Omeros Receives EMA CHMP Negative Opinion On Its Marketing Authorization Application For Narsoplimab For Treatment Of Hematopoietic Stem Cell Transplant-Associated Thrombotic Microangiopathy

Decision follows re-examination of its original negative opinion adopted in June 2026. An eight-member ad hoc expert group (AHEG) consisting of hematologists, statisticians, and transplant physicians, together with two patient representatives, was convened by CHMP as part of the re-examination process. The AHEG was charged with addressing a single, three-part question prepared and posed by CHMP. CHMP’s final minutes from its closed meeting with the AHEG state that "[t]he AHEG recommended a review of individual patient-level data by external experts to better understand the factors associated with treatment response and survival." Omeros had submitted substantial patient-level data to CHMP in August as part of its grounds for re-examination. CHMP did not provide patient-level data to the AHEG.

Narsoplimab was approved under the brand name YARTEMLEA® by the U.S. Food and Drug Administration (FDA) in December 2025. YARTEMLEA is the first and only therapy to receive regulatory approval for TA-TMA and is broadly indicated in the U.S. for TA-TMA patients two years of age and older. YARTEMLEA targets MASP-2, the effector enzyme of the lectin pathway of complement and, with a unique safety profile, is the only systemic complement inhibitor on the market without a boxed warning, risk evaluation and mitigation strategy (REMS), or vaccination requirement. There is no approved therapy for TA-TMA in Europe.

Omeros is commercializing YARTEMLEA with its own field force in the U.S. market and plans to license commercialization rights to a third party in the European Union (EU) if EU marketing authorization is granted.

"We are deeply disappointed in the re-examination process and outcome," said Gregory A. Demopulos, M.D., chairman and chief executive officer of Omeros. "We believe that our YARTEMLEA efficacy and safety data, FDA’s recent approval with a broad indication for both adults and children, a decade of compassionate use requests by European transplant physicians for their TA-TMA patients, and the rapid U.S. commercial adoption speak clearly to the favorable benefit-risk profile of the drug. As YARTEMLEA continues to progress toward becoming the standard of care in the U.S., it is disheartening that patients in Europe will not have routine access to its potentially life-saving benefits. As we advance our efforts to expand YARTEMLEA’s use and indications worldwide and to develop our MASP-2 franchise further, we are working to enable fully reimbursed, named-patient access to YARTEMLEA for those with TA-TMA where permitted in Europe and other regions."

Due to increasing demand for YARTEMLEA drug supply in the U.S. commercial market, Omeros has informed CHMP of its intention to terminate the YARTEMLEA compassionate-use program. Compassionate-use TA-TMA patients currently receiving YARTEMLEA will be provided sufficient drug to complete their respective treatment courses.

Omeros is pursuing additional indications for its MASP-2 franchise, including YARTEMLEA, the long-acting antibody OMS1029, and the company’s orally available small-molecule inhibitors. Clinical studies in acute respiratory distress syndrome (ARDS) and for prevention of high-risk TA-TMA in pediatric patients are planned to begin later this year.