The study will enroll participants with moderate-to-severe uncontrolled asthma who are on low-dose inhaled corticosteroid (ICS) - a long-acting beta-agonist (LABA) or medium-to-high-dose ICS with or without LABA background treatment.~The study will be performed as a 2-part study Part 1 and Part 2 with a Lead-in pharmacokinetics (PK) cohort.~In the Lead-in PK cohort, participants will be randomised to AZD5718 or placebo.~In Part 1 of the study, participants will be selected and randomised 1:1 to AZD5718 or placebo. Participants found to be uLTE4-low at Screening for Part 1 (Visit 0 or Visit 1), can be rescreened for Part 2.~In Part 2 of the study, participants with uLTE4-low and uLTE4-high at Screening (Visit 0 or Visit 1) will be randomised to 1 of 5 treatment groups (AZD5718: Dose A, B, C, montelukast or placebo).
This is a randomised, placebo-controlled, double-blind study with an active comparator (montelukast) arm to assess the efficacy and safety of AZD5718 administered at multiple dose levels over a 12-week treatment period to adult participants with moderate-to-severe uncontrolled asthma.