EULAR 2026 (the European Alliance of Associations for Rheumatology congress, London, June 3–6) produced three readouts that change how immunology and market-access teams should position the next wave of rheumatology biologics. UCB and Biogen's dapirolizumab pegol became the first CD40L inhibitor to win a positive Phase 3 in systemic lupus erythematosus. UCB's bimekizumab beat AbbVie's risankizumab head-to-head on joint outcomes in psoriatic arthritis, the first IL-17-versus-IL-23 superiority trial in PsA. And Artiva's off-the-shelf natural-killer cell therapy produced CAR-T-comparable responses in refractory rheumatoid arthritis with an outpatient, community-administrable profile that, if it holds, breaks the economics of autologous cell therapy in autoimmune disease.
This guide summarizes the pivotal readouts with the numbers access and formulary teams need — primary and key secondary endpoints, the commercial market each asset enters, and what the evidence changes for payer positioning. It is independent information for professionals, not medical advice.
1. Dapirolizumab pegol: the first CD40L win in lupus
Dapirolizumab pegol (DZP) is an investigational Fc-free, PEG-conjugated anti-CD40L fragment under joint development by UCB and Biogen. CD40L inhibition suppresses B-cell activation, type 1 interferon secretion, and T-cell co-stimulation simultaneously — a mechanism that prior programs abandoned years ago over thromboembolic safety. The Phase 3 PHOENYCS GO trial, presented at EULAR 2026 and published in The Lancet on May 29, 2026, is the first positive registrational readout for the class.
PHOENYCS GO primary and key results
| Endpoint (Week 48) | DZP + SOC | Placebo + SOC | Difference |
|---|---|---|---|
| BICLA response (primary) | 49.5% | 34.6% | 14.6% (p=0.0110) |
| SRI-4 response | 60.1% | 41.1% | 18.8% (nominal p=0.0014) |
| Severe BILAG flares (through Wk48) | 11.6% | 23.4% | −11.5% |
| Steroid taper to ≤7.5 mg/day (in patients >7.5 mg/day at baseline) | 72.4% | 52.9% | +19.5% |
PHOENYCS GO randomized 321 patients 2:1 to intravenous DZP plus standard of care or placebo plus standard of care for 48 weeks. The primary endpoint — BICLA (BILAG-based Composite Lupus Assessment) response at Week 48 — met statistical significance, with 49.5% of DZP-treated patients responding versus 34.6% on placebo (difference 14.6 percentage points; 95% CI 3.3–25.8; p=0.0110). Treatment-emergent adverse events were more common with DZP (82.6% vs 75.0%), but serious adverse events were less frequent (9.9% vs 14.8%). A confirmatory second Phase 3, PHOENYCS FLY (NCT06617325), is ongoing.
The commercially important finding was not the primary endpoint. It was the steroid-sparing signal: among patients entering the trial above 7.5 mg/day prednisone-equivalent, 72.4% of DZP patients tapered to ≤7.5 mg/day by Week 48 versus 52.9% on placebo, and a higher proportion did so while maintaining BICLA or SRI-4 response and remaining free of moderate-to-severe flares. Because cumulative glucocorticoid exposure above 7.5 mg/day is a documented driver of organ-damage accrual in SLE, UCB and Biogen are positioning the steroid-sparing effect as a co-equal outcome — not a secondary measure — for regulators and payers.
The market dapirolizumab enters
The systemic lupus erythematosus biologics market is estimated at roughly $3.71 billion in 2026. Dapirolizumab would enter against two established biologics: belimumab (Benlysta, GSK, approved 2011) and anifrolumab (Saphnelo, AstraZeneca, approved 2021). Its differentiation rests on a novel mechanism and on the steroid-sparing argument neither incumbent has made a primary commercial case. Johnson & Johnson also presented late-breaking Phase 2 lupus data with nipocalimab at the meeting, signaling that the SLE pipeline is finally thickening after a decade of failures.
