A Self‐Assembled Protein Platform for Plug‐and‐Play Customization of Multivalent Artificial Antibodies and Antibody‐Drug Conjugates

Modular assembly of multivalent therapeutics with precise modulation of pharmacokinetic and pharmacological properties remains a critical challenge in drug development. Here, we present ATPlug, a self-assembling protein platform that integrates three crucial functional modules: a trimerization domain to enhance avidity, a SpyCatcher module for efficient conjugation, and an albumin-binding domain to optimize pharmacokinetics and tissue selectivity. This rational design facilitates the modular assembly of multivalent artificial antibodies and antibody-drug conjugates (ADCs), demonstrating remarkable versatility through the successful incorporation of diverse therapeutic modules targeting epidermal growth factor receptor (EGFR), programmed cell death ligand 1 (PD-L1), and vascular endothelial growth factor (VEGF). The trivalent constructs exhibited up to 30-fold enhancement in target binding avidity and extended plasma half-life via endogenous albumin hitchhiking. Notably, the ATPlug-customized modular ADCs achieved binding affinities of 1.8 nM for EGFR and exhibited selective cytotoxicity toward EGFR-overexpressing tumor cells, resulting in potent tumor suppression efficacy. This plug-and-play strategy provides a framework for next-generation therapeutics combining customized multivalency with multidrug synergies.