The activity of nitrosoguanidines against ascites tumors in mice.

1-Methyl-3-nitro-l-nitrosoguanidine (nitrosoguanidine) was tested for activity against leukemia L1~10 (ascites and solid), Sarcoma 180 (ascites and solid), Ehrlich carcinoma (ascites and solid), 6CSHED ascites lymphosarcoma, and Mecca ascites lymphosarcoma in mice. Nitrosoguanidine was active against all the ascites tumors cxcept Mecca; it was inactive against the three solid tumors. When used to treat leukemia L1~10 it was as effective if given in one or two doses as it was when given daily throughout the course of the disease. I t was inactive when given orally at a dose 5 times that effective when given intraperitoneally, and less active when given intramuscularly than when given intraperitoneally. Sixteen analogs of nitrosoguanidine were tested for their capacity to extend the life of mice bearing Ehrlich ascites tumors. Twelve of these were active, increasing life expectancy ~5 per cent or more. In general, the activity of nitrosoguanidines and related compounds against Ehrlich ascites tumors paralleled that of their activity against leukemia LI~10.