title: Plasmin-activated doxorubicin prodrugs containing a spacer reduce tumor growth and angiogenesis without systemic toxicity.
abstract: To generate doxorubicin (Dox) specifically at the tumor site, the chemotherapeutic agent was incorporated into a prodrug by linkage to a peptide specifically recognized by plasmin, which is overproduced in many cancers. ST-9905, which contains an elongated self-elimination spacer, is activated more rapidly in vitro by plasmin than is ST-9802. Prodrug activation in vitro depended on the level of urokinase produced by tumor cells and was inhibited by aprotinin, a plasmin inhibitor. Comparison of equimolar concentrations of ST-9905, ST-9802, and Dox in EF43.fgf-4 and MCF7 models revealed that both prodrugs, in sharp contrast to Dox, displayed antiproliferative and antiangiogenic activities without discernible toxicity. Although MCF7 cells are poor urokinase producers in vitro, prodrug efficacy in this model may be explained by production of plasmin by tumor-infiltrating host cells. Mice treated with equitoxic concentrations (maximum tolerated doses) of prodrugs showed 100% survival and negligible body weight loss, in contrast to results after Dox treatment. ST-9905 was substantially more effective than ST-9802 and induced similar tumor growth inhibition as Dox but without apparent toxicity. This finding may be explained by the elongated spacer, which facilitates enzymatic prodrug activation. These data validate both the use of elongated spacers in vivo and the concept of targeting anticancer prodrugs to tumor-associated plasmin.
authors.affiliation: Laboratory of Tumor and Developmental Biology, University of Liège, Tour de Pathologie (B23), Sart-Tilman, B-4000 Liège, Belgium.
authors.forename: Laetitia
authors.initials: L
authors.lastname: Devy
authors.forename: Franciscus M H
authors.initials: FM
authors.lastname: de Groot
authors.forename: Silvia
authors.initials: S
authors.lastname: Blacher
authors.forename: Amin
authors.initials: A
authors.lastname: Hajitou
authors.forename: Patrick H
authors.initials: PH
authors.lastname: Beusker
authors.forename: Hans W
authors.initials: HW
authors.lastname: Scheeren
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Foidart
authors.forename: Agnès
authors.initials: A
authors.lastname: Noël
mesh_terms: D000230:Adenocarcinoma / Q000098:blood supply / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D000818:Animals; D001711:Biotransformation; D001835:Body Weight / Q000187:drug effects; D001943:Breast Neoplasms / Q000098:blood supply / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology; D045744:Cell Line, Tumor / Q000637:transplantation; D004317:Doxorubicin / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology* / Q000627:therapeutic use / Q000633:toxicity; D005260:Female; D005341:Fibrinolysin / Q000494:pharmacology*; D006801:Humans; D008325:Mammary Neoplasms, Experimental / Q000098:blood supply / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D020714:Maximum Tolerated Dose; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D015394:Molecular Structure; D009363:Neoplasm Proteins / Q000378:metabolism; D009389:Neovascularization, Pathologic / Q000188:drug therapy*; D011355:Prodrugs / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology* / Q000627:therapeutic use / Q000633:toxicity; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
chemical_list: D009363:Neoplasm Proteins; D011355:Prodrugs; C485985:ST 9802; C485986:ST 9905; D004317:Doxorubicin; D005341:Fibrinolysin; D014568:Urokinase-Type Plasminogen Activator