SEATTLE / Oct 16, 2025 / Business Wire / Omeros Corporation (Nasdaq: OMER) today announced the publication of a peer-reviewed manuscript in Blood Advances, a journal of the American Society of Hematology, detailing survival outcomes in adult patients with life-threatening transplant-associated thrombotic microangiopathy (TA-TMA) treated with narsoplimab across both the pivotal clinical trial and the global expanded access program (EAP). Narsoplimab inhibits MASP-2, the effector enzyme of the lectin pathway of complement, and is currently under review for marketing approval by both the U.S. FDA and the European Medicines Agency.

Authored by an international panel of transplant experts, the manuscript – titled “Survival in Adults with High Risk TA-TMA—A Comparative Analysis of Narsoplimab Versus Supportive Care” – reports significant, multifold reductions in mortality risk across pivotal trial and EAP patient cohorts, individually and pooled, treated with narsoplimab compared to a well-matched external control group who did not receive narsoplimab. Consistent with previous narsoplimab clinical studies, no safety signals of concern were observed. The full manuscript is available online.

About Narsoplimab

Narsoplimab (OMS721) is an investigational, fully human monoclonal antibody that inhibits mannan-binding lectin-associated serine protease-2 (MASP-2), the effector enzyme of the lectin pathway of complement. Unlike other complement inhibitors, narsoplimab preserves the lytic function of the classical pathway, which is critical for antibody-mediated immune defense against infection.

A biologics license application (BLA) for narsoplimab in the treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA) is currently under review by the FDA, and a corresponding marketing authorisation application (MAA) is under review by the European Medicines Agency’s (EMA’s) Committee for Medicinal Products for Human Use. Narsoplimab has received breakthrough therapy and orphan drug designations from the FDA for TA-TMA and for the prevention (inhibition) of complement-mediated thrombotic microangiopathies. The EMA has granted orphan drug designation for narsoplimab in hematopoietic stem-cell transplant.

About Hematopoietic Stem Cell Transplant-Associated Thrombotic Microangiopathy

Transplant-associated thrombotic microangiopathy (TA-TMA) is a severe and often fatal complication of hematopoietic stem cell transplantation in both adults and children. TA-TMA is driven by systemic endothelial injury from conditioning regimens, immunosuppressants, infection, graft-versus-host disease, and other transplant-related factors. Activation of the lectin pathway of complement plays a central role in its pathogenesis.

TA-TMA occurs in both autologous and allogeneic transplants, with higher prevalence in the latter. Approximately 30,000 allogeneic transplants are performed annually in the U.S and Europe. Recent studies estimate a 40-percent incidence of TA-TMA in allogeneic transplants, with high-risk features in up to 80 percent of cases. Mortality in severe TA-TMA can exceed 90 percent, and survivors often face long-term renal complications, including dialysis. Currently, there is no approved therapy or established standard of care for TA-TMA.

About Omeros Corporation

Omeros is a clinical-stage biopharmaceutical company focused on discovering, developing, and commercializing first-in-class small-molecule and protein therapeutics for large-market and orphan indications, with a particular emphasis on complement-mediated diseases, cancers, and addictive or compulsive disorders. Omeros’ lead MASP-2 inhibitor narsoplimab targets the lectin pathway of complement and is under regulatory review by both the U.S. FDA and the European Medicines Agency for the treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy. OMS1029, a long-acting MASP-2 inhibitor, has successfully completed Phase 1 clinical trials. Zaltenibart (OMS906), Omeros’ MASP-3 inhibitor, is in clinical development for PNH and C3 glomerulopathy. Under a recently announced agreement, Novo Nordisk will acquire global rights to zaltenibart, including associated intellectual property and related assets. Omeros’ pipeline also includes OMS527, a phosphodiesterase 7 inhibitor in clinical development for cocaine use disorder, fully funded by the National Institute on Drug Abuse, as well as a growing portfolio of novel molecular and cellular therapeutic programs for oncology. For more information visit www.omeros.com.