CD56 expression was evaluated in a MCC cohort (immunohistochemistry on a tissue microarray of 90 tumour samples) and MCC cell lines. Interaction of an unconjugated CD56‐targeting antibody with CD56+ MCC cell lines was investigated by immunohistochemistry and imaging flow cytometry….The CD56‐mediated cytotoxicity of Adcitmer® was demonstrated in vitro in MCC cell lines. Moreover, Adcitmer® significantly reduced tumour growth in a MCC mouse model....Our study suggests that Adcitmer® should be further assessed as a therapeutic option in patients with MCC, as an alternative therapy or combined with immune checkpoint inhibitors.