This global study, sponsored by Teva Pharmaceuticals Ltd, will be reviewing how safe, how tolerable and how effective oral laquinimod is in subjects that have confirmed active moderate to severe Crohn’s disease. The subjects that are suitable for the study will receive either laquinimod (active drug) or placebo (dummy drug), the assignment of which drug the subject with receive will be decided randomly by a computer. There will be 4 separate groups of patients entered into the study, each group receiving a different amount of study drug/placebo. Recruitment into the next group will only occur once it is confirmed safe to do so. Subjects will have screening, baseline visits with further visits at weeks 1,2,4,6 and 8, and an end of study visit at week 12. Various study assessments will be performed at these visits including diary completion, physical exams, blood tests, urinalysis (urine sample), blood samples, stool samples, fistula (abnormal passage) drainage assessments, heart readings, blood pressure, heart rate, temperature monitoring and weight. The subjects will be expected to be in the study for a total of 14 weeks. The aim of the study is to understand if laquinimod is able to induce remission in patients with Crohn's disease and to establish the best and most effective dose with fewer side effects than the current treatments.