Abstract B091: Demonstration of systemic antitumor immunity via intratumoral regulated expression of IL-12 as a gene therapy approach to treatment of cancer
Authors: Barrett John A. , Chan Tim , Cai Hongliang , Miao John , Krishnan Suma , Lebel Francois 
Published: May 2016

Immunotherapy is an attractive approach for cancer therapy. We have developed a replication-incompetent adenovirus engineered to express IL-12 (Ad-RTS-IL-12), via our RheoSwitch Therapeutic System® (RTS®) gene switch, injected directly into a tumor. IL-12 expression is “off” devoid of the activator ligand, veledimex, while IL-12 production is turned “on” (in a dose-dependent manner) by oral administration of veledimex.

Veledimex had good bioavailability in mice (&gt; 53%) following oral administration with apparent terminal half-life of 6-8 hours. In normal mice with intact blood brain barrier (BBB), dose-related increases in veledimex exposure were exhibited in brain tissue with approximately 1% plasma exposure in cerebral spinal fluid, which thereby demonstrated that veledimex crossed the BBB in mice. Mechanistic studies in numerous syngeneic mouse tumor models with Ad-RTS-mIL-12+veledimex have demonstrated a dose-related increase in tumor IL-12 mRNA and IL-12 protein expression. Discontinuation of veledimex resulted in a return to baseline IL-12 mRNA and protein expression. The ability to treat tumors at different physical locations derived from the same tumor lineage was studied in melanoma, colon cancer and glioma syngeneic mouse models. In a B16 mouse melanoma model, 1e6 melanoma cells were placed in both flanks. When the tumors reached 100mm3 one tumor was administered Ad-RTS-mIL-12 (1e10vp) + veledimex administered at ~675mg/m2/day ad lib in the chow). The results of this study showed &gt; 90% tumor growth reduction in both the treated and untreated tumors when compared to control. In the second study, 1e6 CT26-LUC colon cancer cells were placed in the right flank with tumor growth monitored using bioluminescence imaging. On Day 15 Ad-RTS-mIL-12 (1e10vp) was administered intratumorally + veledimex at ~675mg/m2/day ad lib in the chow. On Day 43, 60% were tumor free and remaining mice had smaller tumors. When these mice were rechallenged with CT26-LUC cells in the contralateral flank no tumor growth was observed versus age matched controls for &gt; 21days (end of study). In the glioma study, 1e5 GL-261 cells were implanted in the brain and 5 days later mice were treated with a single cycle of Ad-RTS-mIL-12 (1e10vp) administered intratumoral + veledimex 450mg/m2/day, po. QDx14. Vehicle cohorts all succumbed to the disease by Day 30. The 12 surviving animals from the treatment group on Day 100 were reinoculated with 1e5 GL-261 cells at the same site and survival monitored for an additional 80 days vs. age matched controls. We found &gt;95% of the pretreated animals survived for an additional 80 days (end of study) vs. ~40% of the control animals. Similar results have been observed in patients with metastatic melanoma and breast cancer where nontreated lesions were also observed to decrease in size

In summary, these results demonstrate this novel regulated immunotherapeutic approach may be an effective form of therapy for both primary and metastatic tumors with the same tumor lineage in melanoma, colon cancer and glioma. Further studies are planned in other tumor populations.

Citation Format: John A. Barrett, Tim Chan, Hongliang Cai, John Miao, Suma Krishnan, Francois Lebel. Demonstration of systemic antitumor immunity via intratumoral regulated expression of IL-12 as a gene therapy approach to treatment of cancer. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr B091.