UCB’s BIMZELX shows sustained inflammation control at three years in psoriatic arthritis and axial spondyloarthritis

Belgium-based global biopharmaceutical company UCB has released new three-year data from its Phase 3 clinical trials and open-label extensions evaluating BIMZELX (bimekizumab-bkzx) in patients with active psoriatic arthritis (PsA), non-radiographic axial spondyloarthritis (nr-axSpA), and ankylosing spondylitis (AS). The updated dataset, presented at the American College of Rheumatology (ACR) 2025 annual meeting, reveals sustained disease control across stringent clinical endpoints, further validating BIMZELX as a differentiated anti-inflammatory biologic.

Bimekizumab is the first and only biologic approved to selectively inhibit both interleukin-17A (IL-17A) and interleukin-17F (IL-17F). This dual-target mechanism is now supported by long-term follow-up evidence showing that the therapy provides consistent and clinically significant outcomes across multiple inflammatory domains, including joint, skin, and spinal symptoms. The three-year data confirm not only therapeutic durability but also reinforce UCB’s positioning of BIMZELX as a cornerstone product in its expanding rheumatology franchise.

What do the three-year clinical results reveal about BIMZELX in psoriatic arthritis treatment outcomes?

In patients with psoriatic arthritis, BIMZELX demonstrated robust and durable response across several disease manifestations. According to UCB, one-year improvements were sustained through three years across the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) core domains, including peripheral arthritis, dactylitis, enthesitis, skin psoriasis, and nail psoriasis. These effects were observed in both biologic DMARD-naïve individuals and those with inadequate response or intolerance to prior TNF inhibitor treatment.

The long-term safety profile was also consistent with earlier trial phases. In BE OPTIMAL and BE COMPLETE, the exposure-adjusted incidence rates of uveitis and adjudicated inflammatory bowel disease were low, at 0.2 and 0.3 per 100 patient years respectively, with some subgroups reporting no events at all through Week 156. These findings suggest that the dual IL-17A/IL-17F inhibition mechanism does not increase the risk of gut-related adverse events compared to other agents in its class.

Professor Laura Coates of the University of Oxford noted that psoriatic arthritis remains a challenging condition due to its complex and multi-domain nature. She emphasized that the ability of BIMZELX to deliver consistent improvements across all key disease domains points to its potential as a comprehensive treatment option that could prevent long-term structural damage when administered continuously.

How did BIMZELX perform in axial spondyloarthritis patients, including non-radiographic and AS subgroups?

For the axial spondyloarthritis spectrum, which includes both nr-axSpA and AS, the study results showed that BIMZELX achieved high rates of long-term response on the Ankylosing Spondylitis Disease Activity Score (ASDAS). Starting from Week 16, 50 percent of patients never lost their ASDAS low disease activity (LDA) status—defined as ASDAS below 2.1—at any assessed timepoint through to Week 164. An additional 22.4 percent lost ASDAS LDA at only one timepoint, and just 6.1 percent lost it twice.

Among patients who reached ASDAS LDA at Week 16, a notable 78.8 percent still maintained the same response at the three-year mark. This was consistent across the BE MOBILE 1 and BE MOBILE 2 trials and their open-label extensions under the BE MOVING protocol. These findings point to BIMZELX’s ability to deliver meaningful, sustained control over spinal inflammation, which is a critical outcome for improving long-term quality of life and halting disease progression in patients with axial involvement.

Professor Fabian Proft from Universitätsmedizin Berlin commented that achieving and maintaining ASDAS LDA is a high bar in routine clinical practice. The consistency seen with BIMZELX over three years suggests that the drug could help redefine long-term management expectations for axSpA, particularly as clinicians and payers seek options that reduce flare frequency and maintain patient stability.

What insights have emerged from real-world clinical practice settings on BIMZELX effectiveness?

UCB also shared interim findings from the ongoing SPEAK study, a 52-week, multi-country observational program assessing BIMZELX in everyday clinical settings across Europe. The results, covering approximately 50 percent of enrolled patients as of April 2025, offer early evidence that the efficacy observed in controlled trials is translatable to real-world outcomes.

For patients with psoriatic arthritis, the mean change from baseline in Psoriatic Arthritis Impact of Disease (PsAID-12) scores at Week 24 was −1.9, while the Short Form-36 Physical Component Summary (SF-36 PCS) improved by +4.6 points. Patient Global Assessment of Disease Activity (PGADA) scores also improved significantly, with a −17.5 mean reduction by Week 24. Notably, early signals of benefit were seen as soon as Week 2, with PsAID-12 and PGADA scores improving by −0.8 and −7.1, respectively.

