Open Label Extension Study to Protocol C2/13/DR-6MP-02

The open label extension study (Protocol C2/13/DR-6MP-02 EXT) is designed to evaluate the clinical efficacy and safety of 80 mg DR-6MP test formulation for an additional 12 weeks in subjects who already completed 12 weeks of Protocol C2/13/DR-6MP-02. Crohn's disease (CD) therapy is aimed at reducing inflammation via induction of remission after a flare-up and maintenance of the remission for as long as possible. The questions being asked in this extension study are: 1. For subjects who received 80 mg DR-6MP for 12 weeks: Can the clinical efficacy and safety status achieved following 12 weeks of treatment be maintained or improved following an additional 12 weeks of DR-6MP treatment? 2. For subjects who received oral Purinethol (1-1.5 mg/kg daily) for 12 weeks: Can the clinical efficacy and safety at 12 weeks be maintained or improved following the introduction of 12 weeks of 80 mg DR-6MP treatment?

By following the 2 groups of subjects, i.e, those who originally received the test formulation (80 mg DR-6MP) and are now continuing for another 12 weeks on test drug vs. those who received the reference drug (Purinethol, 1-1.5 mg/kg daily) and are now being introduced to 12 weeks of 80 mg DR6MP test drug, and monitoring the CDAI scores, immunology parameters (ex. ESR and CRP) and safety assessments (i.e., adverse events occurrences, weight changes, laboratory test results) and comparing to the parameters at extension study start, the study will effectively answer the following questions: 1. Does an additional 12 weeks of 80 mg DR6MP test drug treatment maintain or improve CDAI scores? 2. Is an additional 12 weeks of 80 mg DR6MP test drug treatment safer due to negligible drug availability systemically? 3. Can an additional 12 weeks of 80 mg DR6MP test drug treatment evoke a more effective immunological systemic response? 4. In the subset of subjects willing to undergo colonoscopy/ileoscopy, does an additional 12 weeks of 80 mg DR6MP test drug induce effective mucosal healing?