Celgene Corp.'s life sciences arm Impact Biomedicines Inc. gained U.S. Food and Drug Administration approval for Inrebic to treat a rare bone marrow disorder.

Inrebic, or fedratinib, is the second such medicine the FDA has approved for myelofibrosis. This rare form of bone marrow cancer harms the body's ability to produce blood cells for healthy living. Incyte Corp.'s Jakafi was the first medicine approved for the disease in the U.S. in 2011.

Celgene's treatment is approved for patients with intermediate or high-risk myelofibrosis. The approval is based on results of a phase 3 study called Jakarta. About 36.4% of patients exhibited a 35% or greater reduction in spleen volume after six, one-month treatment cycles. About 37.5% of patients showed a 50% or greater reduction in overall symptoms, such as night sweats, itching, abdominal discomfort and bone or muscle pain.

The FDA accepted the marketing application for Inrebic in March and granted it priority review. The U.S. regulator previously granted the therapy orphan drug designation, which would give the medicine market exclusivity for a certain period now that it is approved.