Omeros Corporation Reports Second Quarter 2013 Financial Results Seattle, WA

Omeros Corporation Reports Second Quarter 2013 Financial Results

Seattle, WA August 9, 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 its financial results for the second quarter of 2013.

expenses for the quarter ended June 30, 2013 were $13.3 million and included non-cash expenses of $2.1 million related to rent expense and stock-based compensation. For the same period in 2012, total operating expenses were $9.8 million, which

included non-cash rent and stock-based compensation expenses of $569,000.

The increase in total operating expenses for the quarter ended June

30, 2013 is primarily due to expenses related to advancing our MASP-2 program toward the clinic, the non-cash rent expense and stock-based compensation discussed above, preparing the NDA and MAA for OMS302, the planned commercial launch of OMS302 in

2014, and conducting our Phase 1 clinical program evaluating OMS824. These higher costs were partially offset by lower overall clinical trial expenses related to the completion of our OMS302 Phase 3 clinical program in January 2013 and the

completion of our first OMS103HP Phase 3 clinical trial in arthroscopic partial meniscectomy patients in December 2012.

Total revenue for the

quarter ended June 30, 2013 was $140,000 compared to $1.5 million for the same period in 2012. This decrease was primarily due to lower revenue recognized from the company s GPCR platform development funding agreement with Vulcan Inc. and its

affiliate. While research continues under the company s GPCR program, no additional deferred revenue under the Vulcan agreement remains to be recognized after the first quarter of 2013.

For the quarter ended June 30, 2013, Omeros reported a net loss of $13.6 million, or $0.48 per share, inclusive of the above-referenced $2.1 million of non-cash charges, compared to a net loss of $8.5

million, or $0.38 per share, inclusive of the above-referenced $569,000 of non-cash charges, for the same period in 2012. At June 30, 2013, Omeros had cash, cash equivalents and short-term investments of $20.1 million.

We continue to make significant progress in advancing Omeros along the path to commercialization, said Gregory A. Demopulos, M.D., chairman

and chief executive officer of Omeros. We submitted an NDA to the FDA for OMS302, a major milestone in our plans to bring the first of our products to market, and we remain on track to submit an MAA to the European regulators later this

quarter. Our Phase 1 OMS824 clinical program generated positive results, demonstrating a high level of target occupancy without the movement-related side effects exhibited by other PDE10 inhibitors, and we plan to begin a Phase 2 trial in patients

with Huntington s disease in the fourth quarter. In July, we initiated enrollment in our Phase 1 clinical program for OMS721, further expanding our clinical franchise. We expect continued successes across our pipeline over the remainder of the

year as we prepare for a 2014 market launch of OMS302.

Second Quarter and Recent 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 six 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 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. These statements include, but are not limited to, the submission date for the OMS302 Marketing Authorization

Application; when it will be able to market and sell OMS302 in the United States and in the European Union; Omeros expectations that it will advance OMS824 into Phase 2 clinical programs for Huntington s disease and schizophrenia this

year; the potential benefits of its potential products; the potential for GPR17-targeting compounds to treat nervous system disorders, such as MS; and its 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 Quarterly

Report on Form 10-Q filed with the Securities and Exchange Commission on August 9, 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

Williams Communications, Inc.

Investor and Media Relations

CONSOLIDATED STATEMENTS OF OPERATIONS

(In thousands, except share and per share data)

CONSOLIDATED BALANCE SHEET DATA