Introduction: Gastroesophageal adenocarcinoma has an extremely poor prognosis and remains a major cause of cancer-related mortality worldwide. While chemotherapy remains the primary treatment for metastatic disease and improves survival overall, the prognosis for patients with gastroesophageal adenocarcinoma cancer remains poor; secondary to chemoresistance and limited targeted therapeutic approaches.

LSTA1 (certepetide) is a novel investigational drug designed to selectively target and enhance the uptake of anti-cancer drugs into solid tumours. Clinically, LSTA1 has demonstrated favourable safety, tolerability, and activity when added to gemcitabine and nab-paclitaxel in patients with metastatic pancreatic ductal adenocarcinoma. Given its mechanism of action, LSTA1 is thought to be agnostic to the modality of therapeutics with which it is combined and could bring significant advancement to the treatment outcomes in patients suffering from advanced solid tumours.

Case Presentation: This is a case report involving a subject with metastatic gastroesophageal adenocarcinoma with significant tumour burden. The subject underwent months of treatment with immunotherapy/chemotherapy and achieved a partial response. Upon addition of LSTA1 to their standard-of-care therapeutic regimen, the subject achieved a complete response confirmed radiographically and surgically.

Conclusion: Solid tumours are often inadequately treated with current treatment paradigms due to ineffective tumour targeting, insufficient tumour penetration, and/or a hostile Tumour Microenvironment (TME). Through its unique tumour targeting and penetration-enhancing capabilities, LSTA1, when added to the standard of care has demonstrated the ability to overcome such obstacles and improve treatment outcomes in a range of advanced solid tumours.