Access implication. A CD40L inhibitor entering SLE with a steroid-sparing claim will test whether payers weight glucocorticoid tapering as a co-primary outcome. Formularies that currently step-edit SLE biologics behind belimumab should expect a dapirolizumab launch built on a combined disease-activity-plus-steroid-reduction dossier rather than a single composite endpoint.
2. BE BOLD: bimekizumab beats risankizumab head-to-head in PsA
BE BOLD (UCB) is the first head-to-head trial in psoriatic arthritis to demonstrate superiority of an IL-17 inhibitor over an IL-23 inhibitor, and the first PsA head-to-head for bimekizumab (Bimzelx), which inhibits both IL-17A and IL-17F.
BE BOLD Week 16 results (n=553)
| Endpoint (Week 16) | Bimekizumab | Risankizumab | Difference |
|---|---|---|---|
| ACR50 (primary) | 49.1% | 38.4% | 10.7% (p=0.0078) |
| ACR50 at Week 4 (early separation) | 19.9% | 7.2% | p<0.0001 |
| PASI100 (complete skin clearance) | 53.4% | 46.6% | — |
| ACR50 + PASI100 composite | 33.5% | 24.4% | p=0.08 |
| Minimal disease activity | 43% | 39.9% | numerical |
BE BOLD randomized 553 adults with active PsA (biologic-naïve or after one prior TNF inhibitor) 1:1 to bimekizumab or risankizumab (Skyrizi). The primary endpoint — ACR50 at Week 16 — favored bimekizumab at 49.1% versus 38.4% for risankizumab (difference 10.7 percentage points; p=0.0078). The separation was visible as early as Week 4 (19.9% vs 7.2%; nominal p<0.0001), a clinically relevant timing point because rheumatologists often reassess therapy response at 12 weeks. Secondary endpoints numerically favored bimekizumab without all reaching significance; minimal disease activity was 43.0% versus 39.9% but missed the prespecified hierarchy (p=0.4408), which stopped formal sequential testing. Safety was comparable overall with no new signals, though oral Candida infections — a known IL-17 class effect — were more frequent with bimekizumab; all were mild or moderate and none led to discontinuation.
Access implication. This is the kind of head-to-head evidence that supports a preferred-agent formulary position. Payers and PBMs that today place IL-23 inhibitors (Skyrizi, Tremfya, Ilumya/Omvoh) and IL-17 inhibitors (Cosentyx, Taltz, Bimzelx) on similar or competing tiers now have a randomized, active-controlled superiority trial to reference. Expect bimekizumab's manufacturer to push the ACR50 and early-separation data in formulary negotiations and IL-23 competitors to argue that the secondary endpoints and skin outcomes (where IL-23 has historically led) limit the clinical claim.
3. Izokibep: a miniaturized IL-17 inhibitor reaches Week 52
Affibody presented 52-week data from a global Phase 2b/3 study of izokibep in active PsA (Abstract OP073). Izokibep is not a monoclonal antibody — it is an "affibody" molecule roughly one-tenth the size of an antibody, designed to inhibit IL-17A with high potency. The study previously met its Week 16 ACR50 primary endpoint with high statistical significance; the Week 52 data showed continued improvement over time in patients on either izokibep dose (160 mg every two weeks or weekly), with rapid improvement in patients crossing over from placebo.
Access implication. Izokibep's commercial relevance is structural rather than this single readout: if a smaller, high-potency IL-17 molecule can match the efficacy of antibody IL-17 inhibitors, it could eventually compete on cost of goods, subcutaneous volume, and manufacturing complexity in a class where biosimilars of older agents (Cosentyx, Taltz) will eventually arrive. It is not yet registrational, but it widens the IL-17 competitive set.
4. AlloNK (AB-101): an off-the-shelf cell therapy's cost case
The most commercially disruptive readout at the meeting was not a new biologic. Artiva Biotherapeutics reported that AlloNK (AB-101) — an allogeneic, off-the-shelf, non-genetically modified, cryopreserved natural-killer cell therapy given with rituximab after low-dose cyclophosphamide and fludarabine conditioning — produced clinical responses comparable to autologous CAR-T cell therapy in 31 patients with rheumatologic disease.
