monoclonal antibody (mAb) of the IgG4/kappa isotype designed to directly block the interaction between PD-1 and its ligands, PD-L1 and PD-L2; Recent phase I trial provided evidence of activity of pembrolizumab in advanced platinum-resistant metastatic urothelial carcinoma; Recent phase 3 trial showed an overall survival benefit in patients treated with pembrolizumab in a trial comparing pembrolizumab to chemotherapy in patients who failed first-line platinum-based chemotherapy Neoadjuvant chemotherapy followed by radical cystectomy is the standard of care for cisplatinum-eligible non-metastatic MIBC patients; Many patients with MIBC are unfit for cisplatin-based combination treatment; Given its safety profile, pembrolizumab may be used in unfit patients; Neo-adjuvant setting is a unique opportunity to assess mechanisms of action of pembrolizumab in human