NUDT15 and inflammatory bowel disease: Further, in centers and populations where the biologic use is not common including those where steroids and cyclosporine (as second line therapy in acute severe colitis) continues to be used for IBD, azathioprine is an important drug for maintenance of remission and therefore preemptive testing of NUDT15 polymorphisms may help improve tolerance to thiopurine therapy [21, 24].