Omeros Faces European Regulatory Setback as CHMP Issues Negative Opinion on Narsoplimab

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 the marketing authorization application (MAA) for narsoplimab (Yartemlea) for the treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA).

The decision represents a major regulatory setback for Omeros in Europe, causing its stock price to fall significantly and prompting shareholder class-action investigations.

The CHMP's Negative Opinion

The negative opinion was adopted following an oral explanation meeting with the CHMP, at which Omeros presented its clinical efficacy and safety position alongside four international experts in hematopoietic cell transplantation. Despite this advocacy, the CHMP recommended refusing marketing authorization.

In response, Omeros announced its intention to formally request a re-examination of the CHMP's negative opinion. As part of this re-examination process, the company will seek an assessment by an Ad Hoc Expert Group (AHEG)—an independent panel of external clinical and scientific specialists assembled by the EMA to provide objective expertise.

Divergence from the FDA's Position

The EMA's negative stance diverges sharply from the U.S. regulatory position.¹ The FDA granted approval to narsoplimab (under the brand name Yartemlea) in December 2025² as the first and only approved treatment for TA-TMA in adults and pediatric patients aged two years and older.

The European setback introduces substantial financial and operational uncertainty for Omeros. Because the company's current operating runway is highly dependent on commercial adoption and sales ramp of Yartemlea to support its cash burn, a delay or permanent rejection in Europe increases the likelihood of a future dilutive financing event.

An instance of Identical clinical trial packages no longer secure synchronized transatlantic drug approvals. — European regulators recommended refusing marketing authorization for a drug that the FDA had already approved as the first and only option for TA-TMA. ↩︎
An instance of Identical clinical trial packages no longer secure synchronized transatlantic drug approvals. — The European regulator rejected the identical drug application that the FDA approved just months earlier, showing a clear transatlantic divide. ↩︎

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