FDA Approves Narsoplimab for HSCT-Associated Thrombotic Microangiopathy

The FDA has approved narsoplimab-wuug (Yartemlea) for patients with hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA), according to a press release from the drug’s developer, Omeros.

Narsoplimab selectively inhibits MASP-2, which is the effector enzyme of the lectin pathway. MASP-2 blocks pathway activation but also allows for the preservation of classical and alternative complement functions. The treatment was approved for patients who are 2 years and older.

The approval was based on results from the single-arm TA-TMA study that enrolled 28 patients. Additional data came from an expanded access program (EAP) study (NCT04247906) that assessed 221 patients. In the EAP study, 19 patients had evaluable patient-level response data.

In the TA-TMA study, 61% of patients achieved a complete response vs 68% in the EAP study. Additionally, the 100-day survival from the time of TMA diagnosis was 73% (95% CI, 52%-86%) in the TA-TMA study and 74% (95% CI, 48%-88%) in the EAP study.

“Just as in adults, [narsoplimab’s] indication to treat TA-TMA in children 2 years of age and older is tremendously important,” Michelle Schoettler, MD, assistant professor of Pediatric Oncology and Hematopoietic Cellular Therapy at Emory University, said in the press release. “When used first-line, [narsoplimab] has been associated with approximately 75% 1-year survival; and even in children refractory to 1 or more off-label complement inhibitors, 1-year survival is approximately triple historical rates that have remained below 20%. My clinical experience with [narsoplimab] through the [EAP], including in very young patients, has reinforced that it needs to be readily available for children when TA-TMA emerges. With this approval, effective TA-TMA therapy can become the pediatric standard instead of the exception—and that will save children’s lives.”

The press release highlighted that patients treated with narsoplimab had reports of 3- to 4-fold lower risks of mortality compared with the external control cohort. Additionally, the EAP study showed narsoplimab was used as a first-line therapy for patients with high-risk TA-TMA in which prior therapy had failed them or they had discontinued 1 or more prior treatments. This patient population was shown to have a 1-year survival rate of 50% vs the historical 1-year rates of less than 20%.

The most common adverse effects (AEs) noted in 20% or more of patients included viral infections, sepsis, hemorrhage, diarrhea, vomiting, nausea, neutropenia, pyrexia, fatigue, and hypokalemia. Of note, 61% of patients had serious AEs, including acute kidney injury, confusional state, acute respiratory failure, neutropenic sepsis, septic shock, pulmonary edema, and vomiting. A total of 7% of patients had fatal AEs like neutropenic sepsis and shock.

In the EAP study, there were no new AEs identified for patients receiving narsoplimab.

The drug’s developer has also submitted an authorization application under the same indication to the European Medicines Agency. A decision is expected in mid-2026.

“This approval is a long-awaited breakthrough in hematopoietic cell transplantation and TA-TMA care,” Miguel-Angel Perales, MD, chief of the Adult Bone Marrow Transplantation Service at Memorial Sloan Kettering Cancer Center, said in the press release. “Until now, we’ve lacked an effective TA-TMA therapy and relied largely on supportive measures such as modifying calcineurin inhibitors, which can significantly increase the risk of life-threatening graft-versus-host disease. Based on a compelling data package, narsoplimab delivers robust response rates and improved survival in TA-TMA, with a favorable benefit-risk profile and a safety profile consistent with that seen in patients undergoing hematopoietic stem cell transplantation. As the first and only drug approved for TA-TMA, narsoplimab is a practice-changing advance for patients [with] this devastating complication.”

Reference

FDA approves Omeros’ YARTEMLEA® – first and only therapy indicated for TA-TMA. News release. Omeros Therapeutics. December 24, 2025. Accessed January 2, 2026. https://tinyurl.com/auemckkw