Ibalizumab, a Treatment Option for Multidrug Resistant HIV-1 Infection

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.

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.”

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.

Reference

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.