Comparative study of adverse drug reactions associated with anifrolumab and belimumab for the treatment of systemic lupus erythematosus.

BackgroundAnifrolumab and belimumab are the two biologic agents currently approved for moderate-to-severe systemic lupus erythematosus (SLE), targeting distinct immunological pathways. While their efficacy has been established in randomized controlled trials, their comparative safety profiles in real-world settings remain incompletely characterized.MethodsA retrospective pharmacovigilance study was conducted using data from the FDA Adverse Event Monitoring System (AEMS) from January 1, 2011 to March 30, 2026. Individual Case Safety Reports (ICSRs) were extracted using "anifrolumab," "anifrolumab-Fnia," and "belimumab" as search terms. Adverse drug reactions (ADRs) were coded according to MedDRA version 28.1 Preferred Terms. A disproportionality analysis was performed using the Reporting Odds Ratio (ROR) with 95% confidence intervals; a p-value <0.05 was considered statistically significant.ResultsA total of 2124 ICSRs for anifrolumab and 30,107 for belimumab were identified. Female patients predominated in both groups, consistent with SLE epidemiology. Herpes zoster showed a strong and statistically significant association with anifrolumab (ROR = 5.13; 95% CI: 3.97-6.62; p < 0.0001), consistent with its type I interferon receptor antagonism mechanism. Belimumab was more frequently associated with administration-related events, including missed doses, device misuse, and injection site pain. No statistically significant differences were observed for fatigue, arthralgia, headache, nausea, or rash.ConclusionsAnifrolumab and belimumab exhibit distinct safety profiles. Anifrolumab carries a significantly higher risk of herpes zoster infection, warranting pre-treatment vaccination assessment. Belimumab shows a predominance of administration-related and non-serious events. Treatment selection should be individualized based on patient-specific risk factors, infection susceptibility, and adherence considerations.