Progress in second-line antibody therapies for advanced esophageal squamous cell carcinoma

INTRODUCTION: The prognosis of advanced esophageal squamous cell carcinoma (ESCC) is poor. Although cytotoxic drugs have been widely used in advanced ESCC, several antibody agents have recently been reported to be effective. AREAS COVERED: Nivolumab and pembrolizumab are anti-PD-1 antibodies that improve immunosuppression by binding to programmed death-1 (PD-1), leading to an antitumor effect. Randomized phase III trials have found these immune checkpoint inhibitors (ICIs) to be effective as second-line treatment. ATTRACTION-3, which compared nivolumab monotherapy with taxane monotherapy in patients with previously treated advanced ESCC, reported prolonged overall survival in the nivolumab group. KEYNOTE-181 found that overall survival was longer in patients with PD-L1-positive ESCC who received second-line treatment with pembrolizumab than in those who received chemotherapy. Sym004 and amivantamab are antibodies that target the epidermal growth factor receptor and have demonstrated efficacy in the treatment of other tumors in recent phase I studies. Furthermore, clinical trials on antibody-drug conjugates such as enfortumab vedotin and DS-7300 for solid tumors are currently ongoing. EXPERT OPINION: The standard first-line treatments for patients with advanced ESCC contain ICIs. Therefore, drugs with different mechanisms of action that can overcome resistance to ICIs are needed as second-line or later-line treatments to improve clinical outcomes in these patients.