The D-prostanoid receptor and the chemoattractant receptor homologous molecule expressed on T_H2 cells (CRTH2) are implicated in asthma pathogenesis. AMG 853 is a potent, selective, orally bioavailable, small-molecule dual antagonist of human D-prostanoid and CRTH2.

We sought to determine the efficacy and safety of AMG 853 compared with placebo in patients with inadequately controlled asthma.

Adults with moderate-to-severe asthma were randomized to placebo; 5, 25, or 100 mg of oral AMG 853 twice daily; or 200 mg of AMG 853 once daily for 12 weeks. All patients continued their inhaled corticosteroids. Long-acting β-agonists were not allowed during the treatment period. Allowed concomitant medications included short-acting β-agonists and a systemic corticosteroid burst for asthma exacerbation. The primary end point was change in total Asthma Control Questionnaire score from baseline to week 12. Secondary and exploratory end points included FEV₁, symptom scores, rescue short-acting β-agonist use, and exacerbations.

Among treated patients, no effect over placebo (n = 79) was observed in mean changes in Asthma Control Questionnaire scores at 12 weeks (placebo, −0.492; range for AMG 853 groups [n = 317], −0.444 to −0.555). No significant differences between the active and placebo groups were observed for secondary end points. The most commonly reported adverse events were asthma, upper respiratory tract infection, and headache; 9 patients experienced serious adverse events, all of which were deemed unrelated to study treatment by the investigator.

AMG 853 as an add-on to inhaled corticosteroid therapy demonstrated no associated risks but was not effective at improving asthma symptoms or lung function in patients with inadequately controlled moderate-to-severe asthma.