Trial design innovations: Clinical trials for treatment of neuropsychiatric symptoms in Alzheimer's Disease

Challenges and proposed solutions to conducting Alzheimer's disease psychosis trials

Alzheimer's disease psychosis (ADP) produces a significant burden for patients and their care partners, but at present there are no approved treatments for ADP. The lack of approved treatments may be due to the challenges of conducting clinical trials for this disease. This perspective article discusses distinct challenges and proposed solutions of conducting ADP trials involving seven key areas: (1) methods to reduce the variable and sometimes high rates of placebo response that occur for treatments of neuropsychiatric symptoms; (2) the use of combined or updated criteria that provide a precise, consensus definition of ADP; (3) the use of eligibility criteria to help recruit individuals representative of the larger ADP population and overcome the difficulty of recruiting patients with moderate-to-severe ADP; (4) consideration of multiple perspectives and implementation of technology to reduce the variability in the administration and scoring of neuropsychiatric symptom assessments; (5) the use of clinically appropriate, a priori-defined severity thresholds and responder cutoffs; (6) the use of statistical approaches that address absolute effect sizes and a three-tier approach to address the fluctuation of neuropsychiatric symptoms; and (7) the implementation of feasible diagnostic and target-engagement biomarkers as they become available. The goal of these proposed solutions is to improve the evaluation of potential ADP therapies, within the context of randomized, placebo-controlled trials with clinically meaningful endpoints and sustained treatment responses.

An Update on Apathy in Alzheimer's Disease

Apathy is a complex multi-dimensional syndrome that affects up to 70% of individuals with Alzheimer's disease (AD). Whilst many frameworks to define apathy in AD exist, most include loss of motivation or goal-directed behaviour as the central feature. Apathy is associated with significant impact on persons living with AD and their caregivers and is also associated with accelerated cognitive decline across the AD spectrum. Neuroimaging studies have highlighted a key role of fronto-striatial circuitry including the anterior cingulate cortex (ACC), orbito-frontal cortex (OFC) and associated subcortical structures. Importantly, the presence and severity of apathy strongly correlates with AD stage and neuropathological biomarkers of amyloid and tau pathology. Following from neurochemistry studies demonstrating a central role of biogenic amine neurotransmission in apathy syndrome in AD, recent clinical trial data suggest that apathy symptoms may improve following treatment with agents such as methylphenidate-which may have an important role alongside emerging non-pharmacological treatment strategies. Here, we review the diagnostic criteria, rating scales, prevalence, and risk factors for apathy in AD. The underlying neurobiology, neuropsychology and associated neuroimaging findings are reviewed in detail. Finally, we discuss current treatment approaches and strategies aimed at targeting apathy syndrome in AD, highlighting areas for future research and clinical trials in patient cohorts.

Pathogenesis, Animal Models, and Drug Discovery of Alzheimer's Disease

Alzheimer's disease (AD), the most common cause of dementia, is a chronic neurodegenerative disease induced by multiple factors. The high incidence and the aging of the global population make it a growing global health concern with huge implications for individuals and society. The clinical manifestations are progressive cognitive dysfunction and lack of behavioral ability, which not only seriously affect the health and quality of life of the elderly, but also bring a heavy burden to the family and society. Unfortunately, almost all the drugs targeting the classical pathogenesis have not achieved satisfactory clinical effects in the past two decades. Therefore, the present review provides more novel ideas on the complex pathophysiological mechanisms of AD, including classical pathogenesis and a variety of possible pathogenesis that have been proposed in recent years. It will be helpful to find out the key target and the effect pathway of potential drugs and mechanisms for the prevention and treatment of AD. In addition, the common animal models in AD research are outlined and we examine their prospect for the future. Finally, Phase I, II, III, and IV randomized clinical trials or on the market of drugs for AD treatment were searched in online databases (Drug Bank Online 5.0, the U.S. National Library of Medicine, and Alzforum). Therefore, this review may also provide useful information in the research and development of new AD-based drugs.

Evaluation of the efficacy of pimavanserin in the treatment of agitation and aggression in patients with Alzheimer's disease psychosis: A post hoc analysis

OBJECTIVES

Patients with Alzheimer's disease psychosis (ADP) commonly experience concomitant agitation and aggression. We investigated whether a reduction in ADP following pimavanserin treatment conferred a reduction in associated agitation and aggression.

METHODS

ACP-103-019 was a 12-week, randomized, double-blind, placebo-controlled study that evaluated the efficacy of pimavanserin (34 mg) in reducing psychotic symptoms in patients with ADP. The primary endpoint was change from baseline in Neuropsychiatric Inventory-Nursing Home Version-Psychosis Score (NPI-NH-PS) at week six. A post hoc analysis examined whether there was a greater reduction in agitation and aggression (NPI-NH domain C [agitation/aggression] and Cohen-Mansfield Agitation Inventory-Short Form [CMAI-SF]) in pimavanserin-treated patients who experienced a reduction of hallucinations and delusions (psychosis responders defined as ≥50% reduction from baseline in NPI-NH-PS, week six) when compared with those who did not (nonresponders).

