MELK and breast cancer: OTSSP167, a type I kinase inhibitor, is an inhibitor that markedly suppresses MELK kinase activity by phosphorylating the MELK substrates DBNL and PSMA1.23 The potent anti‐tumour effects of OTSSP167 have been observed in multiple malignant tumours, such as breast cancer,24 myeloma21 and AML.23 Several phase I/II clinical trials in patients with advanced breast cancer and acute myeloid leukaemia have been launched to test the therapeutic potential of OTSSP167.23, 25 Nevertheless, the biological function of MELK and the therapeutic potential of OTSSP167 in BCa are still unclear.