AstraZeneca Imfinzi gets USFDA priority review for resectable early stage gastric, gastroesophageal junction cancers

The FDA grants Priority Review to applications for medicines that, if approved, would offer significant improvements over available options by demonstrating safety or efficacy improvements, preventing serious conditions or enhancing patient compliance. The Prescription Drug User Fee Act date, the FDA action date for their regulatory decision, is anticipated during the fourth quarter of 2025.

Imfinzi was also recently granted Breakthrough Therapy Designation (BTD) by the FDA in this setting. BTD accelerates the development and regulatory review of potential new medicines intended to treat a serious condition and address a significant unmet medical need.

Gastric (stomach) cancer is the fifth most common cancer worldwide and the fifth-highest leading cause of cancer mortality. In 2024, there were approximately 6,500 drug-treated patients in the US with early-stage and locally advanced gastric or GEJ cancer.

Susan Galbraith, Executive Vice President, Oncology Haematology R&D, AstraZeneca, said, “This Priority Review reinforces the potential for a perioperative approach with Imfinzi to transform care for patients with early gastric and gastroesophageal junction cancers, who frequently face disease recurrence or progression even after curative-intent surgery and perioperative chemotherapy. This novel treatment is the only immunotherapy-based regimen to show a statistically significant reduction in the risk of progression, recurrence or death in this setting, and if approved, is poised to change the clinical paradigm."

The sBLA is based on data from the MATTERHORN Phase III trial which was presented during the Plenary Session at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting and simultaneously published in The New England Journal of Medicine.

In the trial, patients were treated with neoadjuvant Imfinzi in combination with chemotherapy before surgery, followed by adjuvant Imfinzi in combination with chemotherapy, then Imfinzi monotherapy. In a planned interim analysis, patients treated with the Imfinzi-based perioperative regimen showed a 29% reduction in the risk of disease progression, recurrence or death versus chemotherapy alone (based on an event-free survival [EFS] hazard ratio [HR] of 0.71; 95% confidence interval [CI] 0.58-0.86; p<0.001). Estimated median EFS was not yet reached for the Imfinzi arm versus 32.8 months for the comparator arm. An estimated 78.2% of patients treated with the Imfinzi-based perioperative regimen were event-free at one year, compared to 74.0% in the comparator arm; the estimated 24-month EFS rate was 67.4% versus 58.5%, respectively, signalling a greater magnitude of benefit over time for the Imfinzi-based regimen.

For the key secondary endpoint of overall survival (OS), a strong trend was observed in favour of the Imfinzi-based perioperative regimen (HR=0.78; 95% CI 0.62-0.97; p=0.025). The trial will continue to follow OS, which will be formally assessed at the final analysis.

The safety profile for Imfinzi and FLOT (fluorouracil, leucovorin, oxaliplatin, and docetaxel) chemotherapy was consistent with the known profiles of each medicine, and the percentage of patients that completed surgery was similar compared to chemotherapy alone. Grade 3 or higher adverse events due to any cause were similar between the two arms.

Regulatory applications are currently under review in the EU, Japan and several other countries based on the MATTERHORN results.