UCB, Biogen Report Positive PHOENYCS GO Results in SLE

UCB and Biogen have reported full Phase 3 PHOENYCS GO (NCT04294667) results for dapirolizumab pegol (DZP), showing significant improvement in disease activity among patients with moderate-to-severe systemic lupus erythematosus (SLE). The peer-reviewed publication in The Lancet provides independent confirmation of previously reported topline findings and supports ongoing late-stage development of the investigational therapy.

Scientific and Clinical Context

Systemic lupus erythematosus is a chronic autoimmune disease that can affect multiple organs and remains challenging to manage despite recent therapeutic advances. Many patients continue to experience disease flares, persistent symptoms, and long-term corticosteroid exposure.

Dapirolizumab pegol is an investigational Fc-free anti-CD40L biologic that targets a key immune pathway involved in B-cell activation, autoantibody production, and inflammatory signaling. By inhibiting CD40L signaling, the therapy may help reduce the immune dysfunction that drives lupus disease activity.

Primary Endpoint Achieved

The study met its primary endpoint, with 50% of patients receiving DZP plus standard of care achieving a British Isles Lupus Assessment Group-based Composite Lupus Assessment (BICLA) response at Week 48, compared with 35% of patients receiving placebo plus standard of care (p=0.011).

While the first key secondary endpoint, BICLA response at Week 24, was not met, multiple disease activity, flare, serologic, and patient-reported outcome measures favored DZP over placebo.

Broad Efficacy Across Measures

DZP demonstrated improvements across several clinical and laboratory endpoints, including severe BILAG flares, SRI-4 responses, SLEDAI-2K scores, skin and joint manifestations, and serological markers such as anti-dsDNA antibodies and complement levels.

The treatment also showed clinically meaningful improvements in fatigue, one of the most burdensome symptoms reported by patients with lupus. In addition, more patients receiving DZP successfully reduced glucocorticoid doses to guideline-recommended levels, suggesting a potential steroid-sparing effect.

Safety Profile

Treatment-emergent adverse events occurred more frequently with DZP than placebo (82.6% vs. 75.0%). However, serious adverse events were less common in the DZP arm (10.0% vs. 14.8%), while discontinuations due to adverse events remained low in both groups.

Overall safety findings were consistent with previous DZP studies and supported continued clinical development of the therapy.

Expert Perspective

Megan Clowse, MD, MPH, Chief of the Division of Rheumatology and Immunology at Duke University and lead author of the publication, said the findings support further evaluation of dapirolizumab pegol as a potential treatment option for people living with SLE. She noted that additional therapies remain urgently needed for patients whose disease remains difficult to control despite available treatments.

Ongoing Development

UCB and Biogen are currently enrolling patients in the confirmatory Phase 3 PHOENYCS FLY trial (NCT06617325), which is intended to support future regulatory submissions. Additional findings from PHOENYCS GO are also being presented at the 2026 European Congress of Rheumatology (EULAR).

Results from PHOENYCS FLY will determine whether the Phase 3 findings can support regulatory filings and potentially expand treatment options for patients living with SLE. Dapirolizumab pegol remains investigational and has not been approved by any regulatory authority worldwide.

Reference

UCB and Biogen Announce Publication in The Lancet of Positive Dapirolizumab Pegol (DZP) Phase 3 Study Results in Systemic Lupus Erythematosus | Biogen