Neuroinflammation is one of the prominent pathologies of Alzheimer’s disease (AD), a
neurodegenerative disorder without cure currently. The pathological roles of neuroinflammation in AD are
strongly supported by molecular, pharmacological, and genetic studies in AD animal models and in AD
patients. Therefore, a novel and useful biomarker of neuroinflammation would be valuable to aid disease
diagnosis, target engagement, and clinical evaluations of AD therapeutics. Recently, the NOD-like receptor
family pyrin domain containing 3 (NLRP3) inflammasome, an essential component of innate immunity that
tightly regulates the immune inflammatory responses, has been indicated critical roles in AD development and
progression. Activation of the NLRP3 inflammasome is responsible for the production of pro-inflammatory
interleukin (IL)-1β and IL-18, ultimately leading to inflammatory responses. Thus, NLRP3 inflammasome
represents a novel neuroinflammation biomarker, and positron emission tomography (PET) radiotracers that
target this protein complex would be important tools to help monitor inflammatory progression in AD. Recently,
our team has successfully developed small molecule NLRP3 inhibitors (NLRP3is) with a novel mechanism of
action (MOA), which is directly binding to the NLRP3 protein via a distinct site from other known inhibitors in
the field. Our drug discovery efforts have also led to a library of small molecules containing > 200 compounds
with various biological characteristics. More importantly, our pilot PET studies in mice and non-human primates
(NHPs) using 11C- and 18F-labeled radiotracers of our current lead NLRP3is already showed desirable brain
uptake, specific binding, and encouraging pharmacokinetic (PK) properties. Furthermore, our accumulated
structure-activity relationship (SAR) studies have identified key structural features of the scaffolds for further
optimization. The central hypothesis of this proposal is that structural optimization of our lead NLRP3is by
focused medicinal chemistry strategies will provide novel PET radiotracers that can be used to quantitatively
measure and differentiate neuroinflammation status in preclinical AD animal models. The goal of this
application is to successfully identify NLRP3 PET radiotracers with suitable PK properties and prepare for
investigational new drug (IND) enabling studies. Three aims are proposed to achieve our objectives. In Aim 1,
the newly identified lead NLRP3is will be structurally optimized to identify candidate NLRP3is for radiolabeling
and building up compound pipeline. In Aim 2, selected PET radiotracers will be evaluated in mouse models
including an AD mouse model for biodistribution, brain uptake and specific binding in brain tissues. In aim 3,
the top candidate PET radiotracers will be evaluated in NHPs for their kinetic properties. The proposed
research is highly significant because we are developing novel PET radiotracers to validate NLRP3 as a
potential neuroinflammation biomarker, to help precisely decipher the pathological contributions of
neuroinflammation in AD development, and to aid clinical development of AD therapeutics.