Study to Evaluate Safety, Tolerability and Efficacy of GSK2330811 in Crohn's Disease

The study will include participants with moderate to severe Crohn's disease. The aim is to evaluate the safety, tolerability, and efficacy of anti-oncostatin M monoclonal antibody (mAb) GSK2330811. This is a parallel group study with Induction and Maintenance periods. During Induction, the first 100 participants randomised will receive a 450mg GSK2330811 SC loading dose followed by 150mg weekly (Q1W), or placebo for 12 weeks. Additional dose-ranging arms will open after the 100th participant is randomized and in addition to placebo and the highest dose arms will also include a 300mg subcutaneous (SC) loading dose followed by 150mg SC every 2 weeks (Q2W) arm, a 300mg loading dose followed by 150mg SC every 4 weeks (Q4W) arm and a 150mg SC every 8 weeks (Q8W) arm. Participants with a clinical response at Week 12 will continue into a 40-week blinded maintenance period and will receive either 150mg SC Q2W, 150mg SC Q4W, 150mg SC Q8W or placebo. Participants without a clinical response at Week 12 will be offered up to 40 weeks of open label treatment with GSK2330811. Approximately 560 participants will be screened to randomize 280.