Omeros Corporation Reports First Quarter 2013 Financial Results Seattle, WA

Omeros Corporation Reports First Quarter 2013 Financial Results

Seattle, WA May 10, 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 first quarter of 2013.

expenses for the quarter ended March 31, 2013 were $11.1 million compared to $9.6 million for the same period in 2012. The increase is primarily due to research and development expenses associated with advancing Omeros MASP-2 program

toward the clinic, employee costs and non-cash rent expense, and to selling, general and administrative expenses related to legal matters and Omeros planned commercial launch of OMS302 in 2014. These higher costs were partially offset by lower

clinical trial expenses related to the completion of Phase 3 clinical trials for Omeros OMS302 and OMS103HP programs in January 2013 and December 2012, respectively. For the quarter ended March 31, 2013, Omeros reported a net loss of

$10.5 million, or $0.40 per share, compared to a net loss of $8.9 million, or $0.40 per share, for the same period in 2012.

2013, Omeros had cash, cash equivalents and short-term investments of $13.3 million. On May 9, Omeros announced that it priced a public offering of 3,903,004 shares of its common stock at a price of $4.14 per share, a two percent premium over

the closing price on May 8, 2013, for estimated net proceeds of $16.1 million. The offering is expected to close on or about May 14, 2013. The shares were offered and are expected to be sold to RA Capital Management and other investors in

a registered direct offering conducted without an underwriter or placement agent. Omeros also did not use its at-the-market sales facility or its committed equity line financing facility, neither of which Omeros has accessed to date.

We are pleased with the progress across our pipeline during the first quarter, including successfully completing both our OMS302 intraocular lens

replacement Phase 3 clinical program and the multiple ascending dose study for our OMS824 program, said Gregory A. Demopulos, M.D., chairman and chief executive officer of Omeros. Looking ahead, we expect to submit the NDA for OMS302

this quarter, which will set the stage for a potential commercial launch in 2014. Our MASP-2 and PDE7 programs are also slated for the clinic this year. There are multiple near-term milestones on the horizon, and 2013 promises to be an exciting

First 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

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 regarding the closing date of the public offering; the submission dates for the OMS302 New Drug Application and Marketing Authorization Application;

when it will be able to market and sell OMS302; when it will commence clinical trials for its MASP-2 and PDE7; the potential benefits of its potential products; 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 May 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

Cook Williams Communications, Inc.

Investor and Media Relations

CONSOLIDATED STATEMENTS OF OPERATIONS

(In thousands, except share and per share data)

CONSOLIDATED BALANCE SHEET DATA