EXEL claims that its JAK inhibitor is specific for JAK2 only. They claim they had a JAK inhibitor that hits both JAK1/2 way before INCY, but decided to refine it further so its selective for JAK2 only. Sorry not doing any homework on the JAK pathways, but does JAK1 and JAK2 mediate different signaling pathways or activate different subset of genes? TIA.