Bis(phenazine-1-carboxamides): Structure-activity relationships for a new class of dual topoisomerase I/II-directed anticancer drugs

Ring-substituted bis(phenazine-1-carboxamides), linked by a -(CH2)(3)NMe(CH 2)(3)- chain, were prepared from the corresponding substituted phenazine-1- carboxylic acids by reaction of the intermediate imidazolides with bis(3-am inopropyl)methylamine. The compounds were evaluated for growth inhibitory a ctivity in a panel of tumor cell lines, including P388 leukemia, Lewis lung carcinoma, and wild-type (JL(C)) and mutant (JL(A) and JL(D)) forms of hum an Jurkat leukemia; The latter mutant lines are resistant to topoisomerase (topo) II targeted agents because of lower levels of the enzyme. Analogues with small, lipophilic substituents (e.g,, Me, Cl) at the 9-position were t he most potent inhibitors, superior to the corresponding dimeric bis(acridi ne-4-carboxamides) (bis-DACA analogues). Several of the compounds were pref erentially (up to 2-fold) more cytotoxic toward the mutant Jurkat lines tha n the wild-type. To test whether this selectivity was related to topoisomer ase action, the most potent of the compounds (9-methyl) was evaluated in a cell-free system. It poisoned topo I at drug concentrations of 0.25 and 0.5 mu M and inhibited the catalytic activity of both topo I and topo II at co ncentrations of 1 and 5 mu M, respectively. Results from the NCI human tumo r cell line panel showed the compounds had preferential activity toward col on tumor lines ton average 9.5-fold more active in the HT29 line than in th e cell line, panel as a whole). Several analogues produced significant grow th delays in the relatively refractory subcutaneous colon 38 tumor model in vivo. In particular, the 9-methyl compound was substantially more potent i n this tumor model than the clinical dual topo I/II poison DACA (total dose 90 versus 400 mg/kg) with comparable activity. The bis(phenazine-1-carboxa mides) are a new and interesting class of dual topo I/II-directed anticance r drugs.