The FDA decision on Omeros Corp.’s (OMER) lead investigational therapy, Narsoplimab, proposed for the treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy/TA-TMA, is due on December 26, 2025.Hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA) is a significant and often lethal complication of stem cell transplantation. It is caused by endothelial cell damage induced by conditioning regimens, immunosuppressant therapies, infection, graft-versus-host disease, and other factors associated with stem cell transplantation.Thrombotic Microangiopathy can present with a range of clinical manifestations, including anemia, thrombocytopenia (low platelet count), impaired kidney function, and petechiae - tiny red or purple skin spots caused by subcutaneous bleeding. Other symptoms may include jaundice, abdominal pain, and neurological complications such as confusion, headaches, seizures, or even strokes.The FDA declined to approve Narsoplimab in October 2021, citing difficulty in estimating the treatment effect of Narsoplimab in HSCT-TMA and asserted that additional information would be needed to support regulatory approval.OMER closed Wednesday’s (November 26, 2025) trading at $9.63, up 1.90%.