2,6-Di(omega-aminoalkyl)-2,5,6,7-tetrahydropyrazolo[3,4,5-mn]pyrimido[5,6,1-de]acridine-5,7-diones: novel, potent, cytotoxic, and DNA-binding agents

DNA-binding agents with potential antitumor activities bearing two cationic side chains, the 2,6-di(omega-aminoalkyl)-2,5,6,7-tetrahydropyrazolo[3,4,5-mn]pyrimido[5,6,1-de]acridine-5,7-diones (4a-r), have been prepared either by reaction of the appropriate 2-(omega-aminoalkyl)-6-chloro-2,3-dihydro-1H,7H-pyrimido[5,6,1-de]acridine-1,3,7-trione with the appropriate (omega-aminoalkyl)hydrazine or by cyclization of the requisite N-6,2-di(omega-aminoalkyl)-2,6-dihydropyrazolo[3,4,5-kl]acridine-6-carboxamide with phosgene. In vitro cytotoxic properties of these derivatives against three human colon adenocarcinoma cell lines (HT29, LoVo, and LoVo/Dx) and against some cell lines of the NCI panel are described and compared to that of reference drugs. Some of the new compounds showed outstanding potency while lacking cross-resistance with anthracyclines. Structure-activity relationships are discussed, and a mechanistic analysis is performed using the COMPARE procedure. The mechanism and efficiency of noncovalent DNA binding of these compounds are examined using gel electrophoresis and fluorometric techniques. The 2,6-di(omega-aminoalkyl)-2,5,6,7-tetrahydropyrazolo[3,4,5-mn]pyrimido[5,6,1-de]acridine-5,7-diones (4) constitute a new class of potent, cytotoxic DNA-binding agents not cross-resistant with doxorubicin.