OncoSec announced positive preliminary results from a Phase II multicenter trial investigating the use of ImmunoPulse in Merkel cell carcinoma (MCC) patients at the 27th Annual Meeting of the Society for Immunotherapy of Cancer (SITC 2012). The data suggest that ImmunoPulse, which locally delivers a DNA-based cytokine coded for the immune stimulating agent interleukin-12 (DNA IL-12) via electroporation, may elicit increased levels of IL-12 in the tumor microenvironment, which has the potential to result in a systemic immune response in treating aggressive cancers like MCC without serious adverse safety events.
The preliminary results were published in the Journal of Immunotherapy (35(9):721-791, November-December 2012) and will be presented in a poster titled “Intratumoral delivery of Interleukin-12 DNA with in vivo electroporation can lead to regression of injected and non-injected tumors in Merkel cell carcinoma: Results of a phase II study.” Dr. Shailender Bhatia, principal investigator and assistant professor at the University of Washington School of Medicine, is lead author and will be presenting the data.
This open-label study is evaluating the ability of ImmunoPulse to increase levels of IL-12 in the tumor microenvironment, in addition to the efficacy and safety of this treatment for patients with MCC. Preliminary results of this study have demonstrated that 100 percent (3/3) of subjects treated with at least one cycle of ImmunoPulse showed an increased level of IL-12 expression in tumor biopsy done three weeks post-treatment as compared to pre-treatment biopsy. Correlative analysis of limited samples demonstrated that at least one subject had increased CD8+ T-cells (also referred to as killer T-cells) in the tumors. Correlative studies of patient samples are ongoing.
Of the first five subjects enrolled, the overall response rate is 20% (1/5). One patient with baseline progressive MCC, despite multiple prior therapies (systemic chemotherapy, surgery, RT, IT interferon) has had a confirmed partial response (greater than 70 percent regression) that persisted for approximately eight months. The regression of injected as well as non-injected tumors, along with no new tumors over six months, suggest successful induction of systemic immune response from local intratumoral immunotherapy in this patient. This subject remains in the study and will receive a third treatment cycle.
Dr. Bhatia commented, “These preliminary results are encouraging, and we are looking forward to continuing our study of ImmunoPulse. We are pleased to see that a patient with progressive MCC, despite failing multiple other therapies, had a confirmed partial response with regression of even distant non-injected tumors. This creative immunotherapy approach to deliver DNA IL-12 directly into the tumors appears to be tolerated well and so far without any systemic side-effects.”
All five subjects treated at the time of this preliminary analysis had distant metastatic disease, and were eligible to receive up to two treatment cycles. Two subjects have withdrawn from the study with progressive disease, and only received one cycle of treatment. Three subjects completed the study and received both treatment cycles. To date, the treatment has been safe and well-tolerated, with treatment-related adverse events including transient grade 1 pain (n=5) and grade 1 injection site reaction (n=1) without any systemic or residual toxicity.
Punit Dhillon, President and CEO of OncoSec Medical, added, “These subset data are positive and validate the results seen in our previous clinical trial. Thus far studies have shown that the administration of IL-12 using electroporation safely results in efficient transfection of the agent and a marked increase in production of the IL-12 protein inside the tumor. These results represent the first human data for a gene therapy using in vivo electroporation in MCC patients, and is a positive step towards advancement of this program.”