Omeros Corporation Receives CHMP Negative Opinion Following Re-Examination of European Marketing Authorization Application for Narsoplimab in TA-TMA

SEATTLE--(BUSINESS WIRE)--Omeros Corporation (Nasdaq: OMER) today announced that the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) issued a negative opinion on the company’s marketing authorization application (MAA) for narsoplimab for the treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA) following re-examination of its original negative opinion adopted in June 2026.

An eight-member ad hoc expert group (AHEG) consisting of hematologists, statisticians, and transplant physicians, together with two patient representatives, was convened by CHMP as part of the re-examination process. The AHEG was charged with addressing a single, three-part question prepared and posed by CHMP. CHMP’s final minutes from its closed meeting with the AHEG state that “[t]he AHEG recommended a review of individual patient-level data by external experts to better understand the factors associated with treatment response and survival.” Omeros had submitted substantial patient-level data to CHMP in August as part of its grounds for re-examination. CHMP did not provide patient-level data to the AHEG.

Narsoplimab was approved under the brand name YARTEMLEA^® by the U.S. Food and Drug Administration (FDA) in December 2025. YARTEMLEA is the first and only therapy to receive regulatory approval for TA-TMA and is broadly indicated in the U.S. for TA-TMA patients two years of age and older. YARTEMLEA targets MASP-2, the effector enzyme of the lectin pathway of complement and, with a unique safety profile, is the only systemic complement inhibitor on the market without a boxed warning, risk evaluation and mitigation strategy (REMS), or vaccination requirement. There is no approved therapy for TA-TMA in Europe.

Omeros is commercializing YARTEMLEA with its own field force in the U.S. market and plans to license commercialization rights to a third party in the European Union (EU) if EU marketing authorization is granted.

“We are deeply disappointed in the re-examination process and outcome,” said Gregory A. Demopulos, M.D., chairman and chief executive officer of Omeros. “We believe that our YARTEMLEA efficacy and safety data, FDA’s recent approval with a broad indication for both adults and children, a decade of compassionate use requests by European transplant physicians for their TA-TMA patients, and the rapid U.S. commercial adoption speak clearly to the favorable benefit-risk profile of the drug. As YARTEMLEA continues to progress toward becoming the standard of care in the U.S., it is disheartening that patients in Europe will not have routine access to its potentially life-saving benefits. As we advance our efforts to expand YARTEMLEA’s use and indications worldwide and to develop our MASP-2 franchise further, we are working to enable fully reimbursed, named-patient access to YARTEMLEA for those with TA-TMA where permitted in Europe and other regions.”

Due to increasing demand for YARTEMLEA drug supply in the U.S. commercial market, Omeros has informed CHMP of its intention to terminate the YARTEMLEA compassionate-use program. Compassionate-use TA-TMA patients currently receiving YARTEMLEA will be provided sufficient drug to complete their respective treatment courses.

Omeros is pursuing additional indications for its MASP-2 franchise, including YARTEMLEA, the long-acting antibody OMS1029, and the company’s orally available small-molecule inhibitors. Clinical studies in acute respiratory distress syndrome (ARDS) and for prevention of high-risk TA-TMA in pediatric patients are planned to begin later this year.

About Hematopoietic Stem Cell Transplant-Associated Thrombotic Microangiopathy

Hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA) is a severe and often fatal complication of hematopoietic stem cell transplantation in adults and children. TA-TMA is driven by systemic endothelial injury triggered by conditioning regimens, immunosuppressants, infection, graft-versus-host disease, and other transplant-related factors, with activation of the lectin pathway of complement playing a central role in disease pathogenesis.

TA-TMA can occur following both autologous and allogeneic transplants, with higher prevalence after allogeneic procedures. Approximately 30,000 allogeneic transplants are performed annually in the U.S. and Europe. Recent studies estimate that TA-TMA develops in up to 56 percent of allogeneic transplant recipients. Mortality in severe TA-TMA can exceed 90 percent, and survivors frequently face long-term renal complications, including dialysis dependence.

YARTEMLEA^® is the only approved therapy for TA-TMA.

About YARTEMLEA^®

YARTEMLEA^® (narsoplimab-wuug), a fully human monoclonal antibody, is the first and only approved inhibitor of the lectin pathway of complement. YARTEMLEA inhibits mannan-binding lectin-associated serine protease-2 (MASP-2), the effector enzyme of the lectin pathway. In hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA), MASP-2 inhibition prevents lectin pathway-mediated cellular injury, including endothelial damage in small blood vessels, and thrombus formation. By selectively blocking activation of the lectin pathway, YARTEMLEA preserves classical and alternative pathway activity, including functions essential to the adaptive immune response.

