Dose optimization of gallium chloride, orally administered, in combination with platinum compounds.

ABSTRACT

An individual dose adaptation for cisplatin (CDDP), etoposide and gallium chloride (GaCl3) was proposed to improve the efficacy of this combination chemotherapy and avoid its toxicity. A clinical study was performed in 28 non small cell lung cancer patients, to verify this hypothesis. CDDP and etoposide were administered as continuous infusions every 3 weeks and GaCl3 orally during and between the CDDP-etoposide sequential infusions. CDDP doses were adjusted to achieve, during each 5 day infusion, an area under the total plasma platinum concentrations versus time curve (AUC Pt 0-120) ranging between 80,000 and 100,000 micrograms/l.h. Etoposide dosages were 120 mg/24 h during days 1-3 of the CDDP infusion. GaCl3 dosages were adjusted to obtain plasma gallium (Ga) concentrations ranging between 200 and 400 micrograms/l. The proposed methods of adaptation were successful from a pharmacokinetic point of view as AUC Pt 0-120 were respectively 81351 +/- 4788, 88268 +/- 8451 and 88331 +/- 8778 micrograms/l.h during the first 3 courses, and plasma Ga concentrations, determined during the 2nd and 3rd CDDP courses, 16 hours after the beginning of the CDDP infusion, were respectively 264 +/- 127 and 313 +/- 186 micrograms/l. However, these results were not pharmacodynamically successful and the therapeutic window was not confirmed. Past clinical trials with GaCl3 will be reviewed, as well as the factors which modify the pharmacokinetics or the pharmacodynamic effects of CDDP and GaCl3. From this review, an optimal dosage of 400 mg GaCl3 could be proposed to potentiate a combination chemotherapy with a platinum compound. The target AUC of the platinum compound should be the AUC avoiding its cumulative toxicity.