The U.S. Food and Drug Administration (FDA) on Wednesday approved Omeros Corporation (NASDAQ:OMER) Yartemlea (narsoplimab-wuug) for hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA).
Yartemlea is approved for use in adults and in children ages two years and older.
TA-TMA is an often-fatal complication of stem-cell transplantation driven by activation of the lectin pathway of complement.
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TA-TMA can occur after both autologous and allogeneic hematopoietic stem cell transplantation, with a higher prevalence following allogeneic transplant. Approximately 30,000 allogeneic transplants are performed each year in the U.S. and Europe.
Recent studies estimate that TA-TMA develops in up to 56% of allogeneic transplant recipients.
First-In-Class Mechanism Of Action
Yartemlea is the first and only approved lectin pathway inhibitor.
Yartemlea selectively inhibits MASP-2, the effector enzyme of the lectin pathway, blocking pathway activation while preserving classical and alternative complement functions important for host defense.
Approval of Yartemlea was based on results from a single-arm, open-label study in adults with TA-TMA (the TA-TMA Study; N=28), supported by additional data from an expanded access program (EAP; N=221 adult and pediatric patients).
In the EAP, 19 patients (13 adult and six pediatric) had evaluable patient-level response data.
Efficacy Outcomes And Survival Data
Efficacy was assessed by TMA complete response (CR), defined as improvement in key laboratory markers of TMA (platelet counts and LDH levels) together with either improved organ function or transfusion independence.
CR was achieved in 17/28 patients (61%) and 13/19 evaluable EAP patients (68%).
Across the TA-TMA Study and the EAP, 100-day survival from the time of TMA diagnosis (based on all-cause mortality) was 73% and 74%, respectively.
In peer-reviewed publications, treatment with Yartemlea was associated with a three- to fourfold lower risk of mortality compared with an external control cohort.
In previously refractory high-risk patients, Yartemlea was associated with 50% one-year survival, compared with historical one-year survival rates reported as less than 20%.
Commercial Launch And Regulatory Outlook
Following FDA approval of Yartemlea, Omeros is finalizing preparations for its U.S. product launch planned for January 2026.
A marketing authorization application for Yartemlea for the treatment of TA-TMA is currently under review by the European Medicines Agency, with a decision expected in mid-2026.
OMER Price Action: Omeros shares were up 73.71% at $15.20 at the time of publication on Wednesday. The stock is trading at a new 52-week high, according to Benzinga Pro data.
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