Trial of antibody for HIV Infection

Tanox, Inc. announced today that it has begun dosing patients in its Phase 2 clinical trial of TNX-355 for the treatment of the human immunodeficiency virus (HIV).

The Phase 2 study is a three-arm, double-blind, placebo-controlled study, which will enroll approximately 80 patients. All patients will be anti- retroviral therapy-experienced, and will also be placed on optimized background therapy during the study.

The objective of the study is to evaluate the safety and pharmacological activity of TNX-355 in combination with optimized background therapy as assessed by viral load reduction. TNX-355 will be administered every two weeks during the 48-week trial duration.

There is a planned interim evaluation at 24 weeks, which results are expected in 2005.

TNX-355 is a humanized, non-immunosuppressive anti-CD4 monoclonal antibody that works by blocking the ability of the virus to enter CD4 positive cells. T

he CD4 receptor on host cell surfaces is considered to be a gateway for HIV infection. This monoclonal antibody is one of a new class of drugs called viral entry inhibitors.

Results from earlier Phase 1 studies showed that TNX-355 was well tolerated and can cause transient but clinically meaningful reduction of viral load in patients infected with HIV, lasting approximately 2-4 weeks. TNX-355 received Fast Track status from the U.S. Food and Drug Administration (FDA) in 2003.

"We are very excited about the initiation of the Phase 2 trial of TNX-355 and its novel mechanism of action" said Nancy T. Chang, President and CEO of Tanox. "Moving this program forward will potentially help the HIV treatment- experienced patient population which currently has a limited number of treatment options."