Evaluation of Toxicity following Electrically Mediated Interleukin-12 Gene Delivery in a B16 Mouse Melanoma Model

Abstract

Purpose: Interleukin-12 (IL-12) has potential as an immunotherapeutic agent for the treatment of cancer but is unfortunately associated with toxicity. Delivery of a plasmid encoding IL-12 with electroporation induces an antitumor effect in the B16 mouse melanoma model without serious side effects. To translate this observation to the clinic, an evaluation of toxicity was done in the mouse model. Experimental Design: Weight change, tumor response, blood chemistry and hematology values, and serum IL-12 levels were evaluated. Multiple tissues were analyzed histopathologically. Results: A pronounced reduction in tumor volume, including a large percentage of complete regressions, was observed after electrically mediated gene therapy. No significant increases in serum IL-12 levels were detected. Tumor-bearing mice showed an increased number of atypical hematology values when compared with normal naive controls. Statistically significant differences in chemistry and hematology values were observed sporadically in most of the standard chemistry and hematology categories in all groups. The only histopathologic abnormality specific to the animals receiving both plasmid and electroporation was inflammation associated with the kidney at the last time point. Conclusions: In general, mice that received both plasmid and electroporation showed the least abnormal histopathologic findings and were found to be in the best health, reflecting the reduced burden of disease. No significant toxic effects due to the IL-12 gene therapy were observed.

Local and systemic antitumor effect of intratumoral and peritumoral IL-12 electrogene therapy on murine sarcoma

“…For example, in melanoma, no significant systemic cytokine levels could be detected, 24,25 even after multiple consecutive plasmid applications. 28 On the other hand, systemic expression of IL-12 similar to ours was achieved in different carcinomas, 32,34 but only after multiple applications of gene therapy. One of the possible reasons for such high local and systemic transgene expression, as well as the better antitumor effect achieved in our study, is the difference in electroporation protocols which were used for transfection of tumor nodules.…”

“…EGT, using a plasmid encoding IL-12, has already been utilized in a number of different tumor models both at the preclinical level [19][20][21] and in clinical trials. 22 Tumor models which favorably responded to IL-12 EGT were melanoma, [23][24][25][26][27][28] lymphoma 27 and a variety of different carcinomas. approximately 20% increase in body weight, compared to day 0, and they all were in very good general condition.…”

Melanoma Treatment with Intratumoral Electroporation of Tavokinogene Telseplasmid (pIL-12, Tavokinogene Telseplasmid)

“…Electroporation of pIL-12 DNA has been demonstrated to yield high levels of IL-12 expression [41] leading to IFN-γ-mediated tumor cell killing [42,43], immune cell recruitment [41] and objective tumor regressions in animal models [43][44][45] including regression of untreated lesions [46]. In vivo tumor regressions have been durable and treated animals may be resistant to tumor reimplantation suggesting that intratumoral electroporation of pIL-12 DNA induces memory immune responses in these models [47,48].…”

“…In the current study protocols, patients receive a series of treatment cycles of IT-tavo-EP at 6-week intervals. Each cycle consists of three administrations, one on each Day 1, 5 and 8, at a dose volume of approximately one quarter the calculated lesion volume at a plasmid concentration of 0.5 mg/ml [45,57,58].…”

“…In order to move the approach to clinical testing, a preclinical toxicity study was performed [45]. Tumors were established in the left flank of C57Bl/6 mice and divided into control and treated groups.…”