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August 26, 2019

Monica Forbes
c/o Sesen Bio, Inc.
245 First St., Suite 1800
Cambridge, Massachusetts 02142

Dear Monica:
It is my pleasure to offer you the position of Chief Financial Officer (“CFO”)
at Sesen Bio (the “Company" or "Sesen Bio"). Your commencement date as the CFO
will be August 26, 2019 (the “Promotion Date”). This letter summarizes important
details about your employment, should you accept this offer (“Letter
Agreement”). This Letter Agreement shall be effective on August 26, 2019, which
shall also be your start date (the “Effective Date”)
1.    Title, Position and Duties: You will hold the position of CFO with the
Company and you will report to the Chief Executive Officer (“CEO”). You will
have such duties and responsibilities as are usually performed by the chief
financial officer of a Delaware corporation, including such duties as are
reasonably and appropriately delegated to you from time to time by the CEO or
the Board of Directors (the “Board”), consistent with your position as CFO, and
you will have the authority and resources consistent with such position, subject
to adjustments in resources consistent with normal operating decisions of the
CEO or the Board in the event of changes in strategy or programs or any other
changes to resources that are reasonable in light of the Company’s then current
financial condition.
2.    Full-Time and Best Efforts: As the Company’s CFO, which is a full-time
position, we expect that you will devote substantially all of your working time
to the performance of your Company duties in a satisfactory manner and to the
best of your abilities at all times. You shall not engage in any other business
or occupation during your employment here, including, without limitation, any
activity that conflicts with the interests of the Company, interferes with the
proper and efficient performance of your duties for the Company, or interferes
with your exercise of judgment in the Company’s best interests. Approval of the
CEO and/or Board will be required for you to serve on other outside boards while
you are employed by the Company, including any outside for-profit boards, which
approval shall not be unreasonably withheld, delayed or conditioned.
Notwithstanding the foregoing, you will be permitted to serve as an officer,
director or trustee of any charitable, educational or non-profit organization,
without the Company’s prior consent, provided that such services do not
interfere with the performance of your duties to the Company or represent an
actual or apparent conflict of interest with your role at the Company.
3.    Compensation: You shall receive an annualized salary of $350,000 (“Base
Salary”), pro-rated for the calendar year 2019 based on your employment
commencement date, and paid in accordance with the Company's standard payroll
practices, and subject to all applicable tax reporting and withholding. In
January 2020, you will be considered for a merit review in conjunction with your
performance review (which generally is conducted annually) and consistent with
the Company’s compensation practices, as determined by the Board in its sole
discretion.
4.Annual Bonus: You will be eligible for an annual target bonus of up to 35% of
your Base Salary, based upon achievement of both corporate and individual goals,
as determined by the Board or a designed committee of the Board (“Annual
Bonus”), and shall be subject to all applicable tax reporting and withholding.
The determination of whether an Annual Bonus will be granted, and the amount of
any such bonus, will be solely determined by the Board or a designated committee
of the Board in its sole discretion based on factors upon which the Board alone
may choose to rely. All Annual Bonuses, if any, will be payable no later than
March 15 of the year following the year in which they were earned. Bonuses are
prorated for percentage of year as a full time employee. Please note that you
must be employed on the date Annual Bonuses, if any, are paid, in order to be
eligible for and to earn such a payment, as such bonuses also serve as retention
incentives. The fact that you may receive a bonus in one year does not mean you
will receive one in any other year.
5.Stock Option: Subject to and upon approval by the Board or a designated
committee of the Board, you will be granted, on your Promotion Date, an
incentive stock option to purchase 280,000 shares of Common Stock, $0.001 par
value per share, of the Company (the “Common Stock”), which option is granted
pursuant to the Company’s 2014 Stock Incentive Plan (the “Plan”). The stock
option shall have an exercise price equal to the closing price of the Common
Stock on the Nasdaq Global Market on the date of the such grant and shall vest
as to 25% of the shares subject to such option on the first anniversary of the
date of the grant of the option and as to an additional 6.25% of the shares
underlying the option at the end of each successive three-month period
thereafter until the fourth anniversary of the date of the option. The stock
option shall be subject to such other terms as are customary for the Company’s
options under the Plan and the previously approved form of stock option
agreement under the Plan. The Board or a designated committee of the Board will
consider annually whether to grant additional equity awards to its employees and
you will be eligible to be considered for such additional annual equity grants.
6.    Employee Benefits: The Company presently offers a comprehensive benefit
package that includes group health, dental and vision plans as well as life and
disability and time-off benefits. Benefits offered by the Company may change
from time to time in the sole discretion of the Board.
7.Vacation Time: As a full-time employee of the Company, you are eligible for up
to fifteen (15) paid vacation days annually that are accrued on a monthly basis
at a rate of 1.25 days (10 hours) per month of full time employment. The use and
accrual of vacation is governed by the Company’s vacation pay policy in effect,
which may change from time to time in the sole discretion of the Board.
