Exelixis, Inc. announced the initiation of STELLAR-305, a phase 2/3 pivotal trial evaluating zanzalintinib in combination with pembrolizumab versus pembrolizumab alone in patients with previously untreated PD-L1-positive recurrent or metastatic squamous cell carcinoma of the head and neck (SCCHN). STELLAR-305 is a global, multicenter, randomized, double-blind phase 2/3 study that will enroll patients with PD-L1-positive recurrent or metastatic SCCHN that is incurable with local therapies. Patients must not have received prior systemic therapy for recurrent or metastatic disease.

Patients will be randomized 1:1 to receive zanzalintinib in combination with pembrolizumab or placebo in combination with pembrolizumab. The primary endpoints of the study are progression-free survival (PFS) per Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 by Blinded Independent Radiology Committee (BIRC) and overall survival. Secondary endpoints include PFS per RECIST 1.1 by investigator and objective response rate and duration of response per RECIST 1.1 by BIRC and by investigator.