Molecular Chemiluminescence Probes for Imaging of Amyloid beta in Animal Models

The highly exciting results from the recent clinical trial of Lecanemab for Alzheimer’s disease (AD) reignite tremendous enthusiasm for AD drug development. Lecanemab is the first drug to meet all the clinical endpoints without controversy over the past decades. However, compared to other diseases like cancer, the progress in AD drug development, both in clinical and preclinical stages, lags behind. The number of AD therapeutics under preclinical discovery is unquestionably dwarfed by the number of cancer drugs at similar stages. Several high- throughput imaging methods, such as bioluminescence imaging, have significantly accelerated drug discovery for cancer research. However, such a high-throughput imaging method is not readily available for AD drug discovery. In this proposal, we plan to develop “smart” (turn-on) chemiluminescence probes that can enable high-throughput imaging for preclinical AD research. “Smart” (turn-on) fluorescence imaging has been routinely used for in vitro, cellular, and in vivo imaging. In contrast, the exploration of smart chemiluminescence imaging has been limited due to its low sensitivity and dependence on reactive oxygen species (ROS) or enzyme activity. To address these challenges, we have developed a novel chemiluminescence probe called ADLumin-1. Through extensive validation, we have confirmed that ADLumin-1 exhibits turn-on chemiluminescence upon interaction with amyloid beta (Aβ) species, resulting in a remarkable 216-fold increase in intensity in vitro. Notably, ADLumin-1 does not rely on ROS or enzyme activity, distinguishing it from other chemiluminescence probes. In vivo two-photon imaging indicated that ADLumin-1 was highly specific for Ab deposits. In vivo whole-brain imaging showed that ADLumin-1 provided a 1.80-fold higher signal from 5-month-old transgenic AD (5xFAD) mice than that from the age-matched wild-type mice. Our recent study has further shown that ADLumin-1 enables high-throughput chemiluminescence imaging, as evidenced by imaging 30 mice within 30 minutes with a $100 imaging fee in a longitudinal therapeutic study. Additionally, our preliminary results have showcased the feasibility of optical 3D brain imaging using our chemiluminescence probe, opening up incredible possibilities for future AD research. This proposal aims to advance the development of ADLumin-X probes through in vitro and in vivo validation, with the ultimate objective of employing the most effective probe for high-throughput monitoring of therapeutic interventions in experimental AD drug studies. Our overarching goal is to offer accessible, highly sensitive, and cost-effective “PET-like” optical imaging methods for expediting preclinical AD drug development.