Rituximab in Myasthenia Gravis: a real-world study using inverse probability of treatment weighting

The role of rituximab in the treatment of myasthenia gravis (MG) remains uncertain due to limited randomized controlled evidence and heterogeneous observational data. While rituximab is often used in refractory MG, its comparative effectiveness against other non-steroidal immunosuppressive therapies (NSISTs) has yet to be fully clarified.

To evaluate the effectiveness of rituximab compared to a second NSIST in achieving a composite clinical outcome in acetylcholine-receptor-antibody (AChR-Ab) positive MG patients using causal inference methods to adjust for confounding.

We conducted a retrospective cohort study of AChR-Ab positive MG patients treated with rituximab or a second NSIST. The primary outcome was time to achieving a composite clinical endpoint representing a patient acceptable symptom state (PASS): Myasthenia Gravis Composite (MGC) score ≤ 3, daily corticosteroid dose ≤ 5 mg prednisolone equivalent, and no rescue therapy use in the preceding month. To reduce confounding by indication and improve causal comparability between treatment groups, inverse probability of treatment weighting (IPTW) based on propensity scores was used to balance baseline covariates. Cox proportional hazards models were applied to estimate the effect of treatment on time to outcome.

169 patients entered into the time-to-event analysis, and after IPTW adjustment, baseline characteristics between treatment groups were balanced. There was no statistical difference in the hazard ratio between Rituximab compared to a second NSIST in achieving the composite clinical outcome (HR = 1.27, 95% CI 0.66-2.45, p = 0.48).

In this IPTW-adjusted analysis, rituximab did not improve the time-to-improvement compared to a second NSIST in AChR-Ab-positive MG.