Stock Markets June 26, 2026 07:12 AM

Omeros Shares Slide After European Committee Opposes Yartemlea Approval

NASDAQ-listed OMER drops after CHMP issues negative opinion on narsoplimab for HSCT-associated complication; two other therapies also receive negative assessments

By Derek Hwang
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Shares of Omeros Corporation (NASDAQ:OMER) declined about 14% on Friday morning following a negative recommendation from the European Medicines Agency’s Committee for Medicinal Products for Human Use (CHMP) on Yartemlea (narsoplimab). The CHMP advised against approving the drug for treatment of adults and children aged two and older with haematopoietic stem cell transplant-associated thrombotic microangiopathy. The committee also issued negative opinions for Tacquell and Xervyteg.

Omeros Shares Slide After European Committee Opposes Yartemlea Approval
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Key Points

  • Omeros shares fell about 14% on Friday morning after a negative CHMP opinion on Yartemlea (narsoplimab).
  • The CHMP recommended against approval of Yartemlea for adults and children from two years of age with haematopoietic stem cell transplant-associated thrombotic microangiopathy.
  • The committee also issued negative opinions for Tacquell (advanced melanoma) and Xervyteg (acute graft-versus-host disease), impacting biotech and healthcare sectors.

Omeros Corporation (NASDAQ:OMER) saw its stock fall roughly 14% on Friday morning after the European Medicines Agency’s Committee for Medicinal Products for Human Use (CHMP) delivered an unfavorable opinion on the company’s candidate Yartemlea, also known as narsoplimab.

The CHMP recommended against approval of Yartemlea for use in adults and children from two years of age to treat haematopoietic stem cell transplant-associated thrombotic microangiopathy. That condition is described as a serious and potentially life-threatening complication that can follow haematopoietic stem cell transplantation, a procedure in which a patient’s bone marrow is replaced by donor stem cells to re-establish healthy blood cell production.

In the same set of decisions, the committee issued negative opinions on two additional medicines: Tacquell, an autologous melanoma-derived tumour infiltrating lymphocytes therapy expanded ex vivo for advanced melanoma, and Xervyteg, an allogeneic pooled faecal microbiota product intended to treat acute graft-versus-host disease.


Summary

The CHMP recommended against approval of Yartemlea (narsoplimab) for treatment of haematopoietic stem cell transplant-associated thrombotic microangiopathy in patients aged two years and older. Following the committee’s negative opinion, Omeros’ stock dropped about 14% in morning trading. The review package also included adverse recommendations for Tacquell and Xervyteg.

Key points

  • Omeros Corporation’s shares fell roughly 14% on Friday morning after a negative CHMP opinion on Yartemlea.
  • The CHMP advised against approving narsoplimab for adults and children from two years of age with haematopoietic stem cell transplant-associated thrombotic microangiopathy.
  • The committee also issued negative opinions for Tacquell (for advanced melanoma) and Xervyteg (for acute graft-versus-host disease).

Sectors affected

  • Biotechnology and pharmaceuticals - regulatory outcomes directly influence product approval prospects and equity valuations.
  • Healthcare - treatments intended for transplant-related complications and oncology were the focus of the committee’s decisions.

Risks and uncertainties

  • Regulatory risk: The CHMP recommendation against Yartemlea leaves the drug’s approval status in the European Union unresolved and could delay or prevent market access.
  • Market reaction risk: The negative opinion prompted a material decline in Omeros’ share price, illustrating sensitivity of company equity to regulatory outcomes.
  • Clinical and commercial uncertainty for other candidates: The simultaneous negative assessments for Tacquell and Xervyteg introduce doubt about those programs’ near-term prospects in the reviewed jurisdiction.

Available information is limited to the CHMP’s adopted opinions and the resulting market reaction. Additional details about next steps, appeals, or resubmissions were not provided in the committee announcement referenced here.

Risks

  • Regulatory risk: CHMP’s negative recommendation could block or delay Yartemlea’s approval in the EU, affecting commercial prospects and investor expectations.
  • Market reaction risk: The stock’s 14% decline shows immediate sensitivity of equity prices to regulatory decisions, introducing volatility for investors in Omeros.
  • Program uncertainty: Negative opinions for Tacquell and Xervyteg create additional uncertainty for those therapies’ regulatory paths and potential market opportunities.

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