Pharmacodynamic and Clinical Outcome Study of Mongersen in Patients With Crohn's Disease

This study is designed to explore mechanism of action of mongersen (GED-0301) 160 mg once daily in patients with active Crohn's Disease

Subjects will be screened to provide 20 enrolled subjects who complete 12 weeks of mongersen (GED-0301) 160 mg QD treatment as open-label therapy. The study will consist of 4 periods: * Screening Period - up to 4 weeks * Induction Period - 12 weeks (Week 0 Visit through Week 12 Visit) * Maintenance Period - 88 weeks (after Week 12 Visit through Week 100 Visit) * Follow-up Period - 4 weeks (ie, no IP taken) Subjects who prematurely discontinue treatment from this study prior to Week 100 will have an Early Termination Visit and also enter the 4-week Follow-up Period. At the Screening Visit, all subjects who meet the entrance criteria will be eligible to enter the study. The number of subjects with previous exposure to Tumor Necrosis Factor-Alpha (TNF-α) blockers is targeted to be approximately 40% (ie, approximately 8 subjects).