PD-1 antibody (Camrelizumab) for metastatic EBV positive gastric cancer: A prospective single-arm, open-label, phase 2 trial.

Abstract

e16014 Background: Programmed cell death 1 (PD-1) inhibitors have been approved as third line therapy for patients with metastatic gastric cancer (mGC). Epstein–Barr virus (EBV)-positive is a potential predictor to response of PD-1 inhibitors. The aim of this study was to assess the efficacy and safety of camrelizumab as salvage treatment in metastatic EBV positive GC patients and explored the potential biomarkers associated with response (NCT03755440). Methods: In this prospective single-arm, phase II study, stage IV EBV positive GC patients received 200 mg camrelizumab by intravenous infusion every 2 weeks until disease progression or unacceptable toxicity. The primary endpoint was objective response rate (ORR), which were based on RECIST V.1.1. Secondary endpoints were progression free survival (PFS), overall survival (OS), disease control rate (DCR), durationn of response (DoR), and toxicity. Exploratory analysis included association between response and tumor mutational burden (TMB) and cell death ligand-1 (PD-L1) expression. Results: According to Simon’s optimum two-stage design with α = 0.05 and β = 0.20. P0 = 15% (null hypothesis), the presence of at least 1 success in the 6 patients enrolled in the first stage allowed the trial to proceed to the second stage in which 13 more patients were needed to be enrolled for the minimum total of 20 patients (5% lost to follow-up calculated). Six eligible patients were enrolled at the first stage. All the patients were HER2 negative and pMMR. None of the patients had an objective response. The DCR was 66.7%. The median PFS was 2.2 months (95% CI: 1.5 months-not reached (NR)) and median OS was 6.8 months (95% CI: 1.7 months-NR). The most common treatment-related adverse event (TRAE) was reactive cutaneous capillary endothelial proliferation. No grade 3 or worse TRAEs were found. Only one patient had PD-L1 combined positive score (CPS) ≥1 but got disease progression. Three patients were TMB > 10Mb and two of them got stable disease while one got disease progression. Conclusions: EBV positive is not a good predictor for response to PD-1 inhibitors. Potential biomarkers are needed to identify EBVaGC patients who might respond to PD-1 inhibitors. Clinical trial information: NCT03755440.