Anti-PD-1 antibody HX008 combined with oxaliplatin plus capecitabine for advanced gastric or esophagogastric junction cancer: a multicenter, single-arm, open-label, phase Ib trial

Anti-PD-1 monoclonal antibody is approved as an option for third-line treatment of advanced gastric and gastroesophageal junction (G/GEJ) cancer in several countries, but no anti-PD-1 monoclonal antibody treatment is yet approved for first-line treatment of advanced G/GEJ cancer. We report a phase Ib trial of HX008, a highly selective, humanized anti-programmed death-1 monoclonal antibody, plus oxaliplatin and capecitabine as first-line treatment for advanced G/GEJ cancer. Patients with previously untreated, locally advanced or metastatic G/GEJ cancer were enrolled. All patients received HX008 3 mg/kg intravenously every 3 weeks, oxaliplatin 130 mg/m² intravenously on day 1 every 3 weeks (up to 6 cycles), and capecitabine 1000 mg/m² orally twice daily for 14 days continuous dosing followed by a 7-day break. The primary end point was the incidence of adverse events and serious adverse events. In total, 35 patients were enrolled. Median follow-up was 12.7 months. Most frequent (>10%) grade ≥3 treatment-related adverse events were anemia (27.5%), neutropenia (20%), thrombocytopenia (17.1%), leukopenia (17.1%) and fatigue (17.3%). Objective response rate was 60.0% (95% confidence interval [CI] 42.1-76.1%). Disease control rate was 77.1% (95% CI 59.9-89.6). Median time to response and duration of response were 1.4 months (range 1.3-2.9) and 12.3 months (range 1.4-17.9+), respectively. Median PFS was 9.2 months (95% CI 5.4-not reached). These results demonstrated that HX008 combined with oxaliplatin plus capecitabine was well tolerated and demonstrated encouraging efficacy as first-line treatment for advanced G/GEJ cancer. This study was registered in china, register number was CTR20181270.