What Was Approved?
On December 23, 2025, the U.S. Food and Drug Administration approved Yartemlea (narsoplimab-wuug) for the treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy, or TA-TMA, in adults and pediatric patients 2 years of age and older.
Yartemlea is the first FDA-approved treatment specifically for TA-TMA.
What Is TA-TMA?
TA-TMA is a serious complication that can occur after a hematopoietic stem cell transplant.
Small blood clots can form in tiny blood vessels, potentially causing damage to organs such as the kidneys, cardiovascular system, and gastrointestinal tract.
How Does Yartemlea Work?
Yartemlea is a MASP-2 inhibitor.
MASP-2 is part of the lectin pathway of the complement system. By inhibiting MASP-2, narsoplimab is intended to reduce complement-related processes involved in vascular injury and thrombotic microangiopathy.
How Is Yartemlea Given?
Yartemlea is administered by intravenous infusion over 30 minutes.
For patients weighing:
- 50 kg or more: 370 mg once weekly
- Less than 50 kg: 4 mg/kg once weekly
The dosing frequency may be increased to twice weekly when there is inadequate improvement in TA-TMA signs and symptoms.
What Did the Clinical Study Show?
FDA evaluated Yartemlea in a single-arm, open-label study of 28 adults, with additional supporting data from 19 patients treated through an expanded access program.
A TA-TMA response was achieved in 61% of patients in the main study. In the expanded access group, responses were observed in 67% of pediatric patients and 69% of adults.
These results describe the patients studied and do not guarantee the same outcome for every patient.
What Are the Main Safety Concerns?
Serious infections can occur in patients receiving Yartemlea.
Common adverse reactions reported in the clinical program included:
- Viral infections
- Sepsis
- Bleeding
- Diarrhea
- Vomiting
- Nausea
- Neutropenia
- Fever
- Fatigue
- Low potassium
Patients require close monitoring because TA-TMA itself and the post-transplant setting can involve substantial medical risks.
Bottom Line
Yartemlea (narsoplimab-wuug) is the first FDA-approved treatment for TA-TMA in adults and children age 2 and older following hematopoietic stem cell transplantation.
It is given by intravenous infusion and requires specialist supervision and careful monitoring for infection and other serious complications.
Sources
- U.S. Food and Drug Administration (FDA) — FDA Approves First Drug to Treat Serious Complication of Stem Cell Transplant, December 2025.
- U.S. Food and Drug Administration (FDA) — Drug Trials Snapshot: Yartemlea.
- U.S. Food and Drug Administration (FDA) — Yartemlea (narsoplimab-wuug) Prescribing Information, 2025.
- U.S. Food and Drug Administration (FDA) — Novel Drug Approvals for 2025.