WILMINGTON, Del. ( TheStreet) --U.S. regulators approved a new medicine from Incyte ( INCY) to treat patients with myelofibrosis, a rare bone marrow disease. Incyte's new drug, Jakafi, is the first approved therapy for myelofibrosis and the first approved drug to emerge from Incyte's labs. The U.S. Food and Drug Administration approval Wednesday came earlier than the expected decision date of Dec. 3. Incyte shares were up $1.30, or 10%, to $13.90 in Wednesday trading following the announcement of Jakafi's approval. Myelofibrosisis is a disorder in which abnormal bone marrow stem cells produce scar tissue that replaces healthy marrow. Patients with myelofibrosis suffer from anemia and enlarged spleens. Approximately 3,500 people in the U.S. are diagnosed with myelofibrosis annually and about one-third of these patients develop acute myeloid leukemia or bone marrow failure. Jakafi, a pill taken twice a day, inhibits enzymes known as JAK1 and JAK2 believed to play a role in diseases like myelofibrosis that cause bone marrow cells to grow uncontrollably. So-called JAK inhibitors are also being studied against immune-related inflammatory diseases such as rheumatoid arthritis. "Jakafi represents another example of an increasing trend in oncology where a detailed scientific understanding of the mechanisms of a disease allows a drug to be directed toward specific molecular pathways," said Richard Pazdur, FDA's director of the Office of Hematology and Oncology Products, in a statement. "The clinical trials leading to this approval focused on problems that patients with myelofibrosis commonly encounter, including enlarged spleens and pain." Two phase III clinical trials demonstrated that treatment with Jakafi significantly reduced the spleen size and ameliorated disease symptoms in patients with myelofibrosis compared to treatment with best alternative care or a placebo. "The availability of Jakafi is a significant medical advancement for people living with myelofibrosis, a debilitating disease," said Incyte CEO Paul Friedman, in a statement. "This milestone marks a tremendous achievement for Incyte because a scientific discovery from our research laboratories has become the first JAK inhibitor to reach the market and provide a clinical benefit to patients." Incyte plans a commercial launch of Jakafi with partner Novartis ( NVS) next week.