Phase I and pharmacokinetic study of LU79553, a DNA intercalating bisnaphthalimide, in patients with solid malignancies.

PURPOSE: To determine the maximum-tolerated dose and characterize the pharmacokinetic behavior of LU79553, a novel bisnaphthalimide antineoplastic agent, when administered as a daily intravenous infusion for 5 days every 3 weeks. PATIENTS AND METHODS: Patients with advanced solid malignancies received escalating doses of LU79553. Plasma sampling and urine collections were performed on both days 1 and 5 of the first course. RESULTS: Thirty patients received 105 courses of LU79553 at doses ranging from 2 to 24 mg/m(2)/d. Proximal myopathy, erectile dysfunction, and myelosuppression precluded the administration of multiple courses at doses above 18 mg/m(2)/d. These toxicities were intolerable in two of six patients after receiving three courses at the 24-mg/m(2)/d dose level. At the 18-mg/m(2)/d dose, one of six patients developed febrile neutropenia and grade 2 proximal myopathy after three courses of LU79553. The results of electrophysiologic, histopathologic, and ultrastructural studies supported a drug-induced primary myopathic process. A patient with a platinum- and taxane-resistant papillary serous carcinoma of the peritoneum experienced a partial response lasting 22 months. Pharmacokinetics were dose-independent, optimally described by a three-compartment model, and there was modest drug accumulation over the 5 days of treatment. CONCLUSION: Although no dose-limiting events were noted in the first two courses of LU79553, cumulative muscular toxicity precluded repetitive treatment with LU79553 at doses above 18 mg/m(2)/d, which is the recommended dose for subsequent disease-directed evaluations. The preliminary antitumor activity noted is encouraging, but the qualitative and cumulative nature of the principal toxicities, as well as the relatively small number of patients treated repetitively, mandate that rigorous and long-term toxicologic monitoring be performed in subsequent evaluations of this unique agent.

Overexpression of the multidrug resistance-associated protein (MRP) gene in vincristine but not doxorubicin-selected multidrug-resistant murine erythroleukemia cells.

Multidrug-resistant sublines of the murine erythroleukemia cell line PC4 were sequentially selected in increasing vincristine concentrations (5-160 ng/ml). The low- and intermediate-level resistant cell lines, selected in < or = 40 ng/ml of vincristine, demonstrated resistance to Vinca alkaloids and to an epipodophyllotoxin but little or none to an anthracycline. The expression of murine mdr genes, as analyzed by Northern blotting, revealed a baseline expression of murine mdr2 in parental cells that was unchanged in the drug-resistant cell lines. Overexpression of mdr3 was observed only in the highest-level resistant cell line, PC-V160, whereas mdr1 mRNA was not detected in any of the cell lines. The polymerase chain reaction, using mdr3-specific primers, excluded the possibility that low levels of P-glycoprotein expression contributed to the resistance phenotype in the low and intermediate-level resistant cell lines. Northern blot analysis using a human complementary DNA probe for the multidrug resistance-associated protein (MRP) demonstrated overexpression of murine mrp in each of the vincristine-selected sublines. Genomic amplification of the mrp gene was coincident with mrp overexpression. The expression of mrp was also examined in two series of previously characterized doxorubicin-selected cell lines derived from parental PC4 and C7D murine erythroleukemia cells. In contrast to the vincristine-selected cell lines, overexpression of mrp was not detected. These studies demonstrate that, in murine erythroleukemia cells selected for vincristine resistance, overexpression of murine mrp occurred prior to that for murine mdr. In contrast to human MRP, selection for vincristine, but not doxorubicin resistance, resulted in the overexpression of murine mrp.

Role of P-glycoprotein in dolastatin 10 resistance.

Dolastatin 10, a cytotoxic pentapeptide isolated from the mollusk Dolabella auricularia, exhibits potent antitumor activity. The present studies demonstrated that sublines of murine PC4 and human U-937 leukemia cells expressing a multidrug resistance (MDR) phenotype are cross-resistant to this agent. We also demonstrated that such resistance was reversed by verapamil. While these findings suggested the involvement of the P-glycoprotein (P-gp) in dolastatin 10 resistance, we performed similar studies in a CHO cell line transfected with the human mdr1 cDNA. Expression of P-gp in the transfected cells was associated with resistance to dolastatin 10 by a verapamil-sensitive mechanism. The demonstration that photoaffinity labeling of P-gp was decreased in the presence of dolastatin 10 further supports the interaction of this cytotoxic peptide with P-gp. Taken together, these findings suggest that resistance to dolastatin 10 is conferred, at least in part, by P-gp and that this cytotoxic peptide is a novel member of the MDR phenotype.

Plasma cell-regulated polyadenylation at the Ig gamma 2b secretion-specific poly(A) site.

We found that the sequences downstream of the Ig gamma 2b secretory-specific (sec) poly(A) site play an important role in the preferential production of sec Ig mRNA during plasma B cell development. The Ig gamma 2b mRNA production in a deletion mutant (delta-Kpn) lacking the Ig sec poly(A) site and downstream consensus element (dsc) has been previously shown to default to the use of the downstream membrane-specific (mb) poly(A) site. In this study restoration of the Ig sec poly(A) site and dsc to the delta-Kpn gene causes a significant increase in the use of the sec poly(A) site vs mb poly(A) site in stable transfectants of plasma but not memory B cell tumors, indicating plasma cell-specific recognition of the Ig sec dsc. Restoration of the poly(A) cleavage site alone to delta-Kpn did not restore regulation. Substitution of an SV40 downstream poly(A) element for the Ig dsc in the delta-Kpn gene also does not restore regulation. The data further indicate that although the Ig dsc is clearly very important in the plasma cell-regulated expression, the difference in the processing ratios of the restored vs the intact Ig gamma 2b gene in plasma cells suggests that there are other yet to be defined sequences that may also play a role in the intact gene. Insertion of a 130-nucleotide segment of the gene containing the Ig sec poly(A) site and dsc into a heterologous, guanosyl phosphotransferase gene resulted in plasma cell-regulated polyadenylation of the sec poly(A) site. Neither the mb nor the SV40 early poly(A) sites and their respective dscs, in similar gpt chimeras, were regulated. Therefore the region downstream of the Ig sec poly(A) site plays an essential role in regulating polyadenylation at the sec poly(A) site in plasma cells but not memory cells. A model involving a plasma cell-specific recognition factor for the Ig sec dsc is presented.