A method of treating a disease selected from cachexia, polycythemia vera (PV), essential thrombocythemia (ET), myeloid metaplasia with myelofibrosis (MMM), chronic myelogenous leukemia (CML), chronic myelomonocytic leukemia (CMML), hypereosinophilic syndrome (HES), systemic mast cell disease (SMCD), acute myelogenous leukemia, multiple myeloma, pancreatic cancer, leukemia, lymphoma, breast cancer, lung cancer, cancer of the head and neck, acute lymphoblastic leukemia, colorectal cancer, and Castleman's disease, comprising administering to said patient a pharmaceutical composition comprising a compound, which is 3-cyclopentyl-3-[4-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)-1H-pyrazol-1-yl]propanenitrile, or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier;
- wherein said composition is suitable for oral administration and for providing sustained release of said compound or said salt.