Di-substituted phthalazines of structural formula depicted herein and pharmaceutically acceptable salts thereof are disclosed, wherein R1 is hydrogen, fluoro, cyano, trifluoromethyl, methoxy, or trifluoromethoxy； R2 is hydrogen or methyl； and R3, R4, R5, R6 and R7 are independently hydrogen, chloro, fluoro, cyano, trifluoromethyl or trifluoromethoxy, provided that at least two of R3, R4, R5, R6 and R7 are hydrogen. These compounds are useful as hedgehog antagonists and are suitable for treating cancer selected from the group consisting medulloblastoma, basal cell carcinoma, esophagus cancer, gastric cancer, pancreatic cancer, biliary tract cancer, prostate cancer, breast cancer, small-cell lung cancer, non-small cell lung cancer, B-cell lymphoma, multiple myeloma, ovarian cancer, colorectal cancer, liver cancer, kidney cancer, and melanoma.
