The invention provides novel prodrug compounds comprising a kinase inhibitor and a reductively-activated fragmenting aromatic nitroheterocycle or aromatic nitrocarbocycle trigger, where the compound carries a positive charge. In preferred embodiments, the compounds are of Formula I: where: X is any negatively charged counterion; R1 is a group of the formula —(CH2)nTr, where Tr is an aromatic nitroheterocycle or aromatic nitrocarbocycle and —(CH2)nTr acts as a reductively-activated fragmenting trigger; and n is an integer from 0 to 6; R2, R3 and R4 may each independently be selected from aliphatic or aromatic groups of a tertiary amine kinase inhibitor (R2)(R3)(R4)N, or two of R2, R3, and R4 may form an aliphatic or aromatic heterocyclic amine ring of a kinase inhibitor, or one of R2, R3 and R4 may be absent and two of R2, R3 and R4 form an aromatic heterocyclic amine ring of a kinase inhibitor. The compounds of the invention are useful in treating proliferative diseases such as cancer.