EXECUTION VERSION Cooperation Agreement This Cooperation Agreement (this " Agreement ") is made and entered into as of

Cooperation Agreement

This Cooperation Agreement (this "Agreement") is made and entered into as of August 18, 2022 (the "Effective Date") by and among

Catalyst Biosciences, Inc., a Delaware corporation (the "Company"), and each of the parties listed on Exhibit A hereto (each, an "Investor" and collectively, the "Investors" or, with their respective controlled Affiliates, except as noted on Exhibit A, the "Investor Group"). The

Company and each of the Investors are each herein referred to as a "party" and collectively, the "parties.")

Whereas, each of the

Investors beneficially owns the number of shares of the Company's common stock, par value $0.001 per share (the "Common Stock") listed on Exhibit A hereto;

Whereas, on April 20, 2022,

JDS1, LLC, a Delaware limited liability company ("JDS1"), filed a lawsuit captioned JDS1,

LLC v. Catalyst Biosciences, Inc., C.A. No. 2022-0350-KSJM (Del. Ch.) against the Company pursuant to Section 220 of the Delaware General Corporation Law (the "DGCL") (the "Section 220 Litigation").

Whereas, on June 15, 2022,

JDS1 filed a lawsuit captioned JDS1, LLC v. Catalyst Biosciences, Inc., et al., C.A. No. 2022-0515-KSJM (Del. Ch.) against the Company and its Board of Directors (the "Board") alleging, among other things, violations of Section 271 of the DGCL (the "Section 271 Litigation").

Whereas, the Company has

reached an agreement with each of the Investors with respect to certain matters as provided in this Agreement.

consideration of the premises and mutual covenants and agreements set forth herein, and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the Investors, on a several and not joint basis, and

the Company hereby agree as follows:

Section 1. JDS1 to Withdraw from Certain Legal Actions.

Section 2. Voting Agreement.

During the Standstill Period (defined in Section 4) each of the Investors agrees to

vote all shares of Common Stock beneficially owned by each Investor and its Affiliates (as defined below) in favor of the election of any director nominee nominated by the Board; provided,

however, nothing in this Agreement (including without limitation with respect to Section 4 below)

shall restrict an Investor from voting freely on any stockholder approval for any merger, material acquisition or disposition, or a liquidation and winding up of the Company that is submitted by the Company for stockholder approval.

Section 3. Reimbursement of Fees and Expenses.

On the same day that JDS1 fulfills its obligations under this Agreement under Sections 1(a) and 1(b) above, and no later than two (2) hours following the later of (a) the Section 271 Litigation Dismissal

Time, and (b) the Section 220 Litigation Dismissal Time (such deadline hereinafter referred to as the "Expense Reimbursement Payment Deadline"), the Company

shall pay to JDS1, via same-day wire transfer of immediately available funds, and following the wire transfer instructions communicated by JDS1, via e- mail or otherwise, to the Company's Chief Executive Officer, Interim Chief Financial Officer, or

the legal counsel referenced in Section 12 hereof, the amount of $400,000 (the "Expense

Reimbursement Amount"), as reimbursement for JDS1's out-of-pocket fees and expenses (including legal expenses) incurred in connection with its involvement with the Company through the Effective Date, including, but not limited to its

filings with the Securities and Exchange Commission (the "SEC"), its notices and correspondence to the Company, its proxy contest against the Company, its

stockholder inspection demand, the Section 271 Litigation and the Section 220 Litigation against the Company, its engagement with the Company's Representatives, and the negotiation and execution of this Agreement. If the Expense Reimbursement

Payment Deadline occurs after the cut-off time of the transferring financial institutions, the Company shall have until 11:00 a.m. EDT of the next Business Day following the day of the Expense Reimbursement Payment Deadline to transfer the Expense

Reimbursement Amount without incurring the Late Payment Fees and Interests (defined below). For the avoidance of doubt, it is expressly understood that JDS1 shall not be required to provide the Company with any documentation with respect to its

expenses incurred. The Company acknowledges that the Company's agreement to pay JDS1 the Expense Reimbursement Amount by the Expense Reimbursement Payment Deadline is a key, material, bargained- for element to this Agreement without which JDS1

would not have agreed, pursuant to the terms hereof, to withdraw the Section 271 Litigation, the Section 220 Litigation, and enter into this Agreement. If the Company does not make payment to JDS1 of the Expense Reimbursement Amount by the Expense

Reimbursement Payment Deadline, JDS1 shall be entitled to all fees and expenses, including attorneys' fees and litigation and court costs that it incurs in connection with its efforts to collect the Expense Reimbursement Amount as well as interest

accruing from and after the Expense Reimbursement Payment Deadline on the unpaid balance of the Expense Reimbursement Amount (the "Late Payment Fees and Interests").

