GB001 is an oral antagonist of the prostaglandin D2 receptor that may inhibit recruitment and activation of airway eosinophils, reducing airway inflammation.

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.

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.

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.

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.