The bacterial topoisomerase II (DNA gyrase) and the mammalian topoisomerase
II represent the cellular targets for quinolone antibacterials and a wide
variety of anticancer drugs, respectively. In view of the mechanistic simil
arities and sequence homologies exhibited by the two enzymes, tentative eff
orts to selectively shift from an antibacterial to an antitumoral activity
was made by synthesizing a series of modified tricyclic quinolones, in whic
h the essential 3-carboxylic function is surrogated by phenolic OH and the
classic C-6 fluorine atom is replaced by a NH2 group. The resulting 7-amino
-9-acridone derivatives were assayed, for their antibacterial as well as cy
totoxic activities. No antibacterial activity was found. On the other hand,
many derivatives showed significant cytotoxic activity against both HL-60
and P388 leukemias and a wide panel of human and rodent solid tumor cells,
derivatives 25 and 26 displaying the best overall antiproliferative activit
y. Against the LoVo cell line, derivative 25 exhibited higher cytotoxic eff
ects than etoposide.