Anti-cancer compounds

A compound of general formula I:

• wherein
• one of X1 and X2 is S, and the other of X1 and X2 is N;
• Z is NH, NHCO, NHSO2, NHCH2, CH2, CH2CH2, or CH═CH;
• R1, R2, and R3 are independently H, alkyl, aryl, aralkyl, heterocycle, halogen, NO2, CN, OH, alkoxy, aryloxy, NH2, NH—R′, N—(R′)(R″), NH—COR′, NH-aryl, N-(aryl)2, COOH, COO—R′, COO-aryl, CONH2, CONH—R′, CON—(R′)(R″), CONH-aryl, CON-(aryl)2, SO3H, SO2NH2, CF3, CO—R′, or CO-aryl, wherein alkyl, aryl, aralkyl, heterocycle and NH-aryl groups may be further substituted with one or more groups selected from halogen, NO2, CN, OH, O-methyl, NH2, COOH, CONH2 and CF3;
• at least one of the groups R1 and R2 being other than H when either X1 or X2 is S;
• R4, R5, R6, R7, and R8 are independently from each other H, substituted or unsubstituted lower alkyl, halogen, amino, carbamoyl, sulfamyl, NO2, CN, OH, substituted or unsubstituted alkoxy, NH2, NH—R′, alkyl-aryl, alkyl-heteroaryl, NH(C═NH)NH2, N(R′)3+, N—(R′)(R″), COOH, COO—R′, CONH2, CONH—R′, CON—(R′) (R″), SO3H, SO2NH2, CF3 or (CH2)nO(CH2)mNR′R″, (CH2)nCO2(CH2)mOR′″ wherein n is 0, 1, 2 or 3 and m is 1, 2 or 3;
• wherein R′, R″ and R′″ are each independently alkyl groups that may be the same or different;
• and pharmaceutically acceptable salts thereof.