Decoding the Bimekizumab SI/B Warning: What Dermatologists Should Know

In this episode of Topical Conversations, Bruce E. Strober, MD, PhD, joins April Armstrong, MD, MPH, to explore the origins and clinical relevance of the suicidal ideation and behavior (SI/B) warning in the bimekizumab label. With bimekizumab now approved in dermatology for adults with moderate to severe plaque psoriasis and moderate to severe hidradenitis suppurativa (HS), many clinicians are asking whether this warning reflects a meaningful safety signal or a cautious interpretation of tightly monitored trial data.

Where did the SI/B language come from?

Dr Armstrong explains that the warning appears in the “Warnings and Precautions” section, advising clinicians to weigh risks and benefits in patients with a history of severe depression or SI/B and to monitor for new or worsening symptoms. Importantly, the label states that a causal association has not been established.

She explains the likely origin of the language: highly sensitive, prospective monitoring in the bimekizumab trials. Compared with older psoriasis studies, these trials used more rigorous tools, such as the Columbia Suicide Severity Rating Scale (C-SSRS), capturing even passive ideation. In psoriasis trials, SI/B rates were 1.8% for bimekizumab vs 0.6% for placebo, but with wide confidence intervals crossing 1, signaling no clear statistical difference.

In HS trials, confidence intervals were again wide and without consistent patterns in suicidal behavior. Across psoriatic arthritis, ankylosing spondyloarthritis, and nonradiographic axial spondyloarthritis studies, short-term data did not show elevated SI/B rates with bimekizumab.

Interpreting the findings: context is critical

Dr Strober emphasizes that no suicides occurred in the trials; the flagged events involved passive ideation captured through structured questionnaires and not clinical suicide attempts or behaviors.

To contextualize, Dr Armstrong reviews background SI/B rates in psoriasis. Patients with psoriasis exhibit roughly double the risk of suicidal ideation and elevated risk of attempts vs the general population, particularly in patients with moderate to severe disease. Across psoriasis studies, SI/B event rates range from 0.1%–0.5% per 100 patient-years.

Bimekizumab’s aggregated phase 2/3 psoriasis data show an SI/B rate of ~0.13% per 100 patient-years, aligning with background disease rates.

How does bimekizumab compare with other biologics?

Notably, SI/B rates for bimekizumab appear comparable to, or lower than, rates reported in trials of IL-17 inhibitors (such as secukinumab and ixekizumab) and IL-23 inhibitors. Dr Strober highlights that nothing in the bimekizumab dataset distinguishes it from patterns seen with other biologics across clinical development programs.

Insights from depression measures in the trials

Dr Armstrong points out that depression severity, measured by PHQ-9, improved substantially with bimekizumab in clinical trials. Additional key details include no dose–response relationship for SI/B, no clustering shortly after dosing, and many events adjudicated as not drug-related.

Long-term extension and emerging real-world data have not revealed a new or consistent SI/B signal.

A clinician’s approach to counseling and monitoring

Dr. Armstrong closes by noting that depression severity improved, on average, for bimekizumab-treated patients as measured by PHQ-9 scores.  

Still, because the language appears in the label, she recommends dermatologists approach patient discussions with clarity: contextualize the data, acknowledge the broader mental health burden in psoriasis, and continue standard monitoring for mood changes as part of comprehensive care.

Key takeaways

• The bimekizumab SI/B warning is precautionary, and a causal relationship has not been established
• Event rates in bimekizumab trials align with background SI/B rates expected in moderate–severe psoriasis populations
• No completed suicides or clear dose-related patterns were identified across the clinical program
• Comparable or lower SI/B rates have been observed relative to other IL-17 and IL-23 inhibitors
• PHQ-9 scores improved with treatment, suggesting overall positive effects on patient well-being
• Clinicians should contextualize the label language when counseling patients, especially given psoriasis’ intrinsic psychiatric comorbidity burden
• Standard monitoring for depression remains appropriate, but current evidence does not indicate a unique or elevated SI/B risk with bimekizumab