Omeros Corp EMA Negative Opinion on Narsoplimab
On 26 June 2026, Omeros Corporation (NASDAQ: OMER) saw its shares tumble 23% in pre‑market trading on Friday after the European Medicines Agency’s Committee for Medicinal Products for Human Use (CHMP) issued a negative opinion on the company’s marketing‑authorization application for narsoplimab in hematopoietic stem cell transplant‑associated thrombotic micro‑angiopathy (TA‑TMA). The CHMP adopted the opinion following an oral explanation meeting held earlier in the week, during which Omeros presented its position together with four international experts in hematopoietic cell transplantation.
Omeros announced that it intends to request a re‑examination of the CHMP opinion and will seek a review by an Ad Hoc Expert Group, an independent panel of external scientific and clinical experts that the EMA will convene. Narsoplimab, marketed under the brand name YARTEMLEA, received approval from the U.S. Food and Drug Administration in December 2025 for TA‑TMA patients aged two years and older, representing the first and only approved therapy for the condition.
Gregory A. Demopulos, chairman and chief executive officer of Omeros, said the company was disappointed by the CHMP’s opinion, emphasizing the lethal nature of TA‑TMA, the absence of an approved treatment in Europe, and the totality of clinical‑trial and real‑world data supporting narsoplimab’s efficacy and safety. The firm will continue to provide YARTEMLEA to TA‑TMA patients through its global compassionate‑use program, prioritising children, although drug‑supply and access constraints limit the number of patients who can be treated compared with the potential reach following EMA approval.
The marketing‑authorization application was supported by data from Omeros’ pivotal trial of narsoplimab in TA‑TMA, survival analyses comparing treated patients with an external registry, and data derived from the company’s compassionate‑use program.