Such interest shall accrue at a rate equal to the annualized Federal Funds Rate plus ten percent (10%) and shall be compounded daily.

Section 4. Standstill.

Each Investor agrees that, for the period commencing immediately following the payment of the Expense Reimbursement Amount pursuant to Section 3 (the "Releases Effectiveness Time") and ending on the earliest of (i) the one year

anniversary of the Agreement, or (ii) a material breach by the Company of its obligations under this Agreement which is not cured within five (5) Business Days after written notice from any Investor (the "Standstill Period"), neither it nor any of its controlled Affiliates will, and it will cause each of its controlled Affiliates not to, directly or indirectly, acting alone or in concert with

(i) submit any stockholder proposal

(pursuant to Rule 14a-8 promulgated by the SEC under the Exchange Act or otherwise) or any notice of nomination or other business for consideration, or nominate any candidate for election to the Board (including by way of Rule 14a-11 of

Regulation 14A), other than as expressly permitted by this Agreement;

(ii) engage in, directly or indirectly,

any "solicitation" (as defined in Rule 14a- 1 of Regulation 14A) of proxies (or written consents) or otherwise become a "participant in a solicitation"(as such term is defined in Instruction 3 of Schedule 14A of Regulation 14A under the

Exchange Act) in opposition to the recommendation or proposal of the Board, or recommend or request or induce or attempt to induce any other person to take any such actions, or seek to advise, encourage or influence any other person with

respect to the voting of the Common Stock (including any withholding from voting) or grant a proxy with respect to the voting of the Common Stock or other voting securities to any person other than to the Board or persons appointed as proxies

(iii) seek to call, or to request the

call of, a special meeting of the Company's stockholders, or make a request for a list of the Company's stockholders or to inspect any books and records of the Company;

(iv) form, join in or in any other way

participate in a "partnership, limited partnership, syndicate or other group" within the meaning of Section 13(d)(3) of the Exchange Act with respect to the Common Stock or deposit any shares of Common Stock in a voting trust or similar

arrangement or subject any shares of Common Stock to any voting agreement or pooling arrangement, other than a group consisting only of some or all of the Investors and their Affiliates;

(v) vote for any nominee or nominees for election to the Board, other than those nominated or supported by the Board;

(vi) seek to place a Representative or

other Affiliate or nominee on the Board or seek the removal of any member of the Board or a change in the size or composition of the Board;

(vii) acquire or agree, offer, seek or

propose to acquire, or cause to be acquired, ownership (including beneficial ownership) of any of the assets or business of the Company or any rights or options to acquire any such assets or business from any person, in each case other than

securities of the Company;

(viii) other than at the direction of the

Board, seek, propose or make any statement (other than to one or more members of the Board or management or its advisors or agents) with respect to, or solicit, or negotiate with or provide any information to any person with respect to, a

merger, consolidation, acquisition of control or other business combination, tender or exchange offer, purchase, sale or transfer of assets or securities, dissolution, liquidation, reorganization, change in structure or composition of the

Board, change in the executive officers of the Company, change in capital structure, recapitalization, dividend, share repurchase or similar transaction involving the Company, its subsidiaries or its business, whether or not any such

transaction involves a change of control of the Company (it being understood that the foregoing shall not restrict the Investors from tendering Common Stock, receiving payment for Common Stock or otherwise participating in any such transaction

on the same basis as other stockholders of the Company, or from participating in any such transaction that has been approved by the Board);

announce an intention to acquire, offer or propose to acquire, or agree to acquire, directly or indirectly, by purchase or otherwise, beneficial ownership of (A) any interests in the Company's indebtedness or (B) an aggregate amount of more

than 9.99% of the Company's outstanding Common Stock (which shall not include Common Stock issued in connection with a stock split, stock dividend or similar corporate action initiated by the Company with respect to any securities beneficially

owned by any of the Investors or their Affiliates); provided, however,

nothing herein shall prevent any Investor from confidentially seeking a waiver from this provision;

(x) short sell the Company's capital

stock, or otherwise pledge, hypothecate or put any liens against the Company's capital stock, except that an Investor may partake in customary margin transactions with a broker regulated by FINRA;

(xi) disclose publicly, or privately in a

manner that could reasonably be expected to become public, any intention, plan or arrangement inconsistent with the foregoing;

(xii) take any action challenging the

validity or enforceability of any provisions of this Section 4; or

(xiii) enter into any agreement,

arrangement or understanding concerning any of the foregoing (other than this Agreement) or encourage or solicit any person to undertake any of the foregoing activities.

