Bimekizumab sustains ACR50 edge over risankizumab in PsA at week 24

By Sophie Lindqvist

At Week 24, 54.9% of adults with active psoriatic arthritis receiving bimekizumab-bkzx achieved an American College of Rheumatology 50% improvement response (ACR50), versus 43.8% receiving risankizumab—an 11.1-percentage-point numerical difference. The difference extended the trial’s statistically significant ACR50 finding at Week 16 numerically; it did not establish statistical superiority at Week 24.

The result comes from BE BOLD, a multicenter, randomized, double-blind, head-to-head Phase 3b trial that enrolled 553 adults with active Psoriatic arthritis (PsA). Participants were biologic-naive or had an inadequate response or intolerance to one tumor necrosis factor inhibitor. UCB announced the findings on November 9, 2026.

Bimekizumab, sold as Bimzelx, selectively inhibits interleukin-17A and interleukin-17F. Risankizumab, sold as Skyrizi, targets interleukin-23.

The joint-response signal stayed ahead

ACR50 responses favored bimekizumab numerically at every assessed time point, beginning as early as Week 4. At the Week 16 primary endpoint, 49.1% of the bimekizumab group and 38.0% of the risankizumab group achieved ACR50, a statistically significant difference (P = .0058).

Several secondary endpoints also favored bimekizumab numerically, but those differences did not reach statistical significance. The first ranked secondary endpoint, minimal disease activity at Week 16, showed a 3.4-percentage-point difference in bimekizumab’s favor (P = .3921). Because that endpoint missed statistical significance, subsequent ranked secondary analyses were considered descriptive.

Joseph F. Merola, MD, MMSc, a rheumatologist, dermatologist and president of the Psoriasis and Psoriatic Arthritis Multicenter Advancement Network, said: “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.”

He added: “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.”

Skin clearance converged by six months

Among participants with psoriasis affecting at least 3% of body surface area at baseline, the Psoriasis Area and Severity Index 100 (PASI100) measured complete skin clearance.

• Week 4: PASI100 responses occurred in 12.5% of the bimekizumab group and 3.4% of the risankizumab group (nominal P < .01).
• Week 16: Complete skin clearance reached 53.4% with bimekizumab and 46.6% with risankizumab, although the difference was not nominally significant.
• Week 24: PASI100 responses were comparable at 59.7% with bimekizumab and 59.1% with risankizumab.

Both treatments therefore achieved similar complete clearance rates by six months, after bimekizumab had produced greater early numerical separation.

Safety comparisons remained exploratory

Overall treatment-emergent adverse event (TEAE) rates were comparable between groups, and serious events did not favor either regimen numerically.

• Overall TEAEs: 58.1% with bimekizumab and 55.3% with risankizumab.
• Serious TEAEs: 1.8% with bimekizumab and 3.3% with risankizumab.
• Discontinuations: Rates due to adverse events were low in both groups, and investigators identified no new safety signals through Week 24.
• Candida infections: These occurred in 2.9% of bimekizumab-treated patients and 0.7% of risankizumab-treated patients. All were mild or moderate; none were serious or systemic, and none prompted treatment discontinuation.
• Death: One death occurred in the risankizumab group, which the investigator considered unrelated to treatment.

Critically, BE BOLD lacked the power to detect differences in safety outcomes between treatment groups. The numerical safety findings therefore need cautious interpretation.

Comparative evidence, not a blanket verdict

PsA is a chronic inflammatory disease affecting both joints and skin, often requiring treatment strategies that address multiple manifestations. BE BOLD adds comparative evidence on dual IL-17A/IL-17F inhibition versus IL-23 inhibition in active PsA.

Donatello Crocetta, chief medical officer at UCB, said: “Head-to-head trials designed to mirror clinical practice are the gold standard for comparative clinical research. 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.”

That is UCB’s treatment-expectation framing. The statistical hierarchy is narrower: Week 16 ACR50 superiority was significant, whereas the ranked secondary differences were not.

What does this change for clinicians?

For adults matching the BE BOLD population, the six-month dataset strengthens the comparative case for bimekizumab when early joint improvement and skin clearance are priorities, particularly in patients with both substantial joint and skin disease. The practical change is incremental: bimekizumab now has head-to-head evidence of a faster and numerically greater ACR50 pattern than risankizumab, while both treatments produced similar PASI100 clearance by Week 24.

It does not support a blanket claim of superiority across outcomes. Clinicians should still weigh individual disease characteristics, safety considerations and treatment goals, assessing joint and skin response together. The higher Candida-infection incidence warrants attention, but the trial’s safety limitations and the mild-to-moderate course of those infections constrain any broader conclusion.

The full Week 24 findings are scheduled for oral presentation on November 10, 2026, during ACR Convergence 2026, which runs November 6–11 in Orlando, Florida. The scheduled report is abstract 2456479, and the study is registered as NCT06624228. The oral presentation should provide the complete dataset needed to judge how much weight to place on the numerical differences and the exploratory safety signal.