Investigational new drug-directed, 5-day repeat dose toxicity study of 4-[3-(2-nitro-1-imidazolyl)-propylamino]-7-chloroquinoline hydrochloride (NLCQ-1, NSC 709257) administered with or without Taxol in Sprague-Dawley rats.

In pre-clinical studies, 4-[3-(2-nitro-1-imidazolyl)-propylamino]-7-chloroquinoline hydrochloride (NLCQ-1, NSC 709257) is a weak DNA-intercalating, hypoxia-selective cytotoxin with a promising profile as an adjuvant to radio/chemotherapy and it is about to enter phase I clinical trials. The present investigation was undertaken to further evaluate potential systemic toxicity induced by i.v. doses of NLCQ-1 alone or in combination with Taxol in Sprague-Dawley rats, in support of an investigational new drug application. Doses of NLCQ-1 were based on previous range-finding studies. In the present study, NLCQ-1 was administered either alone, at 0, 6, 9 or 12 mg/kg/dose to male rats and 8, 12 or 16 mg/kg/dose to female rats or, at 9 (male rats) and 12 (female rats) mg/kg/dose, in combination with Taxol, on a qd x 5 schedule. Taxol was administered i.v. at 3.5 mg/kg/dose 1 hr before NLCQ-1. Observations were recorded for mortality/moribundity, clinical signs of toxicity, body weights, food consumption, haematology, clinical chemistry, gross lesions at necropsy and histopathology. Blood samples were taken from 10 animals from each dose group on each of 2 days (days 8 and prior to scheduled necropsy on day 33). Administration of i.v. doses of NLCQ-1 alone, on a qdx5 schedule, resulted in no signs of toxicity over the 33-day study. Taxol-induced toxicity included minimal decreases in the group mean RBC, haemoglobin and haematocrit values, minimal increases in group mean reticulocyte counts (females), marked decreases in group mean neutrophil counts and minimal decreases in group mean monocyte and eosinophil counts. Lymphoid atrophy of thymus, atrophy of bone marrow and atrophy of the germinal epithelium of the testis were also associated with the administration of Taxol. There was no additional toxicity associated with the co-administration of NLCQ-1 and Taxol. In the present study, the 'no observable adverse effect level' for NLCQ-1, when administered on a qdx5 schedule, was >12 and >16 mg/kg/dose in male and female rats respectively. Daily administration of 9 (male rats) or 12 (female rats) mg/kg of NLCQ-1 1 hr after i.v. administration of Taxol (3.5 mg/kg) had no effect on Taxol-induced toxicity.