1-β-d-Arabinofuranosyl-5-fluorocytosine (5-fluorocytosine arabinoside; ara-FC)2 possesses a high degree of chemotherapeutic activity against transplanted mouse leukemia. It is more active on a molar basis than 1-β-d-arabinofuranosylcytosine (cytosine arabinoside; ara-C), 5-fluorouracil (FU), or 5-fluoro-2′-deoxyuridine (FUDR) against leukemia P815. Ara-FC is somewhat more active than ara-C against leukemia P388. In leukemia L1210, ara-FC is approximately equal to ara-C, but more effective than FU or FUDR. It is less effective than either FU or FUDR, however, against leukemia B82. Both ara-FC and ara-C are highly effective against a line of leukemia P815 made resistant to FU.
Ara-FC and ara-C are equally inhibitory against cells of leukemias P815Y and P388SK in tissue culture. The inhibitory effects of both are blocked by deoxycytidine (CDR) but not by thymidine (TDR). It is concluded that ara-FC is a somewhat more active derivative of ara-C that merits clinical trials.
These studies were supported in part by USPHS Research Contract SA-43-ph-2445 and USPHS Research Grant CA-03190-09, National Cancer Institute; Research Grant T 45 G, American Cancer Society, Delaware Division; and the Campbell Townsend Memorial Grant for Cancer Research from the American Cancer Society.
The abbreviations used are: ara-FC, 1-β-d-arabinofuranosyl-5-fluorocytosine; ara-C, 1-β-d-arabinofuranosylcytosine; FU, 5-fluorouracil; FUDR, 5-fluoro-2′-deoxyuridine; CDR, deoxycytidine; TDR, thymidine; and ara-FU, 1-β-d-arabinofuranosyl-5-fluorouracil.