We collected 275 patients from IMvigor210, a phase 2 trial evaluated efficacy of atezolizumab in UC...In IMvigor210 cohort, patients in KDM6A-Mut group had a significantly prolonged overall survival (OS) than in KDM6A-Wt group (mOS: 12.85 vs. 8.05 months, P = 0.031, HR = 0.62, 95%CI: 0.41-0.96)...Our research revealed that patients with UC harboring KDM6A mutation had a better clinical outcomes of immunotherapy, indicating KDM6A mutation can be regarded as a potential immunotherapy biomarker in UC.