Omeros secures landmark approval for a life-saving therapy in adults and children following stem cell transplant
The U.S. Food and Drug Administration has approved YARTEMLEA® (narsoplimab-wuug), marking a major breakthrough in the treatment of hematopoietic stem cell transplant–associated thrombotic microangiopathy (TA-TMA), a frequently fatal complication of stem cell transplantation. The approval makes YARTEMLEA the first and only FDA-approved therapy specifically indicated for TA-TMA in adults and children aged two years and older.
The decision represents a significant milestone for Omeros Corporation (OMER), which has spent years developing the therapy in close collaboration with the transplant community. TA-TMA is driven by activation of the lectin pathway of complement, and YARTEMLEA is the first approved drug to selectively inhibit MASP-2, the key enzyme in that pathway, while preserving immune functions critical for host defense.
Approval was based on compelling clinical data from a pivotal single-arm study in adults and supported by results from a large expanded access program. In the pivotal trial, 61% of patients achieved a complete response, defined as improvement in key laboratory markers alongside improved organ function or transfusion independence. Among evaluable patients in the expanded access program, complete response rates reached 68%. Importantly, 100-day survival from TA-TMA diagnosis was approximately 73% to 74% across both data sets—an impressive outcome in a population classified as high-risk with historically poor prognoses.
Peer-reviewed publications further demonstrated that treatment with YARTEMLEA was associated with a three- to fourfold reduction in mortality risk compared with external control cohorts. In patients who had failed prior off-label therapies, one-year survival reached 50%, compared with historical survival rates of less than 20%.
Clinicians welcomed the approval as practice-changing. Experts from leading transplant centers emphasized that, until now, care relied largely on supportive measures that carried significant risks. YARTEMLEA also enters the market without a Boxed Warning or REMS requirement, further supporting its clinical adoption.
Following approval, Omeros plans to launch YARTEMLEA in the U.S. in January 2026, supported by dedicated reimbursement codes and the YARTEMLEAssist™ patient support program. With an estimated tens of thousands of patients at risk annually, the approval establishes a new standard of care for a devastating and previously underserved condition.
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