A Randomized, Double-Blind, Double-Dummy, Placebo-Controlled, Three-Treatment, Three 6-Week Period Cross-Over, Multi-Center Study to Evaluate the Effect of Adding GSK2190915 300mg as Compared to Adding Montelukast 10mg or Placebo Tablets QD to Fluticasone Propionate/Salmeterol 250/50mcg Diskus BID

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.