roxyureas are disclosed in, e.g., U.S. Pat. No. 5,066,658, wherein R2 and R3 together with the adjacent nitrogen form: [0069] wherein m is 1 or 2, n is 0-2 and Y is an alkyl group. [0070] In one aspect, the hydroxyurea has the structure: [0071] These compounds are thought to function by inhibiting DNA synthesis.