PURPOSE Gastric cancer is the 5th most common cancer and 4th leading cause of cancer-related mortality world-wid. Gastric signet ring cell carcinoma (GSRC) is often diagnosed late with peritoneal metastases. Adequate surgical resection is the therapeutic goal for GSRC however many patients develop drug resistance to conventional chemotherapy. LM-302 (TPX-4589) is a novel antibody-drug conjugate (ADC) coupled with cytotoxic payload monomethyl auristatin E (MMAE) that targets the transmembrane protein claudin 18 isoform 2 (CLDN18.2) and has demonstrated inhibition of tumour cell proliferation and reduced tumour growth in preclinical data. METHODOLOGY We present a case report of a patient with GSRC and peritoneal metastases, treated in a high volume peritoneal malignancy unit. LM-302 was used as a third-line salvage therapy RESULTS A 56-year-old female with GSRC and peritoneal metastases at time of diagnosis was treated initially with chemotherapy involving fluorouracil, leucovorin, oxaliplatin and docetaxel (FLOT) followed by folinic acid, fluorouracil and irinotecan (FOLFURI) due to disease progression. Despite this, she further progressed and developed Krukenberg tumours so commenced the LM-302 clinical trial. At the time of surgery to resect her symptomatic Krukenberg tumours, there was minimal peritoneal disease and the primary gastric tumour was also resected. Histopathology following cytoreductive surgery confirmed R-0 resection of the primary and treatment response score 1 (minimal tumour). CONCLUSION Advanced gastric cancers remain a challenging therapeutic dilemma. LM-302 appears promising in its ability to improve resectability of advanced gastric cancers, particularly ones that have demonstrated chemoresistance.