cognitive plus antipsychotic activity), "repurposing" strategies for existing compounds that have other clinical indications, and novel "adjunctive" treatment strategies that might enhance the efficacy of the currently available treatments. Interestingly, a variety of ligands at nicotinic acetylcholine receptors (nAChRs) appear to have the potential to fulfill one or more of these desirable properties (i.e., multifunctional, repurposing, or adjunctive treatment potential). The purpose of this review (while not all-inclusive) is to provide an overview of a variety of nAChR ligands that demonstrate potential in these categories, particularly, "multifunctional" properties. Due to their densities in the mammalian brain and the amount of literature available, the review will focus on ligands of the high affinity α4β2 nAChR and the low affinity α7 nAChR.

Regional covariance of muscarinic acetylcholine receptors in Alzheimer's disease using (R, R) [(123)I]-QNB SPECT

Alzheimer's disease (AD) is characterised by deficits in cholinergic neurotransmission and subsequent receptor changes. We investigated (123)I-iodo-quinuclidinyl-benzilate (QNB) SPECT images using spatial covariance analysis (SCA), to detect an M1/M4 receptor spatial covariance pattern (SCP) that distinguished AD from controls. Furthermore, a corresponding regional cerebral blood flow (rCBF) SCP was also derived. Thirty-nine subjects (15 AD and 24 healthy elderly controls) underwent (123)I-QNB and (99m)Tc-exametazime SPECT. Voxel SCA was simultaneously applied to the set of smoothed/registered scans, generating a series of eigenimages representing common intercorrelated voxels across subjects. Linear regression identified individual M1/M4 and rCBF SCPs that discriminated AD from controls. The M1/M4 SCP showed concomitant decreased uptake in medial temporal, inferior frontal, basal forebrain and cingulate relative to concomitant increased uptake in frontal poles, occipital, pre-post central and precuneus/superior parietal regions (F1,37 = 85.7, p < 0.001). A largely different perfusion SCP was obtained showing concomitant decreased rCBF in medial and superior temporal, precuneus, inferior parietal and cingulate relative to concomitant increased rCBF in cerebellum, pre-post central, putamen, fusiform and brain stem/midbrain regions (F1,37 = 77.5, p < 0.001). The M1/M4 SCP expression correlated with the duration of cognitive symptoms (r = 0.90, p < 0.001), whereas the rCBF SCP expression negatively correlated with MMSE, CAMCOG and CAMCOGmemory (r ≥ |0.63|, p ≤ 0.006). (123)I-QNB SPECT revealed an M1/M4 basocortical covariance pattern, distinct from rCBF, reflecting the duration of disease rather than current clinical symptoms. This approach could be more sensitive than univariate methods in characterising the cholinergic/rCBF changes that underpin the clinical phenotype of AD.