For patients undergoing stem cell transplants, the journey is already fraught with risk.
Now, a new FDA approval offers hope against one of the most dangerous and common complications.
On December 24, 2025, the FDA approved Yartemlea (narsoplimab), the first and only treatment for hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA). [1] [2]
This is a landmark achievement for Omeros Corporation, which received its first FDA approval in its 31-year history. More importantly, it is a life-saving breakthrough for the thousands of patients who develop this often-fatal condition each year. [2]
A Deadly Complication with No Approved Treatment
TA-TMA is a severe complication that can occur after a stem cell transplant, affecting up to 56% of recipients. It causes damage to small blood vessels throughout the body, leading to organ failure and a high risk of death. [1]
Until now, doctors had no approved treatments for TA-TMA. They were forced to rely on supportive measures and modifying other medications, which could increase the risk of other life-threatening conditions like graft-versus-host disease. [1]
Yartemlea: A Targeted Solution
Yartemlea is a first-in-class drug that works by inhibiting the lectin pathway of the complement system, a part of the immune system that drives TA-TMA. By selectively blocking a specific enzyme called MASP-2, it stops the disease process while leaving other important immune functions intact. [1]
Impressive Clinical Trial Results
The FDA approval was based on strong evidence from clinical trials showing significant improvements in patient outcomes:
| Metric | Result |
|---|---|
| Complete Response Rate | 61-68% |
| 100-Day Survival Rate | 73-74% |
| Mortality Risk Reduction | 3-4x Lower vs. Control |
| Refractory Patient 1-Year Survival | 50% (vs. <20% historical) |
“This approval is a long-awaited breakthrough in hematopoietic cell transplantation and TA-TMA care,” stated Dr. Miguel-Angel Perales, Chief of the Adult Bone Marrow Transplantation Service at Memorial Sloan Kettering Cancer Center. “As the first and only drug approved for TA-TMA, narsoplimab is a practice-changing advance for patients facing this devastating complication.” [1]
Hope for Children and Adults
Yartemlea is approved for both adults and children as young as two years old. This is especially important for pediatric patients, who have shown strong and consistent benefits from the treatment, even in very high-risk cases. [1]
“With this approval, effective TA-TMA therapy can become the pediatric standard instead of the exception – and that will save children’s lives,” said Dr. Michelle Schoettler of Emory University. [1]
Looking Ahead
Omeros plans to launch Yartemlea in the U.S. in January 2026, with a patient support program called YARTEMLEAssist™ to help with access and reimbursement. The company has also submitted an application for approval in Europe. [1] [2]
This approval marks a new era for stem cell transplant patients. For the first time, there is a targeted, effective, and life-saving treatment for a complication that was once a death sentence for many.
References
[1] Omeros Corporation. (2025, December 24). FDA Approves Omeros’ YARTEMLEA® – First and Only Therapy Indicated for TA-TMA. https://investor.omeros.com/news-releases/news-release-details/fda-approves-omeros-yartemlear-first-and-only-therapy-indicated
[2] Fierce Pharma. (2025, December 26). FDA signs off on Omeros’ stem cell transplant drug Yartemlea. https://www.fiercepharma.com/pharma/omeros-scores-its-first-ever-fda-nod-stem-cell-transplant-treatment-yartemlea
[3] Pharmabiz. (2025, December 29). Omeros’ Yartemlea gets US FDA approval to treat hematopoietic stem cell transplant-associated thrombotic microangiopathy. https://www.pharmabiz.com/NewsDetails.aspx?aid=183281&sid=2
