Omeros Corporation experienced a steep decline in its stock price following a negative opinion from the European Medicines Agency’s Committee for Medicinal Products for Human Use (CHMP) on its application to market Yartemlea (narsoplimab) for the treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy, a severe and frequently fatal complication associated with stem cell transplantation.
The CHMP reached its negative opinion during its June 22-25, 2026 meeting, after an oral explanation session. The committee vote dashed investor expectations for an imminent European launch of Yartemlea, a drug that has already obtained approval from the U.S. Food and Drug Administration and has begun to generate early U.S. revenue.
In midday trading the stock declined nearly 18.9%. The shares opened sharply lower at $7.39, touching an intraday low at that level before recovering somewhat to trade at $8.69, a significant drop from the prior close of $10.72. The move marked a substantial repricing from the stock’s 52-week high of $17.65 toward the lower end of its recent trading range.
Omeros said it plans to contest the CHMP ruling by requesting a formal re-examination and by seeking review from an Ad Hoc Expert Group, an independent panel convened by the EMA. While those appeal paths keep the prospect of eventual European approval alive, they also introduce additional months of uncertainty and postpone any contribution to revenue from the region.
The pullback came despite broadly positive activity in U.S. equity markets on the same day. Major indices including the S&P 500, Dow Jones, and Nasdaq were trading modestly higher, indicating that the selloff was driven by the company-specific regulatory development rather than a wider market decline.
Within the biotech sector Omeros is concentrated on complement biology and rare hematologic diseases. The CHMP’s negative opinion narrows the near-term commercial opportunity for Yartemlea, which is the company’s only approved product. Removing the prospect of near-term European sales eliminated a key international growth pillar that had underpinned bullish expectations and price targets.
With the re-examination process ahead and European approval now uncertain, investors are reassessing the company’s peak sales potential for Yartemlea. That reassessment has been reflected in the sharp downward move in the share price as market participants incorporate the prospect of delayed or foregone European revenue into valuations.
Key context: The CHMP decision was made at the panel’s June 22-25, 2026 meeting following an oral explanation session. Omeros will seek formal re-examination and an Ad Hoc Expert Group review, which will extend the timeline for any potential European authorization.