Vaccinex, Inc. reported positive interim safety data in the Phase Ib “safety run-in” segment of the KEYNOTE B84 combination study of Keytruda® and pepinemab (Vaccinex) in patients with advanced, recurrent or metastatic head and neck squamous cell carcinoma (R/M HNSCC). The Phase 2 segment of the study is now expected to begin enrollment and is expected to accelerate patient accrual. The Phase Ib “safety run-in” segment of the trial (NCT04815720) was intended to evaluate the safety and tolerability of pepinemab (20 mg/kg) in combination with Keytruda (Merck's anti-PD-1 therapy, pembrolizumab, 200 mg Q3W/every three weeks) to determine a recommended Phase 2 dose (RP2D) for the dose expansion phase of the study enrolling patients with R/M HNSCC.

The interim safety analysis was completed by the Data Safety Monitoring Board and signals initiation of the Phase 2 expansion segment. The KEYNOTE B84 combination study of Keytruda® (Merck's anti-PD-1 therapy, pembrolizumab) and pepinemab (Vaccinex's monoclonal antibody inhibitor of SEMA4D) is being conducted for first line treatment of patients with advanced, recurrent or metastatic head and neck squamous cell carcinoma (R/M HNSCC). The study has two segments: Segment 1: The completed Phase 1b “safety run-in” segment assessed the safety and tolerability of the combination and defined a Recommended Phase 2 Dose (RP2D) in 3-6 subjects.

After enrolling the first three subjects, the Data Safety Monitoring Board determined that the RP2D dose of pepinemab (20 mg/kg) and Keytruda (200 mg Q3W) was safe and well tolerated. Segment 2: The Phase 2 “expansion” segment is now expected to proceed to enroll up to 62 subjects across 19 U.S. trial sites. The primary objective of this segment is to evaluate Objective Response Rate (ORR) per Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 of the combination in immunotherapy naïve patients with advanced R/M HNSCC.