RecruitingDrug trialClinical Study of VG161 Combined With Nivolumab Injection in Patients With Advanced Metastatic Gastric CancerVG161 is a recombinant human-IL12/15/PDL1B oncolytic HSV-1 injection. This study will be conducted in combination with nivolumab injection in HSV seropositive subjects with advanced metastatic gastric or gastroesophageal junction adenocarcinoma who have previously received two or more systemic treatment regimens (which must include anti-PD-1 monoclonal antibodies). This is an open-label study divided into two parts. Part 1: This part is an escalating dose trial to explore the safety of the combination and determine the recommended safe dose of the combination. Part 2: This part is an extension trial to investigate the preliminary efficacy of the combination at a safe dose.