Table 1.

Assumptions and power calculations for primary and secondary endpoints

Endpoints	Assumptions	Effective sample size/Group	Power
Change from baseline to week 12 in MG-ADL score for AChRAb+ patients	Difference in change from baseline to week 12 in MG-ADL between the batoclimab and placebo groups is –3.0 Common SD of the change from baseline to week 12 in MG-ADL is 4.0	≈60	>90%
Change from baseline to week 12 in QMG for AChRAb+ patients	Difference in change from baseline to week 12 in QMG between the batoclimab and placebo groups is –5.0 Common SD of the change from baseline to week 12 in QMG is 3.5	≈60	>90%
Change from weeks 12 to 24 in MG-ADL for AChRAb+ randomised withdrawal patients	Participants re-randomised to batoclimab will maintain their MG-ADL scores from week 12, whereas in patients re-randomised to placebo, MG-ADL scores will return to baseline Difference in change from weeks 12 to 24 in MG-ADL between the batoclimab and placebo groups is –3.0 Common SD of the change from weeks 12 to 24 in MG-ADL is 4.0	≈30	80%–<90%
Proportion of AChRAb+ patients with a ≥3-point improvement from baseline to week 12 in QMG	Proportion of patients with an improvement from baseline to week 12 in QMG will be 63% in the batoclimab groups and 14% in the placebo group	≈60	>90%
Proportion of AChRAb+ patients with an MG-ADL score of 0 or 1 by week 12	Proportion of patients achieving an MD-ADL score of 0 or 1 by week 12 will be 40% in the batoclimab groups and 11% in the placebo group	≈60	>90%
Change from baseline to week 12 in MG-ADL score for AChRAb– patients	Difference in change from baseline to week 12 in MG-ADL between the batoclimab and placebo groups is –3.0 Common SD of the change from baseline to week 12 in MG-ADL is 4.0	Batoclimab: ≈40 Placebo: ≈20	70%–<80%

Note: expected dropout rate is 5%.

AChRAb, acetylcholine receptor antibodies; MG-ADL, Myasthenia Gravis Activities of Daily Living; QMG, quantitative myasthenia gravis.