A CD40-ligand blocker improved lupus disease activity in a phase 3 trial
In PHOENYCS GO, dapirolizumab pegol lifted the share of lupus patients reaching a composite response at 48 weeks to 50% from 35% on placebo — a real but modest 14.6-point gain.
| Group | Value (%) |
|---|---|
| Dapirolizumab pegol | 50 |
| Placebo | 35 |
An experimental antibody that blocks CD40 ligand, a signal immune cells use to organise an attack, improved disease activity in people with moderate-to-severe systemic lupus erythematosus in a phase 3 trial — though the size of the benefit was modest and the drug remains investigational [s1]. The result revives a drug target that failed a generation ago for safety reasons.
Systemic lupus erythematosus (SLE) is an autoimmune disease in which the immune system attacks the body's own tissues, and treatment options that add much on top of standard immunosuppression remain limited [s1]. Dapirolizumab pegol is a CD40 ligand inhibitor — a class abandoned in the early 2000s after earlier anti-CD40L antibodies caused blood clots, a problem this pegylated fragment was engineered to avoid [s1]. PHOENYCS GO is the phase 3 test of whether it works.
What the trial did
PHOENYCS GO was a 48-week, randomised, double-blind, placebo-controlled, phase 3 trial conducted at 177 centres in 25 countries [s1]. It enrolled patients aged 16 or older with moderate-to-severe, active SLE despite standard-of-care medication, randomly assigning them 2:1 to intravenous dapirolizumab pegol 24 mg/kg or placebo every four weeks, on top of their existing treatment [s1]. Patients, investigators, and the funders were blinded to assignment [s1]. The primary outcome was the British Isles Lupus Assessment Group-based Composite Lupus Assessment (BICLA) response at week 48 — a composite measure that counts a patient as a responder only if disease activity improves without worsening elsewhere [s1]. Between Aug 12, 2020, and June 8, 2023, 643 patients were screened and 321 randomly assigned, 213 to dapirolizumab pegol and 108 to placebo [s1]. Six were later excluded because one site did not comply with Good Clinical Practice, leaving a full-analysis set of 315 patients (293 female, 22 male) [s1]. The trial was registered before enrolment [s2].
What it found
A significantly greater share of patients on the drug met the BICLA response at week 48: 50% (103/208) versus 35% (37/107) on placebo, a difference of 14.6 percentage points (95% CI 3.3–25.8, p=0.011) [s1].
Safety did not throw up the clotting signal that sank the earlier drugs, but the picture was not spotless. Treatment-emergent adverse events occurred in 83% (176/213) of the dapirolizumab pegol group versus 75% (81/108) on placebo, while serious treatment-emergent events were actually less common on the drug, at 10% (21/213) versus 15% (16/108) [s1]. Hypersensitivity reactions during infusion occurred in 3% (6/213) [s1]. Serious infections occurred in 4% (8/213) on the drug and 6% (6/108) on placebo [s1]. One thromboembolic event, a myocardial infarction, and one death from gangrene-related sepsis each occurred in a single patient in the dapirolizumab pegol group [s1]. Those are single events in a trial of a few hundred people, too few to say whether the class's old clotting concern is truly gone, but the absence of an obvious excess is the signal the developers needed to see [s1].
How to read it
The trial met its primary endpoint, and that is the headline — but the magnitude is worth keeping in view [s1]. A 15-percentage-point improvement in a composite response rate means roughly one in seven treated patients crossed the response threshold who would not have on placebo; the confidence interval, running from 3.3 to 25.8, is wide, so the true effect could be at the smaller end [s1]. BICLA is also a composite of disease-activity measures, not a direct readout of how a patient feels or of long-term organ damage, which this 48-week trial was not designed to capture [s1].
The trial was funded by UCB and Biogen, the companies developing the drug, so the analysis and presentation come from interested parties — standard for a registrational trial, and a reason the independent full publication and regulatory review matter [s1]. The authors frame the result as support for further investigation rather than a finished case [s1].
Related coverage has examined an anti-CD20 antibody, obinutuzumab, tested in active lupus and a JAK inhibitor's mixed record when withdrawn in giant cell arteritis.
What to watch
The questions now are durability and damage: whether the response holds beyond a year, whether it translates into fewer flares and less organ injury over time, and how a revived CD40L blocker will be positioned against the growing roster of lupus biologics [s1]. The drug was given as an intravenous infusion every four weeks, so convenience and cost will also shape where it fits alongside options patients can take at home [s1].
This article describes trial results and is not medical advice. Lupus treatment decisions are for patients and their clinicians.
Sources
- Dapirolizumab pegol in systemic lupus erythematosus (PHOENYCS GO) — The Lancet, 29 May 2026
- PHOENYCS GO trial registration (NCT04294667) — ClinicalTrials.gov, first posted 4 March 2020
Sources
- Efficacy and safety of the CD40 ligand inhibitor dapirolizumab pegol in systemic lupus erythematosus (PHOENYCS GO): a randomised, double-blind, placebo-controlled, phase 3 trial — The Lancet , May 29, 2026
- A Study to Evaluate the Efficacy and Safety of Dapirolizumab Pegol in Study Participants With Systemic Lupus Erythematosus (PHOENYCS GO, NCT04294667) — ClinicalTrials.gov , March 4, 2020
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