Bimekizumab Beats Risankizumab on ACR50 in First IL-17A/F vs IL-23 Head-to-Head

Bimekizumab, a dual IL-17A/F inhibitor, demonstrated superiority over risankizumab, an IL-23 inhibitor, on the primary joint endpoint of ACR50 at week 16 in patients with active psoriatic arthritis (PsA), according to late-breaking results from the phase 3b BE BOLD study presented at the European Alliance of Associations for Rheumatology (EULAR), held June 3-6 in London, United Kingdom — the first head-to-head trial to show superiority in a joint-focused outcome between 2 biologic disease-modifying antirheumatic drugs in PsA.^1,2

Philip Mease, MD, Director of Rheumatology Research at Providence Swedish Medical Center and Clinical Professor of Medicine at the University of Washington School of Medicine, Seattle, served as a co-investigator on the study and sat down with RheumatologyLive to discuss its importance in the field.

BE BOLD (NCT06624228) randomized 553 adults with active PsA per CASPAR criteria (tender joint count ≥3/68, swollen joint count ≥3/66) who were biologic DMARD-naïve or had inadequate response or intolerance to 1 prior TNF inhibitor 1:1 to subcutaneous bimekizumab or risankizumab. Bimekizumab dosing was based on baseline psoriasis severity per label: most patients received bimekizumab 160 mg every 4 weeks (Q4W); those with moderate to severe psoriasis (body surface area ≥10%, Investigator's Global Assessment ≥3, and PASI ≥12) received bimekizumab 320 mg Q4W through week 16 then Q8W. Risankizumab 150 mg was administered at baseline, week 4, and week 16 regardless of psoriasis severity.¹

Baseline characteristics were comparable between arms. Mean age was 51.1 (standard deviation [SD], 13.6) years for bimekizumab (n = 277) and 50.7 (SD, 12.7) years for risankizumab (n = 276); mean tender joint count was 17.3 (SD, 12.7) and 16.6 (SD, 12.2), and mean swollen joint count was 10.1 (SD, 7.4) and 9.5 (SD, 6.8), respectively. Study completion rates through week 16 were high: 96.0% for bimekizumab and 93.1% for risankizumab.¹

For the primary endpoint of ACR50 at week 16, bimekizumab was superior to risankizumab (49.1% vs 38.4%; Δ10.7; P = .0078).¹ The first ranked secondary endpoint, minimal disease activity (MDA) at week 16, was numerically higher with bimekizumab but did not reach statistical significance (43.0% vs 39.9%; P = .4408), halting the sequential testing procedure. Subsequent secondary endpoints were therefore descriptive only: ACR50+PASI100 at week 16 in patients with baseline BSA ≥3% was achieved by 33.5% versus 24.4% (nominal P = .0800), and ACR50 at week 4 by 19.9% versus 7.2% (nominal P <.0001). Additional descriptive outcomes at week 16 included PASI100 in patients with baseline BSA ≥3% (53.4% vs 46.6%; nominal P = .2395) and DAPSA low disease activity or remission (65.3% vs 54.7%; nominal P = .0066).¹

Safety data were collected through a February 23, 2026 cut-off, at which point 83.4% of patients had completed double-blind treatment. Treatment-emergent adverse events (TEAEs) occurred in 57.0% of bimekizumab- and 52.0% of risankizumab-treated patients. Serious TEAEs were reported in 5 (1.8%) and 8 (2.9%) patients, respectively; severe TEAEs in 5 (1.8%) each. Candida infections were more frequent with bimekizumab, consistent with the known mechanism-of-action effect of IL-17 inhibition; all were mild or moderate, none were serious or systemic, and none led to study discontinuation. Rates of serious infection, inflammatory bowel disease, malignant tumors, neutropenia, and cardiovascular disorders were low across both treatment arms. 1 death occurred, attributed by the investigator to myocardial infarction in a patient with coronary artery disease, hypertension, and hyperlipidemia, and deemed unrelated to treatment. There were no cases of suicidal ideation or behavior, anaphylaxis, or active tuberculosis.¹

"Both agents worked very well, and we are excited to see the effectiveness of IL-17A and F, as well as IL-23 in these studies," Mease said. "These are both safer medicines than some of the other medicines that we have historically used, including the anti-TNF group."

BE BOLD is the first head-to-head study comparing these 2 mechanisms of action in PsA, and the first head-to-head bDMARD trial to demonstrate superiority on a joint-focused outcome in the disease.1,2 Week 24 data from the ongoing study are awaited.

Mease’s disclosures include AbbVie, Acelyrin, Amgen, BMS, Century, Cullinan, Eli Lilly and Company, Inmagene, Johnson & Johnson Innovative Medicine, MoonLake Immunotherapeutics, Novartis, Pfizer, Inc., Sana, Spyre, Takeda, and UCB.

References

1. McInnes IB, Gossec L, Gottlieb AB, et al. Bimekizumab efficacy and safety versus risankizumab in patients with active psoriatic arthritis: 16-week results from a head-to-head, multicentre, randomised, phase 3b study (BE BOLD) [abstract LB0001]. Ann Rheum Dis. 2026. doi:10.1136/annrheumdis-2026-eular.LBA_B.10

2. Gossec L, et al. No head-to-head bDMARD study has previously shown superiority in joint-focused outcomes in PsA. Ann Rheum Dis. 2024;83:706–719.