A Study of JNJ-78934804 in Participants With Moderately to Severely Active Ulcerative Colitis

The purpose of this study is to assess how well JNJ-78934804 works (efficacy) and how safe it is (safety) as compared to guselkumab at Week 48 in participants with moderately to severely active ulcerative colitis (UC, a chronic disease of the large intestine in which the lining of the colon becomes inflamed and develops ulcers).

Inclusion criteria: * Diagnosis of ulcerative colitis (UC) established at least 12 weeks before screening including both endoscopic evidence and a histopathology report consistent with a diagnosis of UC. * Moderately to severely active UC defined as baseline (Week 0) modified Mayo score of 5 to 9, inclusive, using the Mayo endoscopy subscore obtained during central review of the screening video endoscopy * An endoscopy subscore \>=2 as obtained during central review of the screening video endoscopy * Have had an inadequate initial response, loss of response, or intolerance to previous approved systemic therapies Exclusion criteria: * Isolated proctitis (UC limited to the rectum only or to less than \[\