TARGETING OF TOXIC AMYLOID-BETA OLIGOMER SPECIES BY MONOCLONAL ANTIBODY PMN310: PRECISION DRUG DESIGN FOR ALZHEIMER’S DISEASE

Abstract

Current evidence suggests that progressive neurodegeneration in Alzheimer's disease (AD) may be catalyzed by the prion-like propagation of soluble toxic amyloid-beta oligomers (AβO) rather than plaque burden. Binding of Aβ monomers and/or fibrils by therapeutic antibodies has been associated with suboptimal efficacy and adverse events (e.g. ARIA-E) in clinical trials. These observations suggest that antibodies capable of specifically or selectively neutralizing toxic AβO are needed to achieve improved efficacy and safety. Computational algorithms were developed to identify epitope sequences and conformations likely to be exposed in toxic AβO but not on monomers or fibrils. The binding profile of monoclonal antibodies raised against predicted epitopes was assessed by surface plasmon resonance (SPR) analysis and immunohistochemistry (IHC). Inhibition of oligomer propagation was assessed by thioflavin-T fluorescence in vitro. Neutralization of AβO neurotoxicity by the antibodies was evaluated in cultures of primary neurons in vitro and in wild-type mice injected intracerebroventricularly with AβO in vivo. Screening of IgG clones raised against 5 distinct AβO epitopes yielded antibodies with the desired profile of selective binding to synthetic oligomers vs monomers, preferential binding to native soluble AβO in CSF and brain extracts of AD patients compared to controls by SPR, and lack of plaque reactivity by IHC on unfixed AD brain sections. Activity assays led to the identification of PMN310 as a lead antibody capable of blocking the propagation and neurotoxicity of AβO in vitro and protecting mice against the AβO-induced loss of short term memory formation in vivo. Computational modeling allowed for the identification and generation of monoclonal antibodies against AβO-specific epitopes. Antibody PMN310 was selected as a lead candidate on the basis of its ability to selectively target and neutralize AβO with no significant cross-reactivity to monomers or fibrils. These unique characteristics distinguish PMN310 from Aβ-reactive antibodies currently undergoing clinical trials, and are designed to address observed issues of efficacy and safety.