cis-Diammine-1,1-cyclobutane dicarboxylate platinum II (CBDCA, JM8), an analogue of cisplatin showing reduced toxicity in preclinical studies, was evaluated in 60 patients. Doses were given initially every 3 weeks and escalated from 20 to 520 mg/m2. Following this, doses were given every 4 weeks and escalated from 300 to 500 mg/m2. The dose-limiting toxicity, thrombocytopoenia, occurred in four-fifths of patients treated at 520 mg/m2, with the nadir occurring 3 weeks after treatment. Leucopoenia and anaemia also occurred but were less severe. Vomiting occurred in all patients receiving over 120 mg/m2 but seldom persisted beyond 24 h. Serial measurements of 51Cr-EDTA clearances, urinary N-acetylglucosaminidase, urinary leucine aminopeptidase, and beta 2-microglobulin did not reveal significant evidence of nephrotoxicity. Detriment to the audiogram has not been seen in the first 13 patients studied. Pharmacological studies showed that most of the dose of platinum was excreted in the urine, and that impairment of renal function may be associated with drug retention and an increased risk of myelosuppression. The previous therapy and age of the patient also affected the tolerance of the drug. Clinical responses were seen in patients with ovarian carcinoma receiving greater than 120 mg/m2. A further dose escalation was performed on a 4-week schedule in patients under 65 with good renal function. The maximum dose it was possible to administer repeatedly without incurring myelosuppression was in the range 400-500 mg/m2. JM8 is not significantly nephrotoxic and is less emetic than cisplatin. It has antitumour activity in man and deserves wider evaluation, along with the other analogues under study in various centres, as an alternative to cisplatin.
Summary The role of glutathione (GSH) and GSH-S-transferase (GST) activity in modulating the cytotoxicity of four platinum drugs and melphalan was evaluated in eight human ovarian carcinoma cell lines. The cell lines were established from solid and ascitic tumours from pretreated and untreated patients, and showed a wide spectrum of sensitivity to several platinum II and in the sensitive (CHI) line after GSH depletion. Moreover the dose modification factor (DMF) for the PtII agents were lower than those for PtIV agents in the three cell lines. The dose modification factor for tetraplatin after BSO treatment was similar to that observed for melphalan in all three cell lines. In the SKOV-3 cell line extending the BSO pretreatment period to 48 h from 24 h marginally reduced the cytotoxicity of cisplatin, whereas the cytotoxicity of the other three drugs remained similar to that observed after 24 h BSO pretreatment. In contrast, extending the BSO treatment to 24 h after drug exposure potentiated the cytotoxicity of cisplatin, CHIP and tetraplatin. The significance of these results in relation to the role of GSH in the mechanism of action of PtII and PtIV drugs is discussed.
SummaryAcquired resistance to cisplatin (cis-diamminedichloroplatinum (II)) has been generated in vitro in the 41M The 4lMcisR6 cells were not found to be cross-resistant to ouabain, a postulated specific inhibitor of sodium-potassium adenosine triphosphatase (Na+, K+-ATPase), suggesting that decreased cisplatin accumulation in these cells is probably not regulated by alterations in their Na+, K+-ATPase levels, and Na+ potential across the plasma membrane. Cellular accumulation of a novel class of platinum (IV) ammine/cyclohexylamine dicarboxylates, which exhibit enhanced cytotoxicity over cisplatin and completely circumvent resistance to cisplatin in the 41McisR line, was also examined. The data suggests that increased accumulation of these compounds, as a result of their enhanced lipophilicity, could account for the dramatic increase in their potency over cisplatin.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.