The Committee for Medicinal Products for Human Use confirmed its original June decision after a review process that drew sharp criticism from the drugmaker. Omeros Chief Executive Gregory Demopulos expressed deep disappointment, citing procedural failures regarding how patient-level data was handled. According to the company, experts had requested specific data points in August, but the committee failed to relay that information to the expert group tasked with the evaluation.

While the drug is already approved in the U.S. under the brand name Yartemlea, this European rejection complicates Omeros’s plans to license commercialization rights across the European Union. Narsoplimab is designed to address hematopoietic stem cell transplant-associated thrombotic microangiopathy, a life-threatening complication that remains a primary focus for the company’s clinical pipeline. Following the news, Omeros stock dropped to $16.60, leaving the company to navigate a difficult path toward regulatory approval in the region.