Effect of Anti-CD4 Antibody UB-421 on HIV-1 Rebound after Treatment Interruption.

BACKGROUND: Administration of a single broadly neutralizing human immunodeficiency virus (HIV)-specific antibody to HIV-infected persons leads to the development of antibody-resistant virus in the absence of antiretroviral therapy (ART). It is possible that monotherapy with UB-421, an antibody that blocks the virus-binding site on human CD4+ T cells, could induce sustained virologic suppression without induction of resistance in HIV-infected persons after analytic treatment interruption. METHODS: We conducted a nonrandomized, open-label, phase 2 clinical study evaluating the safety, pharmacokinetics, and antiviral activity of UB-421 monotherapy in HIV-infected persons undergoing analytic treatment interruption. All the participants had undetectable plasma viremia (<20 copies of HIV RNA per milliliter) at the screening visit. After discontinuation of ART, participants received eight intravenous infusions of UB-421, at a dose of either 10 mg per kilogram of body weight every week (Cohort 1) or 25 mg per kilogram every 2 weeks (Cohort 2). The primary outcome was the time to viral rebound (≥400 copies per milliliter). RESULTS: A total of 29 participants were enrolled, 14 in Cohort 1 and 15 in Cohort 2. Administration of UB-421 maintained virologic suppression (<20 copies per milliliter) in all the participants (94.5% of measurements at study visits 2 through 9) during analytic treatment interruption, with intermittent viral blips (range, 21 to 142 copies per milliliter) observed in 8 participants (28%). No study participants had plasma viral rebound to more than 400 copies per milliliter. CD4+ T-cell counts remained stable throughout the duration of the study. Rash, mostly of grade 1, was a common and transient adverse event; one participant discontinued the study drug owing to a rash. A decrease in the population of CD4+ regulatory T cells was observed during UB-421 monotherapy. CONCLUSIONS: UB-421 maintained virologic suppression (during the 8 to 16 weeks of study) in participants in the absence of ART. One participant discontinued therapy owing to a rash. (Funded by United Biomedical and others; ClinicalTrials.gov number, NCT02369146.).

IgE-neutralizing UB-221 mAb, distinct from omalizumab and ligelizumab, exhibits CD23-mediated IgE downregulation and relieves urticaria symptoms.

Over the last 2 decades, omalizumab is the only anti-IgE antibody that has been approved for asthma and chronic spontaneous urticaria (CSU). Ligelizumab, a higher-affinity anti-IgE mAb and the only rival viable candidate in late-stage clinical trials, showed anti-CSU efficacy superior to that of omalizumab in phase IIb but not in phase III. This report features the antigenic-functional characteristics of UB-221, an anti-IgE mAb of a newer class that is distinct from omalizumab and ligelizumab. UB-221, in free form, bound abundantly to CD23-occupied IgE and, in oligomeric mAb-IgE complex forms, freely engaged CD23, while ligelizumab reacted limitedly and omalizumab stayed inert toward CD23; these observations are consistent with UB-221 outperforming ligelizumab and omalizumab in CD23-mediated downregulation of IgE production. UB-221 bound IgE with a strong affinity to prevent FcԑRI-mediated basophil activation and degranulation, exhibiting superior IgE-neutralizing activity to that of omalizumab. UB-221 and ligelizumab bound cellular IgE and effectively neutralized IgE in sera of patients with atopic dermatitis with equal strength, while omalizumab lagged behind. A single UB-221 dose administered to cynomolgus macaques and human IgE (ε, κ)-knockin mice could induce rapid, pronounced serum-IgE reduction. A single UB-221 dose administered to patients with CSU in a first-in-human trial exhibited durable disease symptom relief in parallel with a rapid reduction in serum free-IgE level.