X0306 4 2013-04-10 0 0001285819 OMEROS CORP OMER 0001472158 Cable Thomas J. 201 ELLIOTT AVENUE WEST SEATTLE WA 98119 1 0 0 0 Common Stock 2013-04-10 4 S 0 5000 3.98 D 82067 D Open market sale pursuant to a 10b5-1 trading plan adopted by the reporting person on July 3, 2012, at which time the trading schedule and the number of shares to be sold was established, in accordance with Rule 10b5-1 of the Securities Exchange Act of 1934, as amended. This transaction was executed in multiple trades at prices ranging from $3.87 to $4.13; 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 were effected upon request to the SEC staff, the issuer, or a security holder of the issuer. /s/ Alex F. Sutter, attorney-in-fact on behalf of Thomas J. Cable 2013-04-12