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UCB's bimekizumab beats risankizumab in first head-to-head psoriatic arthritis biologic trial

Brussels-based UCB announced topline results from BE BOLD, a Phase III trial comparing bimekizumab (BIMZELX) with risankizumab (SKYRIZI) in adults with...

Edited by Robert McTiernan··3 min read

UCB's Bimekizumab Beats Risankizumab in First Head-to-Head Psoriatic Arthritis Biologic Trial

Brussels-based UCB announced topline results from BE BOLD, a Phase III trial comparing bimekizumab (BIMZELX) with risankizumab (SKYRIZI) in adults with active psoriatic arthritis. Bimekizumab achieved statistically significant superiority over risankizumab on the primary ACR50 endpoint at Week 16, making this the first head-to-head study in psoriatic arthritis to demonstrate one licensed biologic's superiority over another using this measure. The result extends bimekizumab's run of head-to-head wins to four across psoriatic disease indications.

Trial specifics

BE BOLD is a multicenter, randomized, double-blind, parallel-group study that enrolled 553 adults with active psoriatic arthritis. Participants were either biologic-naïve or had prior exposure to one tumor necrosis factor inhibitor (TNFi) with an inadequate or intolerant response. They were randomized 1:1 to receive bimekizumab or risankizumab, with double-blinding maintained through Week 24. The primary endpoint, ACR50 at Week 16, requires at least a 50% improvement from baseline in tender and swollen joint counts along with 50% improvement in three of five additional criteria. UCB reported that bimekizumab met this endpoint with statistical significance, though exact response rates and p-values were not disclosed in the topline release. Treatment with bimekizumab was generally well tolerated, with no new safety signals through Week 16.

UCB plans to submit full BE BOLD results at a forthcoming international congress. Emmanuel Caeymaex, Executive Vice President and Head of Patient Evidence at UCB, stated that the data "reinforce bimekizumab's potential to deliver clinically meaningful improvements using the stringent ACR50 measure of disease activity, indicating more complete control of joint inflammation." Bimekizumab is already approved in the EU and the US across multiple indications: plaque psoriasis, psoriatic arthritis, axial spondyloarthritis (including ankylosing spondylitis and non-radiographic axial spondyloarthritis), and hidradenitis suppurativa. No new regulatory filing timelines were disclosed in connection with the BE BOLD data.

Research context

Bimekizumab is a humanized IgG1 monoclonal antibody that selectively neutralizes both IL-17A and IL-17F. Both cytokines drive inflammation in psoriatic arthritis through overlapping but non-redundant pathways, promoting synovial hyperplasia and joint damage. Preclinical work has shown that dual inhibition of IL-17A and IL-17F reduces synovial tissue inflammation beyond what IL-17A blockade alone achieves. Risankizumab, by contrast, targets the p19 subunit of IL-23, acting upstream in the Th17 axis. The BE BOLD result suggests that direct cytokine neutralization at the IL-17 level may yield greater joint-level efficacy than upstream IL-23 blockade, at least on the ACR50 measure at 16 weeks.

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Psoriatic arthritis affects an estimated 0.02% to 0.25% of the general population, with roughly 30% of psoriasis patients progressing to joint involvement. Uncontrolled disease leads to structural joint damage, and treatment options span TNF inhibitors, IL-17 inhibitors, IL-23 inhibitors, and JAK inhibitors. Despite this, no prior head-to-head trial in psoriatic arthritis had demonstrated superiority of one biologic class over another on ACR50.

Key competitors in the same target or indication space include:

  • Novartis's secukinumab, an IL-17A inhibitor approved for psoriatic arthritis and under continued Phase III evaluation.
  • Eli Lilly's ixekizumab, another approved IL-17A inhibitor with ongoing late-stage studies.
  • Janssen's guselkumab, an IL-23p19 inhibitor in Phase III for psoriatic arthritis.
  • Bristol Myers Squibb's deucravacitinib, an oral TYK2 inhibitor in Phase III for psoriatic arthritis, representing a different modality.
  • MorphoSys's sonelokimab, a nanobody targeting both IL-17A and IL-17F in Phase II, the closest mechanistic competitor to bimekizumab.

The BE BOLD data give UCB a differentiation argument against both IL-17A-only and IL-23 inhibitors in psoriatic arthritis, though longer-term comparative data beyond Week 24 and detailed secondary endpoint results remain pending.

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