CZ-112

1. Camptothecin (CPT) and its derivatives are potent candidate compounds in treating cancers. However, their clinical applications are largely restricted by severe toxicities. 2. The solute carrier transporters (SLCs), particularly the organic anion transporting polypeptides and organic anion/cation transporters (OATs/OCTs) are widely expressed in human key organs and responsible for the cellular influx of many substances including endogenous substrates and many clinically important drugs. Drug-drug interactions through SLCs often result in unsatisfied therapeutic outcomes and/or unexpected toxicities. 3. This study investigated the inhibitory effects of CPT and its eight derivatives on the cellular uptake of specific substrates mediated by the essential SLCs in over-expressing Human embryonic kidney 293 cells. 4. Our data revealed that CPT, 10-hydroxycamptothecin (HCPT), 10-methoxycamptothecin (MCPT) and 9-nitrocamptothecin (9NC) significantly inhibit the uptake activity of OAT3. 9NC also inhibited the substrate transport mediated by OAT1. The substrate uptakes of OAT1, OCTN1 and OCTN2 were significantly decreased in the presence of CZ112, while CPT-11 potently down-regulated the transport activity of OCT1 and OCT3. 5. In summary, our study demonstrated that CPT and its eight derivatives selectively inhibit the substrate uptakes mediated by the essential SLCs. This information contributes to understanding the localized toxicity of CPTs and provides novel molecular targets for the therapeutic optimization of CPTs in the future.

To investigate the antitumor activity and the safety of RFS2000, an oral topoisomerase I inhibitor, in patients with advanced or metastatic urothelial tract tumors refractory to one prior chemotherapy regimen.

Eligible patients were to have failed first line treatment for advanced or metastatic disease. Patients received RFS2000 as one daily oral intake at the dose of 1.5 mg/m(2)/day according to a "5 days on/2 days" off schedule continuously. One cycle was arbitrarily defined as a 3 week period. Sufficient oral fluid intake to prevent cystitis previously described in phase I trials with RFS2000 was recommended. Gehan design was used for sample size determination. Anti-tumor activity was evaluated according to the RECIST criteria and toxicity according to CTC version 2.

Twenty patients received a total of 57 cycles (range 1-8). Grade 3-4 toxicity was observed in 10 patients requiring dose or schedule modifications. Hematological grade 3-4 toxicity was observed in 16% of the cycles. Only one patient experienced a partial response.

RFS2000 could be administered orally as a "5 days on/2 days off" schedule continuously with a median dose intensity of 90.6% with an acceptable toxicity profile. However, RFS2000 did not exert significant activity in patients with advanced/metastatic urothelial tract tumors failing prior chemotherapy. The results of this study do not suggest further investigation of RFS2000 at the present dose and schedule for the treatment of urothelial tract tumors in this refractory population.