JAK1 and myelofibrosis: ,4 Ruxolitinib, an inhibitor of the JAK1 and JAK2 protein kinases, is approved for treatment in myelofibrosis.2, 3, 4, 5 Similarly, JAK-STAT signaling pathways have been trialed as a therapeutic target in AA with baricitinib recently becoming the first Food and Drug Administration–approved treatment for adults with severe AA.