Eftilagimod alpha (soluble LAG-3 protein) combined with pembrolizumab as second-line therapy for patients with metastatic head and neck squamous cell carcinoma.

ABSTRACT

PURPOSE: Eftilagimod alpha (efti), a soluble LAG-3 protein, activates antigen-presenting cells (APC) and downstream T-cells. TACTI-002 (Part C) evaluated whether combining efti with pembrolizumab led to strong anti-tumor responses in 2nd line recurrent or metastatic head and neck squamous cell carcinoma (R/M HNSCC) patients, while demonstrating good tolerability. METHODS: In this multinational phase 2 trial using Simon's 2-stage design, R/M HNSCC PD-L(1)-naïve patients who had failed first-line platinum-based therapy, unselected for PD-L1, received intravenous pembrolizumab (200 mg, Q3W) combined with subcutaneous efti (30 mg Q2W for 24 weeks and Q3W thereafter). The primary endpoint was objective response rate (ORR) per iRECIST by investigator assessment. Additional endpoints included duration of response (DoR), progression free survival (PFS), overall survival (OS) and tolerability. Pharmacodynamic effects (absolute lymphocyte count [ALC] and Th1 cytokine biomarkers [IFN-gamma/CXCL-10]) were evaluated in liquid biopsies. RESULTS: Between Mar 2019 - Jan 2021, 39 patients were enrolled; 37 were evaluated for response. All patients received prior chemotherapy and 40.5% were pretreated with cetuximab. 53.1% of patients had PD-L1 CPS <20. With a median follow up of 38.8 months, ORR was 29.7%, including 13.5% complete responders. Median DoR was not reached. Rapid and sustained ALC increase was observed in patients who had an objective response. Th1 biomarkers increased sustainably after first treatment. No unexpected safety signals were observed. CONCLUSION: Efti plus pembrolizumab was safe and showed encouraging antitumor activity and pharmacodynamic effects in 2nd line HNSCC patients, thus supporting further evaluation of this combination in earlier treatment lines.