Efficacy and Safety Study of Narsoplimab in Pediatric Patients With High-Risk Hematopoietic Stem Cell Transplant TMA

This study tests narsoplimab, a drug that blocks a key immune protein called MASP-2 (part of the lectin complement pathway), in children who develop transplant-associated thrombotic microangiopathy (HSCT-TMA) — a serious and often deadly complication after bone marrow or stem cell transplantation. HSCT-TMA occurs when the blood vessel walls inside organs get damaged, causing tiny clots throughout the body that can lead to kidney failure, neurological injury, and death. Eligible participants are children and infants (28 days to under 18 years) who have received an allogeneic stem cell transplant and developed high-risk HSCT-TMA, defined by specific laboratory criteria including low platelets, signs of red blood cell destruction, and at least one serious complication such as kidney injury, neurological abnormality, or elevated blood pressure. Prior treatment with eculizumab or ravulizumab disqualifies patients unless treatment failure is documented. Participants receive narsoplimab via IV infusion over multiple weeks with close monitoring. This research is critically important — high-risk HSCT-TMA carries a mortality rate exceeding 70% and has no established treatment. Narsoplimab has shown promise in adult studies, and this pediatric trial could establish a life-saving standard of care for a population with very few options.