PEG-conjugate zinc protoporphyrin

Examples of agents used include PEG-DAO [33] and PEG-conjugated zinc protoporphyrin IX (PEG-ZnPP), an inhibitor of HO-1 [34-36]. These polymeric dugs achieved tumor-targeted delivery on the basis of the EPR-effect. Thus, both generation of ROS selectively in tiunor tissue and inhibition of the enzyme HO-1 via PEG-ZnPP would result in a marked increase in both ROS and oxystress at the tumor site, and so these agents have marked antitumor effects. 

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