Adenoviral-mediated delivery of a mutated form of IL-13 (IL13.E13.K) fused to Pseudomonas exotoxin A exerts increased efficacy and reduced toxicity when compared to Cintredekin Besudotox in intracranial human glioma xenografts.

AACR Annual Meeting-- Apr 12-16, 2008; San Diego, CA 1349 Attempts to target IL13α2R, that is overexpressed in human Glioblastoma (GBM) have used native human IL-13 fused to Pseudomonas exotoxin A (PE), (hIL-13-PE38QQR, Cintredekin Besudotox), administered intratumorally to human patients as a protein formulation ( J Clin Oncol 2007 25: 837-844 ). However, hIL-13-PE38QQR binds not only to the GBM-associated IL13α2R, but also to the physiological IL-13/IL-4R expressed in the normal brain. Also, this protein has a very short half life, requiring frequent administration. Thus, we constructed an adenoviral vector (Ad) expressing a mutant IL13 (IL13.E13K) fused to PE (muIL-13-PE), which binds to GBM-associated IL13α2R with high affinity and has negligible binding for the physiological IL13/IL4R ( Nat Biotechnol. 1998 16(5):449-453 ) and studied whether this approach would result in increased survival and reduced toxicity when compared to hIL-13-PE38QQR. We constructed the therapeutic Ad-muIL4-TRE-muIL13-PE that expresses the cytotoxin muIL-13-PE, and, as an extra safety feature, a mutated IL-4 (IL4.Y124D, muIL-4) that blocks the binding of IL13 to the physiological IL13/IL4R ( Int J Oncol. 1999 15(3): 481-486 ). To compare the efficacy of Ad-muIL4-TRE-muIL13-PE+Ad-TetON (4x107 pfu) and hIL-13-PE38QQR (1 µg), we administered them intratumorally into intracranial human U251 GBM xenografts in nude mice. Ad-muIL4-TRE-muIL13-PE significantly increased the survival of tumor-bearing mice when compared to saline-treated mice, leading to 80% survival for over 100 days. Although hIL-13-PE38QQR improved the survival of tumor-bearing mice when compared with saline-treated mice, all the hIL-13-PE38QQR-treated mice succumbed due to tumor burden by day 55. Then we administered Ad-muIL4-TRE-muIL13-PE+Ad-TetON and hIL-13-PE38QQR in the striatum of naive Balb/c mice and studied their toxicity profile. While Ad-muIL4-TRE-muIL13-PE+Ad-TetON-injected mice did not show systemic or local side effects, hIL-13-PE38QQR resulted in profuse infiltration of inflammatory cells, reduction in TH expression in the striatum, and local hemorrhages. These neuropathological side effects were also observed when we administered reduced doses of hIL-13-PE38QQR (0.5-0.2 µg). These results suggest that adenoviral delivery of muIL13-PE toxin to glioblastomas will lead to strong antitumoral effect with not adverse consequences to the surrounding non-neoplastic brain. Supported by NIH/NINDS R01 NS44556.01, R21-NSO54143.01; UO1 NS052465.01; RO3 [TW006273][1]-01 to M.G.C.; RO1 NS 054193.01; RO1 NS 42893.01; U54 [NS045309][2]-01, and R21 [NS047298][3]-01 to P.R.L; F32 NS058156.01 to M.C. [1]: /lookup/external-ref?link_type=GEN&access_num=TW006273&atom=%2Fcanres%2F68%2F9_Supplement%2F1349.atom [2]: /lookup/external-ref?link_type=GEN&access_num=NS045309&atom=%2Fcanres%2F68%2F9_Supplement%2F1349.atom [3]: /lookup/external-ref?link_type=GEN&access_num=NS047298&atom=%2Fcanres%2F68%2F9_Supplement%2F1349.atom