The U.S. Food and Drug Administration has approved a new treatment for a rare and life-threatening complication that can occur after stem cell transplants, marking a major milestone for patients and clinicians with limited options until now.
Biotechnology company Omeros announced that its drug Yartemlea has been approved for the treatment of transplant-associated thrombotic microangiopathy, known as TA-TMA. The approval covers both adults and children aged two years and older, making it the first therapy officially authorized for this condition.
The market reacted swiftly to the decision. Omeros shares surged nearly 70% in early trading, reflecting investor confidence after years of regulatory uncertainty surrounding the drug.
TA-TMA is a severe complication that can develop following stem cell transplants, especially those involving donor cells. The condition arises when blood vessels become damaged due to an overactive immune response. This damage triggers inflammation and the formation of tiny blood clots, which can restrict blood flow to vital organs. The kidneys are often affected, but the condition can also lead to multi-organ failure and death if not effectively treated.
Until now, doctors had no approved therapies specifically designed to treat TA-TMA. Some clinicians have relied on off-label use of other immune-targeting drugs, but results have been inconsistent. The FDA approval of Yartemlea fills a long-standing treatment gap in transplant medicine.
Yartemlea, chemically known as narsoplimab-wuug, is a monoclonal antibody that works by blocking MASP-2, a protein involved in the body’s immune response. By targeting this pathway, the drug aims to reduce the immune-driven vessel damage that leads to clot formation in TA-TMA patients.
The approval follows a difficult regulatory journey. The FDA initially declined to approve the drug in 2021, stating that available data did not clearly demonstrate a treatment benefit. Regulators requested additional evidence to support the drug’s effectiveness.
New clinical data helped change that decision. In a small trial involving 28 patients with high-risk TA-TMA, 61% of those who received Yartemlea as a first-line treatment showed improved survival outcomes. While limited in size, the results were considered meaningful given the severity of the condition and lack of alternatives.
Analysts noted that the approval removes a major uncertainty that had weighed on the company for years. With regulatory clearance secured, attention is now shifting to the commercial potential of Yartemlea and Omeros’ broader drug development pipeline.
Currently, AstraZeneca’s drug Soliris is sometimes used off-label for TA-TMA, although it is officially approved for a related but distinct blood disorder. The arrival of a purpose-built therapy could reshape treatment standards in transplant centers.
Omeros expects Yartemlea to reach the U.S. market by January 2026. The company has not yet disclosed pricing details. It also plans to seek approval in Europe, with a regulatory decision anticipated in mid-2026.
For patients facing this dangerous transplant complication, the approval represents a significant step forward and a long-awaited expansion of treatment options.
