Design and Characterization of Prodrugged Anti‐CTLA‐4 Antibodies

Therapeutic antibodies are widely used to treat diseases like cancer and inflammatory conditions by binding with high specificity to their molecular targets. Masking is a strategy to mitigate undesirable activity in non-target tissues, improving safety and pharmacokinetic (PK) profiles by reducing target-mediated drug disposition (TMDD). In this study, we explored masking an anti-CTLA-4 antibody by conjugating a large PEG molecule to specific sites on the antibody. While anti-CTLA-4 immunotherapy benefits solid tumor treatment, its adverse events limit its utility. We evaluated multiple conjugation sites within the complementarity-determining regions (CDRs) and adjacent framework regions to attenuate CTLA-4 binding. We identified the optimal site for maximizing masking efficiency, allowing for efficient bioconjugation and functional restoration upon exposure to a cleaving enzyme in the tumor microenvironment. The prodrugged antibody exhibited reduced binding to CTLA-4 and Fc gamma receptors (FcgRs), high stability, and an extended half-life in a mouse model. This technology has the potential to improve the PK profile and safety attributes of therapeutic antibodies.