Preliminary phase I clinical study and pharmacokinetics of (1,2-diaminocyclohexane) (isocitrato) platinum (II) or PHIC

Abstract

PHIC [NSC-350602; (1,2-diaminocyclohexane) (isocitrato) platinum (II)] is a new highly water-soluble platinum derivative. Preclinical studies showed antitumor activity on a wide range of tumors, no cross-resistance with cisplatin and little or no nephrotoxicity in mice and baboons. A phase I clinical trial was then initiated at doses of 300 mg/m2 infused intravenously over one hour without induced diuresis or hydration. Dosages were escalated up to 1500 mg/m2. A total of 29 patients received 52 courses of treatment. The most important side-effect is thrombocytopenia which is rapidly reversible. Nausea and/or vomiting were mild or moderate with onset 1 hr after the end of the infusion and seldom persisted beyond 24 hrs. Measurements of biological parameters did not reveal significant evidence of nephrotoxicity except in one patient who developed urinary tract infection and for whom hemodialysis became necessary. No change in the audiogram could be demonstrated. Peripheral neuropathy was documented in one patient, and in two other patients to whom morphine was given confusional episodes were observed. Although no antitumor effect was observed, there was apparent stabilization of disease. Pharmacokinetic parameters were calculated in twelve out of these 29 patients. Based upon total platinum plasma concentrations, the elimination half-life is 58.3 hrs and the plasma clearance is 21.2 ml/min with an apparent volume of distribution of 7.6 liters. However, considering both plasma concentrations and urinary excretion, we could estimate the half-life of free filterable species (60 min), the plasma clearance (125 ml/min) and the renal clearance (86 ml/min). Mean urinary excretion is 64.4% of the dose after 6 days and 53.1% at 24 hrs. Other administration protocols are suggested, based upon these pharmacokinetic parameters.