The Immune Response Corporation Announces
Preclinical Results for A Genetically Engineered Cancer
Vaccine
Membrane-Bound GM-CSF Tumor Cell Vaccine Protects Against Aggressive Melanoma
CARLSBAD, Calif., Feb. 22 /PRNewswire/ -- The Immune Response Corporation (Nasdaq: IMNR - news) announced today
that a new patented gene therapy approach for a possible cancer vaccine, which uses tumor cells genetically modified to express a
membrane form of the cytokine GM-CSF (Granulocyte-Macrophage Colony-Stimulating Factor) on the cell surface, appears to
protect against an aggressive form of melanoma (skin cancer) in animal models. The results were recently reported at the
Keystone Symposia on Cellular Immunity and Immunotherapy of Cancer in Santa Fe, New Mexico, by Dr. Soonpin Yei, Scientific
Investigator.
GM-CSF is a naturally occurring protein that helps orchestrate immune responses and has been shown in preclinical and clinical
studies to boost the immune system's ability to recognize and destroy tumor cells.
''Results suggest that tumor cell-based vaccines engineered to express mbGM-CSF on their surface, rather than secrete the
cytokine, may represent a promising approach to stimulating the immune system against this aggressive form of melanoma,'' said
Dr. Richard M. Bartholomew, Executive Director of Research Operations at The Immune Response Corporation. ''The data also
indicate that long lasting protective immunity may result from this form of mbGM-CSF tumor cell vaccine.''
''Previous results of this technology showed that the mbGM-CSF cancer vaccine could effectively lead to rejection of established
tumor,'' said Dr. Bartholomew. ''We have extended these studies to the much more aggressive B16 melanoma animal model and
have shown that the mbGM-CSF tumor cell vaccine appears to induce protective immunity to challenge with viable melanoma
tumor cells.''
The study reported at the symposia involved three experimental groups of mice, which were challenged with viable tumor cells
after having been immunized with either (1) inactivated tumor cells lacking mbGM-CSF (n=10), (2) inactivated tumor cells
genetically modified to express mbGM-CSF on the cell surface (n=10), or (3) inactivated tumor cells engineered to secrete
GM-CSF (rather than express it on the cell surface) (n=10). Nine out of 10 animals in the first group grew large tumors and died
from their disease by day 43 after tumor challenge. In contrast, the second group of animals, which was administered the tumor
cell vaccine genetically engineered to express GM-CSF on the cell surface, had much smaller tumors, and 70% of these animals
were still alive at day 43. Furthermore, surviving animals were also protected against a second tumor challenge after 5 months.
Finally, over 80% of the mice in the third group vaccinated with cancer cells engineered to secrete GM- CSF were dead at day
43.
''Currently, we are evaluating the efficacy of combining mbGM-CSF technology with a second patented technology for cancer
vaccines, which utilizes fibroblasts (skin cells) genetically engineered to secrete another cytokine, interleukin-2 (IL-2),'' said Dennis
J. Carlo, Ph.D., President and CEO. ''In collaboration with Sidney Kimmel Cancer Center, we have shown that our investigational
IL-2 colon cancer vaccine appears to induce immunity in colon cancer patients. We believe that combining the two vaccine
approaches may yield an even more effective vaccine capable of inducing strong immune responses to the patients' tumors.''
Based on these preclinical results, the Company plans to test the mbGM-CSF technology as part of its ongoing clinical vaccine
program in development for colon, glioma, melanoma and prostate cancers.
Results of mbGM-CSF tumor cell technology were first published last year in the Journal of Immunology (Soo Hoo, et al., 1999,
Volume 162, pages 7343-7349). The Company was also issued U.S. Patent Number 5,891,432 covering the technology in April
1999.
GM-CSF background
GM-CSF enhances the ability of the immune system to recognize molecules called antigens found on the surface of the tumor cells
contained in the vaccine. The immune system can only recognize these tumor-associated antigens when they are bound to
specialized cells called ''antigen presenters.'' GM-CSF most likely stimulates the immune system by augmenting the interaction
between tumor-associated antigens found in the vaccine and professional antigen presenting cells, notably dendritic cells at the site
of injection.
The Immune Response Corporation is a biopharmaceutical company based in Carlsbad, California, developing immune-based
therapies to induce specific T-cell responses for the treatment of HIV and autoimmune diseases. In addition, the Company is
working on cancer vaccines and gene therapy.http://biz.yahoo.com/prnews/000222/ca_immune__1.html |
