Disclosed is a compound represented by the Structural Formula (I): Y is a covalent bond, a phenylene group or a substituted or unsubstituted straight chained hydrocarbyl group. In addition, Y, taken together with both >C=Z groups to which it is bonded, is a substituted or unsubstituted aromatic group. Preferably, Y is a covalent bond or —C(R7R8)—. R1 and R2 are independently an aryl group or a substituted aryl group, R3 and R4 are independently —H, an aliphatic group, a substituted aliphatic group, an aryl group or a substituted aryl group. R5-R6 are independently —H, an aliphatic group, a substituted aliphatic group, an aryl group or a substituted aryl group. R7 and R8 are each independently —H, an aliphatic or substituted aliphatic group, or R7 is —H and R8 is a substituted or unsubstituted aryl group, or, R7 and R8, taken together, are a C2-C6 substituted or unsubstituted alkylene group. Z is ═O or ═S. Also disclosed are pharmaceutical compositions comprising the compound of the present invention and a pharmaceutically acceptable carrier or diluent.Also disclosed is a method of treating a subject with cancer by administering to the subject a compound of Structural Formula (I) in combination with Paclitaxel or an analog of Paclitaxel.