Talucci, I.; Leske, T.; Klafki, H.-W.; Hassan, M. M.; Steiert, A.; Morgado, B.; Bothe, S.; van Werven, L.; Liepold, T.; Walter, J.; Schindelin, H.; Wiltfang, J.; Wirths, O.; Jahn, O.; Maric, H. M.

A hallmark of Alzheimer\'s disease (AD), the most common form of dementia, is the progressive accumulation of amyloid-beta (A{beta}) peptides across distinct brain regions. Anti-A{beta} antibodies (A{beta}-Abs) that bind specific A{beta} variants are essential research tools. Furthermore, the monoclonal A{beta}-Abs Aducanumab, Lecanemab, and Donanemab have recently gained approval as the first disease-modifying therapeutics for early AD. In this study, we systematically determined on peptide microarrays the exact binding epitopes of 20 A{beta}-Abs, including biosimilars of Aducanumab, Lecanemab and Donanemab. Precise A{beta}-sequence and modification requirements were resolved through deep mutational scans and synthetically modified peptide libraries. To address the potential limitations of peptide microarrays employing short A{beta} fragments, the observed monovalent A{beta}-Ab reactivities were further studied using biochemical approaches, complementary in vitro analysis of A{beta}-Ab binding to oligomeric and aggregated A{beta}, as well as immunohistochemical staining of patient-derived AD brain samples. The data identifies A{beta}-Abs that preferentially recognize critical truncation and modification variants as well as gain and loss of binding mutants in familial AD. Our work provides insights into the mode of binding of currently available A{beta}-Ab biosimilars and further classifies the immunological tools for detecting and discriminating distinct A{beta} truncations, mutational variants and post-transcriptionally modified derivatives. We expect that this comprehensive resource on A{beta}-Ab sequence and modification selectivity will not only advance fundamental research on AD but potentially also support the development of improved diagnostic tools and therapeutic strategies.