Ibalizumab showed significant antiviral activity in patients with multidrug-resistant HIV-1 infection, advanced disease, and few other treatment options, according to research published in The New England Journal of Medicine.1

A single-group, open-label, phase 3 study enrolled 40 adults living with multidrug-resistant HIV-1. All patients had a viral load of >1000 copies of HIV-1 RNA/mL. Patients underwent a 7-day control period after which a loading dose of 2000 mg ibalizumab was administered. Viral load was assessed 7 days later. Through the rest of the 25-week study, patients received 800 mg of ibalizumab every 14 days, along with an individually optimized background regimen.

A total of 31 patients completed the study. The mean baseline viral load was 4.5 log10 copies/mL and mean CD4 counts were 150/µL. At week 25, patients receiving ibalizumab and an optimized background regimen had a mean decrease of 1.6 log10 copies/mL from baseline and 43% of patients had a viral load of <50 copies/mL. The percentage of patients with viral load of <200 copies/mL increased to 50%. Ten patients had virologic failure or rebound, 9 of whom were identified as having a lower degree of susceptibility to ibalizumab. One patient had a severe adverse event, immune reconstitution inflammatory syndrome, deemed to be related to the ibalizumab treatment.

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The study was limited by small size, uncontrolled study design, and limited time for analyzing secondary and safety end points — all of which are reflective of the scarcity of people with multidrug-resistant HIV-1. Researchers not affiliated with the trial noted2 that the study “had substantial limitations, but it allowed for an informative assessment of ibalizumab’s safety and efficacy in a population that needs new treatment options.”

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Investigators concluded that ibalizumab combined with a background regimen “had antiviral and immunologic activity” in this hard-to-treat population. Further, the findings show the feasibility of a twice-monthly intravenous administration of an antiretroviral therapy.


  1. Sheikh V, Murray JS, Sherwat A. Ibalizumab in multidrug-resistant HIV – accepting uncertainty. N Engl J Med. 2018;379:605-607.
  2. Emu B, Fessel J, Schrader S, et al. Phase 3 study of ibalizumab for multidrug-resistant HIV-1. N Engl J Med. 2018;379:645-654.