AstraZeneca’s Imfinzi Advances in Gastric Cancer With FDA Priority Review

AstraZeneca sign, logo, symbol on the facade of AstraZeneca Poland, multinational pharmaceutical corporation, developer of COVID-19 vaccine. WARSAW, POLAND - NOVEMBER 28, 2021 | Image Credit: © OleksKao - stock.adobe.com

AstraZeneca announced July 28, 2025, that FDA has accepted and granted Priority Review for its supplemental Biologics License Application (sBLA) for Imfinzi(durvalumab) in combination with chemotherapy for the perioperative treatment of adults with resectable Stage II–III gastric or gastroesophageal junction (GEJ) adenocarcinoma (1). FDA has assigned a Prescription Drug User Fee Act (PDUFA) date in the fourth quarter of 2025.

The regulatory submission is supported by positive results from the Phase III MATTERHORN trial, in which the combination of durvalumab with neoadjuvant and adjuvant chemotherapy demonstrated a statistically significant and clinically meaningful improvement in event-free survival (EFS), compared to chemotherapy alone (1). These data reinforce growing clinical momentum around immune checkpoint inhibitors in the curative-intent setting for GI tumors, a field historically dominated by surgery and chemotherapy alone.

“This is the first Phase III trial to show improved efficacy for an immunotherapy-based treatment in the perioperative setting for gastric and GEJ cancer, where patients face high rates of disease recurrence and treatment side effects,” said Susan Galbraith, Executive Vice President, Oncology R&D, AstraZeneca (1). “These promising results with Imfinzi may bring us closer to improving long-term outcomes for these patients.”

Breakthrough and priority designations reflect clinical urgency

In April 2024, the sBLA for durvalumab was granted Breakthrough Therapy Designation, which is reserved for therapies that may offer substantial benefit over existing treatments (1). The subsequent Priority Review designation confirms FDA’s recognition of the urgent unmet need and the potential impact of this regimen for patients with resectable disease.

Durvalumab, a PD-L1 checkpoint inhibitor, has already shown survival benefits in multiple cancers, including lung, liver, and biliary tract tumors (1). The MATTERHORN trial represents the next step in expanding its use into earlier-stage disease in gastric/GEJ adenocarcinoma, for which treatment options remain limited and relapse is common.

The Phase III trial evaluated more than 900 patients across multiple global sites and was designed to reflect real-world, multidisciplinary care pathways (1). Durvalumab was administered both pre- and post-surgery alongside FLOT-based chemotherapy, aligning with current treatment standards and minimizing deviation from surgical timelines.

Implications amid recent regulatory setbacks

The agency’s acceptance of the Imfinzi filing comes as several other oncology sponsors have received complete response letters (CRLs) late in the review process, often due to chemistry, manufacturing, and controls (CMC) concerns or insufficient assay validation, despite earlier regulatory alignment (2). AstraZeneca’s robust data and operational readiness stand in contrast, signaling the importance of early and thorough cross-functional integration of CMC, regulatory strategy, and clinical trial endpoints (1).

As FDA has recently emphasized more rigorous evidence standards for quality and consistency, particularly in biologics, durvalumab’s acceptance with Priority Review suggests high confidence in the manufacturing and analytical data packages. This case highlights the importance of comprehensive submission planning from pre-IND through commercial readiness.

“Gastric and GEJ cancers are among the most common cancers worldwide and often develop without early symptoms, so many patients are diagnosed at an advanced stage when the prognosis is poor,” said Galbraith (1). “Today’s news is a vital step toward delivering a much-needed new treatment option for patients.”

Global outlook and next steps

The MATTERHORN trial continues to evaluate overall survival as a key secondary endpoint (1). Regulatory submissions based on these data are under review by additional health authorities, with decisions anticipated in Europe, Japan, and other key markets over the next 12 months.

If approved, Imfinzi would be the first immunotherapy available in the U. for perioperative gastric and GEJ adenocarcinoma, a milestone that could redefine standard care and help reduce relapse rates in this challenging population.

References

1. AstraZeneca. Imfinzi granted Priority Review and Breakthrough Therapy Designation in the US for Patients with Resectable Early-stage Gastric and Gastroesophageal Junction Cancers. Press Release. July 28, 2025.
2. Cole, C. CMC and Analytical Gaps in CRLs: Why They Persist Despite FDA Guidance and How You Can Position Yourself for Success. PharmTech.com. July 25, 2025.