Lumoxiti is used to treat a type of cancer called hairy cell leukemia. This is a chemotherapy drug that slows or stops the growth of cancer cells.

Hairy cell leukemia is a rare type of blood cancer in which the bone marrow produces too many B lymphocytes, a type of white blood cell that fights infection. Because these excess B cells are abnormal and look "hairy" under a microscope, the condition is called hairy cell leukemia. As the number of cancer cells increases, other blood cells such as red blood cells and platelets decrease, and the person experiences dangerous complications.