FDA Approves First Treatment for HSCT-Associated Thrombotic Microangiopathy
The U.S. FDA has approved narsoplimab (Yartemlea) as the first indicated therapy for hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA) in adults and children aged 2 years and older, marking a significant advancement in the management of this serious post-transplant complication.
YARTEMLEA is the first and only approved lectin pathway inhibitor. YARTEMLEA selectively inhibits MASP-2, the effector enzyme of the lectin pathway, blocking pathway activation while preserving classical and alternative complement functions important for host defense. YARTEMLEA is approved for use in adults and in children ages two years and older.
“This approval is a long-awaited breakthrough in hematopoietic cell transplantation and TA-TMA care,” stated Miguel-Angel Perales, M.D., Chief of the Adult Bone Marrow Transplantation Service at Memorial Sloan Kettering Cancer Center. “Until now, we’ve lacked an effective TA-TMA therapy and relied largely on supportive measures such as modifying calcineurin inhibitors, which can significantly increase the risk of life-threatening graft-versus-host disease.
Approval of YARTEMLEA was based on results from a single-arm, open-label study in adults with TA-TMA (N=28), supported by additional data from an expanded access program (EAP; N=221 adult and pediatric patients).
Efficacy was assessed by TMA complete response (CR), defined as improvement in key laboratory markers of TMA together with either improved organ function or transfusion independence. CR was achieved in 61% of patients in the primary study and 68% of evaluable EAP patients.
Across the study and the EAP, 100-day survival from the time of TMA diagnosis was approximately 73–74%. All patients met international criteria for high-risk TA-TMA.
In peer-reviewed publications, treatment with YARTEMLEA was associated with a three- to fourfold lower risk of mortality compared with an external control cohort.
“YARTEMLEA’s indication to treat TA-TMA in children two years of age and older is tremendously important,” said Michelle Schoettler, M.D., Assistant Professor of Pediatric Oncology and Hematopoietic Cellular Therapy at Emory University.
The most common adverse reactions (≥20%) included viral infections, sepsis, hemorrhage, diarrhea, vomiting, nausea, neutropenia, pyrexia, fatigue, and hypokalemia. Serious adverse reactions occurred in 61% of patients.
Following FDA approval, Omeros is preparing for a U.S. product launch planned for January 2026. Dedicated U.S. billing and reimbursement codes are now in place.
- Diagnosis Code: ICD-10-CM M31.11
- Procedure Codes: ICD-10-PCS XW03357 and XW04357
The YARTEMLEAssist™ patient support program is expected to be available in early 2026.
TA-TMA can occur after both autologous and allogeneic hematopoietic stem cell transplantation. Recent studies estimate TA-TMA develops in up to 56% of allogeneic transplant recipients.
A marketing authorization application for YARTEMLEA is currently under review by the European Medicines Agency, with a decision expected in mid-2026.
