Itacitinib is primarily used in the field of oncology as a selective inhibitor of JAK1, a key enzyme involved in the signaling pathways of cytokines and growth factors. Its application is focused on modulating immune responses and inflammation, making it a potential therapeutic agent for treating various cancers and autoimmune diseases. It is often investigated in combination with other therapies to enhance efficacy, particularly in hematologic malignancies like myelofibrosis and acute graft-versus-host disease (GVHD). Additionally, it is being explored for its role in improving outcomes in solid tumors and inflammatory conditions by targeting the JAK-STAT pathway, which is critical for cell proliferation and immune regulation.