Omeros Corp. (OMER) said Thursday that the U.S. Food and Drug Administration has approved Yartemlea (narsoplimab-wuug) for the treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA), a rare and often fatal complication following stem cell transplantation.
The approval makes Yartemlea the first and only FDA-approved therapy for TA-TMA and the first drug to selectively inhibit the lectin pathway of the complement system. The drug targets MASP-2, blocking disease-driving complement activation while preserving immune functions critical for host defense. YARTEMLEA is approved for adults and children aged two years and older.
FDA approval was based on data from a single-arm study in 28 adult patients, along with supporting evidence from an expanded access program that included adult and pediatric patients. In the pivotal study, 61% of patients achieved a complete response, while 100-day survival reached 73%. Similar outcomes were observed in the expanded access population. All treated patients were classified as high-risk with poor baseline prognosis.
Peer-reviewed studies showed treatment with YARTEMLEA was associated with a three- to fourfold reduction in mortality compared with external control cohorts. In patients who had failed prior off-label therapies, one-year survival reached 50%, significantly above historical rates below 20%.
Omeros plans to launch YARTEMLEA in the U.S. in January 2026, with billing and reimbursement codes already in place. A European regulatory decision is expected in mid-2026.
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