New Treatment for Multi-drug Resistant HIV-1 Is on the Horizon

August 2018

By Amanda Balbi

Ibalizumab, a humanized immunoglobin G4 (IgG4) monoclonal antibody, improved antiviral activity among patients with multidrug-resistant HIV-1, according to results of a new phase 3 trial.

This single-group, open-label trial enrolled 40 adults with HIV-1 in whom multiple antiretroviral therapies had failed.

At their initial assessment, all participants had a viral load of more than 1000 copies of HIV-1 RNA per mL. Then participants continued their usual therapy for 7 days (control period), after which viral load was assessed again (baseline).

For 25 weeks, participants received 800 mg of ibalizumab every 14 days plus a personalized combination background regimen that included at least one fully active agent.

Of the 40 participants enrolled at initial assessment, 31 had completed the treatment period. Mean viral load at baseline was 4.510 copies per mL and CD4 count was 150 per µl.

Of those in the intention-to-treat population, 83% had a decrease in viral load of at least 0.510 copies per mL from baseline, and viral load decreased by a mean 1.110 copies per mL.

At the end of the trial, 43% of participants had a viral load of less than 50 copies per mL, and 50% had less than 200 copies per mL.

Diarrhea was the most common adverse event, and 1 serious adverse event was associated with ibalizumab therapy (immune reconstitution inflammatory syndrome).

“In patients with [multidrug-resistant] HIV-1 infection who had advanced disease and limited treatment options, ibalizumab had significant antiviral activity during a 25-week study,” the researchers concluded. “Evidence of the emergence of diminished ibalizumab susceptibility was observed in vitro in patients who had virologic failure.”

—Amanda Balbi


Emu B, Fessel J, Schrader S, et al. Phase 3 study of ibalizumab for multidrug-resistant HIV-1 [published online August 16, 2018]. N Engl J Med. doi:10.1056/NEJMoa1711460.