Following the approval of the JAK1/2 inhibitor ruxolitinib, TG101348 (fedratinib) was developed as a selective JAK2 inhibitor; clinical trials met the primary endpoint (the proportion of patients with a ≥ 35% reduction in spleen volume) with TG101348 for patients who had MPN and showed no response or intolerance to ruxolitinib [19]. The gene discussed is JAK1; the disease is myeloproliferative neoplasm.