TfR-1-IN-1 (compound C4) is an inhibitor of transferrin receptor 1 ( TfR-1 ) with anticancer activity. TfR-1-IN-1 strongly increases intracellular iron (II) levels as a driving force for the induction of ferroptosis . TfR-1-IN-1 significantly reduces the metabolic activity of ovarian cancer (A2780cis), breast cancer (MDA-MB 231), and leukemia (HL-60) cell lines with IC 50 values of 0.51, 0.46, and 0.48 μM, respectively.