Omeros Corporation Initiates its Phase 3 Program for OMS721 in aHUS Following Meeting with FDA

-- Single Pivotal Study Needed for Phase 3 --

SEATTLE-- Omeros Corporation (OMER), a biopharmaceutical company committed to discovering, developing and commercializing both small-molecule and protein therapeutics for large-market as well as orphan indications targeting inflammation, coagulopathies and disorders of the central nervous system, today announced that it has initiated its Phase 3 OMS721 program for the treatment of atypical hemolytic uremic syndrome (aHUS) after meeting with the U.S. Food and Drug Administration (FDA). OMS721 is Omeros’ lead human monoclonal antibody in its mannan-binding lectin-associated serine protease-2 (MASP-2) program for the treatment of thrombotic microangiopathies (TMAs), including aHUS. The FDA has awarded OMS721 both orphan drug designation for the treatment of TMAs and fast-track status for the treatment of aHUS.

The OMS721 Phase 3 program will consist of one clinical trial – a single-arm (i.e., no control arm), open-label trial in patients with newly diagnosed or ongoing aHUS. The clinical package for the biologics license application (BLA) will be similar to that which formed the basis of approval for Soliris® (eculizumab). For the BLA, safety of OMS721 can be demonstrated in patients across a wide range of diseases instead of only in those with aHUS, including additional renal diseases for which Omeros is already enrolling a clinical trial. As a result, collection of safety data is not expected to delay submission of the BLA. Omeros also received agreement from FDA on its ongoing manufacturing for both the Phase 3 program and commercialization of OMS721 as well as on its nonclinical safety and toxicology plan, most of which has already been successfully completed with no significant adverse findings. Phase 3 enrollment is expected to begin later this year and patients currently being treated in the Phase 2 trial are likely to be included in the Phase 3 program.

Consistent with guidance from the FDA, Omeros plans to pursue accelerated approval for OMS721 in aHUS. Similar to fast track, to qualify for accelerated approval a drug must treat a serious condition and generally provide a meaningful advantage over available therapies. Accelerated approval allows a company to market a drug while it continues to conduct confirmatory clinical assessment to obtain full approval. Omeros believes that, based on ongoing clinical work and well-accepted data directed to the targets for OMS721 (MASP-2) and for Soliris (C5), the conditions for accelerated approval can be met for OMS721.

“The meeting with FDA represents an important milestone in the ongoing development program for OMS721 and helped to solidify further the company’s strategy to achieve commercialization,” stated Gregory A. Demopulos, M.D., chairman and chief executive officer of Omeros. “We hear from aHUS patients and their physicians that additional treatment options are needed. Omeros is dedicated to fulfilling that need and to helping these patients as quickly as possible.”

About Omeros’ MASP 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 is associated with a wide range of autoimmune disorders. 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. Omeros has received both orphan drug status and fast track designation from the U.S. FDA for its lead human MASP-2 antibody OMS721. Omeros has initiated a Phase 3 clinical program for OMS721 in atypical hemolytic uremic syndrome and is continuing its Phase 2 program targeting thrombotic thrombocytopenic purpura and stem cell transplant-related thrombotic microangiopathies. In addition, an OMS721 Phase 2 program has been initiated in complement-related renal diseases. An investigator-requested compassionate use program for OMS721 is also underway. OMS721 has demonstrated no safety concerns in human trials or chronic toxicity studies. In addition to potential intravenous administration, Omeros plans to commercialize OMS721 for one or more therapeutic indications as a 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’s OMS906 program is advancing the development of antibodies targeting MASP-3 that block activation of the alternative pathway.

About Omeros Corporation

Omeros is a biopharmaceutical company committed to discovering, developing and commercializing both 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%, was broadly launched in the U.S. in April 2015 for use during cataract surgery or intraocular lens (IOL) replacement to maintain pupil size by preventing intraoperative miosis (pupil constriction) and to reduce postoperative ocular pain. In the European Union, the European Commission has approved OMIDRIA for use in cataract surgery and lens replacement procedures to maintain mydriasis (pupil dilation), prevent miosis (pupil constriction), and to reduce postoperative eye pain. Omeros has five clinical-stage development programs focused on: complement-related thrombotic microangiopathies; complement-mediated glomerulopathies; Huntington’s disease and cognitive impairment; addictive and compulsive disorders; and preventing problems associated with urologic 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, and a platform used to generate antibodies.

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,” “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 product commercialization including with respect to Omidria®, Omeros’ ability to partner and commercialize Omidria in Europe, Omeros’ unproven preclinical and clinical development activities, regulatory oversight, intellectual property claims, competitive developments, litigation, and the risks, uncertainties and other factors described under the heading “Risk Factors” in the company’s filings with the Securities and Exchange Commission on November 9, 2015. 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.