RESULTS

Pimavanserin-treated patients with ≥50% response in psychotic symptoms (n = 44) showed a greater improvement in agitation and aggression symptoms on the NPI-NH domain C (week six, least squares mean [LSM] difference = -3.64, t = -4.69, P < .0001) and the CMAI-SF (week six, LSM difference = -3.71, t = -2.01, P = .0483) than nonresponders (n = 32). Differences between psychosis responders and nonresponders were also observed in patients with more severe agitation and aggression at baseline on the NPI-NH domain C (responders, n = 26; nonresponders, n = 13; week six, LSM difference = -3.03, t = -2.44, P = .019).

CONCLUSIONS

Patients with ADP, who show improvement in psychotic symptoms after pimavanserin treatment, also experience an improvement in concomitant agitation and aggression.

A 24-week double-blind placebo-controlled study of the efficacy and safety of the AMPA modulator S47445 in patients with mild to moderate Alzheimer's disease and depressive symptoms

Introduction

S47445 is a novel positive allosteric modulator of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptors that may emerge as a favorable candidate for the symptomatic treatment of cognitive and depressive disorders in patients suffering from Alzheimer's disease (AD) of mild to moderate severity and with depressive symptoms.

Methods

For this double-blind, placebo-controlled 24-week phase II trial, 520 outpatients aged between 55 and 85 years, with probable AD at mild to moderate stages (a Mini-Mental State Examination score of 24-15 inclusive) and exhibiting depressive symptoms (Cornell Scale for Depression in Dementia [CSDD] ≥ 8) were recruited in twelve countries and randomized to 3 doses of S47445 (5-15-50 mg) or placebo. The primary end point was the change from baseline in the 11-item Alzheimer's Disease Assessment Scale-Cognitive subscale (ADAS-Cog) total score at week 24. Secondary measures included the Disability Assessment for Dementia, Mini-Mental State Examination, ADAS-Cog 13-item, CSDD, Clinical Global Impression of Change (Alzheimer's Disease Cooperative Study-CGIC), Neuropsychiatric Inventory (NPI), and safety criteria.

Results

Baseline characteristics were comparable between the 4 groups. After 24 weeks, no statistically significant treatment difference was demonstrated between S47445 (5, 15 or 50 mg/d) and placebo on cognition (ADAS-Cog), function (Disability Assessment for Dementia), or depressive symptoms (CSDD). An improvement on neuropsychiatric symptoms assessed by NPI was evidenced at the lower dose 5 mg/d (Δ -2.55, P = .023, post hoc analysis) compared to placebo. CSDD and total NPI scores improved in all groups including placebo. There were no specific and/or unexpected safety signals observed with any of the S47445 doses.

Discussion

S47445 administered for 24 weeks was safe and well tolerated by patients with mild to moderate AD; the compound did not show significant benefits over placebo on cognition, function, or depressive symptoms.

Determinants of Capacity to Consent to Research on Alzheimer's disease

OBJECTIVE

Investigators conducting Alzheimer's disease (AD) research need to consider participants' capacity to consent. Cognitive functioning is a significant predictor of decisional capacity, but there is a dearth of information on the influence of neuropsychiatric symptoms in AD on decisional capacity. We examined the rates of decisional capacity associated with two types of research protocols, and the association of capacity with neuropsychiatric symptoms and other participant characteristics.

METHODS

We comprehensively evaluated decisional capacity among 64 patients with mild-to-moderate AD and 70 healthy comparison (HC) subjects randomized to consider either a medium risk or higher risk hypothetical research protocol. Additional measures included sociodemographics, cognitive deficits, and neuropsychiatric symptoms.

RESULTS

Twenty AD patients (31.3%) and 67 HCs (95.7%) were deemed capable; 44 AD patients (68.8%) and 3 HCs (4.3%) incapable of consent. Age, education, and severity of cognitive deficits were associated with incapable status; there were no significant associations with severity of neuropsychiatric symptoms or protocol risk level.

CONCLUSIONS

Findings highlight the importance of understanding of capacity and its assessment among people with AD, rather than treating AD diagnosis as synonymous with impaired capacity. As novel treatments move from bench to bedside, methods of assessing and addressing capacity impairment must similarly advance.

CLINICAL IMPLICATIONS

In assessing research consent capacity, use structured assessments with population specific cut scores interpreted in the context of the person's background including education, culture, and language. Individuals should be encouraged to execute research proxy documents when able.