Additional Study Information: We are doing this study to find out if the research drug known as Rozanolixizumab can have additional benefit for people who are already receiving IVIG( Intravenous Immune Globulin) treatment for CIDP, and to have further safety evaluation of the research drug as well. If you choose to be part of this research study, the following procedures will occur:Screening period (2-5 weeks): You will be expected to come to a screening visit, where you would undergo evaluation of your medical history, questionnaires and physical exams related to your CIDP, and laboratory testing including blood draw and urine collection. If you pass the screening you may enroll in the study and will begin the 11-week treatment period. If you do not pass the screening you may not enroll in the study.11-week treatment period: During this period, you will be randomly assigned (like flipping a coin) to either trial drug or the placebo drug. However, regardless of which group you are randomized to, you will continue to receive your existing stable regimen of IVIG or subcutaneous IG. If you complete this, you will move on to the observational period. If you complete the Treatment Period without worsening of CIDP symptoms, you will have the option to 1) participate in an open-label study in which you will receive the trial medication for 6 months, or 2) enter an observational period.Observational period (12 weeks): During this observational period, you may either continue your standard IVIG (or subcutaneous IG) treatment or not. If youre not on IVIG and worsen in your CIDP symptoms, you will be treated with IVIG. If you are on IVIG, you will have another opportunity at the end to decide whether you would like to the open-label study.You are expected to come to study visits throughout these periods and have study procedures that may include questionnaires, physical exam and laboratory studies.Study Duration: Up to 28 weeks.Risks: Based on data from earlier study, potential adverse effects of the trial