Safety and efficacy of anti-EGFR monoclonal antibody (SCT200) as second-line therapy in advanced esophageal squamous cell cancer.

Abstract

e16046 Background: The mainstay treatment of esophageal squamous cell carcinoma (ESCC) involves chemotherapy and immunotherapy. However, alternative therapies are required for patients refractory or intolerant to the existing therapies. Methods: 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 six weeks, followed by 8.0 mg/kg once every two 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. Results: 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 was 3.1 months (95%CI: 1.5–4.3) and 6.8 months (95%CI: 4.7–10.1) respectively. Numerical difference without a statistical significance in ORR was observed in patients with different EGFR expression (≥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. Conclusions: SCT200 monotherapy as second- or further-line for advanced ESCC showed favorable efficacy, with an acceptable safety profile. TP53 mutation abundance might serve as potential predictive biomarkers. Clinical trial information: NCT03817567. [Table: see text]