Omeros Corporation Reports First Quarter 2015 Financial Results Omidria Now Widely Available in the U.S. Following Commercial Launch SEATTLE

Omeros Corporation Reports First Quarter 2015 Financial Results

Omidria Now Widely Available in the U.S. Following Commercial Launch

SEATTLE May 11, 2015 Omeros Corporation (NASDAQ: 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 recent highlights and developments as

well as financial results for the first quarter of 2015, which include:

In the first quarter of

2015, we completed the controlled launch of Omidria, which was successful across all of the assessed parameters product was quickly and efficiently received by the facilities, reimbursement was confirmed across Medicare Administrative

Contractors, and the clinical response was uniformly positive, said Gregory A. Demopulos, M.D., chairman and chief executive officer of Omeros. In April, we initiated the broad U.S. launch of Omidria, and are excited to be making

this important product widely available to both ophthalmic surgeons and their patients. The commercialization of Omidria, together with the encouraging results in our Phase 2 OMS721 clinical trial in TMA patients and the anticipated

re-initiation of our Phase 2 OMS824 clinical program for patients with Huntington s disease and schizophrenia, should provide a series of potentially value-driving milestones for Omeros throughout the remainder of 2015 and beyond.

First Quarter and Recent Highlights and Developments

For the quarter ended March 31,

2015, product revenue from the controlled launch of Omidria was $238,000, and grant revenue was $150,000 compared to $100,000 for the same period in 2014.

Total costs and operating expenses for the three months ended March 31, 2015 were $18.3 million compared to $15.8 million for the same period in 2014.

The increase was primarily due to expenses related to the initiation of sales and marketing costs in anticipation of the U.S. commercial launch of Omidria.

Omeros reported a net loss of $18.7 million, or $0.51 per share, which included noncash expenses of $2.8 million ($0.08 per share). This compares to a net

loss of $16.6 million, or $0.54 per share, for the same period in 2014, which included noncash expenses of $2.7 million ($0.09 per share).

March 31, 2015, Omeros had cash, cash equivalents and short-term investments of $70.1 million.

Conference Call Details

To access the live conference call via phone, please dial (844) 831-4029 from the United States and Canada or (920) 663-6278 internationally. The

participant passcode is 35820733. Please dial in approximately 10 minutes prior to the start of the call. A telephone replay will be available for one week following the call and may be accessed by dialing (855) 859-2056 from the United States

and Canada or (404) 537-3406 internationally. The replay passcode is 35820733.

To access the live or subsequently archived webcast of the conference

call, go to the Company s website at www.omeros.com and go to Events under the Investors section of the website. Please connect to the website at least 15 minutes prior to the call to allow for any software download that may be

About Omeros Corporation

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%, has been approved by the FDA 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. 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 Omeros ability to obtain regulatory approval for its Marketing Authorization Application 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 May 11, 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.

Investor and Media Relations

CONSOLIDATED STATEMENTS OF OPERATIONS

(In thousands, except share and per share data)

CONSOLIDATED BALANCE SHEET DATA