Zanubrutinib is a medicine that blocks a protein called BTK in the body. This medication is being tested to see if it can help improve nerve function in people with a specific type of nerve damage caused by antibodies called anti-MAG antibodies. The study will look at whether taking this medicine for 12 months can help patients improve their ability to move, feel sensations, and perform daily activities.

Peripheral Anti-MAG Neuropathy – A rare nerve disorder that occurs when the body produces abnormal antibodies against myelin-associated glycoprotein, a protein found in the protective covering of nerves. These antibodies gradually damage the myelin sheath, leading to progressive weakness and loss of sensation, particularly in the hands and feet. Patients typically experience numbness, tingling, and unsteadiness when walking. The condition develops slowly over months to years, causing increasing difficulty with fine motor tasks like buttoning clothes or writing. Balance problems become more pronounced as the disease progresses. The disorder is associated with abnormal protein production in the blood.

Waldenström Macroglobulinemia – A rare type of slow-growing blood cancer that affects white blood cells called B-lymphocytes. These abnormal cells accumulate in the bone marrow and produce large amounts of an abnormal protein called IgM antibody. The excess protein thickens the blood and can cause various symptoms throughout the body. Patients may experience fatigue, weakness, bleeding problems, and swollen lymph nodes. The condition can affect multiple organs as abnormal cells spread and the thick blood impairs circulation. Some patients may also develop nerve damage due to the abnormal proteins.

Marginal Zone Lymphoma – A slow-growing type of cancer that develops from B-lymphocytes in specific areas of lymphoid tissue called marginal zones. These abnormal cells multiply gradually and accumulate in lymph nodes, spleen, or other organs. The disease progresses slowly over time, often without causing symptoms in early stages. As it advances, patients may notice swollen lymph nodes, enlarged spleen, fatigue, and weight loss. The abnormal cells can spread to various parts of the body including the bone marrow. Some patients may develop abnormal protein production in their blood.

Chronic Lymphocytic Leukemia – A type of blood cancer characterized by the slow accumulation of abnormal white blood cells called lymphocytes in the blood and bone marrow. These cancerous cells gradually crowd out healthy blood cells over months or years. Many patients have no symptoms initially and the disease is discovered through routine blood tests. As it progresses, individuals may experience swollen lymph nodes, fatigue, frequent infections, and easy bruising. The abnormal cells can spread to the spleen and liver, causing these organs to enlarge. The disease typically advances slowly compared to other types of leukemia.

Monoclonal Gammopathy of Undetermined Significance – A condition where the body produces an abnormal protein called monoclonal protein or M protein in the blood. This occurs when a single clone of plasma cells in the bone marrow makes too much of one specific antibody. Most people with this condition have no symptoms and it is usually discovered during routine blood tests. The abnormal protein level remains stable in many cases without causing health problems. However, the condition requires monitoring as it can sometimes progress over time. The presence of M protein does not immediately affect body functions but indicates an abnormality in protein production.