Dual-mechanistic antibody-drug conjugate via site-specific selenocysteine/cysteine conjugation

Abstract

Background: While all clinically translated antibody-drug conjugates (ADCs) contain a single-drug payload, most systemic cancer chemotherapies involve use of a combination of drugs. These regimens improve treatment outcomes and slow development of drug resistance. We here report the generation of an ADC with a dual-drug payload that combines two distinct mechanisms of action. Methods: Virtual DNA crosslinking agent PNU-159682 and tubulin polymerization inhibitor monomethyl auristatin F (MMAF) were conjugated to a HER2-targeting antibody via site-specific conjugation at engineered selenocysteine and cysteine residues (thio-selenomab). Results: The dual-drug ADC showed selective and potent cytotoxicity against HER2- expressing cell lines and exhibited dualmechanisms of action consistent with the attached drugs. While PNU- 159682 caused S-phase cell cycle arrest due to its DNA-damaging activity, MMAF simultaneously inhibited tubulin polymerization and caused G2/M-phase cell cycle arrest. Conclusion: The thio-selenomab platform enables the assembly of dual-drug ADCs with two distinct mechanisms of action.