BE BOLD: Bimekizumab Bests Risankizumab for ACR50 Joint Outcomes in PsA

UCB has announced week 16 data from the BE BOLD trial demonstrating superior ACR50 joint outcomes at week 16 for bimekizumab-bkzx (Bimzelx) versus risankizumab-rzaa (Skyrizi) in adults living with active psoriatic arthritis (PsA).

As described in a May 19, 2026, release from the Company, bimekizumab is the first approved biologic therapy to demonstrate superior, head-to-head ACR50 joint outcomes in PsA, with 49.1% of those receiving bimekizumab versus 38.4% receiving risankizumab achieved the stringent ACR50 primary endpoint at week 16. The 16 week BE BOLD results are being presented at the 2026 EULAR Annual Meeting in London, UK, June 3–6.

"Delivering high-level clinical responses is crucial for people with psoriatic arthritis. Achieving ACR50‑level responses in clinical trials indicates joint improvements that correlate closely with clinically meaningful reductions in disease activity, and inflammation control," Iain McInnes, University of Glasgow, College of Medical Veterinary and Life Sciences, Glasgow, UK, said in a statement. "The new BE BOLD data, showing bimekizumab achieved superiority vs risankizumab in ACR50 at Week 16 in a direct head-to-head trial design, can support clinicians in making early informed decisions for treating this chronic inflammatory disease."

Bimekizumab and BE BOLD

Bimekizumab is the first and only approved medicine to selectively inhibit both interleukin 17A (IL-17A) and interleukin 17F (IL-17F), two key cytokines driving inflammatory processes. In the pivotal BE OPTIMAL and BE COMPLETE trials, 44% and 43% of bimekizumab-treated patients achieved ACR50 at week 16, respectively, compared with 10% and 7% of placebo recipients (BE OPTIMAL: OR 7.1 [95% CI, 4.6–10.9]; P <.0001; BE COMPLETE: OR 11.1 [95% CI, 5.4–23.0], P <.0001).

BE BOLD is a multicenter, randomized, double-blind, active-controlled, parallel-group trial enrolling 553 adults with active PsA who were either biologic-naïve or had prior exposure to 1 TNF inhibitor with inadequate or intolerant response. Participants were randomly assigned in a 1:1 ratio to receive bimekizumab or risankizumab, with double-blinding maintained through week 24. The primary endpoint was ACR50 at week 16.

BE BOLD is the first head-to-head trial in PsA to include an IL‑23 inhibitor and is the fourth head-to-head study demonstrating superiority in the bimekizumab clinical trial program across psoriatic disease, with the previous studies comparing therapies in psoriasis.

16 Week Efficacy, Safety Findings

Results showed bimekizumab met the primary endpoint for BE BOLD of superiority in ACR50 at week 16, achieved by 49.1% receiving bimekizumab versus 38.4% receiving risankizumab, with statistical significance (P = .0078).1

The first ranked secondary endpoint, MDA at week 16, was numerically greater in bimekizumab (43.0%) vs risankizumab (39.9%) at week 16 but did not reach statistical significance within the prespecified testing hierarchy (P = .4408). Of note, sequential testing stopped at this point due to the study design, and subsequent ranked secondary endpoints were descriptive only, with numerically higher proportions achieved with bimekizumab.

Additionally, results showed numerically greater proportions of those treated with bimekizumab versus risankizumab achieved the ranked secondary endpoint of simultaneous ACR50+PASI100 at week 16 (33.5% vs 24.4%; nominal P = .0800).1 The ranked secondary endpoint of ACR50 at week 4 was also considered nominally significant for bimekizumab over risankizumab (19.9% vs 7.2%; nominal P <.0001).

Of the exploratory endpoints, PASI100 at week 16 was met by 53.4% treated with bimekizumab and 46.6% of those treated with risankizumab. DAPSA LDA+REM, DAPSA score ≤14, at week 16 was met by 65.3% treated with bimekizumab and 54.7% of those treated with risankizumab.

No new safety signals were identified in either treatment arm. All Candida infections were mild or moderate; none were serious, systemic, or led to study discontinuation. Rates of treatment-emergent adverse events (TEAEs) were 57.0% (158/277) with bimekizumab and 52.0% (143/275) with risankizumab.

Further safety analyses revealed serious TEAEs occurred in 5 (1.8%) bimekizumab-treated patients and 8 (2.9%) risankizumab-treated patients. Severe TEAEs were reported in 5 (1.8%) bimekizumab-treated patients and 5 (1.8%) risankizumab-treated patients. Discontinuations due to TEAEs were low and identical between treatment arms. Of note, BE BOLD was not statistically powered to compare safety outcomes between bimekizumab and risankizumab.

"We are proud to announce results demonstrating the superiority of bimekizumab over risankizumab in improving joint outcomes, providing significant evidence that can inform the treatment landscape for psoriatic arthritis," Emmanuel Caeymaex, Executive Vice President, Head of Patient Evidence, UCB, said in a statement. "Head-to-head trials are the most rigorous approach to comparative clinical research. BE BOLD reflects UCB's commitment to scientific excellence through generating high-quality evidence, that supports advancing care for people living with psoriatic disease."

References

1. UCB. BIMZELX® (bimekizumab-bkzx) demonstrates superior efficacy over SKYRIZI® (risankizumab-rzaa) in psoriatic arthritis: BE BOLD Week 16 data. May 19, 2026. Accessed May 19, 2026. https://www.prnewswire.com/news-releases/bimzelx-bimekizumab-bkzx-demonstrates-superior-efficacy-over-skyrizi-risankizumab-rzaa-in-psoriatic-arthritis-be-bold-week-16-data-302776715.html

2. Johnson V. Bimekizumab Beats Risankizumab on PsA ACR50 in Preliminary Head-to-Head Data. RheumatologyLive. March 11, 2026. Accessed May 19, 2026. https://www.rheum-live.com/view/bimekizumab-beats-risankizumab-psa-acr50-preliminary-head-to-head-data