RecruitingBiological interventionSwitching to the IL-23 Inhibitor Guselkumab for People With Active IBD Who Previously Used Ustekinumab (SHIFT-IBD)The SHIFT-IBD Study is being conducted at multiple medical centers across Canada to evaluate how well guselkumab (Tremfya) works for people with inflammatory bowel disease (IBD) who haven't responded well enough to ustekinumab. Patients will begin guselkumab based on their doctor's decision. If eligible, they may be invited to participate in the study, which involves monitoring symptoms, test results, and overall health over the course of one year. Guselkumab will be given according to local medical guidelines. Doctors can adjust the treatment as needed, just like in routine care. Researchers believe that switching to guselkumab may be as effective as other advanced treatments. For those who saw some improvement on ustekinumab but not enough, guselkumab may offer better symptom control-without worsening results on medical tests like endoscopy. The goal is to explore better treatment options for people whose IBD has not been well controlled with current therapies.