Amyloid-β (Aβ) immunotherapy for Alzheimer's disease (AD) has good preclinical support from transgenic mouse models and clinical data suggesting that a long-term treatment effect is possible. Soluble Aβ protofibrils have been shown to exhibit neurotoxicity in vitro and in vivo, and constitute an attractive target for immunotherapy. Here, we demonstrate that the humanized antibody BAN2401 and its murine version mAb158 exhibit a strong binding preference for Aβ protofibrils over Aβ monomers. Further, we confirm the presence of the target by showing that both antibodies efficiently immunoprecipitate soluble Aβ aggregates in human AD brain extracts. mAb158 reached the brain and reduced the brain protofibril levels by 42% in an exposure-dependent manner both after long-term and short-term treatment in tg-ArcSwe mice. Notably, a 53% reduction of protofibrils/oligomers in cerebrospinal fluid (CSF) that correlated with reduced brain protofibril levels was observed after long-term treatment, suggesting that CSF protofibrils/oligomers could be used as a potential biomarker. No change in native monomeric Aβ42 could be observed in brain TBS extracts after mAb158-treatment in tg-ArcSwe mice. By confirming the specific ability of mAb158 to selectively bind and reduce soluble Aβ protofibrils, with minimal binding to Aβ monomers, we provide further support in favor of its position as an attractive new candidate for AD immunotherapy. BAN2401 has undergone full phase 1 development, and available data indicate a favorable safety profile in AD patients.
Keywords: Alzheimer's disease; BAN2401; amyloid-β; antibody; biomarker; cerebrospinal fluid; immunotherapy; mAb158; oligomer; protofibrils.