8.Term of Employment; Restrictive Covenant Agreement: It is important for you to
understand that you are an employee “at will”. This means that you have the
right to terminate your employment relationship with Sesen Bio at any time with
or without notice, for any reason or no reason. Similarly, the Company has the
right to terminate its employment relationship with you, with or without notice,
at any time for any or no reason. As a condition of your employment with the
Company, you have executed an Employee Non-Competition, Non-Solicitation,
Confidentiality, and Assignment Agreement dated August 2, 2019. Your employment
and this Letter Agreement will be governed by the laws of the Massachusetts.
9.Severance Benefits: Notwithstanding the foregoing, in the event that Sesen Bio
terminates your employment without “Cause” or you resign with “Good Reason”
(each term as defined below and in either case a “Qualifying Termination”), you
will be eligible for the benefits outlined in sub-paragraphs A or B below (the
“Severance Benefits”), subject to the terms set forth in this Letter Agreement:
A.If a Qualifying Termination occurs: (i) Sesen Bio will pay you severance in
the form of continuation of your Base Salary for a total of 12 months
(“Severance Period”), such amount to be paid in accordance with the Company’s
then current payroll practices, except as otherwise specified in this Letter
Agreement, beginning on the Company’s first regular payroll date that occurs
after the Payment Date (as defined below), and (ii) subject to the terms and
conditions provided for in COBRA, and subject to your timely election of COBRA
and copayment of premium amounts at the active employee’s rate, the Company
shall pay its then current share of premium payments for group health and dental
insurance after the termination date through the earliest of (1) your Severance
Period as outlined above, (2) the date you become employed with benefits
substantially comparable to the benefits provided under the corresponding
Company plan, and (3) the date you become ineligible for COBRA benefits;
provided, however, that such Company-paid premiums may be recorded as additional
income pursuant to Section 6041 of the Internal Revenue Code of 1986, as amended
(the “Code”) and not entitled to any tax qualified treatment to the extent
necessary to comply with or avoid the discriminatory treatment prohibited by the
Patient Protection and Affordable Care Act of 2010 and the Health Care and
Education Reconciliation Act of 2010 or Section 105(h) of the Code. You shall be
responsible for the entire COBRA premium should you elect to maintain this
coverage after the earliest of the dates specified in Sections 9.A.(ii)(1)-(3)
above.
B.
If a Qualifying Termination occurs within twelve (12) months after a Change in
Control Transaction (as defined below), then: (i) you will be eligible for the
same severance payments and COBRA premium assistance as set forth in sections
9.A.i-A.ii above, subject to the same terms, conditions, and limitations as
described therein; and (ii) the vesting of 100% of your then outstanding
unvested equity grants shall be accelerated, such that all unvested equity
grants vest and become fully exercisable or non-forfeitable as of the
termination date for a period of 90 days following the termination date; after
such 90-day period, all unvested equity grants will no longer be exercisable.

For the sake of clarity, it shall not be a “Qualifying Termination” if you
voluntarily resign without Good Reason, your employment terminates For Cause or
your employment terminates because of your death or due to your suffering a
Disability (as defined below).
C.    The Severance Benefits will be subject to the following terms:
i.Solely for purposes of Section 409A of the Code, each salary continuation
payment is considered a separate payment.
ii.Any Severance Benefit under this Letter Agreement will begin only upon the
date of your “separation from service” (as defined under Section
409A(a)(2)(A)(i) of the Code and Treas. Reg. §1.409A-1(h)) which occurs on or
after the date of termination of the employment. To the extent that the
termination of your employment does not constitute a separation from service
under Section 409A(a)(2)(A)(i) of the Code and Treas. Reg. §1.409A-1(h) (as the
result of further services that are reasonably anticipated to be provided by you
to the Company, or any of its parents, subsidiaries or affiliates, at the time
your employment terminates), any severance benefits payable that constitute
deferred compensation under Section 409A of the Code shall be delayed until
after the date of a subsequent event constituting a separation from service
under Section 409A(a)(2)(A)(i) of the Code and Treas. Reg. §1.409A-1(h). For
purposes of clarification, this section shall not cause any forfeiture of
benefits on your part, but shall only act as a delay until such time as a
“separation from service” occurs.
Further, if you are a “specified employee” (as that term is used in Section 409A
of the Code and regulations and other guidance issued thereunder) on the date
your separation from service becomes effective, any severance benefits payable
hereunder that constitute non-qualified deferred compensation under Section 409A
of the Code shall be delayed until the earlier of (i) the business day following
the six-month anniversary of the date your separation from service becomes
effective, and (ii) the date of your death, but only to the extent necessary to
avoid such penalties under Section 409A of the Code. On the earlier of (A) the
business day following the six-month anniversary of the date your separation
from service becomes effective, and (B) your death, the Company shall pay you in
a lump sum the aggregate value of the non-qualified deferred compensation that
the Company otherwise would have paid you prior to that date as described above.
