Organic‐Solvent‐Free “Lego‐Like” Modular Preparation of Fab‐Nondestructive Antibody‐Drug Conjugates with Ultrahigh Drug‐to‐Antibody Ratio

Abstract Antibody‐drug conjugates (ADCs) have exciting possibilities in targeted tumor therapy. However, in the existing ADC preparation processes, the random attachment of the payloads to the antigen‐binding fragments (Fab) greatly increases the risk of disrupting its antigen recognition ability, while the drug‐antibody ratio (DAR) is low, leading to a cumbersome preparation process and low drug delivery efficiency. Herein, poly(glutamic acid) is used to expand the number of drug binding sites, based on the “click chemistry” of azide and DBCO, and the high affinity of Fc‐III‐4C peptide to the crystalline fragment (Fc) of the monoclonal antibodies. Various antibody‐polymer‐drug conjugates are obtained with ultrahigh DAR using this organic‐solvent‐free “Lego‐like” modular construction. Among them, aHER2‐P‐MMAE with DAR of 41.6 achieves tumor growth inhibition (TGI) of 99.7% for both medium‐sized and large SKOV‐3 ovarian tumors, and aPDL1‐P‐MMAE (DAR = 40.7) achieves TGI of 98.5% for MC38 colon tumors. In summary, a universal platform is created to prepare Fab‐nondestructive ADCs with ultrahigh DAR, which can be used to develop precision medicine for personalized anticancer therapy.