 Witte is also a Howard Hughes Medical Institute investigator (1986–present) and a member of the President’s Cancer Panel (2012 to present).Witte's research has contributed to the understanding of human leukemias, immune disorders and stem cell activity in cancers of the epithelium.His discovery of the tyrosine kinase activity in the ABL1 protein and the demonstration of the BCR-ABL oncoproteins in leukemias was one of the preclinical discoveries that led to the development of Gleevec, the first targeted therapy for chronic myelogenous leukemia.