Chemotherapy combined with cadonilimab (AK104) as neoadjuvant treatment for locally advanced gastric/gastro-oesophageal junction adenocarcinoma: study protocol for a single-arm, phase II clinical trial

Introduction Neoadjuvant chemotherapy has been demonstrated to be effective and recommended as the standard treatment option in patients with locally advanced gastric or gastro-oesophageal junction (G/GOJ) cancer. In this study, we will explore the efficacy and safety of chemotherapy combined with cadonilimab, a programmed death-1/cytotoxic T lymphocyte-associated antigen-4 bispecific antibody, in neoadjuvant therapy for locally advanced G/GOJ adenocarcinoma.Methods and analysis This is a single-centre, single-arm, open-label, phase II trial that will enrol 37 patients in total. Eligible patients will be registered and receive three cycles of oxaliplatin and S-1 (SOX) regimen in combination with cadonilimab. Radical D2 (D2 lymphadenectomy) gastrectomy will be performed within 4 weeks after the last administration of chemotherapy plus cadonilimab. The primary endpoint is the pathological complete response rate. Secondary endpoints are R0 resection rate, major pathological response, 2-year disease-free survival rate, 2-year overall survival rate and safety. The first participant was recruited on 1 September 2023 and the enrolment will be completed in July 2025.Ethics and dissemination Written informed consent will be required from and provided by all the patients enrolled. The study protocol (V.3.0, 28 April 2023) has been approved by the independent ethics committee of West China Hospital, Sichuan University (approval number: 2023526) and conducted under the Declaration of Helsinki. The results of the study may provide more evidence for neoadjuvant immunotherapy combined with chemotherapy in locally advanced G/GOJ adenocarcinoma.Trial registration number ClinicalTrials.gov, NCT05948449.