TNX-355 With Optimized Background Therapy (OBT) in Treatment-Experienced Subjects With HIV-1

This 48-week, multicenter, randomized, double-blinded, placebo-controlled, multi-dose, three-arm safety and efficacy study of approximately 80 subjects will compare TNX-355 plus OBT to placebo plus OBT in adult subjects infected with HIV-1. Subjects must: 1) have a stable viral load of 10,000 copies/mL, determined within 8 weeks prior to randomization (Day 1); 2) have been treated with HAART for at least 6 months (cumulatively); 3) be triple class experienced, with historical evidence of exposure to each of the three traditional classes of antiretroviral therapy (ART): nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs), and protease inhibitors (PIs); and 4) be presently failing or have failed a HAART regimen within 8 weeks prior to screening (Screening visit 1). Subjects will be assigned to OBT based upon their past medication history and the results of the virus sensitivity testing (PSGT, ViroLogic, Inc.), and then randomized to a study arm to begin receiving OBT plus study medication at the Day 1 visit. Fusion/entry inhibitors will not be permitted as part of the optimized background therapy. All subjects will be randomized equally (1:1:1 ratio), in a double-blinded fashion, among three arms to receive OBT plus one of the following: Arm A, alternating intravenous infusions of TNX-355, 15 mg/kg and placebo weekly for the first 9 doses (through the Week 8 visit), and then intravenous infusions of TNX-355, 15 mg/kg every two weeks; Arm B, TNX-355, 10 mg/kg intravenous infusions weekly for the first 9 doses (through the Week 8 visit), and then intravenous infusions of TNX-355, 10 mg/kg every two weeks; or Arm C, weekly intravenous infusions of placebo for the first 9 doses (through the Week 8 visit), and then intravenous infusions of placebo every two weeks. Subjects will continue to receive blinded therapy until that therapy fails. Subjects that do not achieve a viral load reduction of at least 0.5 log10 from their baseline value on two consecutive protocol-defined assessments after Week 12 will be considered virologic failures. Subjects that experience virologic failure after Week 16 (i.e., earliest point at which virologic failure can be confirmed after Week 12) will have the option of being assigned to new OBT plus open-label TNX-355 given as a 15 mg/kg infusion every two weeks. Subjects that experience a second virologic failure will be discontinued from the study. The total duration of study treatment will be 48 weeks, with the primary endpoint at Week 24.