D1.147 - Efficacy of benralizumab in Chinese patients with severe eosinophilic asthma: subgroup analysis of the 16-week results from STEP, a phase IIIb study of step-down maintenance therapy

STEP is the first study evaluating benralizumab for reducing background therapy in Chinese patients with severe eosinophilic asthma (SEA); unlike prior global studies, STEP includes patients on medium-dose inhaled corticosteroids-long-acting β₂-agonist (ICS-LABA). This interim analysis explored the efficacy of benralizumab by patient baseline characteristics.

STEP (NCT06465485) is a single-arm, phase IIIb trial in 76 Chinese hospitals. SEA patients aged 12–75 years with ≥1 exacerbation(s) in the prior year, and on stable medium- or high-dose ICS-LABA for ≥2 months were enrolled. Benralizumab 30 mg was given subcutaneously at Week 0, 4, 8 and 16. Patients were stratified by baseline blood eosinophil count (BEC), Asthma Control Questionnaire (ACQ)-5 score, presence of persistent airway obstruction (PAO), body mass index (BMI) and age of asthma onset.

From February 28, 2024 to March 18, 2025, 489 patients were enrolled. At Week 16, 57.4% (264/460) achieved asthma control (ACQ-5 score <1.5 and since last visit, no asthma exacerbations requiring systemic corticosteroids or hospitalization and no clinically significant worsening of ACQ-5 and lung function). Patients with BEC of 150–<300 cells/µL showed improvement in ACQ-5 but not in pre-bronchodilator (BD) forced expiratory volume in 1 second (FEV₁) (mean [SD] change: −0.35 [0.95] and −0.01 [0.29] L); both improvement were seen in those of 300–<500 cells/µL (mean [SD] change: −0.57 [0.90] and 0.11 [0.44] L) and were greater in those ≥500 cells/µL (mean [SD] change: −0.98 [1.05] and 0.32 [0.49] L). In patients with BEC ≥500 cells/µL, 63.3% and 63.7% achieved minimum clinically important difference in ACQ-5 (defined as change ≤−0.5) and pre-BD FEV₁ (defined as change ≥100 mL), respectively. In patients with baseline ACQ-5 ≥1.5, mean (SD) change in ACQ-5 and pre-BD FEV₁ was −1.43 (1.03) and 0.35 (0.52) L. Patients with PAO showed greater improvement than those without PAO (mean [SD] change in ACQ-5: −1.00 [1.26] vs. −0.51 [0.98]; in pre-BD FEV₁: 0.38 [0.51] L vs. 0.12 [0.42] L). Improvements were similar in BMI and age-of-onset subgroups, although patient numbers were small in some subgroups. See Table for full results.

In Chinese patients with SEA, benralizumab treatment led to improvement in symptom control and lung function, especially in patients with higher BEC and those with PAO. The modest efficacy in patients with lower BEC highlights the need for further subgroup analysis.

Funding: This study was supported by AstraZeneca China.