Yartemlea is a fully human monoclonal antibody that selectively inhibits mannan-binding lectin–associated serine protease-2 (MASP-2), a key enzyme in the lectin pathway of the complement system.

It is approved for the treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA) in adults and pediatric patients aged two years and older. By blocking MASP-2, Yartemlea prevents complement-mediated endothelial injury while preserving other immune pathways essential for host defense. TA-TMA is a rare but often fatal complication of stem cell transplantation, and Yartemlea represents the first and only FDA-approved therapy targeting this pathway.