Safety and Efficacy Study Adding GSK2190915 to Mid-dose Inhaled Corticosteroid/Long Acting Beta Agonist Combination Treatment for Asthma

Inclusion Criteria: * Age: 18 years of age or older * Non-, former or current smokers with a documented smoking history of ≤ 10 pack years * Asthma diagnosis as defined by the National Institutes of Health * Best FEV1 of 50% to \<80% of the predicted normal value * For current and former smokers, a post-albuterol FEV1/FVC ratio of \>0.70 at Visit 1/1a (between 5:00AM and 12:00 noon) * ≥ 12% and ≥200mL reversibility of FEV1 * Must have been using FP/SAL 250/50mcg inhalation powder BID for at least 2 weeks just prior to Visit 1. * Must be able to replace their current short-acting beta2-agonists with albuterol inhalation aerosol * Must be able and willing to give written informed consent to take part in the study. * Must be able and willing to comply with all aspects of the study including completion of daily e-Diary. Exclusion criteria: * History of life-threatening asthma * Recent asthma exacerbation * Concurrent respiratory disease * Recent respiratory infection * Liver disease * Other concurrent diseases/abnormalities * Oral candidiasis * Drug allergy * Milk protein allergy * Immunosuppressive Medications * Administration of systemic, oral or depot corticosteroids within 12 weeks of Visit 1 * OATP1B1 substrates within 4 weeks of Visit 1 * Cytochrome P450 3A4 (CYP 3A4) Inhibitors * Cytochrome P450 3A4 (CYP 3A4) Inducers * Investigational Medications * Compliance: any infirmity, disability, or geographical location which seems likely (in the opinion of the Investigator) to impair compliance with any aspect of this study protocol * Affiliation with Investigator's Site