A Plug-and-Play Platform for Customizing Multivalent Degraders and Degrader-Drug Conjugates.

Traditional targeted protein degradation (TPD) strategies are largely ineffective against membrane proteins, which constitute over 60% of drug targets. To address this, we develop a modular "plug-and-play" UPTAB (Ultrahigh-affinity Protein pairs fused to Targeting Binders) platform for TPD. The platform leverages orthogonal ultrahigh-affinity Im/CL protein pairs to assemble complexes between lysosomal trafficking receptor (LTR)-binding modules and protein of interest (POI)-binding modules. Three UPTAB configurations were engineered: Type-I (mono-targeted), Type-II (dual-targeted), and Type-III (tri-targeted). In vitro, Type-I UPTAB achieved near-complete degradation of EGFR and PD-L1 across multiple cancer cell lines, with optimal linker length critical for maximal activity. Type-II and Type-III UPTAB enabled simultaneous degradation of EGFR/c-MET, EGFR/PD-L1, and EGFR/c-MET/HER2. In a breast cancer xenograft model, Type-I UPTAB demonstrated approximately 80% tumor growth inhibition, reduced EGFR levels in tumors, and significantly extended survival. Furthermore, we developed degrader-drug conjugates (DDCs) by site-specific conjugation of the cytotoxic payload MMAE to UPTAB modules, which retained degradation capacity while exhibiting substantially enhanced anti-proliferative activity across diverse cancer cell lines. The UPTAB platform combines modular multivalent design, high degradation efficiency, and excellent bioconjugation capability, offering a versatile tool for membrane protein-targeted degradation and a potential strategy for developing next-generation cancer therapeutics.