Hi HanooN and welcome!
I am currently taking Remicade, Imuran, Prednisone (2.5 mg) and Pentasa. I saw my GI about a week ago and they are considering taking me off the Imuran soon--I am a very slow metabolizer and I think the Imuran is helping but not very quickly, unfortunately.
Like Nanners said, I have also heard that taking both Remicade and Imuran together DOES increase the risk of cancer, once of which is lymphoma, in children and young adults. I am 32 so I am guessing, hoping, and assuming I am past the "young adult" stage, as I honestly believe I will have to be on both to control the Scleritis I have from Crohn's Disease.
I have heard they also use Methotrexate with Remicade--have you tried Methotrexate yet? Unfortunately, Methotrexate did not work for me but I have heard it can be a very good drug for those it does help.
I am pretty sure I have read about others on this forum who are also on both Imuran and Remicade and hopefully they will come along shortly to help out.
Take care and please feel free to ask any questions you may have!