NN103 Primary Manuscript: "Phase 2 Trial of Rituximab in Acetylcholine Receptor Antibody-Positive Generalized Myasthenia Gravis: The BeatMG Study"

Nowak RJ, Coffey CS, Goldstein JM, Dimachkie MM, Benatar M, Kissel JT, Wolfe GI, Burns TM, Freimer ML, Nations S, Granit V, Smith AG, Richman DP, Ciafaloni E, Al-Lozi MT, Sams LA, Quan D, Ubogu E, Pearson B, Sharma A, Yankey JW, Uribe L, Shy M, Amato AA, Conwit R, O'Connor KC, Hafler DA, Cudkowicz ME, Barohn RJ; NeuroNEXT NN103 BeatMG Study Team.

Phase 2 Trial of Rituximab in Acetylcholine Receptor Antibody-Positive Generalized Myasthenia Gravis: The BeatMG Study. Neurology. 2021 December 2; :doi: 10.1212/WNL.00000000.

PubMed: PMID: 34857535


Objective: To determine whether rituximab is safe and potentially beneficial, warranting further investigation in an efficacy trial for acetylcholine receptor antibody-positive generalized MG (AChR-Ab+ gMG).

Methods: The B-Cell Targeted Treatment in MG (BeatMG) study was a randomized, double-blind, placebo-controlled, multicenter phase-2 trial that utilized a futility design. Individuals 21-90 years of age, with AChR-Ab+ gMG (MG Foundation of America Class II-IV) and receiving prednisone ≥15 mg/day were eligible. The primary outcome was a measure of steroid-sparing effect, defined as the proportion achieving ≥75% reduction in mean daily prednisone dose in the 4-weeks prior to week 52 and with clinical improvement or no significant worsening as compared to the 4-week period prior to randomization. The co-primary outcome was safety. Secondary outcomes included MG-specific clinical assessments. Fifty-two individuals were randomized (1:1) to either a two-cycle rituximab/placebo regimen, with follow-up through 52-weeks.

Results: Of the 52 participants included, mean (±SD) age at enrollment was 55.1 (±17.1) years; 23 (44.2%) were female, and 31 (59.6%) were MGFA Class II. The mean (±SD) baseline prednisone dose was 22.1 (±9.7) mg/day. The primary steroid-sparing outcome was achieved in 60% of those on rituximab vs. 56% on placebo. The study reached its futility endpoint (p=0.03) suggesting that the pre-defined clinically meaningful improvement of 30% due to rituximab over placebo was unlikely to be achieved in a subsequent, larger trial. No safety issues identified.

Conclusions: While rituximab was safe and well-tolerated, these results suggest that there is a low probability of observing the defined clinically meaningful steroid-sparing effect over a 12-month period in a phase-3 trial of mild-moderately symptomatic AChR-Ab+ gMG.

Classification of evidence: This study provides Class I evidence that for mild-to-moderate AChR-Ab+ gMG, compared with placebo, rituximab is safe but unlikely to reduce steroid use by an absolute difference of at least 30% at 1 year.

Trial registration: ClinicalTrials.gov Identifier: NCT02110706.