Bimekizumab Sustains Joint Responses Through Week 24 in PsA

UCB has announced new Week 24 findings from the Phase 3b BE BOLD trial evaluating bimekizumab-bkzx (Bimzelx) against risankizumab (Skyrizi) in adults with active psoriatic arthritis (PsA). The results demonstrated sustained numerical advantages in joint responses with bimekizumab through 24 weeks, building on statistically significant superiority observed at Week 16.¹

The findings are being presented at the American College of Rheumatology (ACR) Convergence 2026 meeting, held November 6 to 11 in Orlando, Florida. The randomized, double-blind, head-to-head trial enrolled 553 adults with active PsA who were either biologic-naïve or had experienced an inadequate response or intolerance to 1 tumor necrosis factor inhibitor.

Bimekizumab selectively inhibits interleukin (IL)-17A and IL-17F, whereas risankizumab targets IL-23.

Sustained Improvements in Joint Outcomes

At Week 24, 54.9% of patients receiving bimekizumab achieved an American College of Rheumatology 50% improvement response (ACR50), compared with 43.8% of patients receiving risankizumab, representing an 11.1-percentage-point numerical difference.¹

These findings followed the trial's primary endpoint results at Week 16, when bimekizumab demonstrated statistically significant superiority over risankizumab in ACR50 responses, achieved by 49.1% and 38.0% of patients, respectively (P = .0058).

Numerically higher ACR50 responses with bimekizumab were observed at every assessed time point, beginning as early as Week 4.

"ACR50 is the new standard in PsA, reflecting considerable joint improvements and is known to be associated with clinically meaningful reductions in disease activity and subsequent improvements in quality of life," said Joseph F. Merola, MD, MMSc, rheumatologist, dermatologist, and president of the Psoriasis and Psoriatic Arthritis Multicenter Advancement Network.

"In the BE BOLD head-to-head trial, bimekizumab demonstrated rapid and greater ACR50 responses that were sustained to six months, in addition to delivering high rates of complete skin clearance, both of which are especially important for those living with psoriatic arthritis," Merola added.

Although bimekizumab maintained numerically greater responses across several secondary endpoints, these differences were not statistically significant. The first ranked secondary endpoint, minimal disease activity at Week 16, showed a 3.4-percentage-point difference favoring bimekizumab (P = .3921). Because this endpoint did not meet statistical significance, subsequent ranked secondary analyses were considered descriptive.

Skin Clearance Responses Become Comparable by Week 24

The study also evaluated complete skin clearance using the Psoriasis Area and Severity Index 100 (PASI100) among participants with psoriasis affecting at least 3% of body surface area at baseline.

At Week 4, PASI100 responses were achieved by 12.5% of patients receiving bimekizumab compared with 3.4% receiving risankizumab (nominal P < .01).

At Week 16, complete skin clearance was achieved by 53.4% and 46.6% of patients, respectively, although the difference was not nominally significant.

By Week 24, PASI100 responses were comparable between treatment groups, with 59.7% of bimekizumab-treated patients and 59.1% of risankizumab-treated patients achieving complete skin clearance.

These findings suggest that although bimekizumab demonstrated numerically greater early skin responses, both treatments achieved similar complete clearance rates by 24 weeks.

Safety Findings Remain Consistent With Known Profiles

Overall treatment-emergent adverse event (TEAE) rates were comparable between groups, occurring in 58.1% of bimekizumab-treated patients and 55.3% of risankizumab-treated patients.

Serious TEAEs were reported in 1.8% and 3.3% of patients, respectively. Discontinuations due to adverse events were low in both groups, and no new safety signals were identified through Week 24.

Candida infections occurred more frequently among patients receiving bimekizumab (2.9%) compared with risankizumab (0.7%). All reported Candida infections were mild or moderate, with no serious or systemic cases or treatment discontinuations attributed to these infections.

One death occurred in the risankizumab group and was considered unrelated to treatment by the investigator.

Importantly, the BE BOLD study was not powered to detect differences in safety outcomes between treatment groups.

Implications for Psoriatic Arthritis Management

PsA is a chronic inflammatory disease affecting both the joints and skin, often requiring treatment strategies that address multiple manifestations of disease.

The BE BOLD findings contribute additional comparative evidence regarding the efficacy of dual IL-17A/IL-17F inhibition versus IL-23 inhibition in patients with active PsA.

"Head-to-head trials designed to mirror clinical practice are the gold standard for comparative clinical research," said Donatello Crocetta, chief medical officer at UCB. "The BE BOLD results help redefine treatment expectations for people living with psoriatic arthritis, reinforcing our belief that patients and clinicians can aim higher when setting treatment goals."

Although the Week 24 findings demonstrate sustained numerical differences in joint responses, the lack of statistical significance across ranked secondary endpoints limits conclusions regarding comparative superiority beyond the primary Week 16 analysis.

The results highlight the importance of evaluating both joint and skin outcomes when selecting biologic therapy for patients with PsA, alongside individual disease characteristics, safety considerations, and treatment goals.

The full Week 24 findings are scheduled for oral presentation at ACR Convergence on November 10, 2026.

References

1. McInnes I, et al. Bimekizumab efficacy and safety versus risankizumab in patients with active psoriatic arthritis: 24-week results from a head-to-head, multicenter, randomized, phase 3b study. Presented at: ACR Convergence 2026; November 6-11, 2026; Orlando, FL. Abstract 2456479.
2. UCB. BE BOLD: BIMZELX (bimekizumab-bkzx) builds on superior joint responses versus SKYRIZI (risankizumab) at Week 16, with clinical improvements sustained through Week 24. News release. November 9, 2026.
3. ClinicalTrials.gov. A study to evaluate the efficacy and safety of bimekizumab compared with risankizumab in adults with active psoriatic arthritis (BE BOLD). NCT06624228. https://clinicaltrials.gov/study/NCT06624228