I applaud the Catalyst Board of Directors for its actions in exploring strategic alternatives and for developing the Cash Distribution Plan. I am fully supportive of this Plan, and I call upon JDS1 to drop its proxy contest and litigation so that the Company can make its initial distribution of cash to shareholders. I am pleased to support the Company’s nominees at the Annual Meeting and I look forward to my role as an observer to the Transaction Committee as it works to monetize additional assets and implement the Cash Distribution Plan.” MICHAEL TOROK Managing Director, JEC II Associates, LLC (Catalyst’s largest single stockholder) SUPPORT CATALYST’S CASH DISTRIBUTION PLAN BY VOTING TODAY If you have any questions, or need assistance in voting your shares, please contact D.F. King & Co., Inc. at (866) 207-2239 or by email at CBIO@dfking.com Dear Catalyst Biosciences, Inc. Stockholders: The Catalyst Biosciences, Inc. (“Catalyst” or the “Company”) Annual Meeting of Stockholders (the “Annual Meeting”) is in just a few days, on August 15. We need your support to ensure that we can expeditiously distribute the Company’s available cash and monetize the Company’s remaining assets. The Company has committed to announcing a record date for a substantial distribution of cash to stockholders as soon as the litigation with JDS1 and the proxy contest are resolved. If the litigation and proxy contest are concluded soon and without much additional expense, the Company expects that initial distribution to be $45 million. We estimate that we will ultimately be able to provide stockholders with as much as $65 million in cash, in one or more distributions. The Board is asking you to vote today to support Catalyst’s Cash Distribution Plan by voting “FOR” ALL of the Board’s nominees on the enclosed WHITE proxy card. Each of the Company’s nominees was critical in developing our Cash Distribution Plan and remains committed to executing it. Please read our proxy materials and vote by Internet or phone now. Every vote is important, no matter how many shares you own. Thank you for taking the time to vote. Sincerely, THE CATALYST BIOSCIENCES, INC. BOARD OF DIRECTORS