Tanox Inc. presented data on its lead HIV drug candidate, TNX-355, at the American Society for Microbiology's Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC). The presentation highlighted the compound's unique ability to inhibit entry of HIV-1 into healthy CD4-positive cells regardless of the virus' co-receptor tropism.

According to a company release, TNX-355 is a humanised viral-entry inhibitor monoclonal antibody that coats CD4-positive cells, the primary target of HIV infection. By blocking viral entry into the CD4 cell in this manner, TNX-355 creates a unique new hurdle for HIV, different from entry inhibitors that target viral proteins or chemokine co-receptors. Study results show that TNX-355 is equally active in vitro against virus strains that exhibit tropism for CCR5 as well as CXCR4 - making TNX-355 the most advanced entry inhibitor in development with this crucial property of tropism independence.

"TNX-355 shows significant antiviral activity and could be a powerful new advancement in the treatment of HIV. These new data confirm that unlike other viral-entry inhibitors that target cellular proteins, TNX-355 is equally effective against viruses regardless of tropism. This is extremely important, as a significant proportion of treatment-experienced patients harbour mixed virus or dual-tropic virus," said Dr. Stanley Lewis, Tanox medical director.

Week 24 results of the phase 2 clinical trial demonstrated that, when compared with an optimised background regimen (OBR) alone, TNX-355 in combination with OBR reduces viral loads in HIV-infected patients, without suppressing their immune systems or causing significant side effects.

Tanox's ICAAC abstract also reported results of testing TNX-355 with another entry inhibitor, enfuvirtide. Synergy between the two agents was demonstrated by conventional in vitro techniques. These data support the use of TNX-355 and enfuvirtide together in the clinical setting. Because HIV must be treated with combination therapy, negative drug-drug interactions are a major concern for clinicians treating the disease. These results suggest that co-administration of TNX-355 and enfuvirtide may enhance the activity of both agents, added the release.

Tanox is a biotechnology company specialising 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.