Rationale for development of platinum analogs.

There is a great need for clinical trial of new second-generation platinum coordination compounds that might demonstrate greater clinical activity in a broader spectrum of tumors, decreased renal toxicity and emesis, improved solubility, synergism in combination therapy, and lack of cross-resistance to cis-dichlorodiammineplatinum(II) (cis-platinum). Lack of cross-resistance to cis-platinum is shown by certain 1,2-diamino-saturated cyclic platinum derivatives which also have a high degree of activity against transplanted mouse leukemias. cis-Platinum and these cyclic compounds combine synergistically with derivatives of cytosine arabinoside, VP-16-213, and Adriamycin. These 1,2-diamino cyclic compounds appear to have less renal toxicity than cis-platinum. The toxic and therapeutic effects of both cis-platinum and the diamino cyclic compounds can be blocked by massive doses of thiourea. Varying doses and time intervals of thiourea rescue are being studied in the hope of improving the therapeutic index of the platinum derivatives.