Omeros Corporation (OMER) today announced that the FDA has approved YARTEMLEA for the treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy in adults and children aged two years and older.
Transplant-associated thrombotic microangiopathy (TA-TMA) is a severe and often-fatal complication of stem-cell transplantation, driven by activation of the lectin pathway of complement. Mortality in high-risk cases can exceed 90%, with survivors frequently facing long-term renal complications.
YARTEMLEA (narsoplimab-wuug) is the first and only FDA-approved therapy for TA-TMA. It is a fully human monoclonal antibody that selectively inhibits MASP-2, the effector enzyme of the lectin pathway, while preserving classical and alternative complement functions essential for host defense.
The approval follows an earlier FDA Complete Response Letter, with Omeros resubmitting its application. The decision was supported by results from a pivotal single-arm Phase 2 trial and an expanded access program. Patients treated with YARTEMLEA achieved complete response rates of 61% in the trial and 68% in the expanded access program, with 100-day survival rates of 73% and 74%, respectively. Importantly, no boxed warnings or REMS program are required, and vaccinations are not mandated prior to treatment.
Safety data showed that serious infections occurred in 36% of patients, but overall the benefit-risk profile was considered favorable.
This approval marks a breakthrough in transplant medicine, providing the first effective therapy for TA-TMA.
Omeros plans to launch YARTEMLEA in the U.S. in January 2026, with dedicated billing codes and patient support programs in place.
The company has also submitted a Marketing Authorization Application to the European Mediccines Agency, with a decision expected in mid-2026.
OMER has traded between $2.95 and $12.10 over the past year. The stock is currently trading in the pre-market at $9.00, up 2.86%.
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