In Vitro and In Vivo Fluorescence Imaging of Antibody–Drug Conjugate-Induced Tumor Apoptosis Using Annexin V–EGFP Conjugated Quantum Dots

[Image: see text] Antibody–drug conjugates (ADCs) are conjugates of a monoclonal antibody and a cytotoxic drug that induce tumor apoptosis. The evaluation of ADC-induced tumor apoptosis is crucial for the development of ADCs for cancer therapy. To evaluate the efficacy of ADCs, we present in vitro and in vivo fluorescence imaging techniques for ADC-induced tumor apoptosis using annexin V–EGFP (EGFP: enhanced green fluorescent protein) conjugated quantum dots (annexin V–EGFP–QDs). This probe emits visible (VIS) and near-infrared (NIR) dual fluorescence at 515 nm (EGFP emission) and 850 nm (QD emission), which can be used for the detection of tumor apoptosis at the cellular and whole-body levels. By using annexin V–EGFP–QDs, we achieved VIS and NIR fluorescence imaging of human epidermal growth factor receptor 2-positive breast tumor apoptosis induced by an ADC, Kadcyla (trastuzumab emtansine). The results show that the in vitro and in vivo fluorescence imaging of ADC-induced tumor apoptosis using annexin V–EGFP–QDs is a useful tool to evaluate the efficacy of ADCs for cancer therapy.