A new bimekizumab PsA trial readout from BE BOLD shows dual IL-17A/IL-17F inhibition (bimekizumab, Bimzelx) beats IL-23 inhibition (risankizumab, Skyrizi). The 11.1% gap at week 16 in psoriatic arthritis (PsA) was highly significant.

Joseph Merola, MD, MMSc, presented at the European Alliance of Associations for Rheumatology (EULAR) 2026 Annual Meeting in London. He chairs Dermatology at UT Southwestern Medical Centre, Dallas.

Why the bimekizumab PsA trial matters

Both drugs are approved for plaque psoriasis and PsA, but have not gone head-to-head on joints.

Merola framed the trial as a key data point for treatment guidelines: "We haven't had such high-quality data to date in this space; these [data] will be important for treatment guidelines, and I think it will inform our management of psoriatic arthritis."

How BE BOLD was set up

BE BOLD is a phase 3b study: 24-week treatment plus 12-week safety follow-up. Patients had active PsA with at least three tender or swollen joints. They had to be intolerant to a TNF inhibitor (TNFi), respond poorly to TNFi, or be TNFi-naïve.

Patients went to bimekizumab (n = 277) or risankizumab (n = 276):

• Bimekizumab: 160 mg every 4 weeks for no or moderate psoriasis (n = 248). Moderate to severe psoriasis (~11% per arm) got 320 mg every 4 weeks for 16 weeks, then every 8 weeks.
• Risankizumab: 150 mg at baseline, week 4, then every 12 weeks per label.

Baseline traits lined up across arms:

• Mean age 51 years.
• 51% male.
• Mean time since PsA diagnosis: 6 years.
• Prior TNFi therapy: about one-fifth.
• Any prior csDMARD: 70%.
• Tender/swollen joints: 17.3/10.1 (bimekizumab) vs 16.6/9.5 (risankizumab).

The primary endpoint hit by week 4

The bimekizumab PsA trial primary endpoint was a 50% drop on American College of Rheumatology criteria (ACR50) at week 16. The trial cleared it.

• ACR50 at week 16: 49.1% bimekizumab vs 38.0% risankizumab. Gap: 11.1% (P = .0058).
• ACR50 at week 4: 19.9% vs 7.2% (P < .0001).
• ACR50 at week 24: 54.9% vs 43.8%.

"I think this is relevant to us clinically, insofar as we make our clinical decisions as early as 12 weeks in many patients," Merola said.

"We've [also] talked for many years about how time matters to patients with this disease, both with regard to symptoms but also functional damage over time," he added.

Disease activity and skin endpoints

Most secondary endpoints favoured bimekizumab in this bimekizumab PsA trial. But only numerically. With hierarchical statistical testing, only minimal disease activity (MDA, the first secondary endpoint) showed a numerical edge. Results are exploratory.

• MDA at weeks 4/16/24: 13.7%/43.3%/49.1% bimekizumab vs 6.5%/39.9%/42.4% risankizumab.
• ACR50 + PASI 100: 3.4%/33.5%/39.2% vs 1.1%/24.4%/34.1%.
• Disease Activity Index for Psoriatic Arthritis (DAPSA) low disease activity or remission: 29.6%/65.3%/68.2% vs 21.7%/55.1%/62.3%.

In the ≥3% body surface area psoriasis subgroup, PASI 100 favored bimekizumab at week 4 (12.5% vs 3.4%) and week 16 (53.4% vs 46.6%). Week 24 evened out (59.7% vs 59.1%).

Safety looked comparable

Safety data from the bimekizumab PsA trial tracked closely between arms, with no new signals.

• Treatment-emergent adverse events (TEAEs): 58.1% bimekizumab vs 55.3% risankizumab.
• Serious TEAEs: 1.8% vs 3.3%.
• Severe TEAEs: 1.8% vs 1.8%.
• Discontinuation due to TEAEs: 1.4% vs 1.1%.

Candida infections appeared more often on bimekizumab. None reached serious or systemic status. None caused study withdrawal. One patient with coronary artery disease, hypertension, and dyslipidemia died from a myocardial infarction. The arm was not disclosed. The death was judged unrelated to either drug.

What outside experts said

Jonathan Kay, MD, of the University of Massachusetts School of Medicine, Worcester, weighed in on the bimekizumab PsA trial. He holds the Timothy S. and Elaine L. Peterson Chair in Rheumatology. He was not part of the study.

"It's important to show dual IL-17 inhibition is superior to IL-23 inhibition, which helps to direct the choice of appropriate therapy to patients with psoriatic arthritis," Kay told Medscape Medical News.

UCB funded the trial. Coverage on Medigear.uk tracks how the bimekizumab PsA trial reshapes care.

Source: Originating coverage based on Medscape Medical News reporting on the BE BOLD trial presented by Joseph Merola, MD, MMSc, of UT Southwestern Medical Centre in Dallas at the European Alliance of Associations for Rheumatology (EULAR) 2026 Annual Meeting in London. Outside commentary from Jonathan Kay, MD, University of Massachusetts School of Medicine, Worcester. Funded by UCB.