X0609 4 2026-08-28 0001285819 OMEROS CORP OMER 0001778968 Cancelmo Peter B false 201 ELLIOTT AVENUE WEST SEATTLE WA 98119 1 VP, General Counsel 0 Common Stock 2026-08-28 4 M 0 25000 2.94 A 25200 D Common Stock 2026-08-28 4 S 0 25000 18.6451 D 200 D Common Stock 2026-08-31 4 M 0 25000 2.94 A 25200 D Common Stock 2026-08-31 4 S 0 25000 18.5416 D 200 D Stock Option (Right to Buy) 2.94 2026-08-28 4 M 0 25000 0 D 2033-09-22 Common Stock 25000 75000 D Stock Option (Right to Buy) 2.94 2026-08-31 4 M 0 25000 0 D 2033-09-22 Common Stock 25000 50000 D This transaction was executed in multiple trades at prices ranging from $18.55 to $18.77. The price reported above reflects the weighted average sales price. The reporting person hereby undertakes to provide full information regarding the number of shares and prices at which the transactions referenced in this footnote were effected upon request to the SEC staff, the issuer, or a security holder of the issuer. This transaction was executed in multiple trades at prices ranging from $18.32 to $18.90. The price reported above reflects the weighted average sales price. The reporting person hereby undertakes to provide full information regarding the number of shares and prices at which the transactions referenced in this footnote were effected upon request to the SEC staff, the issuer, or a security holder of the issuer. This option shall vest and become exercisable over 48 equal monthly installments, with a vesting commencement date of April 1, 2023. Installments vest and become exercisable on each monthly anniversary thereafter. /s/ Peter B. Cancelmo 2026-09-01