The Immune Response Corporation Announces Investigational Vaccine Appears To Be Protective Against Tumor Development and Inhibits Spread of Pre-Existing Tumors in Animal Models
Scientists From The Immune Response Corporation Report Preclinical Data on Patented mbGM-CSF Vaccine at Keystone Symposium
CARLSBAD, Calif., March 5 /PRNewswire/ -- The Immune Response Corporation (Nasdaq: IMNR - news) announced today that its novel mbGM-CSF vaccine appears to protect against the development of melanoma (skin cancer) and colorectal cancers, and potentially inhibit metastases (spread) of pre-existing tumors in mouse models. Membrane Bound Granulocyte Macrophage-Colony Stimulating Factor (mbGM-CSF) is the Company's patented version of the protein GM-CSF, which assists the immune system in recognizing cancerous cells. Preclinical data were presented by Company scientists at the Keystone Symposium on Cancer Intervention in Durango, Colorado, on March 2, 2001.
``We have engineered a novel gene for GM-CSF into mouse tumor cells such that they express a membrane form of this cytokine as an integral cell surface component,'' said Soonpin Yei, Ph.D., Senior Scientific Investigator at The Immune Response Corporation. ``These patented mbGM-CSF tumor vaccines appear to provide effective anti-cancer benefits when given both as a preventive measure and as a treatment for already established tumors.''
To test the capacity of the mbGM-CSF vaccine to prevent tumor development, groups of healthy mice (10 animals per group) were first vaccinated with either inactivated melanoma cells, the mbGM-CSF vaccine, or buffer control. The mbGM-CSF vaccine consisted of inactivated melanoma cells that were engineered to express the additional component mbGM-CSF, a molecule intended to boost the immune response to the vaccine. Five days after the two-week period of immunization, all three groups of mice were ``challenged'' with active melanoma cells from B16.F10, a virulent strain of melanoma.
Within 43 days of the melanoma cell challenge, all 10 animals in the buffer control group were dead, as were 7 of 10 animals from the group receiving the inactivated melanoma cells without mbGM-CSF. In contrast, 6 of 10 mbGM-CSF vaccinated animals remained alive, and three of these animals showed no evidence of tumor. These tumor-free survivors were re-challenged with live B16 tumor cells, and retained the ability to resist tumor growth for at least an additional five months.
In order to test for potential therapeutic benefits of the mbGM-CSF vaccine, mice with pre-existing B16.F10 tumors were established by inoculating with active melanoma cancer cells. The mice were then divided into two groups (10 animals per group) and treated with weekly intradermal injections of either inactivated melanoma cells or the mbGM-CSF vaccine. All of the animals that received the vaccine without mbGM-CSF were dead within 27 days. In contrast, 100% of the mbGM-CSF vaccinated animals were still alive. Additionally, the animals that died had large tumors and intensive lung metastases, while the mbGM-CSF vaccinated mice had significantly smaller tumors than the control group and presented no evidence of lung metastases, even when evaluated histologically.
Dr. Yei also reported on similar data regarding the potential preventive and therapeutic use of the mbGM-CSF vaccine obtained in experiments utilizing the CT26 (colorectal cancer) animal model. |
