Nafazatrom: clonogenic in-vitro assessment of activity against human malignancies.

Nafazatrom was tested against a variety of human malignancies with the human tumor stem cell assay at one or more of the following concentrations: 1, 10, 25, and 100 micrograms/ml X 1 h or 0.05, 0.5, or 5 micrograms/ml by continuous exposure. Major (greater than or equal to 70%) inhibition was noted in 7/52 adenocarcinomas, in 0/9 squamous carcinomas, and 1/17 other malignancies. Intermediate levels of inhibition (50 to 69%) were noted in 7/52, 4/9, and 6/17 of these respective subtypes. No clear trend toward superiority of any dose-schedule was noted. Since nafazatrom has proven non-toxic in our nearly completed Phase I study, and since this study suggests activity against several human cancers, Phase II level testing is warranted.