Except as expressly provided in Section 2, each of the Investors shall be entitled to

(i) vote any shares of Common Stock that it beneficially owns as it determines in its sole discretion, and (ii) disclose, publicly or otherwise, how it intends to vote or act with respect to any securities of the Company, any stockholder proposal

or other matter to be voted on by the stockholders of the Company and the reasons therefor. This Section 4 shall not restrict the ability of the Investors and each of

their Affiliates and other Representatives to privately communicate with the Company and its Representatives so long as such private communications would not be reasonably expected to trigger public disclosure obligations for any party.

Section 5. Representations and Warranties of the Company.

The Company represents and warrants to the Investors that (a) the Company has the corporate power and authority to execute this Agreement and to bind it thereto, (b)

this Agreement has been duly and validly authorized, executed and delivered by the Company, constitutes a valid and binding obligation and agreement of the Company, and is enforceable against the Company in accordance with its terms, except as

enforcement thereof may be limited by applicable bankruptcy, insolvency, reorganization, moratorium, fraudulent conveyance or similar laws generally affecting the rights of creditors and subject to general equity principles, (c) the execution,

delivery and performance of this Agreement by the Company does not and will not (i) violate or conflict with any law, rule, regulation, order, judgment or decree applicable to it, or (ii) result in any breach or violation of or constitute a default

(or an event which with notice or lapse of time or both could become a default) under or pursuant to, or result in the loss of a material benefit under, or give any right of termination, amendment, acceleration or cancellation of, any

organizational document, or any material agreement, contract, commitment, understanding or arrangement to which the Company is a party or by which it is bound.

Section 6. Representations and Warranties of the Investors.

Each Investor, on behalf of itself, severally and not jointly represents and warrants to the Company that (a) as of the Effective Date, such Investor beneficially owns only the number of shares of Common Stock as

described opposite its name on Exhibit A, and Exhibit A includes all Affiliates of any

Investors that own any securities of the Company beneficially or of record, (b) this Agreement has been duly and validly authorized, executed and delivered by such Investor, and constitutes a valid and binding obligation and agreement of such

Investor, enforceable against such Investor in accordance with its terms, except as enforcement thereof may be limited by applicable bankruptcy, insolvency, reorganization, moratorium, fraudulent conveyance or similar laws generally affecting the

rights of creditors and subject to general equity principles, (c) such Investor has the authority to execute this Agreement on behalf of itself and the applicable Investor associated with that signatory's name, and to bind such Investor to the

terms hereof, and (d) the execution, delivery and performance of this Agreement by such Investor does not and will not (i) violate or conflict with any law, rule, regulation, order, judgment or decree applicable to it, or (ii) result in any breach or violation of or constitute a default (or an event which with notice or lapse

of time or both could become a default) under or pursuant to, or result in the loss of a material benefit under, or give any right of termination, amendment, acceleration or cancellation of, any organizational document, agreement, contract,

commitment, understanding or arrangement to which such member is a party or by which it is bound.

Section 7. No Litigation and General Release of Claims

From the Releases Effectiveness Time and until the end of the Standstill Period, each party hereby covenants and agrees that it shall not, and shall not permit any of

its Affiliates or Representatives to, directly or indirectly, alone or in concert with others, encourage, pursue, or assist any other person to threaten or initiate any lawsuit, claim, or other proceeding before any court (each, a "Legal Proceeding") against the other party, any of its Affiliates, or its Representatives, except for (a) any Legal Proceeding initiated primarily to remedy a

breach of or to enforce this Agreement, or (b) counterclaims with respect to any proceeding initiated by or on behalf of one party or its Affiliates against any other party or its Affiliates; provided, however, that the foregoing shall not prevent any party or any of its Representatives from responding to oral questions, interrogatories, requests for information or documents, subpoenas, civil investigative

demands or similar processes (each, a "Legal Requirement") in connection with any Legal Proceeding if such Legal Proceeding has not been initiated by, on