Groundbreaking Approval: Yartemlea Becomes First Targeted Therapy for Post-Transplant TA-TMA Complications

Omeros Corp. (OMER) announced a significant regulatory milestone as the U.S. Food and Drug Administration cleared Yartemlea (narsoplimab-wuug), marking the first-ever FDA-approved treatment specifically designed for TA-TMA—a life-threatening condition that develops after hematopoietic stem cell transplantation. This approval represents a watershed moment in transplantation medicine, as no previously approved therapies existed for this rare but devastating complication.

Novel Mechanism Targets Root Cause of TA-TMA

What distinguishes Yartemlea from previous off-label treatment approaches is its selective inhibition of the lectin pathway within the complement system. By specifically blocking MASP-2 activation, the drug disrupts the disease-driving complement cascade while maintaining the immune defense mechanisms essential for transplant recipients. This targeted approach addresses the fundamental pathophysiology of transplant-associated thrombotic microangiopathy, which historically has resulted in poor outcomes for affected patients.

Clinical Data Demonstrates Substantial Survival Improvement

The regulatory clearance rests on compelling efficacy data from a pivotal single-arm study involving 28 adult patients, supplemented by real-world evidence from an expanded access initiative encompassing both adult and pediatric populations. Among study participants, 61% demonstrated complete clinical response, with 73% achieving survival at day 100—a remarkable improvement considering all enrolled patients carried high-risk status and unfavorable baseline prognostic indicators.

The survival advantage becomes even more pronounced when examining Yartemlea-treated patients who had exhausted prior therapeutic options. In this high-risk subset, one-year survival reached 50%, substantially exceeding the historical baseline of approximately 20%. Independent peer-reviewed analyses documented a three- to fourfold reduction in mortality when comparing Yartemlea recipients against external control populations, underscoring the drug’s transformative clinical potential.

Patient Population and Regulatory Pathway

Yartemlea carries approval for use in adults and children aged two years and older, establishing it as a therapeutic option across the transplant-eligible pediatric and adult spectrum. The FDA decision reflects confidence in both the primary efficacy study and the accumulated safety-efficacy profile from the expanded access program, demonstrating consistent therapeutic benefit across diverse patient subgroups.

Market Availability and Global Timeline

Omeros plans to introduce Yartemlea to the U.S. market beginning January 2026, with appropriate billing and reimbursement infrastructure already established to facilitate patient access. European regulatory authorities are expected to render their assessment of the therapy during mid-2026, potentially extending availability to international transplantation programs.