The U.S. FDA approved Omeros Corporation’s Yartemlea (narsoplimab) as the first treatment for hematopoietic stem cell transplant‑associated thrombotic microangiopathy (TA‑TMA), a life‑threatening complication of stem cell transplantation. The approval establishes an indicated therapy for a condition with high morbidity and limited prior options. Omeros’ green light gives transplant centers a targeted complement inhibitor to address TA‑TMA; the drug’s mechanism targets complement pathways implicated in microvascular injury. TA‑TMA is a rare but severe post‑transplant syndrome involving thrombosis and organ dysfunction.