[5'-deoxy-5-fluoruridine, a new antineoplastic pyrimidine antimetabolite]

5'-deoxy-5-fluorouridine (5-DFUR) exerts a marked cytostatic activity, both intraperitoneally and orally, against experimental tumors. It has a strong antitumor effect on the Crocker sarcoma S 180, the Lewis lung carcinoma and a chemically induced squamous cell carcinoma of the skin. Its ratio of antitumor activity toxicity is more favourable than that of 5-fluorouracil, 2'-deoxy-5-fluorouridine and 1-(2-tetra-hydrofuryl)-5-fluorouracil. Mode of action and reasons for the favourable therapeutic ratio are discussed.