Discovery of therapeutic nanobodies targeting the G protein-coupled receptors in the brain for the treatment of Alzheimer Disease

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Project Summary/Abstract Abilita Bio, an innovation-driven biotechnology company, is seeking SBIR Phase I funding for the discovery of novel therapeutic nanobodies targeting the orphan G protein-coupled receptors GPR17 and GPR37, to address the neuropathology of Alzheimer’s disease. More than 5 million Americans suffer from this debilitating disease, which causes memory loss and the progressive impairment of cognitive functions. Despite an abundance of evidence supporting the role of amyloid-β and tau in Alzheimer’s disease etiopathology, amyloid-β targeted clinical efforts have generated little evidence of improvement in cognitive or functional outcomes, which emphasizes the unmet need for novel targets and therapeutic strategies. Recent imaging studies have demonstrated that white matter structural changes and underlying myelin abnormalities are significant components of Alzheimer’s disease and may precede overt amyloid and tau pathologies. Due to the association of white matter changes and myelin loss with the clinical progression of Alzheimer’s disease, the glial cells responsible for the production and repair of myelin, oligodendrocytes, may be critically affected. Therefore, drugs that promote oligodendrocyte maturation and remyelination may represent promising new treatments for Alzheimer’s and other neurodegenerative diseases. Recently, it has been found that two orphan G protein-coupled receptors, GPR17 and GPR37, act to negatively regulate oligodendrocyte development as they mature to myelinating cells, which and ultimately affects their capacity to repair damaged axons. Selective antagonists of GPR17 and GPR37 signaling may unblock oligodendrocyte checkpoints to promote their differentiation and remyelinating activity, which presents an opportunity to repair the pathological damage caused by Alzheimer’s. Despite the potential of GPR17 and GPR37, no specific pharmacological agents are available that can be used to validate the targets in Alzheimer’s disease, or serve as therapeutic leads, which we will address in the proposed research. GPR17 and GPR37 have been exceedingly difficult to drug due to their poorly defined binding pockets, poor functional folding and high constitutively activity, which is typical for orphan receptors. We will address the need for selective target modulators by using a novel approach, where we will use our innovative directed evolution-based protein stabilization technology to optimize GPR17 and GPR37 for use in llama immunization and phage library screening for the discovery of camelid single chain antibodies (nanobodies). Nanobodies have unique properties that enable the recognition of receptor binding pockets and structural elements critical for the functional modulation of G protein-coupled receptors and have been validated by successful clinical development. We plan to discover both agonistic and antagonistic nanobodies that will be pharmacologically characterized and tested for their ability to stimulate oligodendrocyte maturation and myelination activity. Nanobodies verified to exhibit potency and selectivity in these assays will be taken forward to in vivo validation in Alzheimer’s Disease models in a future Phase II SBIR effort, with the aim of clinical development.