UCB and Biogen Inc. (NASDAQ: BIIB) announced data from the Phase 3 PHOENYCS GO study showing that dapirolizumab pegol plus standard care was associated with sustained disease control at lower glucocorticoid doses through Week 48 compared with placebo plus standard care in patients with systemic lupus erythematosus.

The companies presented findings at the European Alliance of Associations for Rheumatology 2026 Congress through two posters and three abstracts. Post hoc analyses showed that in patients with baseline glucocorticoid doses greater than 7.5 mg/day prednisone equivalent, treatment with dapirolizumab pegol plus standard care was associated with a higher proportion of patients achieving disease activity control while enabling glucocorticoid tapering to 7.5 mg/day or less through Week 48.

Additional data presented included improvements in immunological markers, with reduced anti-dsDNA antibodies and increased complement proteins C3 and C4 in patients with abnormal baseline levels. The study also showed lower rates of moderate or moderate/severe BILAG-2004 flares with dapirolizumab pegol plus standard care versus placebo plus standard care through Week 48.

The presentations followed recent publication of the Phase 3 PHOENYCS GO study results in The Lancet, which reported clinically meaningful improvements in disease activity with dapirolizumab pegol at Week 48. The drug demonstrated a generally favorable safety profile, with safety findings consistent with previous studies.

Dapirolizumab pegol is an investigational humanized Fc-free polyethylene glycol-conjugated antigen-binding fragment that inhibits CD40L signaling. The drug is currently in Phase 3 clinical development for systemic lupus erythematosus treatment under the collaboration between UCB and Biogen. The safety and efficacy have not been established, and it is not approved by any health authority worldwide.