Pharmacokinetic and biotransformation studies of ormaplatin in conjunction with a phase I clinical trial.
Ormaplatin is a second-generation platinum (Pt) analogue with in vitro activity against some cisplatin-resistant malignant cell lines. We have evaluated the pharmacokinetics and biotransformations of ormaplatin during a phase I trial in which ormaplatin was administered by daily 30-min infusions on 5 consecutive days every 28 days. Sixteen patients received 25 courses at doses ranging from 5.0 to 11.6 mg/m2 per day. Pharmacokinetic parameters determined for ultrafilterable Pt measured by atomic absorption spectrophotometry revealed a short half-life (t1/2 16 min), moderate volume of distribution (Vd 12 l/m2), and relatively fast systemic clearance (Cls 544 ml/min per m2). Cls and percentage of drug unbound decreased during the 5-day administration period. Average systemic exposure increased with dose; however, inter-individual variability in Cls produced overlap in systemic exposure between the dose levels. The major active biotransformation product [PtCl2(dach)] was evaluated at the highest dose level by HPLC. This product decayed monoexponentially with a mean t1/2 of 13 min and a higher degree of pharmacokinetic variability than that of ultrafilterable Pt at this dose. No unreacted ormaplatin was detected; however, several inactive biotransformation products persisted for at least 120 min. Approximately 32% of the dose was excreted in the urine during the first day, one-third of this during the initial 1.5 h. The human pharmacokinetic characteristics of ormaplatin resemble those of cisplatin; however, additional study will be required to discern which analyte of ormaplatin correlates best with clinical effects.
Petros
W P
WP
Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710.
Chaney
S G
SG
Smith
D C
DC
Fangmeier
J
J
Sakata
M
M
Brown
T D
TD
Trump
D L
DL
D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000493:pharmacokinetics* / Q000627:therapeutic use; D001711:Biotransformation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D009944:Organoplatinum Compounds / Q000493:pharmacokinetics* / Q000627:therapeutic use
D000970:Antineoplastic Agents; D009944:Organoplatinum Compounds; C049777:ormaplatin