PROGRESS TOWARDS AN A‐SYNUCLEIN PET TRACER

Abstract

AbstractBackgroundThe high value for Parkinson’s disease and related disorders of the availability of a potent, selective, brain penetrant α‐synuclein (α‐Syn) PET tracer is widely acknowledged. We aimed to develop such an agent by applying an established radiotracer development strategy that has been successfully used with another misfolded CNS protein target.MethodWe used a proprietary collection of CNS‐focused aggregated protein binding agents that APRINOIA had previously created to map the structure‐activity relationship of its tau PET tracer programs, including [18F]APN‐1607. This tracer has a unique binding site on aggregated tau and has recently been characterized by cryo‐EM.The collection was first screened for selective binding of α‐Syn aggregates vs. tau aggregates using recombinant fibrils. This was followed by fluorescence‐based binding to DLB and MSA tissues. These assays identified 16 promising compounds for progression into autoradiography and homogenate binding assays.ResultTritiation was successful for 13 of the hits. Self‐blocking studies confirmed specific binding in human brain tissue sections and homogenates. A lead compound was selected, and preliminary PK experiments in wild type mice indicated that brain uptake and clearance properties were compatible with a desirable PET tracer profile in a non‐diseased state. Further studies to evaluate the binding properties in the diseased state and optimize the lead are ongoing.ConclusionThe compound collection and tracer development strategy have led to the development of an advanced lead or potentially a viable α‐synuclein PET tracer.