OMER Omeros Corporation

Item 1.01 Entry into a Material Definitive Agreement.

On August 14, 2017, Omeros Corporation (the “Company”) entered into an underwriting agreement (the “Underwriting Agreement”) with Cantor Fitzgerald & Co., as the representative of the several underwriters named therein (collectively, the “Underwriters”) relating to the public offer and sale of 3,000,000 shares of the Company’s common stock, $0.01 par value per share (the “Common Stock”), at a price to the public of $22.75 per share. The Company also granted Cantor Fitzgerald & Co. a 30-day option to purchase up to an additional 450,000 shares of the Common Stock (the “Optional Shares”). The net proceeds to the Company from the sale of the Common Stock, after deducting the underwriting fees and discount and other estimated offering expenses payable by the Company, are expected to be approximately $63.6 million, or approximately $73.1 million if the option to purchase the Optional Shares is exercised in full. The offering is expected to close on August 18, 2017, subject to the satisfaction of customary closing conditions.

The offer and sale of the Common Stock (as well as the Optional Shares) has been registered under the Securities Act of 1933, as amended (the “Securities Act”), pursuant to the Company’s shelf registration statement on Form S-3 (File No. 333-219959), which was filed with the U.S. Securities and Exchange Commission (the “Commission”) on August 14, 2017. The Common Stock is being offered and sold pursuant to a prospectus dated August 14, 2017, as supplemented by a preliminary prospectus supplement that was filed with the Commission on August 14, 2017 and a final prospectus supplement that was filed with the Commission on August 16, 2017.

The Underwriting Agreement contains customary representations, warranties and agreements by the Company, customary conditions to closing, indemnification obligations of the Company and the Underwriters, including for liabilities under the Securities Act, and termination provisions.

The foregoing is a brief description of the material terms of the Underwriting Agreement, does not purport to be a complete description of the rights and obligations of the parties thereunder, and is qualified in its entirety by reference to the Underwriting Agreement which is filed as Exhibit 1.1 to this Current Report on Form 8-K. The Underwriting Agreement contains representations, warranties and covenants that were made only for purposes of such agreement and as of specific dates, were solely for the benefit of the parties to such agreement, and may be subject to limitations agreed upon by the contracting parties. The Underwriting Agreement is not intended to provide any other factual information about the Company.

The legal opinion of Keller Rohrback L.L.P. relating to the Common Stock being offered is filed as Exhibit 5.1 to this Current Report on Form 8-K.