The synthesis, physical properties, and antitumor activity of the cis-, d,l-trans-, d-trans-, and l-trans- stereoisomers of
1,2-diaminocyclohexane tetrachloroplatinum(IV) are described. The objective of the study was to produce a
platinum complex with activity against
cisplatin-resistant
tumor cells and with suitable
pharmaceutical properties for formulation development. The isomers had the following solubilities in saline: cis-, 2 mg/ml; d,l-trans-, 6.5 mg/ml; and d-trans- and l-trans-, 15-16 mg/ml. The four complexes showed slightly better activity than
cisplatin against the ip implanted murine
L1210 leukemia. In contrast to
cisplatin, all complexes produced significant increases in life span against L1210/
cisplatin, a subline of L1210 with acquired resistance to
cisplatin. However, the cis- isomer was less active against L1210/
cisplatin. The d,l-trans- isomer (
tetraplatin) was selected for further studies based on greater ease for large-scale synthesis. It showed superior activity to
cisplatin against P388/
cisplatin and like
cisplatin showed significant and reproducible activity against the ip implanted
B16 melanoma, ip implanted M5076
sarcoma, ip implanted
P388 leukemia, and MX-1 human breast xenograft implanted under the renal
capsule. Purity and stability (greater than 24 hours in saline) were evaluated by high-performance liquid chromatography and found to be suitable for development of a parenteral
dosage form. Preliminary studies in a rat model (to be reported elsewhere) showed it to be less nephrotoxic than
cisplatin on a molar basis and worthy of further study.