Tumor Regression and Curability of Preclinical Neuroblastoma Models by PEGylated SN38 (EZN-2208), a Novel Topoisomerase I Inhibitor

• Published in: Clinical cancer research Vol. 16; no. 19; pp. 4809 - 4821
• Main Authors: PASTORINO, Fabio, LOI, Monica, SAPRA, Puja, BECHERINI, Pamela, CILLI, Michele, EMIONITE, Laura, RIBATTI, Domenico, GREENBERGER, Lee M, HORAK, Ivan D, PONZONI, Mirco
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Association for Cancer Research 01-10-2010
• Subjects: Animals; Antineoplastic agents; Antineoplastic Agents - pharmacology; Antineoplastic Agents - therapeutic use; Apoptosis - drug effects; Biological and medical sciences; Camptothecin - analogs & derivatives; Camptothecin - pharmacology; Camptothecin - therapeutic use; Cell Line, Tumor; Cell Proliferation - drug effects; Disease Models, Animal; DNA Topoisomerases, Type I - metabolism; Drug Screening Assays, Antitumor; Female; Humans; Medical sciences; Mice; Mice, Nude; Neoplasms, Experimental - drug therapy; Neoplasms, Experimental - pathology; Neovascularization, Pathologic - drug therapy; Neuroblastoma - drug therapy; Neuroblastoma - pathology; Neurology; Pharmacology. Drug treatments; Polyethylene Glycols - pharmacology; Polyethylene Glycols - therapeutic use; Survival Rate; Topoisomerase I Inhibitors - pharmacology; Topoisomerase I Inhibitors - therapeutic use; Tumors of the nervous system. Phacomatoses; Nervous system diseases; Preclinical trial; Regression; Models; Neuroblastoma; Malignant tumor; Autonomic neuropathy; Pegylated form; Topoisomerase I inhibitor; Cancer
• ISSN: 1078-0432; 1557-3265
• DOI: 10.1158/1078-0432.ccr-10-1354

Treatment of neuroblastoma is successful in less than half of patients with high-risk disease. The antitumor activity of a water soluble pegylated SN38 drug conjugate, EZN-2208, was compared with CPT-11 (a prodrug for SN38) in preclinical models of human neuroblastoma.
The in vitro cytotoxicity of EZN-2208 was tested by counting trypan blue dye- and Annexin V-positive cells, whereas its therapeutic efficacy was evaluated, in terms of survival, and antitumor and antiangiogenic activities, in s.c. luciferase-transfected, pseudometastatic, and orthotopic neuroblastoma animal models.
EZN-2208 was about 100-fold more potent than CPT-11 in vitro, by inducing apoptosis/necrosis and p53 expression and by reducing hypoxia-inducible factor (HIF)-1α/HIF-2α expression. EZN-2208 gave superior antitumor effects compared with CPT-11 in neuroblastoma xenografts. EZN-2208 treatment always resulted in lack of tumor detection at the end of trials whereas only small therapeutic effects were observed with CPT-11, as assessed by luciferase assay or tumor size, or even by staining histologic sections of tumors with antibodies recognizing neuroblastoma cells and cell proliferation. In a neuroblastoma model resistant to doxorubicin, cisplatin, vincristine, fenretinide, and topotecan, EZN-2208 induced 100% curability. It also blocked tumor relapse after topotecan-vincristine-doxorubicin combined treatment. Mechanistic experiments showed statistically significantly enhanced terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling and Histone H2ax staining as well as decreased vascular endothelial growth factor, CD31, matrix metalloproteinase (MMP)-2, and MMP-9 expression in tumors removed from EZN-2208-treated mice and radiating vessels invading the tumor implanted onto the chorioallantoic membranes.
EZN-2208 should be considered a most promising novel antineuroblastoma agent. An ongoing phase I study in pediatric patients should identify the optimal dose for a phase II study.