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

The primary objective of this study is to evaluate the efficacy and safety of adding GSK2190915 300mg or placebo tablets administered once daily to fluticasone propionate/salmeterol 250/50mcg inhalation powder administered twice daily in uncontrolled asthmatic subjects \> or = 18 years of age over the course of 6 weeks treatment. The secondary objectives are to undertake an exploratory analysis of the efficacy and safety of adding montelukast 10mg administered once daily to fluticasone propionate/salmeterol 250/50mcg inhalation powder administered twice daily and to investigate the pharmacokinetics and pharmacodynamics of GSK2190915 in uncontrolled asthmatic subjects \> or = 18 years of age over the course of 6 weeks treatment.