Post-marketing safety surveillance of fostamatinib: an observational, pharmacovigilance study leveraging FAERS database.

Objective: Fostamatinib, an FDA-approved oral small-molecule spleen tyrosine kinase (SYK) inhibitor, is used to treat thrombocytopenia in adults with chronic immune thrombocytopenia (ITP) who have not responded to previous treatments. However, comprehensive safety data is lacking. This study uses the FDA Adverse Event Reporting System (FAERS) database to explore real-world adverse events (AEs) related to fostamatinib, aiming to inform its clinical use.

Methods: The FAERS database was retrospectively queried to extract reports associated with fostamatinib from 2019 to 2023. To identify and evaluate potential AEs in patients receiving fostamatinib, various disproportionality analyses such as the reporting odds ratio (ROR), the proportional reporting ratio (PRR), the Bayesian confidence propagation neural network (BCPNN), and the multi-item gamma Poisson shrinker (MGPS) were employed.

Results: A total of 23 AE signals were included in our analysis. Among them, hypertension, blood pressure increase, blood pressure abnormality, hepatic enzyme increase, and diarrhea were consistent with the common AEs described for fostamatinib in clinical trials. In addition, unexpected serious AEs were detected including cerebral thrombosis and necrotizing soft tissue infection. The median time to onset of fostamatinib-related AEs was 86 days.

Conclusion: Our investigation revealed several possibly emergent safety concerns associated with fostamatinib in real-world clinical practice, which might provide essential vigilance evidence for clinicians and pharmacists to manage the safety issues of fostamatinib.