It's Groundhog Day! What Can the History of Science Say About the Crisis in Alzheimer's Disease Research?

A philosophy of science approach to the amyloid hypothesis of Alzheimer's disease

Disputes about the scientific validity of the amyloid-β hypothesis of Alzheimer's disease have been held since the early 1990s, with little constructive progress made between opposing sides despite recent therapeutic progress. Here, I argue that philosophy of science can improve the chance of constructive debate by giving researchers technical language to describe and assess scientific progress. To do so, I interpret the amyloid hypothesis using a modified version of the research programme concept from philosopher of science Imre Lakatos. I first outline the amyloid-β hypothesis and study critiques of its central place in Alzheimer's research. Then, I draw on the complexity of amyloid-β and Alzheimer's research to discuss the limits of using concepts from popular philosophers of science Karl Popper or Thomas Kuhn, before finally arguing that an adaptation of the research programme concept can foster constructive debates about the science of Alzheimer's and within it. I will argue that the amyloid-β hypothesis has contributed to significant progress in the Alzheimer's field based on what Lakatos called the "positive heuristic" (motivating the programme to test its predictions) and the "negative heuristic" (protecting the programme from refutation). I consider the amyloid research agenda to be progressive despite the fact that its claims about disease aetiology could be wrong.

Investigating Cu(I) binding to model peptides of N-terminal Aβ isoforms

Amyloid beta (Aβ) peptides and copper (Cu) ions are each involved in critical biological processes including antimicrobial activity, regulation of synaptic function, angiogenesis, and others. Aβ binds to Cu and may play a role in Cu trafficking. Aβ peptides exist in isoforms that vary at their C-and N-termini; variation at the N-terminal sequence affects Cu binding affinity, structure, and redox activity by providing different sets of coordinating groups to the metal ion. Several N-terminal isoforms have been detected in human brain tissues including Aβ1-40/42, Aβ3-42, pEAβ3-42, Aβ4-42, Aβ11-40 and pEAβ11-40 (where pE denotes an N-terminal pyroglutamic acid). Several previous works have individually investigated the affinity and structure of Cu(I) bound to some of these isoforms' metal binding domains. However, the disparately reported values are apparent constants collected under different sets of conditions, and thus an integrated comparison cannot be made. The work presented here provides the Cu(I) coordination structure and binding affinities of these six biologically relevant Aβ isoforms determined in parallel using model peptides of the Aβ metal binding domains (Aβ1-16, Aβ3-16, pEAβ3-16, Aβ4-16, Aβ11-16 and pEAβ11-16). The binding affinities of Cu(I)-Aβ complexes were measured using solution competition with ferrozine (Fz) and bicinchoninic acid (BCA), two colorimetric Cu(I) indicators in common use. The Cu(I) coordination structures were characterized by X-ray absorption spectroscopy. The data presented here facilitate comparison of the isoforms' Cu-binding interactions and contribute to our understanding of the role of Aβ peptides as copper chelators in healthy and diseased brains.

The Case for a Novel Therapeutic Approach to Dementia: Small Molecule Hepatocyte Growth Factor (HGF/MET) Positive Modulators

An estimated 6.5 million Americans aged 65 years or older have Alzheimer's disease (AD), which will grow to 13.8 million Americans by 2060. Despite the growing burden of dementia, no fundamental change in drug development for AD has been seen in > 20 years. Currently approved drugs for AD produce only modest symptomatic improvements in cognition with small effect sizes. A growing mismatch exists between the urgent need to develop effective drugs for symptomatic AD and the largely failed search for disease modification. The failure rate of clinical trials in AD is high overall, and in particular for disease-modifying therapies. Research efforts in AD have focused predominantly on amyloid-β and tau pathologies, but limiting clinical research to these "classical hallmarks" of the disease does not address the most urgent patient, caregiver, or societal needs. Rather, clinical research should consider the complex pathophysiology of AD. Innovative approaches are needed that provide outside-the-box thinking, and re-imagine trial design, interventions, and outcomes as well as progress in proteomics and fluid biomarker analytics for both diagnostics and disease monitoring. A new approach offering a highly specific, yet multi-pronged intervention that exerts positive modulation on the HGF/MET neurotrophic system is currently being tested in mid-to-late-stage clinical trials in mild to moderate AD. Findings from such trials may provide data to support novel approaches for development of innovative drugs for treating AD at various disease stages, including among patients already symptomatic, and may offer benefits for other neurodegenerative diseases.