ANPEP and neoplasm: The lack of activity observed in the CD13-negative RPMI 8226 myeloma model demonstrates that payload release does not occur spontaneously, while the appearance of mitotic catastrophes (consistent with the mechanism of action of the PM050489 payload) in HT1080 tumor cells observed both in vitro and in tumors from xenografted animals that had been treated with MI13010 indicates an adequate intracellular processing of the ADC in CD13-expressing cells, therefore confirming that conjugation to TEA1/8 mAb does not hinder the anti-proliferative properties of the marine drug.