Efficacy, Pharmacokinetics, and Safety Over 48 Weeks With Ibalizumab-Based Therapy in Treatment-Experienced Adults Infected With HIV-1: A Phase 2a Study

J Acquir Immune Defic Syndr. 2021 Apr 1;86(4):482-489. doi: 10.1097/QAI.0000000000002591.


Ibalizumab, a humanized monoclonal antibody targeting CD4, blocks HIV-1 entry into cells and is the first Food and Drug Adminstration-approved long-acting agent for HIV-1 treatment. In this phase 2a study, 82 HIV-infected adults failing antiretroviral therapy were assigned an individually optimized background regimen (OBR) and randomized 1:1:1 to arm A (15 mg/kg ibalizumab q2wk), arm B (10 mg/kg weekly for 9 weeks, then q2wk), or placebo. Subjects with an inadequate response at week 16 were permitted to cross over to a new OBR plus 15 mg/kg ibalizumab q2wk. At week 16, viral load (VL) reduction was significantly greater than placebo (0.26 log10) in arms A (1.07 log10; P = 0.002) and B (1.33 log10; P < 0.001); CD4+ T cell counts increased significantly in arm A. After week 16, 11/27 (arm B) and 19/27 (placebo) subjects crossed over to OBR plus 15 mg/kg ibalizumab; 8/28 in arm A initiated a new OBR. Ibalizumab treatment resulted in VL reduction at week 24 (-0.77 and -1.19 log10 for arms A and B, respectively, versus -0.32 log10 for placebo) and 48 weeks (-0.54 and -0.77 versus -0.22 log10). Compared with placebo, VL differences were statistically significant for arm B at week 24 (P = 0.001) and week 48 (P = 0.027). CD4+ T cell counts increased significantly by week 48 in both arm A and arm B, relative to placebo. No ibalizumab-related serious adverse events were reported. The durable antiviral activity and tolerability of ibalizumab support its use in treating individuals harboring multidrug-resistant HIV-1.

Trial registration: ClinicalTrials.gov NCT00089700.

Publication types

  • Clinical Trial, Phase II
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-HIV Agents / adverse effects
  • Anti-HIV Agents / pharmacokinetics
  • Anti-HIV Agents / therapeutic use*
  • Antibodies, Monoclonal / adverse effects
  • Antibodies, Monoclonal / pharmacokinetics
  • Antibodies, Monoclonal / therapeutic use*
  • CD4 Lymphocyte Count
  • HIV Infections / drug therapy*
  • HIV-1
  • Humans
  • Viral Load / drug effects


  • Anti-HIV Agents
  • Antibodies, Monoclonal
  • ibalizumab

Associated data

  • ClinicalTrials.gov/NCT00089700