Similarly, patients with non-radiographic axSpA and AS in the SPEAK study experienced improvements in ASAS Health Index and PGADA scores. At Week 24, ASAS HI decreased by −1.6, SF-36 PCS increased by +5.7, and PGADA decreased by −1.0. Again, clinically relevant changes were apparent as early as Week 2, reinforcing the drug’s rapid onset of effect in routine care.

These findings support the narrative that BIMZELX is not only effective in controlled trial conditions but also delivers meaningful symptom relief when used in broader, heterogeneous patient populations.

How is institutional sentiment shaping around UCB and its BIMZELX franchise?

Although UCB is not listed on a U.S. exchange and trades under the ticker UCB on Euronext Brussels, institutional investors and analysts are increasingly viewing BIMZELX as a de-risked long-term asset. The three-year data significantly mitigate one of the key concerns associated with novel biologics—durability of effect—and suggest that UCB’s IL-17A/F strategy is gaining traction.

Commentary from industry-facing outlets has characterized the data as a “durability milestone” that differentiates BIMZELX from other IL-17 inhibitors and some JAK inhibitors, many of which face scrutiny over long-term safety and tolerability. Analysts note that therapies with longer maintenance of remission could reduce switching costs, improve adherence, and increase lifetime value per patient—key metrics in payer and formulary negotiations.

With additional indications in dermatology and juvenile autoimmune conditions in development, BIMZELX is becoming central to UCB’s rheumatology pipeline. The biologic also benefits from competitive device improvements, including the 320 mg/2 mL autoinjector now available in key markets.

What future developments are expected for BIMZELX and UCB’s broader clinical strategy?

Looking ahead, UCB is preparing to build on these results with additional label expansions, geographic launches, and real-world outcomes research. The company has indicated that pediatric indications such as juvenile psoriatic arthritis and juvenile idiopathic arthritis are in early-stage trials. Expansion into rare dermatologic diseases such as palmoplantar pustulosis also remains on the roadmap.

From a health system perspective, the big question is whether payers will recognize and reward the long-term disease control offered by BIMZELX. While head-to-head studies remain limited, the three-year data give UCB a stronger position to negotiate in markets where biologic differentiation is key to reimbursement success.

There is also a broader strategic implication: in diseases with overlapping domains such as PsA and axSpA, having a single agent with durable multi-domain control could reduce polypharmacy risks and simplify care pathways. For clinicians, this could shift prescribing behavior toward BIMZELX as a go-to choice for long-term disease control—especially in treatment-naïve or early-switch patients.

How should long‑term durability data from BIMZELX in psoriatic arthritis and axial spondyloarthritis influence clinician confidence and future treatment decision‑making?

The three-year data presented at ACR 2025 mark a decisive turning point for BIMZELX in inflammatory arthritis. While one-year efficacy is often viewed as a proof-of-concept, long-term maintenance of disease control separates promising therapies from those capable of transforming care standards. What stands out here is not just the response durability, but the consistency across multiple disease manifestations, patient subtypes, and trial geographies.

UCB’s dual inhibition of IL-17A and IL-17F continues to look like a well-calculated bet, particularly as other cytokine targets become saturated or face safety hurdles. From a commercial standpoint, BIMZELX is now better positioned to defend market share, increase treatment durations, and drive greater return on clinical investment. For the rheumatology field, it suggests that deeper, more sustained disease remission may be attainable—not just theoretically, but reliably.

Key takeaways: What do the BIMZELX three-year results reveal about long-term inflammation control and treatment outcomes in psoriatic arthritis and axial spondyloarthritis?

• UCB’s BIMZELX (bimekizumab-bkzx) demonstrated sustained efficacy and inflammation control at three years in patients with psoriatic arthritis (PsA), non-radiographic axial spondyloarthritis (nr-axSpA), and ankylosing spondylitis (AS), reinforcing its durability as a long-term biologic therapy.

• In PsA patients, improvements across key GRAPPA domains—peripheral arthritis, dactylitis, enthesitis, and skin and nail psoriasis—were maintained through Year 3 in both biologic-naïve and TNF-inhibitor-experienced groups.

• Axial spondyloarthritis cohorts showed that 50% of patients never lost their ASDAS low disease activity (LDA) status across three years, with 78.8% of Week 16 responders maintaining that response at Week 164.

• Interim real-world data from the ongoing SPEAK study revealed early quality of life improvements in both PsA and axSpA patients, with clinical benefits appearing as early as Week 2 and sustained through Week 24.

• The consistent three-year performance, coupled with a favorable safety profile, positions BIMZELX as a potentially differentiated option in the competitive IL-17 and chronic inflammatory care market.

• Analysts view the data as reducing long-term efficacy risk, potentially improving UCB’s pricing leverage, payer positioning, and physician preference within its rheumatology strategy.

• UCB continues to expand BIMZELX into new indications and device formats while pursuing pediatric and dermatologic programs, signaling a long-horizon commercial lifecycle strategy.