Form of PSU Award Agreement for Retention Awards

This Performance-Based Restricted Stock Unit Agreement (this “Agreement”) is made as of the Agreement Date between Sesen Bio, Inc. (the “Company”), a Delaware corporation, and the Participant.

This Agreement includes this Notice of Grant and the following Exhibit, which is expressly incorporated by reference in its entirety herein:

Exhibit A – General Terms and Conditions

IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of the Agreement Date.

For valuable consideration, receipt of which is acknowledged, the parties hereto agree as follows:

1.Award of Restricted Stock Units.

In consideration of services rendered and to be rendered to the Company by the Participant, the Company has granted to the Participant, subject to the terms and conditions set forth in this Agreement and in the Company’s 2014 Stock Incentive Plan, as amended (the “Plan”), an award with respect to the number of performance-based Restricted Stock Units (the “PSUs”) set forth in the Notice of Grant that forms part of this Agreement (the “Notice of Grant”). Each PSU represents the right to receive one share of common stock, $0.001 par value per share, of the Company (the “Common Stock”) upon vesting of the PSU, subject to the terms and conditions set forth herein.

2.Vesting.

The PSUs may be earned based on the achievement of one or more of the performance milestones (each, a “Performance Milestone”) set forth in the table below. The number of PSUs that may be earned based on the achievement of each Performance Milestone is set forth in the table below. The determination of whether, and to what extent, each Performance Milestone has been achieved shall be made by the Compensation Committee in its sole discretion. Any PSUs that are earned based on the achievement of the Performance Milestones shall vest on September 30, 2023 (the “End Date”). Upon the vesting of the PSUs, the Company will deliver to the Participant, for each PSU that becomes vested, one share of Common Stock, subject to the payment of any taxes pursuant to Section 7. The Common Stock will be delivered to the Participant within fourteen (14) days of the End Date.

1The Clinical Performance Milestone shall be achieved if the timing for completing full patient enrollment for the new study to be determined based on regulatory feedback and as endorsed by the Board of Directors of the Company (the “Board”), is achieved.

2The Employee Retention Performance Milestone shall be achieved if 80% of the thirty-two (32) employees that are employed by the Company and its subsidiaries on the Grant Date remain employed by the Company and its subsidiaries on the End Date.

3The Financial Performance Milestone shall be achieved if the Company’s cash balance is no lower than 90% of the Board approved budget/forecast as of both December 31, 2022 and June 30, 2023.

3.Forfeiture of Unvested PSUs Upon Cessation of Service.

(a)Except as otherwise provided in Section 3(b), in the event that the Participant ceases to perform services to the Company for any reason or no reason, with or without cause, all of the PSUs that are unvested as of the time of such cessation shall be forfeited immediately and automatically to the Company, without the payment of any consideration to the Participant, effective as of such cessation. The Participant shall have no further rights with respect to the unvested PSUs or any Common Stock that may have been issuable with respect thereto. If the Participant provides services to a subsidiary of the Company, any references in this Agreement to provision of services to the Company shall instead be deemed to refer to service with such subsidiary.

(b)If, prior to the End Date, the Participant’s employment with the Company and its subsidiaries is terminated by the Company or one of its subsidiaries without Cause (as defined below), then each PSU that has become earned as of the time of such termination of employment based on the achievement of the applicable Performance Milestone, as determined by the Compensation Committee in its sole discretion, shall become immediately and automatically vested as of the date of the Participant’s termination of employment, and the shares of Common Stock underlying such PSU will be delivered to the Participant as soon as practicable following the date of the Participant’s termination of employment, but in any event within fourteen (14) of such date. For purposes of this Agreement, the term “Cause” shall have the meaning specified in the Participant’s employment agreement with the Company.

4.Restrictions on Transfer.

The Participant shall not sell, assign, transfer, pledge, hypothecate or otherwise dispose of, by operation of law or otherwise (collectively “transfer”) any PSUs, or any interest therein. The Company shall not be required to treat as the owner of any PSUs or issue any Common Stock to any transferee to whom such PSUs have been transferred in violation of any of the provisions of this Agreement.

5.Rights as a Shareholder.

The Participant shall have no rights as a stockholder of the Company with respect to any shares of Common Stock that may be issuable with respect to the PSUs until the issuance of the shares of Common Stock to the Participant following the vesting of the PSUs.

6.Provisions of the Plan.

This Agreement is subject to the provisions of the Plan, a copy of which is furnished to the Participant with this Agreement.

7.Tax Matters.

