This is a Phase 2a, double-blind, placebo-controlled, parallel group study in subjects with active ulcerative colitis and a non-remission (partial) response to infliximab. All enrolled subjects must have been on infliximab for a minimum of 14 weeks with last dose 8 weeks prior to the date of randomization. Subjects will be randomly assigned to 1 of 2 treatment arms (PF-06687234 or placebo) administered subcutaneously every week for a total of 12 doses. Blood, stool and tissue samples will be collected at various time points throughout the study to evaluate efficacy, safety, tolerability, pharmacokinetics and immunogenicity. Duration of participation for subjects will be approximately 6 months.