Aberrant protein self-assembly underlies over 30 human diseases called amyloidoses, for which there are no cures. In these diseases, particular proteins misfold and self-assemble into toxic oligomers that disrupt cellular function, and proceed to form insoluble amyloid fibrils that deposit in specific tissues. A promising strategy for preventing and treating amyloidoses is inhibition or modulation of the self-assembly process to disrupt the formation of the toxic oligomers. In practice, this has proven immensely difficult because the oligomer structures are unknown, are metastable, and do not have distinct binding sites.
In this dissertation, three primary studies are presented that evaluate and characterize a small molecule, CLR01, which utilizes a novel strategy circumventing these challenges and has been found to be efficacious as an aggregation and toxicity inhibitor in vitro and in vivo. In the first study, CLR01 was evaluated for its ability to rescue synaptic toxicity in cell culture and brain slices. Additionally, it was tested in a transgenic mouse model of AD for its ability to reduce the pathological hallmarks of AD: amyloid plaques and neurofibrillary tangles. This study found positive results in all domains tested; a rescue from amyloid β-protein (Aβ)-induced depletion of synaptic spine density, a rescue of Aβ-induced disruption of basal synaptic transmission and long-term potentiation, and reduction of brain Aβ, hyperphosphorylated tau, and microglia burden. CLR01 also showed low propensity for causing metabolic toxicity or drug-drug interaction, indicating favorable drug-like characteristics.
In the second study, CLR01's safety and pharmacological profile were characterized in mice. CLR01 was found not to disrupt normal protein assembly, to have a high safety margin in mice, and to penetrate the blood-brain barrier (BBB) at 1-3%. Interestingly, brain levels of CLR01 remained stable for 72 hours following administration despite rapid clearance from the plasma. These results suggest a large safety margin for CLR01 and a pharmacokinetic profile that allows reaching high levels in the brain by administering relatively low doses.
The third study delineates a detailed optimization of behavioral testing of mice for detection of memory deficits using the Barnes maze, and validates for the first time memory deficits in a triple-transgenic mouse model of AD at the youngest age described in the literature. The study provides a framework for analysis of CLR01's influence on learning and memory deficits in this triple transgenic model. Additionally, the study provides specific and detailed guidelines for optimizing both the performance and the analysis of the Barnes maze in a manner that increases the likelihood of detecting subtle changes in future studies using mouse models of AD. The work described in this dissertation provides a strong foundation supporting formal pre-clinical development of CLR01 as a promising disease-modifying therapeutic drug for AD.