YARTEMLEA is approved by the U.S. FDA for the treatment of TA-TMA in adults and children two years of age and older.

IMPORTANT SAFETY INFORMATION FOR YARTEMLEA

Contraindications

None.

Warnings and Precautions

Serious and life-threatening infections, regardless of causality or relatedness to YARTEMLEA, were reported in 36% (10/28) of clinical trial patients treated with YARTEMLEA, including sepsis, viral infections, pneumonia, bacteremia, fungal infection, gastroenteritis, respiratory tract infections, and urosepsis. If YARTEMLEA is administered to patients with active infections, monitor closely for signs and symptoms of worsening infection and treat promptly.

Adverse Reactions

The most common adverse reactions (≥ 20%), regardless of causality or relatedness to YARTEMLEA, were viral infections, sepsis, hemorrhage, diarrhea, vomiting, nausea, neutropenia, pyrexia, fatigue, and hypokalemia.

Use in Specific Populations

Pregnancy: Available data on the use of YARTEMLEA during pregnancy are insufficient to evaluate for a drug-associated risk of major birth defects, miscarriage, or other adverse maternal or fetal outcomes.

Lactation: There are no data on the presence of YARTEMLEA in human milk, the effects on the breastfed child, or the effects on milk production.

To report suspected adverse reactions, contact Omeros Corporation at 1-844-YARTEM1 (1-844-927-8361), or contact FDA at 1-800-FDA-1088 or through FDA MedWatch.

Please see the Full Prescribing Information for YARTEMLEA.

About Omeros Corporation

Omeros is an innovative biotechnology company that discovers, develops, and commercializes first-in-class protein and small-molecule therapeutics for both large-market and orphan indications, with a focus on the treatment of complement-mediated diseases, cancers, and addictive or compulsive disorders. Omeros’ lead complement inhibitor YARTEMLEA® (narsoplimab-wuug), which targets the lectin pathway’s effector enzyme MASP-2, is FDA-approved and commercially available in the U.S. for the treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA) in adult and pediatric patients two years of age and older. OMS1029, Omeros’ long-acting MASP-2 inhibitor, has successfully completed Phase 1 clinical trials.

Under an asset purchase and licensing agreement, Novo Nordisk acquired global rights to zaltenibart (formerly OMS906), an inhibitor of MASP-3, the alternative pathway’s key activator, which is in clinical development for PNH and other alternative pathway indications, along with associated intellectual property and related assets. Omeros’ pipeline also includes OMS527, a phosphodiesterase 7 inhibitor in clinical development for cocaine use disorder, which is fully funded by the National Institute on Drug Abuse, and a growing portfolio of novel recombinant antibodies targeting multidrug-resistant organisms and novel molecular and cellular therapeutic programs for oncology. For more information about Omeros and its programs, visit www.omeros.com.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934, which are subject to the “safe harbor” created by those sections for such statements. All statements other than statements of historical fact are forward-looking statements, which are often indicated by terms such as “anticipate,” “believe,” “could,” “estimate,” “expect,” “goal,” “intend,” “likely,” “look forward to,” “may,” “objective,” “plan,” “potential,” “predict,” “project,” “should,” “slate,” “target,” “will,” “would,” and similar expressions and variations thereof. Forward-looking statements, including statements regarding the anticipated therapeutic benefits of drug candidates within our development pipeline and plans for compassionate use and named-patient access to YARTEMLEA, are based on management’s beliefs and assumptions and on information available to management only as of the date of this press release. Omeros’ actual results could differ materially from those anticipated in these forward-looking statements for many reasons, including, without limitation, our financial condition and results of operations, including our ability to raise additional capital for our operations or complete other transactions on favorable terms or at all, regulatory processes and oversight, challenges associated with manufacture or supply of our products to support clinical trials, regulatory inspections and/or commercial sale following any marketing approval, changes in reimbursement and payment policies by government and commercial payers or the application of such policies, intellectual property claims, competitive developments, litigation, and the risks, uncertainties, and other factors described under the heading “Risk Factors” in our Annual Report on Form 10-K filed with the Securities and Exchange Commission on March 31, 2026 and in our subsequently filed Quarterly Reports on Form 10-Q. Given these risks, uncertainties, and other factors, you should not place undue reliance on these forward-looking statements, and we assume no obligation to update these forward-looking statements, whether as a result of new information, future events or otherwise, except as required by applicable law.