Omeros Corporation (NASDAQ:OMER) saw its shares fall about 23% in premarket trading on Friday after a Committee for Medicinal Products for Human Use - CHMP - opinion went against the firm's marketing authorisation application for narsoplimab to treat hematopoietic stem cell transplant-associated thrombotic microangiopathy, commonly referred to as TA-TMA.
The negative recommendation followed an oral explanation meeting held this week, during which Omeros presented its regulatory case alongside four international experts in hematopoietic cell transplantation. After that session, the CHMP adopted a negative opinion on the application.
In response, Omeros stated it will seek a re-examination of the CHMP decision. The company said it will request that the EMA assemble an Ad Hoc Expert Group - an independent panel made up of external scientific and clinical experts - to review the opinion.
Narsoplimab, marketed under the brand name YARTEMLEA, received approval from the U.S. Food and Drug Administration in December 2025 for the treatment of TA-TMA in patients aged two years and older. That approval made it the first and only regulatory-authorised therapy for the condition in the United States.
Gregory A. Demopulos, chairman and chief executive officer of Omeros, commented that the company was disappointed by the CHMP’s decision, citing the lethal nature of TA-TMA, the absence of an approved treatment for the condition in Europe, and what the company describes as the totality of clinical trial and real-world data supporting narsoplimab’s efficacy and safety.
Omeros also said it will continue to provide YARTEMLEA to TA-TMA patients through its global compassionate use program, with a stated priority for children. The company noted, however, that drug supply and access limitations restrict the number of patients who can receive treatment under the compassionate use program when compared with the broader treatment access that would follow an EMA marketing authorisation.
The marketing authorisation application submitted to the EMA was supported by several data sources: Omeros' pivotal trial of narsoplimab in TA-TMA, survival analyses that compared outcomes for narsoplimab-treated patients against an external registry, and data generated from the company’s compassionate use program.
With the CHMP opinion now negative, Omeros has formally signalled its intent to pursue re-examination and to request an independent expert review by the EMA. The company will continue limited patient access through compassionate use while those regulatory review steps are pursued.
Context and next steps
The CHMP's negative opinion does not represent a final European Commission decision; Omeros has said it will request re-examination and an ad hoc expert review. The company maintains access for a limited set of patients through compassionate use, prioritising paediatric cases, but acknowledges supply constraints that restrict patient numbers relative to what EMA approval would allow.