Omeros Suffers Regulatory Setback as EMA's CHMP Adopts Negative Opinion on Narsoplimab in TA-TMA
On June 26, 2026, Omeros Corporation announced that the European Medicines Agency's (EMA) Committee for Medicinal Products for Human Use (CHMP) adopted a negative opinion on its Marketing Authorization Application (MAA) for narsoplimab. The drug was being reviewed for the treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA), a rare and often fatal post-transplant complication.
The negative opinion followed an oral explanation meeting held with the CHMP, during which Omeros and four international transplant experts presented clinical evidence supporting the application.1 The decision caused Omeros's stock to plunge 19.12% on the day of the announcement. Omeros has indicated plans to request a formal re-examination of the negative opinion and seek an independent Ad Hoc Expert Group (AHEG) review, though the decision significantly clouds the drug's near-term regulatory and commercial outlook in Europe.
"Following an oral explanation meeting with the CHMP held this week, at which Omeros presented its position together with four international experts in hematopoietic cell transplantation, Omeros was informed that the CHMP has adopted a negative opinion on the MAA for narsoplimab in TA-TMA."
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An instance of Identical clinical trial packages no longer secure synchronized transatlantic drug approvals. — The European CHMP refused to approve narsoplimab based on the same clinical package that Omeros submitted to global regulators. ↩︎