AlloNK refractory RA results (late-breaking, ≥6 months follow-up)
| Measure | Result |
|---|---|
| ACR50 response in refractory RA | 71% |
| Patients relapsing or needing a new immunomodulatory agent | 0 |
| Cytokine release syndrome (CRS) | 0 |
| ICANS (neurotoxicity) | 0 |
| AlloNK-related treatment discontinuations | 0 |
In severe rheumatoid arthritis with inadequate response to multiple prior targeted therapies, AlloNK plus rituximab produced an ACR50 response in 71% of patients at six or more months of follow-up, with no patients relapsing and no CRS or ICANS. The company estimates that 150,000–200,000 US patients with RA have failed two or more biologic or targeted synthetic DMARD classes — roughly 25% of the treated RA population — and that real-world ACR50 rates with currently available therapies in that setting are only 11–19%. AlloNK targets an ACR50 of at least 50% versus an expected 20–25% for rituximab alone. Artiva announced FDA agreement to initiate a Phase 3 registrational trial in RA in 2026, and the program has now treated more than 70 autoimmune patients across 40+ largely community sites. Data in Sjögren disease (the first patient treated) and systemic sclerosis were also presented.
Why the cost case matters. Autologous CAR-T therapies (the engineered T-cell products first approved in oncology and now being tested in autoimmune disease) carry list prices in the hundreds of thousands of dollars and require apheresis, manufacturing, lymphodepletion, and inpatient monitoring for CRS and ICANS. AlloNK is cryopreserved, off-the-shelf, outpatient-administered, and so far free of the cytokine-release and neurotoxicity syndromes that drive CAR-T's cost and site restrictions. Artiva has separately presented cost-effectiveness analyses (at the TANDEM 2026 meeting) arguing AlloNK is more cost-effective than CAR-T in rheumatologic disease. If the Phase 3 confirms the RA signal, the access question will not be whether payers cover a cell therapy for refractory autoimmune disease — it will be whether a community-infusible, off-the-shelf product can reset the price ceiling the autologous CAR-T class had begun to establish.
Other EULAR 2026 readouts to track
- REPLENISH (secukinumab in relapsing polymyalgia rheumatica) and JAK-Spare (baricitinib in new-onset PMR): two shots at a disease with no approved targeted therapy, one via IL-17 and one via JAK.
- CD19 CAR-T in ACPA-positive rheumatoid arthritis: deepens the autologous cell-therapy evidence base that AlloNK is trying to undercut on cost.
- TOGETHER-PsA (ixekizumab plus tirzepatide): the first formal combination of an IL-17 inhibitor with a GLP-1 in PsA patients with obesity, reflecting the convergence of cardiometabolic and inflammatory care.
- Guselkumab plus golimumab (AFFINITY, Phase 2a): dual IL-23 + TNF inhibition in PsA — a mechanism-combination strategy distinct from the IL-17-versus-IL-23 head-to-head framing of BE BOLD.
- argenx efgartigimod (Vyvgart) in myositis and Sjögren: expansion of the FcRn blocker beyond its myasthenia gravis base into rheumatology.
What this means for formulary and access teams
1. SLE is becoming a multi-mechanism market, and steroid-sparing is the new payer lever. Dapirolizumab pegol's launch will be the first to lead with glucocorticoid reduction as a co-equal endpoint. Payers building SLE policies around belimumab and anifrolumab should prepare to evaluate a CD40L dossier on combined disease-activity and steroid-taper evidence, and to expect nipocalimab and other mechanisms to follow.
2. Head-to-head data will reshape the IL-17 and IL-23 formulary competition. BE BOLD gives IL-17 (specifically bimekizumab) the first randomized superiority evidence over IL-23 in PsA. Preferred-agent positioning, step edits, and tier placement across the IL-17/IL-23 class will increasingly be argued from active-comparator trials, not placebo-controlled label data.
