Mutations in the p53 tumor suppressor are found in many different neoplastic cells. PRIMA-1 restores sequence-specific DNA binding and transactivational activity to mutant p53 proteins at relatively high µM to mM concentrations. It is therefore a unique anti-oncogenic substance, working as a re-activator of the apoptotic function of mutant p53 via conformational modulation of function-specific epitopes. PRIMA-1 represents a novel lead compound which may be further modified to provide more potent therapeutic agents acting via the reactivation mechanism.