– Permanent, product-specific J-code facilitates efficient claims and reimbursement –

Omeros Corporation (NASDAQ:OMER) today announced that the U.S. Centers for Medicare & Medicaid Services (CMS) has assigned a permanent Healthcare Common Procedure Coding System (HCPCS) J-code for YARTEMLEA^®. The J-code for YARTEMLEA (J1289) simplifies and streamlines billing and reimbursement for patients covered by U.S. government programs (e.g., Medicare) and commercial payers. The J-code will become effective July 1, 2026.

"For patients with TA-TMA, access to effective treatment without unnecessary delay is critical," said Gregory A. Demopulos, M.D., Chairman and Chief Executive Officer of Omeros. "The assignment of a permanent, product-specific J-code for YARTEMLEA establishes a clear and consistent reimbursement pathway across payors, reducing administrative burden, supporting faster access for patients, and delivering more predictable reimbursement for providers."

YARTEMLEA is the first and only approved treatment for hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA), an often-fatal complication of hematopoietic stem cell transplantation. TA-TMA is driven by activation of the lectin pathway of complement. YARTEMLEA inhibits MASP-2, the effector enzyme of the lectin pathway, and is indicated for treatment of TA-TMA in adults and children ages two years and older.

Together with the ICD-10-CM diagnosis code for TA-TMA (M31.11), the availability of the HCPCS J-code for YARTEMLEA (J1289) will support accurate and standardized coding and billing. The permanent J-code for YARTEMLEA has been published by CMS and is available here.

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 transplant, 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.

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 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 ages two years and older. A marketing authorization application for YARTEMLEA for TA-TMA is under review by the European Medicines Agency (EMA) with a decision expected in mid-2026.

YARTEMLEA has received breakthrough therapy and orphan drug designations from the FDA for TA-TMA, and the EMA has granted it orphan drug designation in hematopoietic stem-cell transplantation.

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 aged two years and older. A marketing authorization application seeking approval of YARTEMLEA for TA-TMA is currently under review at the European Medicines Agency. OMS1029, Omeros' long-acting MASP-2 inhibitor, has successfully completed Phase 1 clinical trials.

Under a recently announced 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," "target," "will," "would," and similar expressions and variations thereof. Forward-looking statements, including statements regarding the marketing authorization application for YARTEMLEA^® in Europe, prospects for obtaining EMA approval of YARTEMLEA in any indication, plans and expectations regarding the commercial launch of YARTEMLEA in the U.S., and in the EU following any EMA approval, our expectations regarding the effectiveness of the J-code and its utility, expectations regarding the sufficiency and availability of our capital resources to fund current and planned operations, including the commercialization 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 the YARTEMLEA MAA, inability to respond satisfactorily to information requests during regulatory review of the YARTEMLEA MAA, potential differences between the diagnostic criteria used in our pivotal trial and in the external registry, and whether the EMA determines the registry used in our statistical analysis is sufficiently representative of TA-TMA patients, 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. 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 because 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/20260416836277/en/

Jennifer Cook Williams

Cook Williams Communications, Inc.

Investor and Media Relations

IR@omeros.com

CMS Assigns Permanent Reimbursement J-Code for YARTEMLEA® (narsoplimab-wuug)