Biotechnology company Omeros Corporation (Nasdaq:OMER) announced on Friday that the European Medicines Agency's Committee for Medicinal Products for Human Use (CHMP) maintained its negative opinion on the marketing authorisation application for narsoplimab to treat transplant-associated thrombotic microangiopathy (TA-TMA), following a re-examination of its original June 2026 decision.

During the re-examination, CHMP convened an eight-member expert group comprising haematologists, statisticians and transplant physicians, alongside two patient representatives. The group recommended an external review of individual patient data to better understand treatment response and survival, while Omeros said it had submitted substantial patient-level data to CHMP in August.

Narsoplimab, marketed as YARTEMLEA, received US Food and Drug Administration (FDA) approval in December 2025 for the treatment of TA-TMA in adults and paediatric patients aged two years and older. It is the first and only therapy approved for the condition, for which no treatment is currently approved in Europe.

Omeros CEO Gregory A. Demopulos criticised the re-examination outcome, citing the drug's efficacy and safety data, broad US approval for adults and children aged two and older, and commercial adoption. The company plans to pursue global expansion of YARTEMLEA and further development of its MASP-2 inhibitor portfolio.

Citing growing US commercial demand, Omeros informed CHMP of its intention to terminate the YARTEMLEA compassionate-use programme. Patients currently receiving treatment through the programme will receive sufficient supply to complete their courses.

Omeros is also advancing its MASP-2 franchise, including the long-acting antibody OMS1029 and oral small-molecule inhibitors, with clinical studies in acute respiratory distress syndrome and prevention of high-risk TA-TMA in paediatric patients planned to begin later in 2026.