PROJECT SUMMARY Therapy for Alzheimer’s disease and related dementias (AD/ADRD), slow-progressing neurodegenerative diseases, remains elusive. Therapeutic approaches focusing on beta amyloid (Aβ) removal from the brain or on targeting genes for which strong associations between their polymorphism and AD/ADRD are established, have had a mixed record of success. We propose a novel strategy to reverse AD/ADRD associated neuroinflammation and mitochondrial dysfunction via targeting pathological lipid rafts in inflammatory and activated cells. These cholesterol-rich plasma membrane structures become stable and enlarged to host the assembly of many inflammatory receptors and other molecules involved in pathological processes leading to neuronal cell death and neurodegeneration. We have identified apoA-I binding protein (AIBP, encoded by Apoa1bp gene) as a key regulator of cellular cholesterol metabolism, which can selectively target pathological lipid rafts via its binding to TLR4, without damaging physiological lipid rafts. In preliminary studies, the Apoa1bp-/- mice crossed with APP/PS1 transgenic mice presented more Aβ plaques, an exacerbated dysfunctional microglia phenotype and increased neuronal cell death when compared to APP/PS1 mice. In addition, mitochondria in the brain of AIBP- deficient APP/PS1 mice were morphologically distorted, with a characteristic hyper-branched and cupped shape, typically associated with oxidative stress. The adeno-associated virus (AAV)-mediated overexpression of a secreted form of AIBP in the brain of Apoa1bp-/- APP/PS1 mice restored the microglial homeostatic phenotype. RAFT Pharmaceuticals proposes the development of an AAV-AIBP based therapy to provide effective neuroprotection in AD/ADRD. Specifically in this Phase 1 STTR project, we propose to construct and optimize an AAV-AIBP vector (RFT1041), which will be used in efficacy studies of Aim 2 and is expected to enter IND- enabling development for human clinical applications. We will explore intracranial and intrathecal routes of delivery and test if a single AAV-AIBP injection achieves sustained AIBP expression in the brain. The efficacy of RFT1041 (3 different doses) will be tested in APP/PS1 and 3xTg mouse models to evaluate survival, changes in memory and learning, the extent of Aβ plaques and tau tangles, microglia activation, synaptotoxicity, neuronal cell death, autophagy, ER stress, and mitochondrial dysfunction. In addition, advanced EM will be used to assess mitochondrial morphology and function. Results of these studies will be used to prepare for and conduct an INTERACT meeting with the FDA to receive preliminary FDA feedback on the proposed development program and assists in minimizing the time spent in product development and reduce time to market.