(R,R)-2,2'-[1,2-ethanediylbis[imino(1-methyl-2,1-ethanediyl)]]- bis[5-nitro-1H-benz[de]isoquinoline-1,3-(2H)-dione] dimethanesulfonate (DMP 840), a novel bis-naphthalimide with potent nonselective tumoricidal activity in vitro.

(R,R)-2,2'-[1,2-ethanediylbis[imino(1-methyl-2,1-ethanediyl)]]- bis[5-nitro-1H-benz[de]isoquinoline-1,3-(2H)-dione] dimethanesulfonate (DMP 840), is a bis-naphthalimide anticancer tumoricidal agent currently in phase I clinical trials. DMP 840 exhibits curative activity in human tumor xenografts, where it shows selectivity for human solid tumors over murine leukemias. In contrast to the selectivity found for DMP 840 in vivo, DMP 840 exhibits potent antiproliferative activity in vitro against a variety of human and murine leukemia and solid tumor cell lines in culture, with inhibitory doses that reduce the number of treated cells to one half (IC50) values ranging from 2.3 to 53 nM. DMP 840 was growth inhibitory to three doxorubicin-resistant cell lines with IC50 values also in the nanomolar range. Clonogenic survival experiments showed that DMP 840 was equally cytotoxic to both exponentially growing and quiescent human clone A colon carcinoma cells. A 1-h incubation of DMP 840 (1.22-12 microM) caused 5-log cell kill in KB-3-1 human epidermoid carcinoma, clone A human colon carcinoma, and L1210 murine leukemia cell lines. The rapid cell killing by DMP 840 in clonogenic survival experiments and initial mechanism of action studies was consistent with a DNA-interactive mechanism for DMP 840 cytotoxicity. Mechanism of action studies in L1210 leukemia cells demonstrated that DMP 840 inhibited the incorporation of thymidine and uridine into DNA and RNA with IC50 values of 0.55 and 0.08 microM, respectively. DMP 840 produced DNA single-strand breaks in a dose-dependent manner. Double-strand breaks were not observed with DMP 840 treatment, even at higher concentrations of compound. Chinese hamster ovary (CHO) and P388 cells resistant to camptothecin and containing a mutant form of topoisomerase I were also used to evaluate whether DMP 840 was cross-resistant with agents active against topoisomerase I. While the CHOR line was 163-fold resistant to camptothecin, the CHOR line was only 1.7-fold resistant to DMP 840. In summary, DMP 840 is a DNA-interactive agent that demonstrates excellent antiproliferative activity in vitro against cultured tumor cells from both human and murine sources. Its mechanism of tumoricidal activity may be novel.

XB596, a promising bis-naphthalimide anti-cancer agent.

We have synthesized a promising class of bis-naphthalimide anti-tumor agents. A representative compound in this series, XB596, exhibits potent in vitro growth inhibitory activity against several human and murine leukemic and solid tumor lines in culture, with IC50 values ranging from 7.2 to 147.5 nM. XB596 was almost as equally growth inhibitory against three doxorubicin-resistant cell lines compared with their parental lines. Using a human tumor colony-forming assay, XB596 demonstrated cytocidal activity against fresh human tumors taken directly from patients, with 23 of 25 evaluable tumors responding to a continuous exposure of 1 microgram/ml of XB596. When L1210 cells were incubated with XB596 for 1 h, the incorporation of uridine and thymidine into RNA and DNA, respectively, was inhibited with IC50 values of 0.14 microM. DNA single-strand breaks, but not double-strand breaks, were detected in XB596-treated L1210 cells. XB596 bound to DNA with guanine-cytosine sequence selectivity as shown by an indirect ethidium bromide displacement assay. XB596 was shown to interact with DNA by a spectrophotometric titration assay, with an estimated binding constant of 4.7 +/- 2.2 +/- 10(6) M-1. XB596 unwound supercoiled DNA as measured by agarose gel electrophoresis. These data are consistent with XB596 being a DNA intercalator. In vivo, XB596 demonstrated good anti-tumor activity against two human solid tumors (DLD-2 colon adenocarcinoma and MX-1 mammary carcinoma) xenografted in nude mice, but has not demonstrated anti-leukemic activity. In summary, XB596 is a pre-clinical anti-cancer agent which interacts with DNA and demonstrates good in vivo anti-tumor activity against human solid tumor xenografts.