A Study To Monitor Long-Term Treatment With PF-00547659

The rationale for conducting this open-label extension (OLE) study is primarily to evaluate long term safety of PF 00547659. This protocol also provides the opportunity for continued treatment for subjects responding to treatment from the feeder study. It also provides an opportunity for initial treatment for subjects randomized to placebo in the feeder study. This is a multi center Phase 2, open label, safety extension study for feeder studies which evaluate PF 00546759 in subjects with moderate to severe Crohn's disease. Subjects eligible for this study will have completed the 12 week double blind induction period in study A7281006 and will be stratified by responders or non responders based on change in CDAI in that study, without unblinding treatment assignment from study A7281006. Additionally, subjects who have completed study A7281008 with a clinical response, as defined by that protocol, will also be eligible for this study and treated as "responders". All subjects entering this study must have discontinued immunosuppressant therapy. Subjects entering this study will be given a 75 mg SC dose at baseline and then every 4 weeks through Week 72. After the active treatment period, the subjects will enter a 24 month follow up period including 6 monthly visits followed by 18 month extended contact (every 6 month telephone contacts). At Week 96, subjects will undergo an End of Study visit but will continue the every 6 month telephone contacts until Week 168.