ABSTRACT
Reducing amyloid-ß peptide (Aß) burden at the pre-symptomatic stages of Alzheimer's disease (AD) is currently the advocated clinical strategy for treating this disease. The most developed method for targeting Aß is the use of monoclonal antibodies including bapineuzumab, solanezumab and crenezumab. We have synthesized these antibodies and used surface plasmon resonance (SPR) and mass spectrometry to characterize and compare the ability of these antibodies to target Aß in transgenic mouse tissue as well as human AD tissue. SPR analysis showed that the antibodies were able to bind Aß with high affinity. All of the antibodies were able to bind Aß in mouse tissue. However, significant differences were observed in human brain tissue. While bapineuzumab was able to capture a variety of N-terminally truncated Aß species, the Aß detected using solanezumab was barely above detection limits while crenezumab did not detect any Aß. None of the antibodies were able to detect any Aß species in human blood. Immunoprecipitation experiments using plasma from AD subjects showed that both solanezumab and crenezumab have extensive cross-reactivity with non-Aß related proteins. Bapineuzumab demonstrated target engagement with brain Aß, consistent with published clinical data. Solanezumab and crenezumab did not, most likely as a result of a lack of specificity due to cross-reactivity with other proteins containing epitope overlap. This lack of target engagement raises questions as to whether solanezumab and crenezumab are suitable drug candidates for the preventative clinical trials for AD.