ADCY2 and neoplasm: Despite relevant affinity differences between Ac2 (KD: 130 nM) and Ec4.1 (KD: 0.2 nM, ca. tenfold improved over the previously published Ec4, cf. “Materials and Methods” [28]), we found that TBRs and tumor MFIs of both DARPin tracers were sufficiently high to allow adequate tumor visualization.