The mainstay treatment of esophageal squamous cell carcinoma (ESCC) involves chemotherapy and immunotherapy. However, alternative therapies are required for patients who are refractory or intolerant to existing therapies.

In this single-arm, multicenter, open-label phase Ⅰb study, 30 patients received an intravenous infusion of SCT200, an anti-epidermal growth factor receptor (EGFR) monoclonal antibody, 6.0 mg/kg once a week for 6 weeks, followed by 8.0 mg/kg once every 2 weeks until disease progression or intolerable toxicity. The primary endpoint was the objective response rate (ORR). The secondary endpoints were progression-free survival (PFS), overall survival (OS), and safety.

Thirty patients were enrolled between July 2018 and May 2019. The ORR was 16.7% (95% CI: 5.6%–34.7%). The median PFS and OS were 3.1 months (95% CI: 1.5–4.3) and 6.8 months (95% CI: 4.7–10.1), respectively. A numerical difference without any statistical significance in ORR was observed in patients with different EGFR expressions (≥ 50%: 25.0% vs. < 50%: 0%, P = 0.140) or TP53 mutation abundance (< 10%: 23.8% vs. ≥ 10%: 0%, P = 0.286). Improved median PFS (3.4 vs. 1.4 months, P = 0.006) and OS (8.0 vs. 4.2 months, P = 0.027) were associated with TP53 mutation abundance of < 10%. The most common treatment-related adverse events of grade 3 or 4 (occurring in ≥ 2 patients) were hypomagnesemia [7 (23.3%)] and rash [2 (6.7%)]. No treatment-related death occurred.

SCT200 monotherapy as the second- or further-line treatment for advanced ESCC showed favorable efficacy, with an acceptable safety profile. TP53 mutation abundance might serve as a potential predictive biomarker.