What is TNX-355?

• TNX-355 is an experimental entry inhibitor being developed by Tanox, Inc. It has not yet been evaluated by the U.S. Food and Drug Administration (FDA) for use by people living with HIV.
   
• TNX-355 contains genetically engineered antibodies, known as monoclonal antibodies. These antibodies bind to the CD4 receptor on T-cells. Once TNX-355 binds to these receptors, HIV cannot successfully connect with the surface of T-cells, thus preventing the virus from infecting healthy cells.
   
• TNX-355 will most likely need to be used in combination with other anti-HIV drugs.
   
• Genentech, Inc., a biotechnology company in South San Francisco, plans to buy Tanox.  While the deal was supposed to be completed in early 2007, the U.S. Federal Trade Commission has requested additional information before allowing the purchase.  It is unclear how this transaction will affect the future development of TNX-355.

• A dose for TNX-355 has not yet been determined. The drug is administered intravenously, once every two weeks, using a dose that depends on body weight.
   
• TNX-355 holds promise for HIV-positive patients who no longer respond to other anti-HIV drugs. Because TNX-355 targets HIV differently than most currently available drugs, chances are that most people living with the virus – regardless of which drugs they have tried (and failed) in the past – will likely benefit from using TNX-355.
   
• It is not known how quickly resistance to TNX-355 develops if resistance does occur.
   
• TNX-355 might interact with other medications, including those used to treat HIV. It is important that your personal physician and/or the research nurse or study investigator be aware of all drugs you are taking, including those you buy without a prescription.

• Clinical trials looking at the effectiveness of TNX-355 against HIV are now being conducted.
   
• In one small study, 22 HIV-positive adults received IV infusions of TNX-355 at different doses, either every week or every two weeks, for a total of nine to 10 weeks. No other anti-HIV medications were given during the study. Thirty-six percent of study volunteers who received 15mg of TNX-355 per kilogram (kg) of body weight saw their viral loads decrease by at least 1 log (90%) after 24 weeks in the study. Among patients receiving 10mg/kg TNX-355, 44% saw their viral loads decrease by at least 1 log after 24 weeks. However, in some volunteers, viral loads started increasing before the treatment course was completed, indicating that resistance might be a problem and that the drug will definitely need to be combined with other anti-HIV drugs.
   
• A phase II clinical trial has been conducted. It enrolled 82 HIV-positive people who had tried and failed other anti-HIV drugs in the past. All of the patients enrolled in the study received optimized background treatment (any combination of approved anti-HIV drugs), based on the results of drug-resistance testing. Two-thirds of the patients also received one of two doses of TNX-355 (10mg or 15mg per kilogram of body weight); the remaining one-third of the patients received placebo. The drug (or placebo) was administered through an IV line once a week for the first nine weeks and then once every other week for the remainder of the study.
   
  After 48 weeks, treatment with the 10mg/kg dose of TNX-355 resulted in a viral load reduction of 0.96 log; treatment with the 15mg/kg dose resulted in a viral load reduction of 0.71 log. In the placebo group, there was a viral load reduction of 0.14 log. Patients in both TNX-355 treatment groups experienced greater T-cell increases compared to those in the placebo group (an average increase of 48 T-cells in the 10mg/kg group, an average increase of 51 T-cells in the 15mg group, and an average increase of 1 T-cell in the placebo group). Both doses of TNX-355 were well tolerated.
   
• Before the drug can move into phase III clinical trials, the FDA has requested that the company first conduct additional early-stage phase II studies to determine the correct dose of the drug.

• Information regarding the safety and possible side effects of TNX-355 in HIV-positive people is not yet available.

• It is not known whether TNX-355 will harm an unborn baby. It is very important to treat HIV/AIDS during pregnancy to reduce the risk of infecting your baby. Talk to your doctor about your treatment options.
   
• It is not known whether TNX-355 passes into breast milk and what effect it may have on a nursing baby. To prevent transmission of the virus to uninfected babies, it is recommended that HIV-positive mothers not breast-feed.

• If you would like to find out if you are eligible for any clinical trials that include TNX-355, there is an interactive web site run by ACRIA, the AIDS Community Research Initiative of America.
   
• Another useful service for finding clinical trials is AIDSinfo.nih.gov, a site run by the U.S. National Institutes of Health. They have "health information specialists" you can talk to at their toll-free number at 1-800-HIV-0440 (1-800-448-0440).