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Argos Therapeutics Presents Positive Transplantation and Immunosuppression Data for Soluble CD83 at the Canadian Society of Transplantation Congress

Durham, NC- March 6, 2009 — Argos Therapeutics today announced the presentation of two abstracts on its soluble CD83 (sCD83) protein program at the 2009 Annual Scientific Conference of the Canadian Society of Transplantation, held March 5 - 8 in Banff, Alberta. The presentations, to be made on March 7 by Argos´ collaborating scientists from the University of Western Ontario, detail positive preclinical data for sCD83 in organ transplantation models, as well its ability to induce and maintain immune tolerance via its generation of tolerogenic dendritic cells (DC) and its direct suppressive effects on T cells and B cells.

The first abstract, titled “Modulation of Dendritic Cells by Soluble CD83 Induces Kidney Allograft Tolerance,” received a conference “Top-5 Basic Science” abstract award. According to the abstract, treatment with sCD83 in an animal model of kidney transplantation effectively prevented rejection and achieved long-term graft tolerance, significantly improved survival, and inhibited development of anti-donor antibodies when compared to untreated kidney graft recipients. Additionally, DCs from tolerant sCD83 recipients exhibited significantly decreased expression levels of MHC II, CD40, CD80 and intracellular IL-12, all of which are important to triggering an immune response. These data suggest that sCD83 is multifunctional, and may function via direct mechanisms involving B and T cells and indirectly through DC attenuation.

The second abstract is titled “Soluble CD83 Mediated Suppression of B-cell Activation and Differentiation Prolongs Murine Cardiac Allograft Survival.” In a heart transplantation animal model, allograft recipients treated with sCD83 exhibited markedly decreased intragraft B cell infiltration, reduced Immunoglobulins M and G deposition, and significantly lower circulating anti-donor antibody levels. Treatment with sCD83 alone was capable of controlling antibody-mediated rejection and prolonging survival of cardiac allografts by twofold when compared to untreated controls.

“These abstracts demonstrate that, as a monotherapy, sCD83 is capable of inducing kidney allograft tolerance via the generation of tolerogenic dendritic cells, and that sCD83-mediated B cell suppression contributes to delayed graft rejection,” said Dr. Hao Wang of the University of Western Ontario.

“These important characteristics, as well as sCD83´s human origin, suggest that the protein may hold significant promise as a therapy for transplantation rejection and other immune-mediated disorders,” added Charles Nicolette, Ph.D., Chief Scientific Officer and Vice President of Research and Development at Argos Therapeutics. “Argos is continuing its preclinical evaluations of sCD83 and looks forward to advancing the program toward clinical development.”

The first abstract was authored by: Zhu Lan, Wei Ge, Miren L. Baroja, Jacqueline Arp, Jifu Jiang, Weihua Liu, Stephen Brand, Charles Nicolette, Bertha Garcia and Hao Wang. The second abstract was authored by: Wei Ge, Siobhan I. Ramcharran, Jacqueline Arp, Miren L. Baroja, Zhu Lan, Jifu Jiang, Weihua Liu, Anthony Jevnikar, Stephen Brand, Charles Nicolette, Bertha Gardia and Hao Wang.

About Soluble CD83
CD83 is a glycoprotein expressed on the cell surface of mature dendritic cells (DCs), the most potent stimulators of immune responses. The strong up-regulation of this protein during DC maturation suggests that it plays an important functional role in the induction of immune responses. Experimental data demonstrate that soluble CD83 can potently down-regulate immune responses, indicating that it can be developed to treat transplantation rejection and variety of autoimmune disorders. Importantly, data from animal models demonstrate that soluble CD83 exerts its effects without a requirement for chronic administration and does not leave the subject globally immunosuppressed. The development of CD83 is part of Argosí research and development collaboration with its Canadian partner, DC Bio.

About Argos Therapeutics, Inc.
Argos is an immunotherapy company developing new treatments for cancer, infectious and autoimmune diseases, and transplantation rejection. The Company has generated multiple platform technologies and a diverse pipeline of products based on its expertise in the biology of dendritic cells — the master switch that turns the immune system on or off. www.argostherapeutics.com

Jennifer Greenleaf-Conrad
MacDougall Biomedical Communications
(781) 235-3060

Jeff Abbey
Argos Therapeutics
(919) 287-6308

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