The FDA approved Omeros Corporation’s narsoplimab (Yartemlea) for hematopoietic stem cell transplant‑associated thrombotic microangiopathy (TA‑TMA), marking the first approved therapy for this life‑threatening transplant complication. The approval followed a Biologics License Application decision with a Dec. 26 PDUFA date. Clinical context: narsoplimab is a fully human monoclonal antibody that inhibits mannan‑binding lectin‑associated serine protease‑2 (MASP‑2). TA‑TMA is a microvascular occlusive disorder that can arise after hematopoietic stem cell transplantation and carries high morbidity and mortality. Why it matters: approval establishes a regulatory precedent for targeting the lectin pathway in TA‑TMA, creates an immediate market for a previously unmet need in transplant centers, and could influence development strategies for complement and lectin pathway modulators.