Compound-Specific Toxicities Detected in CFU-GM, Rat Kidney NRK Cells, Rat Bladder RBLAK Cells, and Rat Liver Slices following Batracylin or N-Acetyl Batracylin Exposure

The investigational anticancer agent batracylin (BAT; 8-aminoisoindolo [1,2-b]quinazolin-10(12H)-one; NSC320846) causes γ-H2AX foci development in exposed tumor cells and has demonstrated activity against solid tumors and adriamycin-resistant leukemia. Reports indicate BAT has wide interspecies variation of adverse effects, including myelosuppression, kidney, bladder, and liver damage, including biliary hyperplasia. The effects of BAT and its metabolite N-acetyl batracylin (NAB) were evaluated in the CFU-GM bone marrow toxicity assay, rat kidney (NRK) cells, bladder epithelial (RBLAK) cells, and rat precision cut liver slices (PCLS). Exposure effects were evaluated biochemically and histologically. Human, dog, and rat exhibited similar CFU-GM IC90 values for BAT (21–29？μM). The ATP assay and γ-H2AX staining showed time- and concentration-dependent toxicity in RBLAK (more severe than NRK at <72？hr) NRK and cells ( ？μM after 96？hr BAT exposure). BAT (5？μM and 25？μM) caused biochemical and histology changes to PCLS by day 3 and 25？μM produced centrilobular hepatotoxicity. NAB (≤5？μM) produced no toxicity in CFU-GM, NRK, or RBLAK cells. However, both BAT and NAB caused biliary epithelial cell proliferation in PCLS. Our studies demonstrated species similarities in sensitivity to BAT-induced myelosuppression, and implicate the metabolite NAB in biliary hyperplasia. 1. Introduction Batracylin, 8-aminoisoindolo 1, 2-b quinazolin-12(10H)-one (BAT), is a heterocyclic arylamine first synthesized by Bayer AG, Leverkusen, Germany, and was acquired through the NCI as a potential pharmacodynamics agent for development to clinical trial based on its activity in the refractory colon adenocarcinoma 38 model [1]. It has demonstrated activity against solid tumors and adriamycin-resistant leukemia [1, 2] and has been evaluated preclinically in multiple species. Studies have confirmed BAT induces ATP-independent topoisomerase II (Topo II) inhibition [3, 4] and subsequent DNA strand breaks that can be detected using the γ-H2AX marker [5]. IND-directed toxicology studies of BAT were conducted in 3 mammalian species (1 dose, p.o., per day for 9 consecutive days). The variation in tolerated doses across species (mice, rats, and dogs) yielded an MTD range of at least 60-fold [6]. The major toxicities were myelosuppression in all species. Variable amounts of renal, hepatic, testicular, ovarian, gastrointestinal, and lethargy were found in the various species tested, and the rat was found to be the most sensitive for adverse effects. For rats, the severe toxic effects occurred at