A comparative analysis of semiannual versus annual rituximab maintenance in patients with refractory idiopathic inflammatory myopathies: a retrospective longitudinal real-world study.

OBJECTIVE

The aim of this study was to explore the real-world effectiveness of semiannual versus annual rituximab maintenance administration in patients with refractory idiopathic inflammatory myopathies.

METHODS

In this single-center, retrospective longitudinal study (2010-2025), 45 adults with refractory idiopathic inflammatory myopathies received two initial rituximab infusions (1 g on days 0 and 15). Maintenance rituximab was administered every 6 months (semiannual group, n=14) or every 12 months (annual group, n=31). Baseline immunosuppressive therapy was maintained, and glucocorticoid tapering was guided by clinical and laboratory parameters. Outcomes at months 6-12 and 18-24 included the need for rescue therapies: intravenous methylprednisolone (3 g total) and immunoglobulin (2 g/kg), or prednisone dose escalation.

RESULTS

Baseline demographics, refractory idiopathic inflammatory myopathies subtypes, rituximab indications (cutaneous, muscular, articular, and/or pulmonary activity), and peri- rituximab medications (within 2 months before/after infusion) did not differ significantly between groups (p>0.05). No statistically significant differences in the frequency of rescue therapy use at 6-12 and 18-24 months were detected between the two regimens. Intragroup analysis demonstrated significant reductions in relapse rates and rescue therapy requirements over time (p<0.05), suggesting improvement in both cohorts.

CONCLUSION

In this exploratory cohort, no statistically significant differences were detected between semiannual and annual rituximab maintenance regimens with respect to clinical outcomes, although numerically higher relapse rates were observed in the annual group. These findings suggest that extended rituximab intervals may be feasible in resource-limited settings, but further prospective studies are needed to confirm these observations.