Esterase hydrolysis, therefore, represents an interesting potential strategy for selective activation of anticancer drugs within cancer cells that overexpress esterases, or which express esterases with different specificities, while minimising toxic effects on healthy cells and tissues.6 The study of esterase expression in cancer is still in its infancy, but interest is growing as a result of the development of novel PDCs such as melflufen (melphalan flufenamide), which utilises intracellular aminopeptidases and esterases to release a cytotoxic payload in multiple myeloma cells.3,12. This evidence concerns the gene CPQ and cancer.