Mild asthma

This is a pharmacodynamic bioequivalence bronchoprovocation study using single-dose, double-blind, double-dummy, randomized, study consisting of four study treatments (zero dose [Placebo], E.Q. 90 mcg Base dose of R inhalation aerosol, E.Q. 180 mcg Base dose of R inhalation aerosol, E.Q. 90 mcg Base dose of T inhalation aerosol) and four Periods (Period 1 to Period 4). Randomization procedure at Period 1 will assign any one study treatment to be administered in each Period in a cross-over manner. By the end of Period 4, a subject who completes dosing in all four Periods would have administered all four treatments in the study.
The efficacy variable, post-dose PC20 obtained during each Period is the provocative concentration of the methacholine challenge agent required to reduce the FEV1 by 20% following administration of differing doses of albuterol (or placebo) by inhalation. The 20% reduction in FEV1 is determined as compared to post-saline FEV1 measured before the Placebo or Albuterol administration.
The pharmacodynamic equivalence will be based on the dose-scale method of analysis of the post-dose PC20 If the 90% confidence interval for the relative bioavailability (F) falls within 67.00% -150.00% then it will be considered that pharmacodynamic equivalence is established.

The purpose of this study is to compare the efficacy and safety of albuterol/budesonide to albuterol in changes in airway inflammation, asthma symptoms, and rescue therapy utilization in adults with mild asthma.
Study details include:
* The study duration will be up to 15 weeks.
* The treatment duration will be 12 weeks.
* The visit frequency will be once every 4 weeks, with 3 clinic visits and 2 video calls in total.

The primary objectives of the study are:
* Part 1: to characterize the potency and variability of dose response on efficacy (Provocative concentration of methacholine causing at least a 20% fall in forced expiratory volume (FEV1) [PC20]) of salbutamol administered via MDI with salbutamol HFA-134a or salbutamol HFA-152a in participants with mild asthma.
* Part 2: to compare the comparative dose response on efficacy (PC20) of salbutamol when administered via MDI with salbutamol HFA-134a or salbutamol HFA-152a in participants with mild asthma.