Pharmacodynamic analyses of end-of-treatment CP50C and CP341 tumours confirmed the antiproliferative effect of DS-7300a shown by a marked reduction in Ki67 in PDX-Os treated with DS-7300a (10 mg/kg) compared with the vehicle, non-targeting IgG1-ADC, and anti-B7-H3 antibody at corresponding concentrations. This evidence concerns the gene MKI67 and neoplasm.