Ibalizumab (TNX-355), an entry inhibitor, has been approved by the FDA for use in persons with an extensive ARV treatment history and multidrug resistant HIV who are on a failing ARV regimen. Ibalizumab (trade name: Trogarzo) is a monoclonal antibody that binds the CD4 receptor and blocks HIV entry to CD4 cells. It is given by IV infusion every 14 days, in combination with a full regimen of daily oral ARVs.
Clinical data on the efficacy and safety of ibalizumab are limited. FDA approval was based largely on the results of a single-arm Phase III study of 40 persons on failing ART regimens with multidrug resistant HIV-1 and limited treatment options; mean HIV RNA was 100,000 copies/mL, and mean CD4 count was 150 cells/µL (17 patients had CD4 counts of <50 cells/µL). Ibalizumab was added to the failing regimen for 1 week, and then subjects were given both ibalizumab and individualized optimized background ARV regimens (including at least one ARV with predicted activity against the person's virus). After 24 weeks, 50% of recipients had HIV viral loads of <200 copies/µL, and 43% had viral loads of <50 copies/µL; the mean decrease in HIV RNA was 1.1 log10 copies. Adverse effects of persons treated in this study included nausea, diarrhea, dizziness, and rash.
Clinical Bottom Line
Ibalizumab is the first ARV in recent years that has been approved specifically for use in persons with extensive drug resistance to existing ARV classes. As with other ARVs, it must be combined with additional active agents in order to be effective, but it will be very useful in the small group of patients whose HIV cannot be suppressed with available ARVs. Given the paucity of data on ibalizumab (as well as the requirement for IV infusion), its use should be limited to these patients.
Lewis S, Fessel J, Emu B, et al. Long-acting ibalizumab in patients with multi-drug resistant HIV-1: a 24-week study. In: Program and abstracts of the 2017 Conference on Retroviruses and Opportunistic Infections; February, 13-16, 2017; Seattle. Abstract 449LB.