Evidence demonstrating that elevated expression of dUTPase protects breast cancer cells from the expansion of the intracellular uracil pool, translating to reduced growth inhibition following treatment with 5-FU is provided. The implementation of in silica drug development techniques to identify and develop small molecule inhibitors of dUTPase are reported. As 5-FU and the oral 5-FU pro-drug capecitabine remain central agents in the treatment of a variety of malignancies, the clinical utility of a small molecule inhibitor to dUTPase represents a viable strategy to improve the clinical efficacy of these mainstay chemotherapeutic agents.