“A First in Human Study of BAY2701439 to Look at Safety, How the Body Absorbs, Distributes, and Excretes the Drug, and How Well the Drug Works in Participants With Advanced Cancer Expressing the HER2 Protein” (NCT04147819) is a combination of the alpha-emitting radionuclide thorium-227, an antibody targeting HER2, and a chelator molecule that strongly attaches the thorium-227 to the antibody. The gene discussed is ERBB2; the disease is cancer.