1. A method of ameliorating or inhibiting a myeloproliferative disorder in a patient, comprising administering to said patient a compound, which is ((2R,5S)-5-{2-[(1R)-1-hydroxyethyl]-1H-imidazo[4,5-d]thieno[3,2-b]pyridin-1-yl}tetrahydro-2H-pyran-2-yl)acetonitrile, or a pharmaceutically acceptable salt thereof, wherein the myeloproliferative disorder is polycythemia vera (PV), myelofibrosis, primary myelofibrosis (PMF), post polycythemia vera myelofibrosis (Post-PV MF), post-essential thrombocythemia myelofibrosis (Post-ET MF), essential thrombocythemia (ET), myelofibrosis with myeloid metaplasia (MMM), hypereosinophilic syndrome (HES), idiopathic myelofibrosis (IMF), or systemic mast cell disease (SMCD).