OBJECTIVES: In the absence of head-to-head trials, an indirect treatment comparison (ITC) was conducted to compare the efficacy of Efgartigimod vs Rituximab in adult patients with generalized myasthenia gravis (gMG) and autoantibodies against the acetylcholine receptor.

METHODS: The ITC was based on published aggregate data for Rituximab from BeatMG and individual patient data (IPD) from ADAPT for Efgartigimod. Both a matching-adjusted (MAIC) and a Bucher’s adjusted comparison were explored. In the context of the MAIC, the ADAPT population was restricted to align with the inclusion criteria of BeatMG (n=54) and reweighted to match the baseline characteristics of the population in BeatMG for treatment effect modifiers, including baseline MG-ADL score, time from diagnosis, use of prednisone alone and in combination with other non-steroidal immunosuppressive drugs (NSID). Conversely, no adjustment for the baseline characteristics was done in the Bucher’s adjusted comparison. The endpoint of interest was the difference in the change from baseline in MG-ADL vs placebo, estimated using a multivariate linear regression model with treatment group, baseline MG-ADL and baseline use of NSID as predictor variables. The efficacy of Efgartigimod vs Rituximab was compared at time of best-response (week 4 for Efgartigimod and week 52 for Rituximab).

RESULTS: Both the adjusted and unadjusted comparison showed significantly greater improvement in MG-ADL of Efgartigimod vs Rituximab at time of best-response (MAIC: -3.20; 95%CI=[-4.6,-1.8], p<0.001; Bucher’s adjustment: -2.9; 95%CI=[-4.6,-1.2], p<0.05). Because of considerable differences in the baseline characteristics, the MAIC was based on a very small effective sample size (ESS) (n = 1.32, 2.44 % of the included sample).

CONCLUSIONS: The ITC showed improved efficacy of Efgartigimod vs Rituximab. However, due to limited ESS in the MAIC and the strong assumptions underlying the Bucher’s adjusted comparison, these results should be interpreted with caution.