X0306 4 2016-05-16 0 0001285819 OMEROS CORP OMER 0001472163 Kelbon Marcia S. 201 ELLIOTT AVENUE WEST SEATTLE WA 98119 0 1 0 0 VP Patent and General Counsel Common Stock 2016-05-16 4 M 0 15900 0.98 A 179497 D Common Stock 2016-05-16 4 S 0 15900 9.9407 D 163597 D Stock Option (Right to Buy) 0.98 2016-05-16 4 M 0 15900 0.00 D 2016-12-11 Common Stock 15900 63700 D Open market sale pursuant to a 10b5-1 trading plan adopted by the reporting person on June 3, 2014, at which time the trading schedule, including sale periods, price and the number of shares to be sold, was established in accordance with Rule 10b5-1 under the Securities Exchange Act of 1934, as amended. This Rule 10b5-1 plan provides for fixed sales of a total of 175,000 shares, by exercise of options otherwise expiring on December 11, 2016, over a one-year period beginning in November 2015, with sale periods commencing approximately monthly and with approximately 15,900 shares to be sold in each sale period. Following the establishment of the 10b5-1 trading plan on June 3, 2014, and consistent with its applicable trading rules, Ms. Kelbon has had no further input or control over the specific share sales or timing of those sales under the plan. (Continued from Footnote 1) A portion of the proceeds are being used to fund the exercise and holding of other options and may also be used to fund the costs of and taxes on the future exercise and holding of additional other options. These sales of shares reflect the seventh monthly sale period under this trading plan. This transaction was executed in multiple trades at prices ranging from $9.86 to $10.15; 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. The option vested and became exercisable in 48 equal monthly installments. The first installment became exercisable on November 1, 2005 and subsequent installments became exercisable on each monthly anniversary thereafter. /s/ Marcia S. Kelbon 2016-05-18