Ruxolitinib is a drug that works by inhibiting two proteins called JAK1 and JAK2. These proteins are involved in signaling pathways that help regulate immune function and blood cell production. In diseases like myelofibrosis (MF) and polycythemia vera (PV), these pathways are often overactive, leading to abnormal cell growth. Ruxolitinib blocks this signaling, reducing the growth of abnormal cells and lowering inflammation. In animal models, it has been shown to decrease spleen size, reduce mutant blood cells, and lower inflammatory cytokines. It also helps reduce inflammation and immune cell infiltration in diseases like graft-versus-host disease (GvHD).