S314 Comparative Adverse Events of Mirikizumab-mrkz and Etrasimod Arginine in Ulcerative Colitis: A Pharmacovigilance Analysis Using the FAERS Database

Introduction: Mirikizumab-mrkz is a humanized IgG4 monoclonal antibody that inhibits the IL-23 pathway, and etrasimod arginine is a sphingosine 1-phosphate receptor modulator that partially and reversibly blocks the capacity of lymphocytes to egress from lymphoid organs. Both drugs have been promising treatments for ulcerative colitis (UC) and were approved by the FDA in October 2023. This study aimed to review the adverse events (AEs) of these drugs using real-world data. Methods: The data were collected from the FDA Adverse Event Reporting System (FAERS), reviewing reports from October 2023 to March 2025. Only adverse events related to UC treatment were included, while reports for other indications, ambiguous or unspecified reasons were excluded. Outcomes of AEs were compared between mirikizumab-mrkz and etrasimod arginine using the Chi-square test. A P-value of 0.05 was considered statistically significant. Results: In patients with ulcerative colitis, 282 AEs were reported for mirikizumab-mrkz and 276 for etrasimod arginine. Among these, 152 cases (53.90%) were classified as serious for mirikizumab-mrkz, compared to 96 cases (34.78%) for etrasimod arginine. Excluding UC, the most common AEs with mirikizumab-mrkz were injection site pain (40 [14.18%]), respiratory infection (26 [9.22%]), and arthralgia (11 [3.90%]). For etrasimod arginine, the most frequent AEs were headache (26 [9.42%]), dizziness (24 [8.70%]), and fatigue (19 [6.88%]). Hospitalization was significantly higher with mirikizumab-mrkz than etrasimod (25.89% vs 7.97%, P < 0.001). Additionally, 10 deaths were reported with mirikizumab-mrkz, linked to cardiac failure, acute kidney injury, intestinal ischemia, asphyxia, and ulcerative colitis, while no deaths were reported with etrasimod arginine. Conclusion: Mirikizumab-mrkz has a higher incidence of serious adverse events and hospitalizations compared to etrasimod arginine in patients with UC. While Mirikizumab-mrkz is more commonly associated with local and respiratory complications, etrasimod arginine is linked to neurological complications. The significantly higher hospitalization rate and reported deaths with mirikizumab-mrkz underscore the need for further research to better understand the comparative safety of these treatments.