Horizon Therapeutics plc announced that a new post hoc analysis of the UPLIZNA N-MOmentum Phase 2/3 pivotal trial has been published in Multiple Sclerosis and Related Disorders showing that prior rituximab exposure did not impact the efficacy of UPLIZNA, and that UPLIZNA demonstrated comparable efficacy to trial participants without prior exposure to rituximab. UPLIZNA is the first and only B-cell-depleting humanized monoclonal antibody approved by the U.S. Food and Drug Administration (FDA) for the treatment of NMOSD in adults who are anti-aquaporin-4 (AQP4) antibody positive. UPLIZNA is a next-generation B-cell-depleting therapy engineered for optimized efficacy and tolerability. UPLIZNA specifically targets and depletes CD19-expressing B cells, including plasmablasts and some plasma cells not targeted by anti-CD20 therapies like rituximab. Rituximab is not approved by the FDA for the treatment of NMOSD. This analysis assessed the efficacy and safety of UPLIZNA among participants who were previously treated with rituximab to determine any impact of prior treatment on rates of adjudicated attacks, secondary efficacy outcomes and treatment-emergent adverse events. Of the 17 participants who had previously been treated with rituximab, 13 were randomly assigned to the UPLIZNA treatment group. Notably, all seven participants who had pre-study attacks despite rituximab use (annualized attack rate, 0.78 attacks per person year) did not experience any attacks after being treated with UPLIZNA. Key analysis findings: 92% of participants previously treated with rituximab did not experience an NMOSD attack while being treated with UPLIZNA during the randomized-controlled period (RCP) of N-MOmentum (hazard ratio vs all placebo, 0.16; 95% confidence interval: 0.02-1.20) and remained attack-free through the open-label extension period (OLP). Annualized attack rate reduced to 0.08 attacks per person year after the first administration of UPLIZNA, similar to recipients without prior rituximab exposure (0.10 attacks per person year). Two participants previously treated with rituximab each experienced an attack during the OLP, both of whom originally received placebo during the RCP. Two participants with prior rituximab use experienced serious treatment-emergent adverse events related to UPLIZNA, and three experienced serious or grade =3 infections. UPLIZNA had a similar safety profile in participants with and without prior rituximab use.