Identification of promethazine as an amyloid-binding molecule using a fluorescence high-throughput assay and MALDI imaging mass spectrometry

• We developed a fluorescence assay for screening amyloid-binding compounds.
• The known compounds have been repurposed for secondary role.
• We used MALDI-IMS to confirm the lead identified from fluorescence assays.
• We identify promethazine as an amyloid-binding compound.

The identification of amyloid-binding compounds is a crucial step in the development of imaging probes and therapeutics for the detection and cure of Alzheimer's disease. Unfortunately, the process typically lags during the translation from in vitro to in vivo studies due to the impenetrable nature of the blood brain barrier (BBB). Here, we integrate fluorescence assay with MALDI imaging mass spectrometry to screen known compounds and repurpose their properties to enable the second function of binding to amyloid plaques. Through this approach, we identified an antihistamine compound, promethazine, that can bind to amyloid plaques. Finally, we demonstrate that promethazine is retained in the amyloid-burdened brain compared to a normal brain and that its distribution within the brain corroborates with that of amyloid plaques.