--Provides additional Medicare reimbursement to hospitals and supports patient access for eligible Medicare patients with TA-TMA--

Omeros Corporation (NASDAQ:OMER) today announced that the Centers for Medicare & Medicaid Services (CMS) has granted New Technology Add-On Payment (NTAP) status for YARTEMLEA^® (narsoplimab-wuug) under the Fiscal Year (FY) 2027 Hospital Inpatient Prospective Payment System (IPPS) Final Rule. Beginning October 1, 2026, eligible hospitals treating Medicare patients with YARTEMLEA for hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA) will receive additional Medicare reimbursement. YARTEMLEA is the first and only FDA-approved treatment for TA-TMA, a rare, life-threatening complication of hematopoietic stem cell transplantation (HCT). Approximately 30% of patients undergoing allogeneic HCT in the United States are Medicare beneficiaries, representing a growing segment of the transplant population at risk for TA-TMA.

The NTAP program provides additional reimbursement to eligible hospitals for new technologies before their costs are fully reflected in standard hospital payment rates. Under the FY 2027 IPPS Final Rule, eligible hospitals will receive up to $287,079 in additional reimbursement per eligible Medicare inpatient treated with YARTEMLEA, helping to reduce the financial burden on hospitals caring for Medicare beneficiaries with TA-TMA and supporting timely access to YARTEMLEA. NTAP payments are made to hospitals and do not affect the amount Omeros receives for YARTEMLEA.

"CMS’s decision is an important step in further facilitating hospital adoption of YARTEMLEA for Medicare patients," said Gregory A. Demopulos, M.D., chairman and chief executive officer of Omeros. "This additional reimbursement should help ensure that treatment decisions for Medicare patients are guided by clinical need rather than constrained by reimbursement considerations."

Omeros is committed to supporting patient and provider access to YARTEMLEA. The YARTEMLEAssist^® patient support program helps identify potential financial assistance options. Providers and patient representatives can call 1‑844‑YARTEM1 (1-844-927-8361) or visit YARTEMLEA.com for more information.

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 treatment 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. Omeros is pursuing approval for YARTEMLEA from the European Medicines Agency (EMA).

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 and develops first-in-class protein and small-molecule therapeutics for both large-market and orphan indications, with a focus on 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 license agreement completed in December 2025, 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 paroxysmal nocturnal hemoglobinuria (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, statements of intention or expectations regarding our marketing authorization application for narsoplimab in Europe, plans and expectations regarding commercialization of narsoplimab in the European Union following any EMA approval, estimates and projections regarding relevant patient populations or segments thereof, and expectations regarding the impact of NTAP-eligibility on hospital adoption of 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, unfavorable or unexpected regulatory conclusions or interpretations related to the clinical data, external registry data, statistical analyses or other information and data included in our marketing authorization application or our inability to respond satisfactorily to information requests during regulatory review, unanticipated or unexpected outcomes or requirements of regulatory processes in relevant jurisdictions, 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.

View source version on businesswire.com: https://www.businesswire.com/news/home/20260803485721/en/

Jennifer Cook Williams

Cook Williams Communications, Inc.

Investor and Media Relations

IR@omeros.com