-- Poster Presentation Slated for Upcoming Annual Meeting of the American Society of Hematology --

Omeros Corporation (Nasdaq: OMER) today announced online publication of a report detailing treatment with narsoplimab of 15 adult and pediatric patients with hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA), 14 of whom had “high-risk” TA-TMA. Narsoplimab is Omeros’ investigational antibody targeting MASP-2, the effector enzyme of the lectin pathway of the complement system. The report was authored by an external group of investigators involved in the treatment of these patients with narsoplimab provided under Omeros’ compassionate use program.

The report will be featured as a poster presentation at the 65th Annual Meeting of the American Society of Hematology (ASH), to be held December 9-12, 2023 in San Diego. The abstract (#3543) is available on the ASH website at www.hematology.org or by clicking here.

The poster will be presented by Dr. Marta Castelli, Department of Oncology and Hematology, University of Milan and Azienda Socio-Sanitaria Territoriale Papa Giovanni XXIII, Bergamo, Italy. Details of the presentation are as follows:

Clinical Safety and Efficacy of Narsoplimab in Pediatric and Adult Patients with Transplant-Associated Thrombotic Microangiopathy: A Real-World Experience (Abstract #3543)

Session Name: 721. Allogeneic Transplantation: Conditioning Regimens, Engraftment and Acute Toxicities: Poster II

Date: Sunday, December 10, 2023

Presentation Time: 6:00 p.m. - 8:00 p.m. PT

Location: San Diego Convention Center, Halls G-H

About Narsoplimab

Narsoplimab, also known as “OMS721,” is an investigational fully human monoclonal antibody targeting mannan-binding lectin-associated serine protease-2 (MASP-2), a novel pro-inflammatory protein target and the effector enzyme of the lectin pathway of complement. Importantly, inhibition of MASP-2 has been demonstrated to leave intact the antibody-dependent classical complement activation pathway, which is a critical component of the acquired immune response to infection. A biologics license application (BLA) is pending before the U.S. FDA for use of narsoplimab in the treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA), and Omeros expects to resubmit the BLA to include additional information supporting approval of narsoplimab in this indication. Narsoplimab is also in clinical development programs focused on other complement-mediated disorders, including COVID-19. FDA has granted narsoplimab breakthrough therapy and orphan drug designations for TA-TMA and orphan drug status for the prevention (inhibition) of complement-mediated thrombotic microangiopathies as well as for the treatment of TA-TMA. The European Medicines Agency has granted orphan drug designation to narsoplimab for treatment in hematopoietic stem-cell transplant.

About Omeros Corporation

Omeros is an innovative biopharmaceutical company committed to discovering, developing and commercializing small-molecule and protein therapeutics for large-market and orphan indications targeting immunologic disorders including complement-mediated diseases, cancers, and addictive and compulsive disorders. Omeros’ lead MASP-2 inhibitor narsoplimab targets the lectin pathway of complement and is the subject of a biologics license application pending before FDA for the treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy. Omeros’ long-acting MASP-2 inhibitor OMS1029 is currently in a Phase 1 multi-ascending dose clinical trial. OMS906, Omeros’ inhibitor of MASP-3, the key activator of the alternative pathway of complement, is advancing in clinical programs for paroxysmal nocturnal hemoglobinuria and complement 3 glomerulopathy. Funded by the National Institute on Drug Abuse, Omeros’ lead phosphodiesterase 7 inhibitor OMS527 is in clinical development for the treatment of cocaine use disorder and, in addition, is being developed as a therapeutic for other addictions as well as for a major complication of treatment for movement disorders. Omeros also is advancing a broad portfolio of novel immuno-oncology programs comprised of two cellular and three molecular platforms. 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,” “expect,” “intend,” and similar expressions and variations thereof. Forward-looking statements, including statements regarding Omeros’ investigational drug candidates, anticipated next steps in relation to the biologics license application for narsoplimab or in relation to other development programs 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, unanticipated or unexpected outcomes of regulatory processes in relevant jurisdictions, unproven preclinical and clinical development activities, the Company’s financial condition and results of operations, regulatory processes and oversight, challenges associated with manufacture or supply of our investigational or clinical products, intellectual property claims, competitive developments, litigation, and the risks, uncertainties and other factors described under the heading “Risk Factors” in the company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission on March 13, 2023. Given these risks, uncertainties and other factors, you should not place undue reliance on these forward-looking statements, and the company assumes 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.

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