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Alzheimer's disease (AD) represents a slowly progressing neurodegenerative disorder with complicated, multifactorial pathophysiology that remains poorly understood. The past two decades of AD research have been marked by numerous attempts at developing therapies, which have resulted in five approved agents and multiple failures. All of the five agents represent symptomatic treatments. Disease-modifying drugs that slow down neurodegeneration and clinical progression have been an area of particular interest and active research but have been associated with uniform failure. The last 16 putative disease-modifying agents failed to meet the primary efficacy objective in Phase 3 trials, the most resource intense and expensive stage of development. While these failures in part are due to our incomplete understanding of the underlying pathophysiology of the disease, they also reflect many challenges with designing and executing clinical development programs for such potential disease-modifying therapies. In the disease modification area, the interest has moved to patients with early stages of AD, such as mild cognitive impairment (MCI) due to AD or prodromal AD and mild AD dementia, when neuronal damage is still limited and a clinical meaningful change in the underlying neurodegenerative process and the corresponding clinical state is still possible. At the same time, these early disease stages are characterized by difficult to identify heterogeneous target populations, slow disease progression, and uncertain outcome measures that often lack the necessary sensitivity to establish clinical efficacy. Putative disease-modifying agents have been moving from small Phase 1 studies to large and long Phase 2b/3 trials in which failure is particularly costly and may be due to deficiencies in designs and not necessarily inherent lack of efficacy for an investigational agent. In this chapter, we address issues of trial efficiency that have become key to the development of AD therapies and, particularly, disease-modifying therapies. We review innovative trial designs and new clinical outcomes, which the AD field is bringing forward. We examine each of these components by focusing on select examples from recently completed or ongoing development programs, including more flexible adaptive trial designs and new clinical outcomes, such as composite scores and performance-based functional tools. These new methodologies hold the promise for trials that are likely to obtain evidence of success or failure earlier in a development program and to provide more robust investigations of putative therapeutic agents.

Introduction Recent failures in phase 3 clinical trials in Alzheimer's disease (AD) suggest that novel approaches to drug development are urgently needed. Phase 3 risk can be mitigated by ensuring that clinical efficacy is established before initiating confirmatory trials, but traditional phase 2 trials in AD can be lengthy and costly. Methods We designed a Bayesian adaptive phase 2, proof-of-concept trial with a clinical endpoint to evaluate BAN2401, a monoclonal antibody targeting amyloid protofibrils. The study design used dose response and longitudinal modeling. Simulations were used to refine study design features to achieve optimal operating characteristics. Results The study design includes five active treatment arms plus placebo, a clinical outcome, 12-month primary endpoint, and a maximum sample size of 800. The average overall probability of success is ≥80% when at least one dose shows a treatment effect that would be considered clinically meaningful. Using frequent interim analyses, the randomization ratios are adapted based on the clinical endpoint, and the trial can be stopped for success or futility before full enrollment. Discussion Bayesian statistics can enhance the efficiency of analyzing the study data. The adaptive randomization generates more data on doses that appear to be more efficacious, which can improve dose selection for phase 3. The interim analyses permit stopping as soon as a predefined signal is detected, which can accelerate decision making. Both features can reduce the size and duration of the trial. This study design can mitigate some of the risks associated with advancing to phase 3 in the absence of data demonstrating clinical efficacy. Limitations to the approach are discussed.

E2212, a novel γ-secretase modulator, is under development for the treatment of Alzheimer's disease. The safety, tolerability, pharmacokinetics, and pharmacodynamics of single ascending oral doses (10-250 mg, double-blind, placebo-controlled, randomized) of E2212 were evaluated. In this phase I clinical trial, E2212 was found to be well tolerated in single doses. Maximum tolerated dose was not achieved up to 250 mg. Most AEs were mild to moderate in severity with no identifiable dose related pattern. There were no clinically significant findings on physical and ophthalmologic examinations as well as vital signs, laboratory, ECG and C-SSRS assessments. E2212 was rapidly absorbed, with median tmax values ranging from 0.5 to 1.0 h. E2212 exhibited biphasic disposition with the terminal t1/2 of 12.5-19.0 h. Renal excretion was the minor pathway for E2212 elimination. Increased PD response (reduction in plasma concentrations of Aβ(x-42)) was observed with increasing doses. The maximum PD response was observed in the highest dose 250 mg cohort, with ΔAUAC(0-24 h) of 44.1% and Amax of 53.6%. These results support further clinical development of E2212.

Precompetitive collaborations have been successful in several disease areas and industries. Such collaborations are critical to address the gaps and challenges in therapeutic development for chronic neurodegenerative diseases. On November 5, 2012, members of the scientific community, advocates, regulators, industry, and government officials met at the US Food and Drug Administration to develop tools to expedite drug development and maximize the potential for success in future drug trials for Alzheimer disease and Parkinson disease. The meeting established that multiple collaborative approaches are essential for accelerating drug development. Such approaches include precompetitive data sharing, regulatory qualification of biomarkers and clinical outcome assessments, implementation of data standards, and development of quantitative drug disease trial models. While challenges to collaboration among industry partners are formidable, they are not insurmountable. The Coalition Against Major Diseases (CAMD) has several positive examples to highlight. This review represents proceedings from CAMD's annual conference and discusses the key themes that are being advanced by the Critical Path Institute.