(a)Acknowledgments; No Section 83(b) Election. The Participant acknowledges that he or she is responsible for obtaining the advice of the Participant’s own tax advisors with respect to the award of PSUs and the Participant is relying solely on such advisors and not on any statements or representations of the Company or any of its agents with respect to the tax consequences relating to the PSUs. The Participant understands that the Participant (and not the Company) shall be responsible for the Participant’s tax liability that may arise in connection with

the acquisition, vesting and/or disposition of the PSUs. The Participant acknowledges that no election under Section 83(b) of the Internal Revenue Code, as amended, is available with respect to PSUs.

(b)Withholding. The Participant acknowledges and agrees that the Company has the right to deduct from payments of any kind otherwise due to the Participant any federal, state, local or other taxes of any kind required by law to be withheld with respect to the vesting of the PSUs. At such time as the Participant is not aware of any material nonpublic information about the Company or the Common Stock, the Participant shall execute the instructions set forth in Schedule A attached hereto (the “Automatic Sale Instructions”) as the means of satisfying such tax obligation. If the Participant does not execute the Automatic Sale Instructions prior to an applicable vesting date, then the Participant agrees that if under applicable law the Participant will owe taxes at such vesting date on the portion of the PSUs then vested the Company shall be entitled to immediate payment from the Participant of the amount of any tax required to be withheld by the Company. The Company shall not deliver any shares of Common Stock to the Participant until it is satisfied that all required withholdings have been made.

8.Miscellaneous.

(a)Authority of Compensation Committee. In making any decisions or taking any actions with respect to the matters covered by this Agreement, the Compensation Committee shall have all of the authority and discretion, and shall be subject to all of the protections, provided for in the Plan. All decisions and actions by the Compensation Committee with respect to this Agreement shall be made in the Compensation Committee’s discretion and shall be final and binding on the Participant.

(b)No Right to Continued Service. The Participant acknowledges and agrees that, notwithstanding the fact that the vesting of the PSUs is contingent upon his or her continued service to the Company, this Agreement does not constitute an express or implied promise of continued service relationship with the Participant or confer upon the Participant any rights with respect to a continued service relationship with the Company.

(c)Section 409A. The PSUs awarded pursuant to this Agreement are intended to be exempt from or comply with the requirements of Section 409A of the Internal Revenue Code of 1986, as amended, and the Treasury Regulations issued thereunder (“Section 409A”). The delivery of shares of Common Stock on the vesting of the PSUs may not be accelerated or deferred unless permitted or required by Section 409A.

(d)Participant’s Acknowledgements. The Participant acknowledges that he or she: (i) has read this Agreement; (ii) has been represented in the preparation, negotiation and execution of this Agreement by legal counsel of the Participant’s own choice or has voluntarily declined to seek such counsel; (iii) understands the terms and consequences of this Agreement; and (iv) is fully aware of the legal and binding effect of this Agreement.

(e)Governing Law. This Agreement shall be construed, interpreted and enforced in accordance with the internal laws of the State of Delaware without regard to any applicable conflicts of laws provisions.

I hereby acknowledge that I have read this Agreement, have received and read the Plan, and understand and agree to comply with the terms and conditions of this Agreement and the Plan.

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PARTICIPANT ACCEPTANCE

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Name: [_____]

(a)    Upon any vesting of PSUs pursuant to Sections 2 or 3 hereof, as applicable, the Company shall sell, or arrange for the sale of, such number of shares of Common Stock issuable with respect to the PSUs that vest pursuant to Section 2 or Section 3, as applicable, as is sufficient to generate net proceeds sufficient to satisfy the Company’s minimum statutory withholding obligations with respect to the income recognized by the Participant upon the vesting of the PSUs (based on minimum statutory withholding rates for all tax purposes, including payroll and social security taxes, that are applicable to such income), and the Company shall retain such net proceeds in satisfaction of such tax withholding obligations.

(b)    The Participant hereby appoints the President and Chief Executive Officer and Secretary of the Company, and either of them acting alone and with full power of substitution, to serve as his or her attorneys in fact to sell the Participant’s Common Stock in accordance with this Schedule A. The Participant agrees to execute and deliver such documents, instruments and certificates as may reasonably be required in connection with the sale of the Shares pursuant to this Schedule A.

(c)    The Participant represents to the Company that, as of the date hereof, he or she is not aware of any material nonpublic information about the Company or the Common Stock. The Participant and the Company have structured this Agreement, including this Schedule A, to constitute a “binding contract” relating to the sale of Common Stock, consistent with the affirmative defense to liability under Section 10(b) of the Securities Exchange Act of 1934 under Rule 10b5-1(c) promulgated under such Act.