FDA Approves Omeros’ Yartemlea as First Treatment for Transplant-Associated Thrombotic Microangiopathy

Washington, Dec. 24, 2025 — The U.S. Food and Drug Administration has approved Yartemlea, a monoclonal antibody developed by Omeros Corporation, as the first treatment for transplant-associated thrombotic microangiopathy (TA-TMA), a serious and potentially life-threatening complication after stem cell transplantation affecting both adults and children aged 2 years and older.

TA-TMA is characterized by widespread damage to small blood vessels caused by excessive immune activation, leading to clot formation and organ dysfunction, particularly in the kidneys. Until now, no FDA-approved therapy existed for this condition, leaving clinicians to rely on off-label or supportive treatments with limited effectiveness.

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The approval of Yartemlea follows clinical data from a trial involving 28 high-risk TA-TMA patients, which showed that first-line use of the drug resulted in a 61% improvement in overall survival versus historical controls. Based on this evidence, the agency granted accelerated approval, with the treatment expected to be commercially available in the U.S. by January 2026.

Yartemlea works by blocking MASP-2, a protein involved in the lectin pathway of complement activation, thereby reducing immune-mediated endothelial injury and improving microvascular blood flow. Previously rejected by the FDA in 2021 for insufficient data, the new trial outcomes have supported a successful regulatory outcome.

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The approval has already boosted investor confidence, with Omeros’ stock rising significantly following the announcement. The company continues to await a decision from the European Medicines Agency, expected in mid-2026, which could broaden global access to this novel therapy.

Source: Reuters, US FDA approves Omeros’ drug to treat dangerous transplant complication, December 24, 2025.