Abstract
The blood-brain barrier (BBB) remains a critical bottleneck for central nervous system (CNS) drug development, and transferrin receptor 1 (TfR1/CD71) represents one of the most clinically validated targets for receptor-mediated transcytosis across the BBB. In this work, we identified and generated a panel of novel fully human anti-CD71 heavy-chain single-domain antibodies (VHHs) using our proprietary RenNano discovery platform. These monovalent VHH clones exhibit high cross-reactivity with cynomolgus monkey TfR1 and do not compete with endogenous transferrin for receptor binding, thus avoiding interference with physiological iron homeostasis.
In vivo pharmacokinetic studies in humanized TfR1 mice showed that these VHH shuttles significantly outperform clinical-stage benchmark molecules in brain delivery capacity, delivering over 1.5-fold or even higher total brain exposure compared with JR141 and DNL310, respectively. When formatted as a bispecific antibody against BACEI, the CD71 VHH shuttle improved brain Aß40 clearance efficiency by more than 3-fold. Furthermore, the shuttle retains equivalent BBB penetration performance when fused to either the N- or C-terminus of the therapeutic payload, providing a flexible and modular toolkit for developing brain-penetrating multispecific biotherapeutics.
