Pathogen‐Centric Activation of an Azoreductase‐Responsive Antibody‐Antibiotic Conjugate for the Targeted Eradication of MRSA

ABSTRACT Antibody‐antibiotic conjugates (AACs) provide a transformative platform for eradicating intracellular methicillin‐resistant Staphylococcus aureus (MRSA). However, current AACs largely follow antibody‐drug conjugates (ADCs) design principles and rely on host‐lysosomal proteases for activation, rendering them ineffective against extracellular (planktonic) bacteria. Furthermore, we demonstrate that high bacterial burden induces host‐lysosomal dysfunction, fundamentally compromising the efficacy of host‐dependent AACs against intracellular reservoirs. To address these limitations, we developed a pathogen‐centric AAC (AZO‐AAC) featuring an azobenzene‐based linker that is triggered by bacterial‐secreted azoreductase. This strategy shifts the activation mechanism from host‐cell machinery to the pathogen itself, enabling antibiotic release independent of host‐cell integrity. Surprisingly, our designed AZO‐AAC achieves nanomolar‐scale eradication of both planktonic and intracellular MRSA, reaching levels below the limit of detection in scenarios where traditional AACs fail. In murine models of peritonitis and septicemia, a single dose (60 mg/kg) of AZO‐AAC resulted in a six‐log reduction in bacterial burden and the preservation of normal tissue architecture. By decoupling activation from host‐cell status, this pathogen‐responsive platform provides a robust strategy for the targeted elimination of complex, multi‐niche MRSA infections.