Targeting intracellular cancer proteins with tumor‐microenvironment‐responsive bispecific nanobody‐PROTACs for enhanced therapeutic efficacy

Abstract Proteolysis targeting chimeras (PROTACs) are pivotal in cancer therapy for their ability to degrade specific proteins. However, their non‐specificity can lead to systemic toxicity due to protein degradation in normal cells. To address this, we have integrated a nanobody into the PROTACs framework and leveraged the tumor microenvironment to enhance drug specificity. In this study, we engineered BumPeD, a novel bispecific nanobody‐targeted PROTACs‐like platform, by fusing two nanobodies with a Furin protease cleavage site (RVRR) and a degron sequence (ALAPYIP or KIGLGRQKPPKATK), enabling the tumor microenvironment to direct the degradation of intracellular proteins. We utilized KN035 and Nb4A to target PD‐L1 (programmed death ligand 1) on the cell surface and intracellular Survivin, respectively. In vitro experiments showed that BumPeD triggers Survivin degradation via the ubiquitin‐proteasome pathway, inducing tumor apoptosis and suppressing bladder tumor cell proliferation and migration. In vivo experiments further confirmed BumPeD's robust anti‐tumor efficacy, underscoring its potential as a precise protein degradation strategy for cancer therapy. Our platform provides a systematic approach to developing effective and practical protein degraders, offering a targeted theoretical basis and experimental support for the development of novel degradative drugs, as well as new directions for cancer therapy.