Studies characterizing the pharmacokinetics and toxicokinetics of CZ48 and its active metabolite camptothecin after either single- or repeat-dose administration were conducted in mice and dogs. The repeat-dose studies were toxicokinetic evaluations conducted as part of the pivotal toxicology program using validated bioanalytical methods. No extensive distribution studies were conducted with CZ48; however, drug distribution into tumor, liver and kidney tissues of tumor-bearing mice was evaluated. Several in vitro and in vivo metabolism studies were conducted to examine the metabolic conversion of CZ48 to its active moiety, camptothecin. Excretion studies were limited to measurement of CZ48 in the feces of nude mice following single-dose administration. Pharmacokinetic drug interaction studies were not conducted with CZ48.