The Alzheimer's Therapeutics Screening Assay: a high-throughput drug-discovery platform utilizing neurons and microglia derived from human induced pluripotent stem cells and Kinetic Image Cytometry - Alzheimer’s Disease (AD), the most common cause of dementia, increases with age, afflicts 5.5 million people
in the US, and there is no cure. This phase I project will initiate development of the Alzheimer’s Therapeutics
Screening Assay (ATSA), which will utilize neurons, microglia, and astrocytes, derived from human induced
pluripotent stem cells. A new testing system is desperately needed as previously FDA-approved therapeutics
for AD have limited and temporary effects, and no new drug has been approved for AD since 2003; the many
failed clinical trials since then illustrate that current preclinical models are not sufficiently predictive for AD. As
amyloid beta peptide (A¿) plaques accumulate in the brains of AD patients, pharmaceutical companies have
exhaustively targeted the beta-amyloid cascade pathway for drug-discovery. However, while many of these
agents reduced plaques, none effectively slowed or prevented memory loss in clinical trials. Functional
magnetic resonance (fMRI) studies show that subjects with amnestic mild cognitive impairment (aMCI), a
prodromal symptom of AD, display hyperactive hippocampal neurons prior to plaque formation, suggesting that
dysregulation of neuronal calcium may underlie AD. Relatedly, microglia, the resident immune cells of the brain,
are activated in AD and secrete glutamate and inflammatory cytokines that may alter neuronal calcium.
Furthermore, the greatest genetic risk for AD is isoform 4 of apolipoprotein E (APOE4), and proteolytic
fragments of APOE4 cause dysregulation of intracellular calcium and are toxic to neurons and microglia. For
the ATSA, methods will be developed in which hiPSC-neurons, -MG, and -astrocytes are cocultured and AD-
relevant stresses (e.g., APOE4 fragments or A¿ oligomers) added, and the cells monitored for alterations in
calcium (or voltage) using Kinetic Image Cytometry, a digital microscopy method that quantifies calcium
transient activity on a cell-by-cell basis. Cell morphology (neurites, synaptic puncta) and relevant biomarkers
will also be quantified. The ATSA will be versatile, and phase II goals will include utilizing iPSCs from patients
with inherited or sporadic AD, representing both genders, will be incorporated to further interrogate AD-relevant
pathways. Once developed, the ATSA platform will enable testing of hundreds of compounds per day to
identify those with beneficial effects against AD related stresses. The ATSA will be marketed by Vala Sciences
Inc for contract research to pharmaceutical companies developing novel therapeutics for AD, and used for
internal drug-discovery by Vala researchers.
