An orally bioavailable inhibitor of inosine 5'- monophosphate dehydrogenase (IMPDH), with potential antineoplastic activity. Upon administration, IMPDH inhibitor FF-10501-01 competitively inhibits the enzyme IMPDH, thereby preventing the conversion of inosine monophosphate to xanthosine monophosphate. This inhibits the synthesis of guanine nucleotides, deprives cancer cells of guanosine triphosphate (GTP), disrupts DNA and RNA synthesis, and decreases tumor cell proliferation. Tumor cells are highly susceptible to IMPDH inhibition because they are rapidly dividing cells that are dependent on rapid DNA synthesis, which requires a high concentration of nucleotides. IMPDH, an enzyme that catalyzes the rate-limiting step in the synthesis of guanosine triphosphate (GTP), is overexpressed in numerous tumor cell types.