The novel drug CAP7.1 (EDO-S7.1) is activated by the enzyme carboxylesterase 2 (CES), which is expressed in the liver, gallbladder and gastrointestinal tract tissues [22,24], giving rise to the hypothesis that local tumour expression may permit intra-tumoural activation of CAP7.1 and thus contribute to drug accumulation, making CAP7.1 a candidate for the treatment of BTC. This evidence concerns the gene CES2 and neoplasm.