Omeros Corporation Reports Fourth Quarter and Year-End 2012 Financial Results Seattle, WA

Omeros Corporation Reports Fourth Quarter and Year-End 2012 Financial Results

Seattle, WA March 18, 2013 Omeros Corporation (NASDAQ: OMER), a clinical-stage biopharmaceutical company committed to

discovering, developing and commercializing products targeting inflammation, coagulopathies and disorders of the central nervous system, today announced financial results for the fourth quarter and year ended December 31, 2012.

expenses for the three months ended December 31, 2012 were $9.1 million, compared to $11.0 million for the same period in 2011. Omeros received a $3.95 million payment from its insurer during the 2012 period as reimbursement for an expense

recognized by Omeros in the third quarter of 2012. Excluding this reimbursement, Omeros operating expenses increased during the 2012 period related to advancing its MASP-2 program toward the clinic, marketing expenses in connection with the

planned 2014 commercial launch of OMS302, and increased legal costs and employee compensation, including non-cash stock-based compensation. These increases were partially offset by lower expenses related to Omeros OMS302 and OMS103HP Phase 3

clinical programs and its PDE10, PDE7 and Plasmin programs.

Total operating expenses for the year ended December 31, 2012 were $42.9

million, compared to $31.9 million in 2011. The increase was primarily due to higher expenses related to Omeros OMS302 Phase 3 clinical program and marketing costs tied to the drug s planned 2014 commercial launch, advancing its PDE10 and

MASP-2 programs into and toward the clinic, respectively, the Company s GPCR program, and increased legal costs and employee compensation, including non-cash stock-based compensation. These increases were partially offset by lower expenses in

Omeros OMS103HP program and in several of its preclinical programs, including its PDE7 and Plasmin programs.

For the quarter ended

December 31, 2012, Omeros reported a net loss of $7.7 million, or $0.30 per share, compared to a net loss of $10.2 million, or $0.46 per share, for the same period in 2011. For the year ended December 31, 2012, Omeros reported a net loss

of $38.4 million, or $1.59 per share, compared to a net loss of $28.5 million, or $1.29 per share, in 2011.

At December 31, 2012, Omeros

had cash and cash equivalents and short-term investments of $22.4 million. Omeros expects that, taking into account its at-the-market equity facility with MLV & Co. LLC and its committed equity line financing facility with Azimuth

Opportunity Ltd., it has sufficient resources to fund anticipated operating expenses, capital expenditures and note payments for at least the next 12 months.

In 2012, our lead program, OMS302 for lens replacement surgery, completed two successful Phase 3 clinical trials we are preparing to submit the NDA and MAA in the coming months and are

planning the drug s commercial launch in 2014, said Gregory A. Demopulos, M.D., chairman and chief executive officer of Omeros. OMS103HP, our product for arthroscopic surgery, delivered statistically significant

and clinically important pain reduction in a Phase 3 clinical trial and will enter its next pivotal Phase 3 trial later this year. In addition, we are planning to report data soon from our PDE10

Phase 1 program for schizophrenia and cognitive disorders, and our MASP-2 and PDE7 programs are on track to enter the clinic this year. All of these programs, together with our GPCR program and the rest of our pipeline, provide us multiple

opportunities for success in 2013.

Fourth Quarter Highlights

About Omeros Corporation

Omeros is a clinical-stage biopharmaceutical company committed to discovering, developing and commercializing products targeting inflammation, coagulopathies and disorders of the central nervous system.

The Company s most clinically advanced product candidates, OMS302 for lens replacement surgery and OMS103HP for arthroscopy, are derived from its proprietary PharmacoSurgery platform designed to improve clinical outcomes of patients

undergoing a wide range of surgical and medical procedures. Omeros has five clinical development programs. Omeros may also have the near-term capability, through its GPCR program, to add a large number of new drug targets and their corresponding

compounds to the market. Behind its clinical candidates and GPCR platform, Omeros is building a diverse pipeline of protein and small-molecule preclinical programs targeting inflammation, coagulopathies and central nervous system disorders.

Forward-Looking Statements

This press release contains forward-looking statements as defined within the Private Securities Litigation Reform Act of 1995, which are subject to the

safe harbor created by those sections. These statements include, but are not limited to, Omeros expectations that it has sufficient resources to fund operations for at least the next 12 months; that it will submit a New Drug

Application and Marketing Authorization Application for OMS302 in 2013; that it will be able to market and sell OMS302 in 2014; when it will be able to announce data from its PDE10 Phase 1 program; that it will advance its MASP-2 and PDE7 programs

into this clinic this year; that it will conduct two additional Phase 3 clinical trials evaluating OMS103HP, with enrollment in the first trial beginning in the first half of 2013; and that Omeros may have capability, through its GPCR program, to

add a large number of new drug targets and their corresponding compounds to the market. 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, 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 18, 2013. 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 publicly, even if new information becomes available in the future.

Jennifer Cook Williams

Cook Williams Communications, Inc.

Investor and Media Relations

CONSOLIDATED STATEMENTS OF OPERATIONS

(In thousands, except share and per share data)

CONSOLIDATED BALANCE SHEET DATA