4-demethoxy-3'-deamino-3'-aziridinyl-4'-methylsulphonyl-daunorubicin (PNU-159548) belongs to a novel class of antitumor compounds (termed alkycyclines) and is currently undergoing Phase II clinical trial. In the present study, we investigated the in vitro and in vivo antitumor activity, the pharmacokinetics, and the toxicological profile of this compound.
PNU-159548 showed good cytotoxic activity in murine and human
cancer cells growing in vitro, with an average concentration for 50% growth inhibition of 15.8 ng/ml. The
drug showed strong antitumor efficacy in vivo after i.v. and p.o. administration against rapidly proliferating murine
leukemias and slowly growing transplantable human xenografts. At non-toxic doses,
PNU-159548 produced complete regression and cures in ovarian, breast, and human small cell lung
carcinomas. Fourteen of 16 models studied, including colon, pancreatic, gastric, and
renal carcinomas,
astrocytoma and
melanoma, were found to be sensitive to
PNU-159548. In addition,
PNU-159548 was effective against intracranially implanted
tumors. Toxicological studies revealed myelosuppression as the main toxicity in both mice and dogs. The maximum tolerated doses, after a single administration, were 2.5 mg/kg of
body weight in mice, 1.6 mg/kg in rats, and 0.3 mg/kg in dogs. In the cyclic studies, the maximum tolerated doses were 0.18 mg/kg/day (cumulative dose/cycle: 0.54 mg/kg) in rats and 0.05 mg/kg/day (cumulative dose/cycle: 0.15 mg/kg) in dogs.
PNU-159548 showed minimal
cardiotoxicity, when compared with
doxorubicin in the chronic rat model at a dose level inducing similar myelotoxicity. Animal pharmacokinetics, carried out in mice, rats, and dogs, was characterized by high volumes of distribution, plasma clearance of the same order of the hepatic blood flow, and short terminal half-life. These findings support the conclusion that
PNU-159548 is an excellent candidate for clinical trials in the treatment of
cancer.