A phase 2 study to evaluate the safety, efficacy and pharmacokinetics of DP2 antagonist GB001 and to explore biomarkers of airway inflammation in mild‐to‐moderate asthma

BACKGROUND: GB001 is an oral antagonist of the prostaglandin D2 receptor that may inhibit recruitment and activation of airway eosinophils, reducing airway inflammation. OBJECTIVE: To assess GB001 safety, efficacy and pharmacokinetics from a Phase 2 study and explore the association between type 2 biomarkers (fractional exhaled nitric oxide and blood eosinophils) and asthma control markers following GB001 administration. METHODS: A randomized, placebo‐controlled, double‐blind study evaluating 36 patients with mild‐to‐moderate atopic asthma. Patients receiving fluticasone propionate ≤500 mcg/day or equivalent were randomized (2:1) to GB001 (30 mg) or placebo once daily for 28 days. Safety, pharmacokinetics, forced expiratory volume in 1 second, asthma control questionnaire and rescue medication use were assessed. Clinical outcomes were analysed post hoc by baseline fractional exhaled nitric oxide (<35 and ≥35 ppb) and blood eosinophil (<250 and ≥250 cells/µL) subgroups. RESULTS: GB001 was well tolerated and rapidly absorbed with a 14.5‐hour terminal half‐life. Overall, GB001 demonstrated greater improvement relative to placebo in forced expiratory volume in 1 second at Day 28 (102 mL [95% CI: −110, 314]). Greater effects on forced expiratory volume in 1 second were observed in the high baseline fractional exhaled nitric oxide and blood eosinophil subgroups (207 mL [95% CI: −283, 698];133 mL [95% CI: −422, 687], respectively). These effects were observed as early as Day 2 (229 mL [95% CI: −170, 628]; 163 mL [95% CI: −223, 550] for the high baseline fractional exhaled nitric oxide and blood eosinophil subgroups, respectively) and were sustained through treatment completion. CONCLUSION AND CLINICAL RELEVANCE: GB001 was well tolerated, with the estimated half‐life supporting once‐daily (QD) dosing. GB001 may have a rapid and sustained effect on lung function, particularly in patients with type 2 phenotype. Further studies are needed to confirm these findings.