Cycloplatam: a novel platinum compound exhibiting a different spectrum of anti-tumour activity to cisplatin.
Cycloplatam is a novel platinum compound which has shown anti-tumour activity in murine tumour models. In this study, cycloplatam was found to have anti-tumour activity in vitro and in vivo in human tumour models. In 15 cell lines (mainly ovarian), cycloplatam showed similar cytotoxicity as cisplatin, using the sulphorhodamine B assay. Determination of the resistance factor (IC50 of cisplatin-resistant divided by IC50 of parental cell line) clearly showed lower values for cycloplatam than for cisplatin. In the parental ovarian cell line CH1 and the cisplatin-resistant CH1 cisR model, we observed no cross-resistance of cycloplatam and cisplatin. The in vitro anti-tumour activity was confirmed in human tumour xenografts using the clonogenic assay. Mean IC70 values of cycloplatam were 0.54 microgram/ml (1.25 microM) and of cisplatin 0.42 microgram/ml (1.4 microM), respectively. In the murine subcutaneously implanted ADJ/PC6 plasmacytoma in vivo cycloplatam showed less activity than cisplatin, with a 2-fold smaller therapeutic index than cisplatin. In ovarian cancer xenografts cycloplatam was less active than cisplatin. However, anti-tumour activity of cycloplatam in lung cancer xenografts was quite different from cisplatin. In LXFS 538, a model moderately sensitive to cisplatin, a partial remission was observed, but in LXFL 529, a cisplatin-sensitive model, cycloplatam was inactive, cycloplatam thus demonstrating a different spectrum of anti-tumour activity. Based on these results, further preclinical investigations with other tumours, such as cisplatin-sensitive and -resistant gastric cancer models, are warranted with cycloplatam.
Drees
M
M
Department of Internal Medicine, University of Freiburg, FRG.
Dengler
W M
WM
Hendriks
H R
HR
Kelland
L R
LR
Fiebig
H H
HH
D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D016923:Cell Death / Q000187:drug effects; D002945:Cisplatin / Q000627:therapeutic use*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy*; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D014411:Neoplastic Stem Cells / Q000187:drug effects; D009944:Organoplatinum Compounds / Q000627:therapeutic use*; D010051:Ovarian Neoplasms / Q000188:drug therapy*; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured / Q000187:drug effects
D000970:Antineoplastic Agents; D009944:Organoplatinum Compounds; C055928:cycloplatam; D002945:Cisplatin