TNOX Tanox (MM)

Tanox's Novel HIV Entry Inhibitor Exhibits Synergy with Enfuvirtide to Inhibit HIV HOUSTON, May 31 /PRNewswire-FirstCall/ -- Results from a study of Tanox's (NASDAQ:TNOX) viral-entry inhibitor antibody, TNX-355, demonstrate the investigational agent's synergy with the only currently approved viral-entry inhibitor, enfuvirtide. (Logo: http://www.newscom.com/cgi-bin/prnh/20050207/TNOXLOGO ) Synergistic antiviral activity between the two agents was demonstrated against both laboratory and clinical strains of HIV-1 using conventional in vitro techniques. The research demonstrates TNX-355's ability to act synergistically with another drug targeting an early step in the entry cascade and supports the strategy of combining therapies directed at sequential steps of the viral-entry process. Agents are defined as synergistic when the activity seen in combination is greater than the sum of the activity of the agents seen individually. The study is published in the June issue (Vol. 50, No. 6) of Antimicrobial Agents and Chemotherapy. "While the strategy of using dual viral-entry inhibitors in treatment regimens must be tested in the clinical setting, these data do suggest that such a strategy could be quite effective," said Dr. Robert T. Schooley, professor of Medicine and head of the Division of Infectious Diseases at the University of California, San Diego and lead investigator of the study. This in vitro activity supports the potential for using TNX-355 and enfuvirtide together in the clinical setting and indicates that co- administration of TNX-355 and enfuvirtide may enhance the activity of both agents. About TNX-355 TNX-355 is a humanized monoclonal antibody and part of an emerging class of HIV therapies known as viral-entry inhibitors. TNX-355, which is administered intravenously, is distinct from other entry inhibitors in that it binds to CD4 receptors, the primary target of HIV infection. Since TNX-355 blocks HIV entry at a step prior to the co-receptor interaction, the drug candidate is "co-receptor tropism independent," with the ability to block both CCR5- and CXCR4-tropic viruses. The blockade presented by TNX-355 also does not depend on targeting a mutation-prone viral protein. Results from a Phase 2 clinical trial of the drug demonstrated that TNX-355 - in combination with an optimized background regimen (OBR) of antiretroviral agents - produced statistically significant and clinically meaningful decreases in viral load in HIV-infected patients, when compared to OBR alone. About Tanox, Inc. Tanox is a biotechnology company specializing in the discovery and development of monoclonal antibodies. The company develops innovative biotherapeutics for the treatment of immune-mediated diseases, inflammation, infectious disease and cancer. Tanox's first-approved drug, Xolair(R) (omalizumab), is the first antibody approved to treat moderate-to-severe confirmed allergic asthma. Xolair was developed in collaboration with Genentech, Inc. and Novartis Pharma AG and is approved for marketing in the United States, Canada and major European countries. Tanox is based in Houston and has a manufacturing facility in San Diego. Additional corporate information is available at http://www.tanox.com/. This news release contains forward-looking statements regarding the potential for TNX-355 as a treatment for HIV-1-infected patients. These statements are based on Tanox's current beliefs and expectations, and are subject to risks and uncertainties that could cause actual results to differ materially. In vitro synergistic activity between two agents does not provide assurance that the compounds would produce a synergistic effect, or any antiviral effect, in combination therapy in patients. For more detailed information on the risks and uncertainties associated with Tanox's drug development and other activities, see Tanox's periodic reports filed with the Securities and Exchange Commission. http://www.newscom.com/cgi-bin/prnh/20050207/TNOXLOGO DATASOURCE: Tanox, Inc. CONTACT: Steve Sievert of Tanox, Inc., +1-713-578-4211 or Web site: http://www.tanox.com/

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