UCB's Bimzelx Triumphs Over AbbVie's Skyrizi in Psoriatic Arthritis

UCB's Bimzelx Triumphs Over AbbVie's Skyrizi in Psoriatic Arthritis

UCB's Bimzelx has shown superior efficacy compared to AbbVie's Skyrizi in treating psoriatic arthritis, marking a significant milestone in the competitive landscape. This article analyzes the implications for pharmaceutical business development teams. With the Phase IIIb BE BOLD data now public and an FDA approval in hand, UCB has positioned itself to carve into AbbVie's entrenched immunology franchise at a moment when payers and physicians are actively seeking differentiated mechanisms.

Key Takeaways

• Bimzelx demonstrated a 49% reduction in disease activity score compared to Skyrizi's 38% at 16 weeks, a statistically significant gap that reshapes the clinical narrative around IL-17 versus IL-23 inhibition in psoriatic arthritis.
• The FDA approved Bimzelx for active psoriatic arthritis in September 2024, building on its existing plaque psoriasis authorization and giving UCB two approved indications for its dual IL-17A/IL-17F inhibitor within a single calendar year.
• AbbVie now faces a direct, head-to-head efficacy challenge against one of its blockbuster immunology assets. Analysts tracking the immunology market should reassess Skyrizi's growth trajectory in PsA as Bimzelx gains formulary access and launches comparative promotional campaigns.

The Development

UCB dropped top-line data from the Phase IIIb BE BOLD trial in early 2024, and the full presentation followed at a major medical congress later that year, as reported by Fierce Pharma. The trial pitted Bimzelx (bimekizumab), a humanized monoclonal IgG1 antibody that selectively inhibits both IL-17A and IL-17F, against AbbVie's Skyrizi (risankizumab), an IL-23 inhibitor, in adults with active psoriatic arthritis who had an inadequate response to conventional disease-modifying antirheumatic drugs. The primary endpoint, the proportion of patients achieving at least a 50% improvement in disease activity as measured by the American College of Rheumatology criteria (ACR50) at week 16, came in at 49% for Bimzelx versus 38% for Skyrizi (ClinicalTrials.gov). That 11-percentage-point difference carried a p-value confirming statistical superiority, and it held across multiple secondary endpoints, including skin clearance measures and patient-reported outcomes.

UCB's executive vice president of immunology, Emmanuel Caeymaex, framed the BE BOLD data as validation of the company's broader "pipeline-in-a-product" thesis for Bimzelx. The drug's dual inhibition of IL-17A and IL-17F — a mechanistic differentiator from both IL-23 inhibitors like Skyrizi and single-target IL-17A inhibitors like Cosentyx — was designed to deliver a more complete blockade of the inflammatory cascade. The BE BOLD results suggest that design is paying out in clinical practice. The trial enrolled across multiple geographies, and UCB has been methodical about building a comparative evidence package that can support payer negotiations globally.

Implications for Pharma Teams

For business development and strategy teams, the BE BOLD readout changes the deal calculus in immunology. Bimzelx's ability to beat Skyrizi in a head-to-head setting — not just against placebo or an older TNF inhibitor — gives UCB a potent differentiator that compounds the drug's already strong showing in plaque psoriasis. BD teams at mid-sized biotechs and large-cap pharma with immunology gaps should evaluate whether assets targeting complementary nodes of the IL-17/IL-23 pathway could become acquisition targets as companies look to compete against UCB's expanding footprint. The trial also signals that head-to-head comparative data is becoming table stakes in the psoriatic arthritis market; companies running Phase II or III programs should budget for active comparator arms if they want to force formulary switches.

Regulatory affairs teams should monitor how the FDA and EMA handle comparative efficacy claims in labeling. UCB secured FDA approval for Bimzelx in psoriatic arthritis in September 2024 (FDA Novel Drug Approvals 2024), and the company will almost certainly pursue inclusion of the BE BOLD data in its prescribing information through a supplemental filing. If the agency permits explicit comparative superiority language, that sets a precedent for how head-to-head immunology data gets translated into commercial claims. Regulatory teams at competitor firms should scenario-plan for a more permissive environment around comparative labeling.

Regulatory Landscape

The FDA's September 2024 approval of Bimzelx for active psoriatic arthritis followed the drug's earlier U.S. approval in plaque psoriasis, and the European Medicines Agency had already endorsed the psoriatic arthritis indication through its centralized procedure (EMA Bimzelx EPAR). Both regulators reviewed the BE BOLD data as part of their decision-making, though the EMA historically moves faster on comparative efficacy claims than the FDA. The approval trajectory reflects a broader regulatory appetite for mechanistically novel biologics that can demonstrate differentiation against existing standards of care. Companies developing IL-17 or IL-23 pathway assets should anticipate that regulators will increasingly expect head-to-head evidence, not just placebo-controlled trials, as part of the benefit-risk assessment — particularly in crowded indications like psoriatic arthritis where multiple effective therapies already exist.

Market Response

Initial market reaction to the BE BOLD data was measured but pointed. UCB shares ticked up on the top-line readout, and sell-side analysts have since revised Bimzelx peak sales estimates upward, with consensus now approaching the $4 billion range across all indications. AbbVie, meanwhile, reported Skyrizi global revenues of approximately $11.7 billion in 2024 — including both psoriasis and psoriatic arthritis contributions — and the company has acknowledged in its SEC filings that competitive launches represent a material risk factor (AbbVie SEC Filings). The question for investors is pace of erosion: Bimzelx won't displace Skyrizi overnight, but UCB's comparative data gives pharmacy benefit managers a reason to renegotiate rebates, and dermatology and rheumatology practices that have grown comfortable with IL-23 inhibition now have a clinical reason to re-evaluate. Pay attention to 2025 first-half prescription data for early signals of switching behavior.

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• BIMZELX
• SKYRIZI

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