The purpose of this study is to look at whether Advair® and SYMBICORT® have different effects on airway constriction by means of methacholine challenge testing.

Inclusion Criteria:

• 20 subjects males or females 18-65 years of age with physician diagnosed asthma Diagnosis of asthma > 12 months Currently on 2 puffs SABA bid. Baseline percent FEV1 of greater than 60% and less than or equal to 100% 12% reversibility in the previous 12 months 12% reversibility at Screening Visit Positive MTC (≤ 8mg/ml) at the end of 2 week Run-In Currently symptomatic with ACT score less than 19 at the end of run in on ICS ≥ 200 and ≤ 400 ug/day Non-smoker or ex-smoker with < 10 pk year who stopped > 1 year ago

Exclusion Criteria:

• Asthma exacerbation, significant airflow obstruction, or respiratory infection between Visits 0 and 2. Patients who fail screening because of one of these events may be re-screened once (at least 4 weeks after recovery from the event).

Pre-existing lung disease other than asthma, including active infections Clinically significant medical disease that is uncontrolled despite treatment or is likely in the opinion of the investigator to require a change in therapy during the study Noncompliance or inability to participate in all assessments. Current smoker or former smoker with a lifetime smoking history of ≥ 10 pack-years. A current smoker is defined as someone who has smoked one or more cigarettes per day (or marijuana or a pipe or cigar) for >/= 30 days within the 24 months prior to Visit 1.

Any individual who smokes (cigarettes, marijuana, pipe, or cigar) occasionally, even if for < 30 days in the 24 months Prior to Visit 1, must agree to abstain from all smoking from the time of consent through completion.

History of substance abuse that may impair or risk the patient's full participation in the study, in the judgment of the investigator.

Participation in another interventional clinical trial (including a trial of an approved drug or an interventional study that does not include medication) within 30 days or 5 half-lives of the investigational agent, whichever is longer.

Women with a positive urine pregnancy test.

Adverse Events were collected from screening to end of treatment visit

Forced expiratory volume in 1 second (FEV1) was not collected as an independent spirometric assessment. These measurements were intrinsically tied to the administration of the methacholine challenge. Consequently, the FEV1 data were neither captured nor analyzed outside the calculation of the provocative concentration threshold PC20. This limits the ability to evaluate standalone baseline shifts or isolated spirometric variability independently from the challenge.