Evaluation of novel platinum complexes, inhibitors of topoisomerase I and II in non-small cell lung cancer (NSCLC) sublines resistant to cisplatin.

We determined the in vitro cytotoxicities of promising new platinum complexes, an inhibitor of topoisomerase I, and novel anthracycline derivatives, and examined using clonogenic assay whether these compounds are cross-resistant in CDDP-resistant sublines derived from human non-small cell lung cancer (NSCLC) cell lines. Cytotoxicities were evaluated by means of the relative antitumor activity (RAA = peak plasma concentration/IC50 values), which we reported previously as a model for predicting antitumor activity. Of the CDDP analogues tested, including carboplatin (CBDCA), [(glycolate-0,0') diammineplatinum (II) (254-S)], ormaplatin [tetrachloro-(d,1-trans)- 1,2-diaminocyclohexaneplatinum (IV) (OP)] and oxaliplatin [oxalato (trans-1-1,2-diaminocyclohexane) platinum (II) (1-OHP)], no agent showed superior antitumor activity compared to CDDP. ME2303 [7-O-(2,6-dideoxy-2-fluoro-alpha-L-talopyranosyl) adriamycinone-14-O -pimelate], a new anthracycline derivative, showed higher antitumor activity than adriamycin (ADM). The CDDPresistant sublines, PC-9/CDDP and PC-14/CDDP, were 18.3- and 7.7-fold more resistant to CDDP compared to the respective parent cell lines. The CDDP analogues were all cross-resistant to CDDP and the order of relative resistance values was CBDCA > 254-S > 1-OHP > OP for PC9/CDDP and 254-S > CBDCA > 1-OHP > OP for PC-14/CDDP. Although OP showed cross-resistance to CDDP, OP was the most active against the CDDP-resistant sublines with relative resistance values of 3.8 and 1.6 for PC-9/CDDP and PC-14/CDDP, respectively. ME2303 and CPT-11, [7-ethyl-10-(4-[1-piperidino]-1-piperidino) carbonyloxycamptothecin], an inhibitor of topoisomerase I, was active against CDDP-resistant human NSCLC cell lines. These results suggest that OP, ME2303 and CPT-11 could be active in patients with, NSCLC clinically resistant to CDDP.