Often, before moving to the biological agents (Remicade- humira - cimzia -etc), it is not rare that CD patient will try some antimetabolite immunosuppressants drugs like Purinethol (active compound is mercaptopurine, also known as 6-MP), Imuran (azathioprine, AZA) or methotrexate (MTX).
These treatments have been used for a long time (especially the first two) for the treatment of CD. They are considered safe even though if you read about them, they come with a long list of side effects (biological agents, corticosteroid do to). When they provide you satisfying results, they can be taken on a long basis without being of too much concerns (provided you do your follow-up properly which consist mostly in CBC).
Those are the most common approaches regarding CD management. There is also the ASA class but these are less prone to be efficient in crohn treatment compared to the two previous classes (biological agents and immunosuppressant drugs).