The purpose of this study is to evaluate safety and effectiveness of an experimental drug called DNTH103 for the treatment of chronic inflammatory demyelinating polyneuropathy (CIDP) when compared to a placebo (inactive substance). Participants are those who have or possibly have CIDP, a condition in which the body’s immune system mistakenly attacks and damages the protective covering of nerves (called myelin) throughout the body. This damage disrupts the normal communication between the nerves and muscles, leading to weakness, numbness, pain, and tingling sensations. The most common form of CIDP typically affects both sides of the body, particularly the lower limbs (e.g. legs) and upper limbs (e.g. hands & wrists), leading to movement and balance problems. Study procedures include administration of the experimental medication or placebo, questionnaires, evaluations, electrocardiograms, and blood samples. Participants will receive DNTH103 in the first part of the study (Part A). If the patient’s CIDP improves, they may qualify for the second part of the study (Part B), during which they will receive DNTH103 or placebo. Researchers believe that DNTH103 may decrease or prevent the injury (caused by CIDP) to the nerves that control the muscles.