Blood clearance of radioactively labelled cis-diammine 1,1-cyclobutane dicarboxylate platinum (II) (CBDCA) in cancer patients.

The blood and urinary clearances of cis-diammine 1,1-cyclobutane dicarboxylate platinum(II) (CBDCA, JM8) were determined in four patients with malignancy. A 40 muCi iv injection of 191 Pt/193 Pt (3:1)-labelled CBDCA was followed by serial blood and urine sampling to 72 h. The blood clearance was triphasic, mean values for the fast, intermediate, and slow phases being 10.8 min, 2.5 h, and 125 h, respectively. The fraction of activity excreted in the urine within the first 6 h had a mean value of 66.7%, contrasting with 26.4% for cisplatin. There was only a small fraction of CBDCA excreted by the slow phase (1.5%) as against an average of 20% for CHIP and 27% for cisplatin. The early and rapid renal clearance of CBDCA may account for reduced nephrotoxicity.