X0508 4 2026-02-18 0001285819 OMEROS CORP OMER 0001472160 Demopulos Gregory A MD 201 ELLIOTT AVENUE WEST SEATTLE WA 98119 1 1 Chairman, CEO & President 0 Common stock 2026-02-18 4 M 0 400000 10.27 A 1826986 D Common stock 2026-02-18 4 F 0 357678 11.93 D 1469308 D Common stock 300000 I By trust Common stock 300000 I By trust Common stock 123945 I By spouse Stock option (right to buy) 10.27 2026-02-18 4 M 0 400000 0 D 2026-02-19 Common stock 400000 0 D Represents shares withheld by Omeros Corporation ("Omeros") in connection with net share settlement to satisfy the exercise price and tax liability associated with the reporting person's exercise of stock options. The number of shares withheld was determined based on the closing price of Omeros' common stock on February 17, 2026. The transaction did not involve any open-market sale of securities, and all 357,678 withheld shares remained in the Omeros treasury. The reporting person disclaims beneficial ownership of these securities except to the extent of his pecuniary interest therein, if any, and nothing in this report shall be deemed an admission that the reporting person is the beneficial owner of such securities under Section 16 of the Securities Exchange Act of 1934 or for any other purpose. Shares held in the [Demopulos Child #1] Gift Trust, an irrevocable trust established for the benefit of a minor child of the reporting person. Shares held in the [Demopulos Child #2] Gift Trust, an irrevocable trust established for the benefit of a minor child of the reporting person. This option vested and became exercisable over 48 equal monthly installments, with a vesting commencement date of April 1, 2015. /s/ Peter B. Cancelmo, Attorney-in-Fact 2026-02-20