Background Several monoclonal antibodies for the treatment of Alzheimer’s disease (AD) have been in development over the last decade. BAN2401 is a monoclonal antibody that selectively binds soluble amyloid β (Aβ) protofibrils. Methods Here we describe the first clinical study with BAN2401. Safety and tolerability were investigated in mild to moderate AD. A study design was used with staggered parallel single and multiple ascending doses, from 0.1 mg/kg as a single dose to 10 mg/kg biweekly for four months. The presence of amyloid related imaging abnormalities (ARIA, E for edema, H for hemorrhage) was assessed with magnetic resonance imaging (MRI). Cerebrospinal fluid (CSF) and plasma samples were analyzed to investigate pharmacokinetics (PK) and effects on biomarkers. Results The incidence of ARIA-E/H on MRI was comparable to that of placebo. BAN2401 exposure was approximately dose proportional, with a serum terminal elimination half-life of ~7 days. Only a slight increase of plasma Aβ(1-40) was observed but there were no measurable effects of BAN2401 on CSF biomarkers. On the basis of these findings Phase 2b efficacy study has been initiated in early AD. Conclusions BAN2401 was well-tolerated across all doses. The PK profile has guided us for selecting dose and dose regimens in the ongoing phase 2b study. There was no clear guidance for an effective dose based on biomarkers. Trial registration number NCT01230853 ClinicalTrials.gov Registered October 27, 2010.

Background Development of new therapies for Alzheimer9s disease (AD) is increasingly focused on more mildly affected populations, and requires new assessment and outcome strategies. Patients in early stages of AD have mild cognitive decline and no, or limited, functional impairment. To respond to these assessment challenges, we developed a measurement approach based on established scale items that exhibited change in previous amnestic Mild Cognitive Impairment (aMCI) trials. Methods Partial least squares regression with a longitudinal clinical decline model identified items from commonly used clinical scales with the highest combined sensitivity to change over time in aMCI and weighted these items according to their relative contribution to detecting clinical progression in patients’ early stages of AD. The resultant AD Composite Score (ADCOMS) was assessed for its ability to detect treatment effect in aMCI/prodromal AD (pAD) clinical trial populations. Results ADCOMS consists of 4 Alzheimer9s Disease Assessment Scale–cognitive subscale items, 2 Mini-Mental State Examination items, and all 6 Clinical Dementia Rating—Sum of Boxes items. ADCOMS demonstrated improved sensitivity to clinical decline over individual scales in pAD, aMCI and in mild AD dementia. ADCOMS also detected treatment effects associated with the use of cholinesterase inhibitors in these populations. Improved sensitivity predicts smaller sample size requirements when ADCOMS is used in early AD trials. Conclusions ADCOMS is proposed as new standard outcome for pAD and mild AD dementia trials, and is progressing in a CAMD-sponsored qualification process for use in registration trials of pAD.

The symptomatic drugs currently on the market for Alzheimer's disease (AD) have no effect on disease progression, and this creates a large unmet medical need. The type of drug that has developed most rapidly in the last decade is immunotherapy: vaccines and, especially, passive vaccination with monoclonal antibodies. Antibodies are attractive drugs as they can be made highly specific for their target and often with few side effects. Data from recent clinical AD trials indicate that a treatment effect by immunotherapy is possible, providing hope for a new generation of drugs. The first anti-amyloid-beta (anti-A beta) vaccine developed by Elan, AN1792, was halted in phase 2 because of aseptic meningoencephalitis. However, in a follow-up study, patients with antibody response to the vaccine demonstrated reduced cognitive decline, supporting the hypothesis that A beta immunotherapy may have clinically relevant effects. Bapineuzumab (Elan/Pfizer Inc./Johnson & Johnson), a monoclonal antibody targeting fibrillar A beta, was stopped because the desired clinical effect was not seen. Solanezumab (Eli Lilly and Company) was developed to target soluble, monomeric A beta. In two phase 3 studies, Solanezumab did not meet primary endpoints. When data from the two studies were pooled, a positive pattern emerged, revealing a significant slowing of cognitive decline in the subgroup of mild AD. The Arctic mutation has been shown to specifically increase the formation of soluble A beta protofibrils, an A beta species shown to be toxic to neurons and likely to be present in all cases of AD. A monoclonal antibody, mAb158, was developed to target A beta protofibrils with high selectivity. It has at least a 1,000-fold higher selectivity for protofibrils as compared with monomers of A beta, thus targeting the toxic species of the peptide. A humanized version of mAb158, BAN2401, has now entered a clinical phase 2b trial in a collaboration between BioArctic Neuroscience and Eisai without the safety concerns seen in previous phase 1 and 2a trials. Experiences from the field indicate the importance of initiating treatment early in the course of the disease and of enriching the trial population by improving the diagnostic accuracy. BAN2401 is a promising candidate for A beta immunotherapy in early AD. Other encouraging efforts in immunotherapy as well as in the small-molecule field offer hope for new innovative therapies for AD in the future.

Results: E2012 reduced plasma Aβ40 and Aβ42 in healthy subjects in a dose-related manner. Aβ42 decreased to a greater extent than Aβ40 (maximum reductions at 400 mg ~ 50% and ~30%, respectively) at 4-6 hrs post-dose, without a rebound effect. AUC0-inf increased proportionally up to 400 mg. Cmax increased proportionally up to 200 mg and less than proportionally thereafter. Results from rat studies with E2012 were predictive of the results obtained in humans for plasma Aβ effect over 24 hr. Effects on rat CSF and brain Aβ followed similar trends, supporting the use of CSF as a surrogate matrix for effects on brain Aβ in humans.

Current research including the basic biology of Alzheimer's disease (AD) provides a foundation to explore whether our current state of knowledge is sufficient to initiate prevention studies and allow us to believe prevention of AD is possible. Current research and recently revised criteria for the diagnosis of AD by the National Institutes on Aging and the Alzheimer's Association suggest a continuum of disease from preclinical asymptomatic to symptomatic Alzheimer's dementia. In light of these revised criteria, the possibility of secondary prevention and even primary prevention is under discussion. The Alzheimer's Association Research Roundtable convened a meeting to discuss the rationale and feasibility of conducting secondary prevention trials in AD.