Safety and efficacy of narsoplimab in pediatric and adult patients with transplant-associated thrombotic microangiopathy: a real-world experience.

Transplant-associated thrombotic microangiopathy (TA-TMA) is a severe complication following hematopoietic stem cell transplantation (HSCT). No approved treatments are currently available. This study presents real-world data obtained with narsoplimab, a human immunoglobulin G4 monoclonal antibody that inhibits MASP-2, the effector enzyme of the lectin pathway of the complement system. Between January 2018 and August 2023, 20 (13 adult and 7 pediatric) patients diagnosed with TA-TMA received narsoplimab under an ongoing compassionate use program. The diagnosis was based on internationally defined criteria for pediatric and adult patients. Fifteen patients fulfilled the criteria recently established by an international consensus on TA-TMA. Nineteen patients exhibited high-risk characteristics. Thirteen patients (65%) responded to narsoplimab, achieving transfusion independence and significant clinical improvement. The one-hundred-day Overall Survival (OS) post-TA-TMA diagnosis was 70%, and 100% for responders. Narsoplimab proved to be effective and safe in the treatment of high-risk TA-TMA, with no increased infectious complications or other safety signals of concern across all age groups. The high response rates and the encouraging survival outcomes underscore the potential of narsoplimab as a valuable therapeutic option, particularly for high-risk cases.