 An interim analysis of fecal markers and disease activity data will be performed by the end of Cohort 3. Based upon results, the study may be stopped or continued by recruiting either Cohort 4 if data on an additional dose level would be warranted to establish or clarify a dose-response relationship or, in the case of a robust efficacy signal at any dose level previously studied, Cohort 5 to expand the sample size for given dose level in order to evaluate the efficacy of GSK1399686. The number of patients and randomization allocation ratio may be altered in Cohort 5 and it may not include an active control arm. If Cohort 4 is initiated upon interim analysis, then a second interim analysis may be performed at the end of Cohort 4, to assess whether progression into Cohort 5 as defined above would be justifiable. 