May 6, 2025

Rilzabrutinib in Antihistamine-Refractory Chronic Spontaneous Urticaria The RILECSU Phase 2 Randomized Clinical Trial

Giménez-Arnau A, Ferrucci S, Ben-Shoshan M, et al. JAMA Dermatol. Published online April 23, 2025. doi:10.1001/jamadermatol.2025.0733

Key Points

Question  What is the efficacy and risk profile of rilzabrutinib, an oral reversible covalent Bruton tyrosine kinase inhibitor, in adults with antihistamine-refractory chronic spontaneous urticaria (CSU)?

Findings  In this randomized clinical trial of 160 patients with moderate to severe CSU, rilzabrutinib, 1200 mg/d, significantly decreased patients’ weekly Urticaria Activity Score and its components (weekly Itch Severity Score and weekly Hives Severity Score) at week 12 and as early as week 1. No new risks were observed.

Meaning  Rilzabrutinib reduced itch and hives while maintaining a favorable risk-benefit profile, suggesting rilzabrutinib may be an efficacious treatment for patients with antihistamine-refractory moderate to severe CSU.

Abstract

Importance  Chronic spontaneous urticaria (CSU) is a skin disease driven mainly by the activation of cutaneous mast cells through various mechanisms.

Bruton tyrosine kinase (BTK), expressed in B cells and mast cells, plays a critical role in multiple immune-mediated disease processes.

Objective  To determine the efficacy and risk profile of rilzabrutinib (SAR444671), an oral, reversible, covalent, next-generation BTK inhibitor, in treating patients with CSU.

Design, Setting, and Participants  The Rilzabrutinib Efficacy and Safety in CSU (RILECSU) randomized clinical trial was a 52-week phase 2 study comprising a 12-week, double-blind, placebo-controlled, dose-ranging period, followed by a 40-week open-label extension. The trial was conducted from November 24, 2021, through April 23, 2024. Fifty-one centers enrolled and randomized participants across 12 countries in Asia, Europe, North America, and South America. The trial participants included adults aged 18 to 80 years with moderate to severe CSU (weekly Urticaria Activity Score [UAS7] of 16 or more; weekly Itch Severity Score [ISS7] of 8 or more) not adequately controlled with H1-antihistamine treatment.

Interventions  Patients were randomized 1:1:1:1 to rilzabrutinib, 400 mg, once every evening (400 mg/d), twice per day (800 mg/d), 3 times per day (1200 mg/d), or matching placebo.

Main Outcomes  The primary end point was change from baseline at week 12 in ISS7 (for US and US reference countries) or UAS7 (for non-US reference countries).

Results  A total of 160 omalizumab-naive and omalizumab-incomplete responders were randomized (mean [SD] age, 44.1 [13.4] years; 112 [70.0%] female). The primary analysis population included only the 143 omalizumab-naive patients. Significant reductions at week 12 were observed with rilzabrutinib, 1200 mg/d, vs placebo from baseline in ISS7 (least squares [LS] mean, −9.21 vs −5.77; difference, −3.44 [95% CI, −6.25 to −0.62]; P = .02) and UAS7 (LS mean, −16.89 vs −10.14; difference, −6.75 [95% CI, −12.23 to −1.26]; P = .02). In addition, improvements in weekly Hives Severity Score (HSS7) and weekly Angioedema Activity Score (AAS7) were observed. Improvements in ISS7, UAS7, HSS7, and AAS7 were observed as early as week 1. CSU-related biomarkers, including soluble Mas-related G protein–coupled receptor X2, immunoglobulin (Ig)-G antithyroid peroxidase, IgG anti-Fc-ε receptor 1, and interleukin-31, were reduced compared to placebo at week 12. Rilzabrutinib demonstrated a favorable risk-benefit profile; adverse events occurring at a higher frequency with rilzabrutinib vs placebo included diarrhea, nausea, and headache.

Conclusions and Relevance  The results of the RILECSU randomized clinical trial demonstrated efficacy and rapid onset of action of rilzabrutinib, 1200 mg/d, over 12 weeks, in addition to an acceptable adverse event profile. Together, these data support the use of rilzabrutinib in treating patients with moderate to severe CSU refractory to H1-antihistamines. Further research is needed to determine long-term efficacy and potential harms.

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