In locally advanced and metastatic malignancies, antibiotic (ATB) therapy has a negative effect on immunotherapy efficacy. Therefore, we aimed to evaluate whether ATB therapy and use of specific ATB classes with concomitant neoadjuvant pembrolizumab affected pathologic complete response (ypT0N0) and relapse-free survival (RFS) for patients with clinical T2-4N0M0 bladder cancer enrolled in the PURE-01 study.