OMEROS CORP

SCHEDULE 14A INFORMATION

Proxy Statement Pursuant to Section 14(a)

of the Securities Exchange Act of 1934

(Amendment No. )

Filed by the Registrant ☒

Filed by a Party other than the Registrant ☐

Check the appropriate box:

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check all the boxes that apply):

Dear Fellow Shareholder:

You are cordially invited to attend the 2025 Annual Meeting of Shareholders of Omeros Corporation. We plan to hold an entirely virtual meeting this year via live webcast on the Internet on Friday, June 27, 2025, at 10:00 a.m. Pacific time. You will be able to attend the meeting, vote and submit your questions via the Internet at www.virtualshareholdermeeting.com/OMER2025.

The attached Notice of Annual Meeting of Shareholders and Proxy Statement contain details of the business to be conducted at the annual meeting.

Whether or not you attend the annual meeting, it is important that your shares be represented and voted. Therefore, please vote as soon as possible by telephone, via the Internet or by completing and mailing the enclosed proxy card. Voting by any of these methods will ensure your representation at the annual meeting. If you decide to attend the annual meeting, you will be able to vote virtually via the Internet even if you have previously submitted your proxy.

On behalf of our board of directors, I would like to express our appreciation for your continued support of Omeros. We look forward to your participation in the annual meeting.

Sincerely,

GREGORY A. DEMOPULOS, M.D.

Chairman and CEO

The Omeros Building

201 Elliott Avenue West

Seattle, Washington 98119

NOTICE OF ANNUAL MEETING OF SHAREHOLDERS

To our Shareholders:

We cordially invite you to the 2025 Annual Meeting of Shareholders (the 2025 Annual Meeting) of Omeros Corporation, a Washington corporation, to be held on Friday, June 27, 2025, at 10:00 a.m. Pacific time. The meeting will be held virtually via live webcast on the Internet at www.virtualshareholdermeeting.com/OMER2025 for the following purposes:

The foregoing items of business are more fully described in the proxy statement accompanying this notice. The proxy statement accompanying this notice is being issued in connection with the solicitation by the board of directors of a proxy on the enclosed form of proxy card for use at the 2025 Annual Meeting.

Shareholders of record at the close of business on May 23, 2025 will be entitled to vote at the 2025 Annual Meeting, or any adjournment or postponement of the meeting.

There is no physical location for the 2025 Annual Meeting. You will be able to attend and participate in the 2025 Annual Meeting online, vote your shares electronically and submit your questions during the meeting by visiting: www.virtualshareholdermeeting.com/OMER2025 at the meeting date and time described in the accompanying proxy statement and entering the 16-digit control number included on your proxy card or in the instructions that accompanied your proxy materials. If you plan to attend the meeting virtually via the Internet, please see “Information Concerning Proxy Solicitation, Voting and the Meeting—Attending the 2025 Annual Meeting.”

We look forward to your participation in the 2025 Annual Meeting.

By Order of the Board of Directors,

Peter B. Cancelmo

Vice President, General Counsel and Secretary