XR3054 is a novel inhibitor of farnesyl protein transferase (FPTase). XR3054 inhibited the proliferation of the prostatic cancer cell lines LnCAP and PC3 and the colon carcinoma SW480 and HT1080 (IC50 values of 12.4, 12.2, 21.4 and 8.8 microM, respectively) but was relatively inactive when tested against a panel of breast carcinoma cell lines. The activity did not relate to the presence of mutant or wild-type ras in the cell lines tested. In conclusion XR3054 inhibits ras farnesylation, MAP kinase activation and anchorage-independent growth in NIH 3T3 transformed with v12 H-ras. Since the antiproliferative effect of the compound is not related to the ras phenotype, XR3054 may also have effects on other cell signaling mechanisms.