Kadcyla is a conjugate between a humanized monoclonal anti-HER2 (human epidermal growth factor receptor 2)36 antibody and maytansinoid (DM1), a highly potent microtubule polymerization inhibitor.35 Kadcyla acts as an anti-cancer drug against HER2 positive cancer.37 By using the dual-colour (NIR/VIS) emitting annexin V probes, we achieved in vitro and in vivo imaging of apoptosis of HER2-positive breast tumour cells (KPL-4) treated with Kadcyla. This evidence concerns the gene ERBB2 and cancer.