Highlights
Superior Long-Term Efficacy
Bimekizumab maintained high rates of complete skin clearance (PASI 100) in approximately 68.8% of patients through three years of treatment.
Rapid and Durable Symptom Relief
Patients treated with bimekizumab reported significantly faster and more profound reductions in itching, skin pain, and scaling compared to those on secukinumab, with benefits sustained for 144 weeks.
Effective Treatment Switching
Patients who switched from secukinumab to bimekizumab at week 48 achieved similar levels of skin clearance and quality-of-life improvements by year three as those who received continuous bimekizumab.
Consistent Safety Profile
No new safety signals emerged over three years, with the most common adverse events being nasopharyngitis and oral candidiasis, the latter being a known pharmacological effect of IL-17F inhibition.
The Evolving Landscape of Psoriasis Management
Moderate-to-severe plaque psoriasis is a chronic, systemic inflammatory disease that profoundly impacts physical health and psychological well-being. Historically, the therapeutic goal was a 75% improvement in the Psoriasis Area and Severity Index (PASI 75). However, with the advent of biologics targeting the interleukin (IL)-23/IL-17 axis, the clinical standard has shifted toward PASI 90 or PASI 100, representing clear or almost clear skin.
While IL-17A inhibitors like secukinumab have revolutionized care, some patients fail to achieve or maintain complete clearance. Bimekizumab, a humanized IgG1 monoclonal antibody, offers a novel approach by dual inhibition of both IL-17A and IL-17F. Since IL-17F is overexpressed in psoriatic lesions and shares structural homology with IL-17A, dual inhibition is hypothesized to provide more comprehensive suppression of the inflammatory cascade. The BE RADIANT trial was designed to test this hypothesis against a high-standard comparator, secukinumab.
Study Design: The BE RADIANT Phase 3b Trial and Extension
The BE RADIANT trial was a multicenter, Phase 3b randomized controlled trial followed by an open-label extension (OLE). The study was divided into two main phases:
Phase 1: Double-Blind Period (Weeks 0–48)
Patients were randomized to receive either bimekizumab (320 mg every 4 or 8 weeks) or secukinumab (300 mg weekly to Week 4, then every 4 weeks). The primary objective was to compare the efficacy of bimekizumab versus secukinumab in achieving PASI 100 at week 16 and week 48.
Phase 2: Open-Label Extension (Weeks 48–144)
At week 48, patients who completed the initial phase entered the OLE. All patients received bimekizumab 320 mg. Those originally on bimekizumab continued their regimen, while those on secukinumab switched to bimekizumab. By week 64, all patients were transitioned to an every-8-week dosing schedule. This extension phase allowed for the assessment of long-term durability, the impact of switching therapies, and cumulative safety over a total of three years.
Clinical Efficacy: Achieving and Maintaining PASI 100
Data from the BE RADIANT trial highlight the superior performance of dual IL-17A/F inhibition. At the end of the one-year double-blind period, 74.8% of patients randomized to bimekizumab achieved PASI 100, compared to 52.8% of those on secukinumab. This clinical superiority was not only statistically significant but also clinically meaningful for patients seeking total skin clearance.
As the study progressed into the three-year mark, the results remained robust. In the continuous bimekizumab group, 68.8% of patients maintained PASI 100 at year three (using modified non-responder imputation). Perhaps most strikingly, patients who switched from secukinumab to bimekizumab saw their PASI 100 response rates rise from 52.8% at year one to 68.8% at year three, effectively matching the efficacy of the continuous bimekizumab group. This suggests that bimekizumab can successfully rescue patients who may have had a sub-optimal or plateaued response to IL-17A inhibition alone.
The Patient Perspective: Itching, Pain, and Scaling
Clinical indices like PASI are vital, but they do not always capture the daily burden of disease. The BE RADIANT trial utilized the Psoriasis Symptoms and Impacts Measure (P-SIM) to assess patient-reported outcomes (PROs).
At week 4, a significantly higher proportion of bimekizumab-treated patients reported a total absence of symptoms compared to the secukinumab group:
– No itching: 34.0% vs. 25.1%
– No skin pain: 74.5% vs. 60.0%
– No scaling: 46.1% vs. 21.6%
By year one, the gap remained significant, with bimekizumab-treated patients reporting higher rates of being symptom-free across all categories. During the OLE, these high rates of P-SIM = 0 were maintained through year three. For patients, the rapid relief from itching and pain is often the most valued aspect of treatment, and bimekizumab’s ability to provide this early in the induction phase is a significant clinical advantage.
