Cytoxan, a cyclic phosphamide ester of nitrogen mustard, was tested for tumor-inhibiting activity in the transplantable human tumor-rat host experimental chemotherapy systems with the use of the sarcoma H.S. #1 and the epidermoid carcinoma H.Ep. #3. The compound inhibited the growth of both tumors when the initial dose was given 24 hours after tumor transplantation, by the intraperitoneal or oral route of administration. Cytoxan was found to have limited ability to suppress growth of established human tumors.

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This study was supported in part by a research grant CY-3784 from the National Cancer Institute, National Institutes of Health, U.S. Public Health Service, Bethesda, Maryland; in part by a contract SA-43-ph-19723 and SA-43-ph-2445 from the Cancer Chemotherapy National Service Center, National Cancer Institute, Bethesda, Maryland; and in part by a grant T-47 from the American Cancer Society.

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