PRECiSE 4A Phase III Multi-national, Multi-centre, Open Label, Safety Study to Assess the Safety of Re-exposure After a Variable Interval and Subsequent Chronic Therapy With the Humanised Anti-TNF PEG Conjugate CDP870 400 mg sc, (Dosed at Weeks 0, 2 and 4 Then Every 4 Weeks), in the Treatment of Patients With Active Crohn's Disease Who Have Previously Been Withdrawn From Studies CDP870-031 or CDP870-032 Due to an Exacerbation of Crohn's Disease.

Study start date: February 1, 2004

Inclusion Criteria: * Participation in either of the CDP870-031 \[NCT00152490\] or CDP870-032 \[NCT00152425\] clinical studies in which the subject completed the Week 2 assessment in CDP870-031 \[NCT00152490\] or the Week 6 randomization in CDP870-032 \[NCT00152425\] but whose Crohn's Disease was significantly worse as determined by the investigator and whose Clinical Disease Activity Index (CDAI) score at entry to this study is either (subjects may have received active or placebo treatment): 1. At least 70 points higher then Baseline (Week 0 CDP870-031 \[NCT00152490\]; Week 6 CDP870 032 \[NCT00152425\] responders) OR 2. Higher than Baseline (Week 0 CDP870-031 \[NCT00152490\]; Week 6 CDP870-032 \[NCT00152425\] responders) with an absolute score of at least 350 points * Subjects must be able to understand the information provided to them and give written informed consent Exclusion Criteria: * Any exclusion criterion that would have prevented the subject's participation in the qualifying pivotal study (CDP870-031 \[NCT00152490\] or CDP870-032 \[NCT00152425\]), although the upper limit of 450 in the CDAI score is not applicable. In addition the criterion that excludes previous participation in a clinical trial of Certolizumab Pegol does not apply