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OMS721 Inhibits Thrombus Formation in Sera from aHUS Patients

- Data Bode Well for Success of Ongoing Phase 2 Trial in Thrombotic Microangiopathies -

SEATTLE, Nov. 19, 2014 /PRNewswire/ -- Omeros Corporation (NASDAQ: OMER) today announced positive data using OMS721, the lead human monoclonal antibody for its mannan-binding lectin-associated serine protease-2 (MASP-2) program, to inhibit thrombus formation in an ex vivo pathophysiologic system of human atypical hemolytic uremic syndrome (aHUS), a form of thrombotic microangiopathy (TMA). TMAs are a family of rare, debilitating and life-threatening disorders characterized by excessive thrombi (clots) in the microcirculation of the body's organs, most commonly the kidney and brain. OMS721 is currently in a Phase 2 clinical program evaluating the drug's efficacy in treating TMAs, including aHUS.

The data announced today resulted from studies in a well-established experimental model of TMA aimed at assessing the potential therapeutic benefits of OMS721 in TMA using serum samples from aHUS patients with different etiologies obtained during the acute phase of disease as well as during remission. The studies were conducted by Prof. Giuseppe Remuzzi and colleagues Marina Noris and Miriam Galbusera at the Mario Negri Institute for Pharmacological Research in Bergamo, Italy, and the Clinical Research Center for Rare Diseases "Aldo e Cele Dacco" of the same institute, a European center for the study of TMA. The experimental model is based on the finding that sera from aHUS patients promote the formation of thrombi on human microvascular endothelial cells, the defining pathological feature of TMA.

The studies reported today showed that OMS721 significantly inhibited thrombus formation when added to serum samples from aHUS patients obtained during the acute phase of disease (p<0.01) as well as during remission (p<0.0001). OMS721 was as effective at inhibiting thrombus formation as the positive control in the studies – soluble complement receptor 1, an agent that completely blocks the complement system.

Earlier this year, Omeros reported that OMS721 also significantly inhibited complement deposition compared to control treatment in an experimental ex vivo pathophysiologic system of complement activation in TMA, again using serum samples from aHUS patients obtained during the acute phase of disease (p<0.01) and during remission (p<0.001). Prof. Remuzzi's laboratories have previously shown in the same complement-activation model that eculizumab (Soliris®), a monoclonal antibody blocking the complement factor C5 that is approved by the FDA and the European Medicines Agency to treat patients with aHUS, also inhibited complement deposition. Data recently published indicate that the ex vivo pathophysiologic system established by Prof. Remuzzi and his colleagues may be useful in assessing the clinical effectiveness of anti-complement therapy in aHUS (Noris et al., Blood (2014) 124:1715).

"We believe that the notable anti-complement and anti-thrombotic activities of OMS721 in serum samples from aHUS patients bode well for the therapeutic potential of OMS721 in thrombotic microangiopathies," stated Prof. Remuzzi, MD, FRCP, Research Coordinator at the Mario Negri Institute and international expert in the study of kidney disease who has contributed major advances to the understanding of the pathophysiology of hemolytic uremic syndrome.

Having demonstrated that the lectin pathway, and MASP-2 specifically, are involved in the pathophysiology of aHUS, Prof. Remuzzi and his team are currently conducting additional experiments to understand the mechanism by which OMS721 blocks ex vivo thrombus formation in aHUS and its effect on endothelial cells, platelets and the alternative pathway of complement.

"Thrombus formation is the central pathological feature of aHUS and other TMAs, so we are particularly pleased with the robust anti-thrombotic activity in serum samples from aHUS patients," stated Gregory A. Demopulos, M.D., chairman and chief executive officer of Omeros. "We believe that these most recent data from Prof. Remuzzi's laboratories meaningfully de-risk our '721 Phase 2 program in TMAs, including aHUS, and we look forward to reporting preliminary efficacy and safety data from the ongoing clinical trial."

About Omeros' MASP-2 Program

Omeros controls the worldwide rights to MASP-2 and all therapeutics targeting MASP-2, a novel pro-inflammatory protein target involved in activation of the complement system, which is an important component of the immune system. The complement system plays a role in the inflammatory response and becomes activated as a result of tissue damage or microbial infection. MASP-2 appears to be unique to, and required for the function of, one of the principal complement activation pathways, known as the lectin pathway. Importantly, inhibition of MASP-2 does not appear to interfere with the antibody-dependent classical complement activation pathway, which is a critical component of the acquired immune response to infection, and its abnormal function is associated with a wide range of autoimmune disorders. MASP-2 is generated by the liver and is then released into the circulation. Adult humans who are genetically deficient in one of the proteins that activate MASP-2 do not appear to be detrimentally affected by the deficiency. Therefore, Omeros believes that it may be possible to deliver MASP-2 antibodies systemically and OMS721, its lead MASP-2 antibody, is designed to be self-administered by subcutaneous injection.

Omeros also believes that it has identified the proteins that activate the complement system's alternative pathway in humans, which is linked to a wide range of immune-related disorders. In addition to its lectin pathway inhibitors, the Company is advancing the development of antibodies that would block activation of the alternative pathway alone or in combination with the lectin pathway.

About Omeros Corporation

Omeros is a biopharmaceutical company committed to discovering, developing and commercializing small-molecule and protein therapeutics for large-market as well as orphan indications targeting inflammation, coagulopathies and disorders of the central nervous system. Derived from its proprietary PharmacoSurgery® platform, the company's first drug product, Omidria (phenylephrine and ketorolac injection) 1%/0.3%, has been approved by the FDA for use during cataract surgery or intraocular lens replacement (ILR) to maintain pupil size by preventing intraoperative miosis (pupil constriction) and to reduce postoperative ocular pain. Omeros is completing preparations for a planned U.S. product launch in early 2015. Omidria is currently under review for marketing approval by the European Medicines Agency. Omeros has six clinical-stage development programs focused on: complement-related thrombotic microangiopathies; Huntington's disease, schizophrenia, and cognitive impairment; addictive and compulsive disorders; and preventing problems associated with surgical procedures. In addition, Omeros has a proprietary GPCR platform, which is making available an unprecedented number of new GPCR drug targets and corresponding compounds to the pharmaceutical industry for drug development.

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," "look forward to," "may," "plan," "potential," "predict," "project," "should," "will," "would" and similar expressions. Forward-looking statements 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, risks associated with effectiveness of Omidria sales and marketing efforts, Omidria market acceptance, product pricing and reimbursement, Omeros' ability to obtain regulatory approval for its Marketing Authorization Application and to partner in the EU for the commercialization of Omidria, Omeros' unproven preclinical and clinical development activities, regulatory oversight, product commercialization, intellectual property claims, competitive developments, litigation, and the risks, uncertainties and other factors described under the heading "Risk Factors" in the company's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on November 10, 2014. 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, even if new information becomes available in the future.

SOURCE Omeros Corporation

Jennifer Cook Williams, Cook Williams Communications, Inc., Investor and Media Relations, 360.668.3701,