The development of safe active ingredients is a key issue in pharmaceutical research. Animal studies are mostly used here to assess the safety of novel active ingredients. In particular, hybrid active ingredients such as conjugates of extremely strong toxins (such as amanitin from the tuber cap mushroom) and monoclonal antibodies, which ensure target recognition (ADCs, “antibody-drug conjugates”), require a particularly precise toxicological assessment. The assumption of an exclusive release of the toxin in the target tissue must also be checked. Here the use of 3D cell cultures from human cells is becoming more and more important. If a test system is successfully established, animal studies can be avoided or reduced, costs can be saved and throughput can be increased.