A Phase III Randomized, Controlled Clinical Trial of Pembrolizumab with or without Platinum-Based Combination Chemotherapy Versus Chemotherapy in Subjects with Advanced or Metastatic Urothelial Carcinoma (KEYNOTE 361)

Merck Sharp & Dohme Corp.
Study Design: 
Similar to the above trial, this is a Phase III, 3-armed randomized clinical trial that includes both cisplatin eligible and ineligible patients with first line unresectable or metastatic stage IV urothelial cancer. The trial compares in a 1:1:1 randomization single agent. Tumor PD-L1 status, with Immunohistochemical (IHC) assay confirmed by a reference laboratory, must be known prior to randomization.
With the approvals of checkpoint inhibitors for urothelial cancer it has become of interest to assess the PD-1 checkpoint inhibitor, pembrolizumab, versus the combination of platin-based chemotherapy and a checkpoint inhibitor versus chemotherapy alone in the front line setting in both cisplatin eligible and ineligible patients. The primary hypotheses are that pembrolizumab plus chemotherapy is superior to chemotherapy alone with respect to Progression-free Survival (PFS) and Overall Survival (OS) in participants with programmed cell death ligand 1 (PD-L1) positive tumors (Combined Positive Score [CPS] ≥10%) and in all participants (includes those participants with PD-L1 positive tumors and those with PD-L1 negative tumors [CPS <10%]).
PFS and OS
Pembrolizumab has approval in the first-line setting in patients with cisplatin-ineligible advanced/metastatic urothelial carcinoma based on the Phase 2 KEYNOTE 052 trial (5,6). In this study, durable responses were seen with objective responses in 106/370 (29%) patients, including complete responses in 25 (7%). The median duration of response was not reached after a median follow-up of 8 months. In the Phase 3 KEYNOTE-045 study, in the second-line setting, for patients with platinum-resistant/refractory disease, survival was superior to investigator's choice of chemotherapy at a median follow-up of 22.5 months (7).