A medicament for enhancing an effect of a cancer therapy based on a mode of action of DNA injury, which comprises as an active ingredient a compound represented by the general formula (I) or a physiologically acceptable salt thereof: ##STR00001## wherein R represents an aryl-substituted alkyl group, an heteroaryl-substituted alkyl group, a cycloalkyl-substituted alkyl group, or a cyclic hydrocarbon group wherein said cyclic hydrocarbon group may be saturated, partly saturated, or aromatic; or Z may bind to R to form a cyclic structure, Z represents a hydrogen atom or a C.sub.1 to C.sub.6 alkyl group. The medicament enhanced the effect of the cancer therapy and decreases a dose of an anticancer agent and/or radiation, and therefore, can reduce side effects resulting from the cancer therapy.
