Individualized Ofatumumab versus Fixed Low-Dose Rituximab in MuSK-Antibody-Positive Myasthenia Gravis: A Multicenter Retrospective Cohort Study.

Purpose

This study aimed to compare the effectiveness and safety of ofatumumab (OFA) versus rituximab (RTX) in patients with muscle-specific kinase myasthenia gravis (MuSK-MG).

Methods

This multicenter retrospective cohort study included 17 OFA-treated and 10 RTX-treated MuSK-MG patients from 3 centers. The individualized OFA protocol comprised induction (one or two 20 mg doses within 2 months), followed by maintenance dosing (20 mg) guided by CD19 + B-cell repopulation (≥5/µL) or clinical exacerbation. Over 6 months, the OFA group received a median cumulative dose of 60 mg (IQR 40-60). RTX-treated group used 600 mg. Primary endpoints included changes in QMG and MG-ADL scores from baseline to month 3 and month 6. Secondary endpoints covered prednisone reduction, 6-month minimal symptom expression (MSE) rate, time to MSE, early exacerbation, and safety.

Results

Both agents achieved significant clinical improvement in QMG (p = 0.011) and MG-ADL (p < 0.001).OFA-treated patients showed progressive improvement through 6 months (ΔQMG: -8.45, ΔMG-ADL: -4.44), while RTX-treated patients presented early improvement at month 3 (ΔQMG: -4.42, ΔMG-ADL:-2.52) but attenuated by month 6 (ΔQMG: 0.01, ΔMG-ADL: -1.31), with a significant group × time interaction (ΔQMG p = 0.020). Prednisone‑sparing effect, 6‑month adjusted MSE rates, time to MSE, early exacerbation, and severe infection rates did not differ significantly between groups.

Conclusion

These hypothesis-generating observations suggest OFA, administered at this individualized dosing regimen, may be associated with more sustained 6-month responses than low-dose RTX, warranting validation in prospective controlled trials.