AIDS 2006: TNX-355 Produces Significant Reduction in HIV Viral Load at 48 Weeks


Data on several investigational anti-HIV drug candidates were presented at the XVI International AIDS Conference last week in Toronto, including the latest results from a study of Tanox’s investigational monoclonal antibody, TNX-355. TNX-355 is a recombinant human antibody that binds to domain 2 of the CD4 receptor, thereby blocking the entry of HIV into host cells. 

Researchers conducted a randomized, double-blind, placebo-controlled Phase II study to assess the safety and efficacy of TNX-355 versus placebo, both in combination with an optimized background regimen (OBR) of other antiretroviral drugs.

The study included 82 patients who had previously used triple-class antiretroviral therapy. Most (87%) were men, about half (46%) were white, and the mean age was 46 years. Participants were randomly assigned to receive either placebo or intravenous TNX-355 in one of two dose regimens:

If they experienced virological failure (defined as less than a 0.5 log drop in HIV RNA from baseline by week 16), patients could receive 15 mg/kg open-label TNX-355 once every 2 weeks in combination with a new OBR. 

Virological and immunological responses were assessed at 24 and 48 weeks using an intent-to-treat analysis.


In conclusion, the researchers wrote, “TNX-355 in combination with OBR resulted in a statistically significant difference in viral load reduction compared to placebo plus OBR at Week 48. Treatment with TNX-355 is associated with durable viral load reductions and clinically meaningful increases in CD4 counts in treatment-experienced patients.”



D Norris, J Morales, E Godofsky, and others. TNX-355, in combination with optimized background regimen (OBR), achieves statistically significant viral load reduction and CD4 cell count increase when c ompared with OBR alone in phase 2 study at 48 weeks. XVI International AIDS Conference. Toronto, August 13-18, 2006. Abstract THLB0218.