Fludarabine, cyclophosphamide, and mitoxantrone are chemotherapy drugs that are used in the treatment of CLL. Rituximab is a monoclonal antibody that binds to CLL cells and causes cell death. Pegfilgrastim (Neulasta) is a growth factor that helps the bone marrow to produce white cells (neutrophils) and is an approved drug to treat the suppression of marrow function caused by chemotherapy.