An Argument for Simple Tests of Treatment of Alzheimer's Disease

Improving Clinical Trials of Antioxidants in Alzheimer's Disease

Maintaining diversity in drug development in research into Alzheimer's disease (AD) is necessary to avoid over-reliance on targeting AD neuropathology. Treatments that reduce or prevent the generation of oxidative stress, frequently cited for its causal role in the aging process and AD, could be useful in at-risk populations or diagnosed AD patients. However, in this review, it is argued that clinical research into antioxidants in AD could provide more useful feedback as to the therapeutic value of the oxidative stress theory of AD. Improving comparability between randomized controlled trials (RCTs) is vital from a waste-reduction and priority-setting point of view for AD clinical research. For as well as attempting to improve meaningful outcomes for patients, RCTs of antioxidants in AD should strive to maximize the extraction of clinically useful information and actionable feedback from trial outcomes. Solutions to maximize information flow from RCTs of antioxidants in AD are offered here in the form of checklist questions to improve ongoing and future trials centered around the following dimensions: adhesion to reporting guidelines like CONSORT, biomarker enrichment, simple tests of treatment, and innovative trial design.

Finding the falsification threshold of the toxic proteinopathy hypothesis in neurodegeneration

A biomedical hypothesis is a theoretical assumption amenable to being tested in a randomized clinical trial. The main hypotheses in neurodegenerative disorders are based on the concept that proteins accumulate in an aggregated fashion and trigger toxicity. The toxic proteinopathy hypothesis posits that neurodegeneration is caused by toxicity of aggregated amyloid in Alzheimer's disease (toxic amyloid hypothesis), aggregated α-synuclein in Parkinson's disease (toxic synuclein hypothesis), and aggregated tau in progressive supranuclear palsy (toxic tau hypothesis). To date, we have accumulated 40 negative anti-amyloid randomized clinical, 2 anti-synuclein trials, and 4 anti-tau trials. These results have not prompted a major reconsideration of the toxic proteinopathy hypothesis of causality. Imperfections in trial design and execution (incorrect dosage, insensitive endpoints, too-advanced population) but not in the underlying hypotheses have prevailed as explaining the failures. We review here the evidence suggesting that the threshold of hypothesis falsifiability may be too high and advocate in favor of a minimal set of rules that facilitate the interpretation of negative clinical trials as falsifying the driving hypotheses, in particular if the desirable change in surrogate endpoints has been achieved. We propose four steps to refute a hypothesis in future-negative surrogate-backed trials and argue that for the actual rejection to take place, refutation must be accompanied by the proposal of an alternative hypothesis. The absence of alternative hypotheses may be the single greatest reason why there remains hesitancy in rejecting the toxic proteinopathy hypothesis: in the absence of alternatives, we have no clear guidance as to where to redirect or focus.

Avoiding Over-Reliance on Multi-Domain Interventions for Dementia Prevention

Given the unknown therapeutic value of targeting Alzheimer's disease pathology and the discovery of robust risk factors for dementia, non-pharmacological risk reduction (RR) is increasingly offered as an alternative to targeting Alzheimer's disease pathology. While RR will surely be a useful tool to make public health gains, we propose solutions to three possible issues with over-reliance on multi-domain interventions to achieve RR: limited individual impact, an exclusive focus on later life, and overlooking social determinants of dementia. We argue in favor of a broader debate within the research community and greater society about how different therapeutic avenues should be explored.