D1.449 - A Phase 2, Open-Label Extension Study to Evaluate the Long-Term Safety and Efficacy of Briquilimab in Adults with Chronic Urticaria (Trial in Progress)

Briquilimab blocks the SCF binding to KIT, resulting in inhibition and apoptosis of mast cells, the central drivers of CSU pathogenesis and its key symptoms, itch and hives.  Two phase 1b/2a studies are currently ongoing to evaluate briquilimab in CU. We present an overview of a phase 2, open-label extension (OLE) study (NCT06736262) of the phase1b/2a clinical trials for adult participants with chronic spontaneous urticaria (CSU) (BEACON, NCT06162728) and chronic inducible urticaria (CIndU) (SPOTLIGHT, NCT06353971). The objective of this OLE study is to evaluate the long-term safety and efficacy in participants with CU previously treated with briquilimab. 

Briquilimab 180mg was administered subcutaneously every 8 weeks (Q8W) to adult participants from the parent CSU and CIndU studies, regardless of previous dose/regimen.

As of December 11, 2025, at Week 12 in CSU participants, mean change from baseline in UAS7 is -22.4 (n=36) (Figure 1), complete Response (CR), defined as UAS7 of 0, is 58% (21/36), and CR plus Well-Controlled disease (WC), defined as UAS7>0 and <6, is 75% (27/36). CR is seen as early as 2 weeks at 30% (13/43) and, so far, achieved through Week 20 at 62% (21/34).

At Week 16 in CINDU participants, 41.2% (7/17) had CR and 64.7% (11/17) had Partial Response (PR).

There were 61.9% (39/63) participants who experienced TEAEs, all of which were GR 1/2, except for 4 GR3 AEs which were not related to treatment.  There were 2 non-treatment-related SAEs (large intestinal obstruction and breast injury). One treatment-related TEAE resulted in treatment discontinuation (GR 1 hypogeusia).  There were no hypersensitivity or anaphylactic reactions. The most common TEAEs were nasopharyngitis 15.9% (10/63), taste disorder 11.1% (7/63), COVID 19 6.3% (4/63), and fatigue 4.8% (3/63).  Taste disorder AEs are considered possibly related to the mechanism of KIT blockade.  

Briquilimab is well-tolerated and results in rapid, clinically meaningful disease control in patients with moderate-to-severe CSU and CINDU refractory to H1-AH. The onset of clinical responses is associated with substantial reductions in mast cell activity; the depth and durability of responses increase in a dose-dependent manner. This study is currently enrolling patients across the US and Germany. 

The data to date support further development of briquilimab for CSU and CINDU.