Efficacy and Safety of 2 Fixed Doses of Ibalizumab Plus Optimized Background Regimen in Treatment-Experienced HIV-Positive Individuals

Abstract

Background: Sustained viral suppression in patients with multidrug-resistant (MDR) HIV infection remains difficult; accordingly, agents targeting different steps in the HIV life cycle are needed. Ibalizumab, a humanized immunoglobulin G4 monoclonal antibody, is a cluster of differentiation (CD4)-directed postattachment inhibitor.

Methods: In this phase 2b study, 113 patients with MDR HIV-1 and limited treatment options were assigned an optimized background regimen (OBR) and randomized to either 800 mg ibalizumab every 2 weeks (q2wk; n = 59) or 2000 mg ibalizumab every 4 weeks (q4wk; n = 54) up to week 24.

Results: Viral loads (VL) below the detection limit were achieved in 44% and 28% of patients in the 800 mg q2wk and 2000 mg q4wk groups, respectively, at week 24. Mean (SD) VL (log 10 copies/mL) decreased from Baseline [4.6 (0.8), 800 mg q2wk; 4.7 (0.7), 2000 mg q4wk] to week 2, with the reduction maintained through week 24 [2.9 (1.5), 800 mg q2wk; 3.2 (1.4), 2000 mg q4wk]. Baseline CD4 + counts were 80.5 and 54.0 cells/μL in the 800 mg q2wk and 2000 mg q4wk groups, respectively. Mean CD4 + T-cell count was increased at week 24 in both groups. No serious adverse events were related to ibalizumab.

Conclusions: In heavily treatment-experienced patients with HIV (PWH) at a more advanced baseline disease severity, clinically significant response rates at week 24 were achieved with ibalizumab plus OBR. Ibalizumab's unique mechanism of action and lack of cross-resistance to other antiretroviral agents make it an important component of combination treatment regimens for PWH with limited treatment options.