Translating Clearance into Quality of Life
The ultimate goal of psoriasis therapy is to restore the patient’s quality of life. The Dermatology Life Quality Index (DLQI) is a standard tool where a score of 0 or 1 indicates that the disease has no impact on the patient’s life.
The BE RADIANT trial analyzed the concurrent achievement of PASI 100 and DLQI 0/1. At week 4, 11.5% of bimekizumab patients had already reached this dual milestone, compared to 4.6% for secukinumab. By year one, this increased to 61.7% for bimekizumab versus 42.7% for secukinumab. In the OLE, approximately 62.2% of continuous bimekizumab patients and 63.8% of switchers maintained this high level of health-related quality of life through year three. This correlation between complete skin clearance and life quality underscores the importance of striving for PASI 100 in clinical practice.
Safety and Tolerability Over the Long Term
Long-term safety is a critical consideration for chronic biologic therapy. Over the three-year observation period, bimekizumab was generally well tolerated. The exposure-adjusted incidence rates (EAIR) of treatment-emergent adverse events (TEAEs) did not increase with longer exposure.
The most common TEAEs were:
– Nasopharyngitis (12.2/100 patient-years)
– Oral candidiasis (10.0/100 patient-years)
– Upper respiratory tract infection (5.5/100 patient-years)
Oral candidiasis is a known effect of inhibiting IL-17F, which plays a role in mucosal antifungal defense. Most cases were reported as mild or moderate and rarely led to treatment discontinuation. Other adverse events of interest, such as inflammatory bowel disease (IBD), serious infections, and suicidal ideation/behavior, remained very low and did not show an upward trend over time. This profile provides clinicians with the confidence needed for long-term prescribing.
Mechanistic Insights: Why Dual Inhibition Matters
The superior results of bimekizumab over secukinumab can be attributed to its unique mechanism of action. While IL-17A is the most potent pro-inflammatory cytokine in the IL-17 family, IL-17F is more abundant in psoriatic skin and also contributes to the inflammatory milieu. By neutralizing both, bimekizumab achieves a deeper suppression of downstream signaling in keratinocytes and immune cells. This likely explains the faster onset of action and the higher ceiling for complete skin clearance observed in the BE RADIANT trial.
Conclusion and Clinical Implications
The three-year data from the BE RADIANT trial and its open-label extension solidify bimekizumab’s position as a highly effective long-term treatment for moderate-to-severe plaque psoriasis. The findings demonstrate that:
1. Bimekizumab is superior to secukinumab in achieving and maintaining complete skin clearance.
2. Clinical efficacy translates directly into profound improvements in patient-reported symptoms and quality of life.
3. Switching from an IL-17A inhibitor to a dual IL-17A/F inhibitor can provide additional clinical gain.
4. The safety profile remains consistent and manageable over three years of continuous use.
For clinicians, these results support the use of bimekizumab as a first-line biologic or a potent switch option for patients who prioritize rapid and sustained total skin clearance and an improved quality of life.
Funding and ClinicalTrials.gov
The BE RADIANT trial and its open-label extension were funded by UCB Pharma.
ClinicalTrials.gov Identifier: NCT03536884.
References
1. Augustin M, Feldman SR, Warren RB, et al. Three-Year Patient-Reported Outcomes From Bimekizumab for Plaque Psoriasis: The BE RADIANT Randomized Clinical Trial With Open-Label Extension. JAMA Dermatol. 2026 Feb 18. doi: 10.1001/jamadermatol.2025.6055.
2. Strober B, Paul C, Blauvelt A, et al. Bimekizumab efficacy and safety in patients with moderate to severe plaque psoriasis: Two-year interim results from the open-label extension of the randomized BE RADIANT phase 3b trial. J Am Acad Dermatol. 2023 Sep;89(3):486-495. doi: 10.1016/j.jaad.2023.04.063.
3. Warren RB, Lebwohl M, Thaçi D, et al. Bimekizumab efficacy and safety through 3 years in patients with moderate-to-severe plaque psoriasis: long-term results from the BE RADIANT phase IIIb trial open-label extension period. Br J Dermatol. 2025 Jun 20;193(1):44-55. doi: 10.1093/bjd/ljaf032.
