Statistical analysis
PD
The sample size for this study was intended to generate descriptive data that would evaluate the proof‐of‐concept that SC injection of batoclimab can successfully reduce pathogenic antibodies in the population studied. The sample size of 14 patients receiving batoclimab and 7 patients receiving placebo was posited to allow the current study to show a 33% difference between either batoclimab arm and the placebo arm, assuming 90% power, equal standard deviations (SDs) of 20, and an alpha of 0.05 using a two‐sided z‐test for the primary endpoint of percentage change from baseline in IgG at 6 weeks post‐baseline.As specified in the statistical analysis plan, the full analysis set included all randomized patients who received at least 1 dose of randomized study medication with at least one valid post‐treatment value. An interim analysis of all endpoints was performed after the last patient completed the double‐blind treatment period and constituted the primary analysis because of COVID‐19‐related disruptions. (See Impact of COVID‐19 pandemic below.) As this analysis occurred at the end of the double‐blind phase, no adjustments to the alpha level were necessary. A final analysis was performed after the completion of the study and database lock. Comparisons between active treatment arms and placebo for efficacy endpoints were performed using an analysis of covariance (ANCOVA) model with treatment and baseline values incorporated in the model; an alpha of 0.05 was used to determine statistical significance. Categorical values were analyzed using Fisher's exact test. Follow‐up and OLE, PK, and PD data were analyzed descriptively. All data were processed and summarized using SAS®, version 9.4.