UCB, the drugmaker based in Brussels, Belgium, reported six-month results from a direct comparison of its Bimzelx treatment with Skyrizi in adults with psoriatic arthritis, extending a study that had already met its main goal at 16 weeks. The new figures show a higher joint-response rate for Bimzelx at 24 weeks, but do not establish a fresh claim of statistical superiority at that later point.
In the 553-patient BE BOLD trial, 54.9% of patients assigned to Bimzelx reached an ACR50 response at week 24, compared with 43.8% assigned to Skyrizi, UCB said in its November 9 release. The full 24-week findings are scheduled for presentation November 10 at the American College of Rheumatology meeting in Orlando, Florida.
ACR50 is a measure of improvement, not a cure. Patients must have at least a 50% improvement in tender and swollen joint counts, together with improvement in several other measures such as pain, physical function and assessments by the patient and doctor.
Psoriatic arthritis is a long-term inflammatory disease that can affect joints and skin. It can cause pain, stiffness, swollen fingers and toes, and inflammation where tendons or ligaments attach to bone. Uncontrolled disease can cause lasting structural damage. A comparison between active treatments helps doctors weigh options for people whose disease needs better control.
The trial’s main test was ACR50 at week 16. As previously reported, 49.1% of patients receiving Bimzelx reached that response, compared with 38.0% receiving Skyrizi. That difference was statistically significant, with a p-value of 0.0058. The 24-week update follows that earlier result; it is not the first report that the trial met its primary goal.
A separate result limits how broadly the findings can be read. The first ranked secondary measure, minimal disease activity at week 16, did not show a statistically significant difference. That stopped the planned sequence of statistical tests. Later ranked secondary results are descriptive, meaning that higher percentages alone cannot be treated as proof that one drug is better on those measures. The week-24 ACR50 result is exploratory.
BE BOLD is a randomized Phase 3b study, with patients assigned by chance to one of the two treatments. It was double-blind through week 24, meaning patients and investigators did not know which treatment each patient received. Participants either had not used a biologic treatment before or had an inadequate response or intolerance to one earlier TNF-inhibitor treatment.
Bimzelx, the brand name for bimekizumab, blocks two inflammatory signaling proteins called IL-17A and IL-17F. Skyrizi, or risankizumab, blocks IL-23. UCB’s U.S. prescribing information lists Bimzelx as approved for adults with active psoriatic arthritis. This announcement concerns comparative trial evidence, not a new drug approval.
Safety also matters to that comparison. Adverse events arising during treatment were reported in 161 of 277 Bimzelx-treated patients, or 58.1%, and 152 of 275 Skyrizi-treated patients, or 55.3%. Candida infections occurred in 2.9% and 0.7%, respectively; all were mild or moderate and none led to discontinuation. The study was not large enough by design to establish a reliable safety comparison between the drugs.
For patients, the question is how sustained joint improvement weighs against side effects and their own treatment needs. For UCB, the update adds follow-up evidence for an existing medicine. It does not show that Bimzelx is better on every measure or safer than Skyrizi, and the full conference presentation is still to come.
JBizNews Desk | Brussels
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