3. Off-the-shelf cell therapy is the structural threat to autologous CAR-T economics in autoimmune disease. AlloNK's community-administrable, outpatient, CRS-free profile, if confirmed in Phase 3, gives payers a lower-cost alternative that could discipline the price ceiling of engineered autologous cell therapies before that class establishes its reimbursement precedent.
4. The rheumatology pipeline is thickening across mechanisms. CD40L, off-the-shelf NK cells, affibody IL-17, dual IL-23/TNF, IL-17+GLP-1, FcRn, and CAR-T all had meaningful data at a single meeting. For portfolio and access teams, the practical consequence is that rheumatology biologics positioning will require more active head-to-head and real-world evidence investment, because placebo-controlled efficacy is no longer enough to win preferred placement.
Sources
- Clowse MEB, Isenberg DA, Merrill JT, et al. "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, published online May 29, 2026. doi:10.1016/S0140-6736(26)00691-4. BICLA response 49.5% vs 34.6%, p=0.0110.
- ClinicalTrials.gov, NCT04294667 — PHOENYCS GO (dapirolizumab pegol in SLE), 48-week Phase 3. https://clinicaltrials.gov/study/NCT04294667
- ClinicalTrials.gov, NCT06617325 — PHOENYCS FLY (confirmatory Phase 3 of dapirolizumab pegol in SLE), ongoing. https://clinicaltrials.gov/study/NCT06617325
- UCB / Biogen, "EULAR 2026: Dapirolizumab Pegol Shows Potential to Reduce Flare Rates and Maintain Disease Control in Systemic Lupus Erythematosus," June 4, 2026. https://www.ucb.com/newsroom/press-releases/article/eular-2026-dapirolizumab-pegol-shows-potential-to-reduce-flare-rates-and-maintain-disease-control-in-systemic-lupus-erythematosus
- UCB, "BIMZELX (bimekizumab-bkzx) demonstrates superior efficacy over SKYRIZI (risankizumab-rzaa) in psoriatic arthritis: BE BOLD Week 16 data," May 19, 2026. ACR50 49.1% vs 38.4%, p=0.0078. https://www.ucb.com/newsroom/press-releases/article/bimzelxrbimekizumab-demonstrates-superior-efficacy-over-skyrizir-risankizumab-in-psoriatic-arthritis-be-bold-week-16-data
- Medscape, "Bimekizumab Trumps Risankizumab in Head-to-Head Psoriatic Arthritis Trial," EULAR 2026. https://www.medscape.com/viewarticle/bimekizumab-trumps-risankizumab-head-head-psoriatic-2026a1000iz5
- RheumNow, "EULAR 2026 Industry Press Releases" — izokibep (Affibody) Week 52 PsA data, OP073. https://rheumnow.com/news/eular-2026-industry-press-releases
- Artiva Biotherapeutics, "Artiva Announces Positive Initial Clinical Data with AlloNK Across Multiple Autoimmune Diseases and FDA Alignment to Initiate Phase 3 Registrational Trial in Rheumatoid Arthritis in 2026," EULAR 2026. 71% ACR50 in refractory RA; 150,000–200,000 US refractory RA patients. https://investors.artivabio.com/News-and-Events/news/news-details/2026/Artiva-Announces-Positive-Initial-Clinical-Data-with-AlloNK-Across-Multiple-Autoimmune-Diseases-and-FDA-Alignment-to-Initiate-Phase-3-Registrational-Trial-in-Rheumatoid-Arthritis-in-2026/default.aspx
- RheumNow, "EULAR 2026 Rheumatology RoundUp" (REPLENISH/secukinumab PMR, JAK-Spare/baricitinib PMR, CD19 CAR-T in RA). https://rheumnow.com/news/eular-2026-rheumatology-roundup
- PsOPsA Hub, "EULAR 2026 | Top abstracts: What's hot in psoriatic disease?" (TOGETHER-PsA ixekizumab+tirzepatide, AFFINITY guselkumab+golimumab, izokibep). https://psoriasis-hub.com/medical-information/eular-2026-top-abstracts
