Zolbetuximab-associated adverse event reporting signals in gastric cancer: a FAERS disproportionality analysis.

Background: Zolbetuximab has an established upper gastrointestinal tolerability profile, but the broader post-marketing spectrum of gastric mucosal events and findings related to albumin, protein loss, and fluid balance remains incompletely characterized. Methods: We conducted an indication-restricted, report-level US Food and Drug Administration Adverse Event Reporting System (FAERS) analysis from 2024 Q1 through 2026 Q1, comparing 597 zolbetuximab reports with 1,231 pooled nivolumab/pembrolizumab reports. Reporting odds ratios (RORs) were used for primary screening, with five contextual reporting backgrounds, adjusted Firth models, and chemotherapy-, drug-role-, geographic-, calendar-time-, and submission-channel analyses. Time to onset and co-reporting were summarized descriptively. Results: Among 1,041 screened preferred terms, 58 met the ROR criterion and 48 were clinically retained. The findings clustered into three groups: upper gastrointestinal and intake-related findings, gastric mucosal findings, and findings related to albumin, protein loss, and fluid balance. The eight Conclusion: The analysis reinforced established upper gastrointestinal findings. Gastritis and findings related to albumin, protein loss, and fluid balance require clinical confirmation, while protein-losing gastroenteropathy was reported sparsely. Overall, the results characterize reporting disproportionality in an early, Japan-dominant setting, not incidence or comparative clinical risk.