Tanox Inc announced that the U.S. Food and Drug Administration (FDA) has granted fast track status to TNX-355 for the treatment of patients with human immunodeficiency virus 1 (HIV-1) infection who have failed or are failing antiretroviral therapy. Under the FDA Modernization Act of 1997, designation as a fast track product means that the FDA will facilitate the development and expedite the review of a drug if it is intended for the treatment of a serious or life-threatening condition and demonstrates the potential to address unmet medical needs for such a condition.

Fast track status enables close interaction with the FDA to discuss and receive guidance on future development plans and allows priority review of the Biologics License Application for the specified indication.

"We are excited to continue further development with TNX-355 while working with the FDA to incorporate their feedback into protocols for upcoming studies since it has received fast track designation at this early stage of its development," stated Nancy T. Chang, CEO and founder of Tanox.

TNX-355 is a humanized monoclonal antibody that binds to domain 2 of the CD4 molecule, the primary receptor for HIV-1 that is present on the surface of certain cells (referred to as CD4+ cells). In this way, TNX-355 prevents the entry of HIV-1 into CD4+ cells. Unlike other anti-CD4 antibodies that target domain 1 of CD4, TNX-355 does not interfere with immunologic functions involving antigen presentation. This monoclonal antibody is one of a new class of drugs called viral entry inhibitors that represent a potential treatment approach to HIV-1 that has become resistant to standard antiretroviral therapies.

Tanox presented data from the TNX-355 open-label single dose Phase 1a safety trial at the 10th Conference on Retroviruses and Opportunistic Infections in February 2003. In this study of patients with treatment-refractory HIV-1 infection, the drug was well tolerated and patients had a significant decrease in viral load. Tanox is conducting an open-label, multiple-dose Phase 1b trial of TNX-355. Tanox expects to present the results from the Phase 1b trial in 1Q 2004 and initiate a Phase 2 trial with TNX-355 in the first half of 2004. Tanox holds exclusive rights to TNX-355 through a license with Biogen Inc.