Comparison of 2,2'-anhydro-1-beta-D-arabinofuranosyl-5-fluorocytosine and cytosine arabinoside in the treatment of murine brain tumor.

2,2'-Anhydro-1-beta-D-arabinofuranosyl-5-fluorocytosine (anhydro-ara-FC) was compared with cytosine arabinoside (ara-C) in the treatment of ic implanted murine Glioma 261. Both drugs given in ip doses of 500 mg/kg immediately inhibited the uptake and incorporation of tritiated thymidine into the DNA of brain tumor, small intestine, and spleen. Inhibition of DNA synthesis in the tumor recovered within 12 hours of anhydro-ara-FC administration, yet it remained depressed greater than 50% of control 12 hours after ara-C administration. Inhibition in the small intestine recovered within 24 hours of drug administration with either agent while inhibition in the spleen remained depressed greater than 24 hours. Anhydro-ara-FC administered ip in single doses less than or equal to 1500 mg/kg or in multiple doses less than or equal to 200 mg/kg three times a week for ten doses failed to prolong the survival of tumor-bearing mice, and minimal increased survival followed drug administration of 200 mg/kg every 24 hours for five doses. In contrast, ara-C in doses of 50, 100, or 200 mg/kg three times weekly for ten doses significantly increased the survival of tumor-bearing animals between 17% and 36%.