Bisantrene shows an outstanding ability to form a complex with DNA. Bisantrene exhibits the most effective binding (even neglecting electrostatic contacts), followed by the 9-substituted compounds and finally by 1-IHA. Bisantrene congeners retained a remarkable capacity for binding to the single-stranded structure. In comparison with the K _i values found for double-stranded DNA, 9-IHA shows a 2-fold increase, 1-IHA maintains the same values, and aza-9-IHA exhibits a modest reduction. On the other hand, Bisantrene, although undergoing a 6-fold reduction in K _i , still exhibits an affinity constant of the order of 10 ⁶ M ^-1 . Bisantrene promots DNase I cleavage at oligopurine-oligopyrimidine tracts; conversely, it slightly reduces the cleavage activity at alternating purine-pyrimidine sequences. Bisantrene is an active new drug in the treatment of metastatic breast cancer. Bisantrene is an inhibitor of [ ³ H]uridine incorporation into RNA and [ ³ H]thymidine incorporation into DNA.