The relatively restricted C4.4a expression pattern provides a target for the selective delivery of a cytotoxic drug to C4.4.a-expressing tumor cells by means of a suitable antibody-drug conjugate. The subject population eligible for the current study will be those subjects with advanced malignancies known to express C4.4a, which are refractory to standard therapy or those without standard therapy or actively refusing any treatment, which would be regarded as standard and in whom, in the opinion of the investigator, experimental therapy with BAY1129980 may be beneficial.Depending on the number of dose-escalating steps and the occurrence of DLTs, the planned numbers of subjects could vary.It is expected that up to 90 subjects may participate in the dose-expansion phase of the study and up to 6-9 subjects may particpate in the dose re-esclation phase.The study assessments in the expansion phase of the study are identical to those in the dose-escalation phase.