After the protocol was completed at UCB, but before it was submitted to any regulatory authorities or IRBs/IECs, it was updated to better align it with the current understanding of available data from completed and ongoing studies with rozanolixizumab. The updated protocol was then submitted to regulatory authorities and the study began.

The purpose of Amendment 2 was to provide clarification on the dose of IMP administered (including an allowance of ±10% compared with the target dose A), as well as a flexible infusion rate. Sensitivity analyses were introduced to account for deviations outside the ±10% target dosage; the descriptive analyses were to inform about actual doses administered to the study participants. The visit windows and the scheduling of the Randomization Visit in view of the Ig treatment at study start were clarified. The predominance of objective criteria over the investigator’s judgement was confirmed for the assessment of CIDP relapse. The timeframe of expected use of contraception poststudy completion was extended to 90 days in view of the probable half-life of rozanolixizumab. Exclusion Criterion No. 3 was extended to a prediabetic condition. The expectation with regards to the use of cannabidiols and medicinal marijuana was clarified in the concomitant medication section. This amendment confirmed the expectation of a single rater for the INCAT assessment to ensure consistency of the rating during the course of the study.