Dapirolizumab pegol shows higher lupus response rates on new measure at ACR 2026

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UCB and Biogen said on Monday that their experimental lupus drug dapirolizumab pegol helped more patients reach a meaningful response than placebo in a fresh look at their Phase 3 trial, using a new yardstick designed to capture how the disease behaves across different organs. The data were presented in five posters at ACR Convergence 2026, the American College of Rheumatology's annual meeting in Orlando, Florida, which runs November 6 to 11.

The headline analysis applied the Treatment Response Measure for Systemic Lupus Erythematosus, known as TRM-SLE, to the PHOENYCS GO trial for the first time. Through Week 48, patients on dapirolizumab pegol plus standard care hit the TRM-SLE-50 mark — a clinically meaningful response in at least half of their active organ domains, mainly joints and skin — 61.2% of the time, against 43.2% for placebo plus standard care. For TRM-SLE-100, a response in all active organ domains, the figures were 52.5% against 36.8%.

The trial itself was already a success. PHOENYCS GO, published in The Lancet in May 2026, met its primary endpoint: 50% of patients on the drug plus standard care achieved a BICLA response at Week 48, compared with 35% on placebo plus standard care, a difference the trial's authors reported as statistically significant. A separate set of posters at the meeting showed more patients on the drug sustaining low disease activity and remission across Weeks 40, 44 and 48, including sustained low disease activity in 24.0% against 10.3% for placebo.

The numbers come from the two companies' own announcement, and the new figures need to be read with care. TRM-SLE was applied after the trial had finished rather than as a pre-specified endpoint, and it was not part of any regulatory submission; the authors themselves say the measure still needs further validation. Dapirolizumab pegol remains an investigational drug, not approved by any health authority, and a second Phase 3 trial, PHOENYCS FLY, is still recruiting patients.

For people living with lupus, a chronic autoimmune disease that can attack joints, skin, kidneys and other organs, the draw of the drug is that it works differently from existing treatments: it blocks CD40L, a protein that drives the immune overactivity behind the disease. The companies' pitch is that a measure like TRM-SLE, built by a global taskforce with input from regulators, could give doctors a clearer picture of whether a treatment is working across the organs a patient actually has affected.

What happens next depends on the confirmatory PHOENYCS FLY trial, which the companies say is intended to support future regulatory filings. No timeline for a filing was given in Monday's announcement, and the drug's path to patients still runs through that second large trial.