Tumor-specific cathepsin B-triggered fluorescence imaging and prodrug activation

Bioorthogonal activation chemistries have great potential in the development of novel drug treatments due to their versatility, tunability, and the ability to generate therapies with improved spatial targeting. The upregulation of Cathepsin B is highly correlated with the development of cancers, however, few fluorescent probes or prodrugs-based on Cathepsin B activity have demonstrated high tumor selectivity, since Cathepsin B is expressed in a variety of normal tissues. In this study, we report a strain-promoted azide-alkyne cycloaddition-activation strategy whereby a para-azido safety-catch linker is triggered by the tumor locating Biotin-TCO (trans-cyclooctene) conjugate, with subsequent tumor-specific Cathepsin B-triggered activation, generating a fluorescent reporter/cytotoxic drug, with high tumor selectivity. Our results suggest that this dual AND-Gate strategy of orthogonal Biotin AND Cathepsin B action would be advantageous for tumor-specific fluorescence labelling, fluorescence-guided surgery and targeted treatment.