December 24, 2025 — Leads & Copy — The U.S. Food and Drug Administration (FDA) has approved Omeros Corporation’s YARTEMLEA® (narsoplimab-wuug) for the treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA), a complication of stem-cell transplantation.
YARTEMLEA is the first and only approved lectin pathway inhibitor, selectively inhibiting MASP-2, the effector enzyme of the lectin pathway, while preserving classical and alternative complement functions. The drug is approved for adults and children ages two years and older.
According to Miguel-Angel Perales, M.D., Chief of the Adult Bone Marrow Transplantation Service at Memorial Sloan Kettering Cancer Center, this approval is a breakthrough in hematopoietic cell transplantation and TA-TMA care. Perales noted the previous lack of effective TA-TMA therapy and the reliance on supportive measures that can increase the risk of graft-versus-host disease. He added that narsoplimab delivers response rates and improved survival in TA-TMA, with a favorable benefit-risk profile.
The FDA approval was based on results from a single-arm, open-label study in adults with TA-TMA (N=28), supported by data from an expanded access program (EAP; N=221 adult and pediatric patients). In the EAP, 19 patients (13 adult and 6 pediatric) had evaluable patient-level response data.
Efficacy was assessed by TMA complete response (CR), defined by improvement in key laboratory markers and either improved organ function or transfusion independence. CR was achieved in 17/28 patients (61%) in the TA-TMA Study and 13/19 evaluable EAP patients (68%). Across the TA-TMA Study and the EAP, 100-day survival from TMA diagnosis was 73% and 74%, respectively. All patients met international harmonization criteria for high-risk TA-TMA.
Treatment with YARTEMLEA was associated with a three- to fourfold lower risk of mortality compared with an external control cohort. In the EAP, YARTEMLEA was used as first-line therapy and in high-risk patients who had failed or discontinued prior regimens. In these patients, YARTEMLEA was associated with 50 percent one-year survival, compared with historical rates reported as less than 20 percent.
Michelle Schoettler, M.D., Assistant Professor of Pediatric Oncology and Hematopoietic Cellular Therapy at Emory University, stated that YARTEMLEA’s indication to treat TA-TMA in children two years of age and older is important. She noted that YARTEMLEA has produced benefit in children, including those with organ dysfunction and those who have failed prior complement-inhibition therapy. She added that effective TA-TMA therapy can become the pediatric standard.
In the TA-TMA Study, the most common adverse reactions (≥20%) were viral infections, sepsis, hemorrhage, diarrhea, vomiting, nausea, neutropenia, pyrexia, fatigue, and hypokalemia. Serious adverse reactions occurred in 61% of YARTEMLEA-treated patients. Fatal adverse reactions were reported in 7% of patients. No new clinically significant safety signals were identified in patients treated with YARTEMLEA in the EAP.
Omeros is finalizing preparations for its U.S. product launch planned for January 2026. Dedicated U.S. billing and reimbursement codes are in place. The YARTEMLEAssist™ patient support program is expected to be available in the first quarter of 2026. Providers and patient representatives can call 1-844-YARTEM1 (1-844-927-8361) for personalized services.
Gregory A. Demopulos, M.D., chairman and chief executive officer of Omeros, stated that the FDA approval marks a milestone for Omeros and for patients and families facing TA-TMA. He added that the company’s focus is on ensuring rapid access to YARTEMLEA.
TA-TMA can occur after hematopoietic stem cell transplantation, with higher prevalence following allogeneic transplant. Recent studies estimate that TA-TMA develops in up to 56 percent of allogeneic transplant recipients.
A marketing authorization application for YARTEMLEA for the treatment of TA-TMA is currently under review by the European Medicines Agency with a decision expected in mid-2026.
To report suspected adverse reactions, contact Omeros Corporation at 1-844-YARTEM1 (1-844-927-8361), or contact FDA at 1-800-FDA-1088 or through FDA MedWatch.
Omeros is an innovative biotechnology company that discovers, develops, and commercializes first-in-class small-molecule and protein therapeutics for large-market and orphan indications.
Conference Call and Webcast on December 29, 2025 at 4:30 p.m. Eastern Time.
Contact: Gregory A. Demopulos, M.D., chairman and chief executive officer of Omeros.
Source: Omeros Corporation
