Efficacy and Safety of Inhaled AZD1402 Administered for Four Weeks in Adults With Asthma on Medium-to-High Dose Inhaled Corticosteroids

Part 1 of the study will be randomised, double blind, placebo-controlled, and conducted in parallel for the 2 lower dose levels (Part 1a) followed by an unblinded safety review and escalation to the highest dose (Part 1b) dependent on the outcome of the safety review. Part 1a will consist of 30 participants who will be randomised 1:1:1 to receive 1 of the 2 lower AZD1402 dry power inhaler (DPI) doses (Dose 1 or Dose 2) or placebo in parallel. Part 1b will consist of 15 participants who will be randomised 2:1 to receive the highest AZD1402 DPI dose (Dose 3) or placebo. Part 1a Lead-in Cohort * AZD1402 Dose 1 * AZD1402 Dose 2 * Placebo Part 1b Lead-in Cohort * AZD1402 Dose 3 * Placebo Part 2 will be randomised, double blind, placebo controlled and will include approximately 165 participants randomised 2:1 (active to placebo) to evaluate 2 inhaled dose levels of AZD1402 versus placebo. Part 2 will be started after the unblinded safety review for Part 1a. Part 2 will include: * AZD1402 Dose 1 * AZD1402 Dose 2 * Placebo