Neither the Company nor you shall have the right to accelerate or defer the
delivery of any such payments or benefits except to the extent specifically
permitted or required by Section 409A of the Code. The Company makes no
representation or warranty and shall have no liability to you or any other
person if any provision of this Letter Agreement is determined to constitute
deferred compensation subject to Section 409A of the Code, but do not satisfy an
exemption from, or the conditions of, Section 409A of the Code.
iii.Sesen Bio’s obligations to make the above Severance Benefits payments will
be contingent upon your execution of and compliance with a release of claims in
a form reasonably acceptable to the Company (the “Release”), which Release must
be signed and any applicable revocation period with respect thereto must have
expired by the sixtieth (60th) day following the date of termination (i.e., last
employment day with the Company). The Severance Benefits payments shall be paid
or commence on the first payroll period following the date the waiver and
release becomes effective (the “Payment Date”). Notwithstanding the foregoing,
if the 60th day following the date of termination occurs in the calendar year
following the termination, then the Payment Date shall be no earlier than
January 1 of such subsequent calendar year. In addition, you must comply with
all post-employment obligations, including those in the Employee
Non-Competition, Non-Solicitation, Confidentiality and Assignment Agreement as a
condition of employment, in order to be entitled to the Severance Benefits. In
the event that you are in breach of any post-employment obligations, the Company
shall cease providing the Severance Benefits.
iv.The Company’s obligations to pay or provide the Severance Benefits will be
contingent upon your having tendered your resignation from any position on the
Board, if applicable (and any other boards on which you serve at the request of
the Company), effective as of the date of termination.
v.You agree to give prompt written notice of any reemployment during the
Severance Period or CIC Severance Period that results in eligibility for
comparable medical and dental benefits. If the Company makes any overpayment of
COBRA Benefits, you agree to promptly return any such overpayment to the
Company. The foregoing shall not create any obligation on your part to seek
reemployment after the date of termination of your employment.
10.    Definitions: For purposes of this Letter Agreement, “for Cause” shall
mean the Company has complied with the “Cause Process”, as defined below,
following your committing one or more of the following (each a “Cause
Condition”): (i) an act of material dishonesty involving the Company,
embezzlement, or misappropriation of assets or property of the Company; (ii)
gross negligence or willful misconduct in connection with the performance of
your duties, theft, fraud or breach of fiduciary duty to the Company; (iii) your
willful, sustained, or repeated failure to substantially perform the duties or
obligations of your position (other than due to illness or injury); (iv) a
violation of federal or state securities law; (v) the conviction of a felony or
any crime involving moral turpitude, including a plea of nolo contendere; (vi) a
material breach of any of the Company’s written policies related to conduct,
ethics, equal employment or harassment; or (vii) a material breach of your
Non-Competition, Non-Solicitation, Confidentiality and Assignment Agreement.
“Cause Process” shall mean that (i) the Company reasonably determines, in good
faith, that one of the Cause Conditions has occurred; (ii) the Company notifies
you in writing of the first occurrence of the Cause Condition within thirty (30)
days of the Board becoming aware of such condition; (iii) the Company cooperates
in good faith with your efforts, for a period not less than thirty (30) days
following such notice (the “Cause Cure Period”), to remedy the Cause Condition;
(iv) notwithstanding such efforts, the Cause Condition continues to exist; and
(v) the Company terminates your employment within thirty (30) days after the end
of the Cause Cure Period, provided that the Company will not be required to
provide a Cause Cure Period in the event that a Cause Condition (x) is of the
type described in clauses (iv), (v) or (vi) of the first sentence of this
Section 10; (y) is incapable of being cured; or (z) is required to be publicly
disclosed under applicable securities law or stock exchange rule.
If you cure to the Company’s satisfaction any Cause Condition during the
applicable Cause Cure Period, Cause shall be deemed not to have occurred. If the
Company is not required to provide a Cause Cure Period, the Cause Process will
be satisfied if the Company notifies you in writing of the first occurrence of
the Cause Condition within thirty (30) days of the Board becoming aware of such
condition and terminates your employment within thirty (30) days of such notice.
You are eligible for no more than two “cure” opportunities during your
employment.
“Change in Control Transaction” shall mean (i) a merger or consolidation of the
Company with or into another corporation under circumstances where the
stockholders of the Company immediately prior to such merger or consolidation do
not own after such merger or consolidation shares representing at least fifty
percent (50%) of the voting power of the Company or the surviving, resulting or
parent corporation, as the case may be, (ii) a transfer of shares representing
fifty percent (50%) or more of the voting power of the Company to any person who
was not, on the Effective Date, a holder of stock of any class or preference or
any stock option of the Company, (iii) a liquidation of the Company, or (iv) a
sale or other disposition of all or substantially all of the Company’s assets.
“Good Reason” shall mean you have complied with the “Good Reason Process” as
defined below, following the occurrence of one or more of the following events:
(i) any material diminution in your duties, authority or responsibilities, (ii)
any material diminution in your Base Salary; (iii) the relocation of your
primary place of work more than fifty (50) miles from Philadelphia, PA, or (iv)
the material breach by the Company of any provision of this Letter Agreement or
any other employment-related agreement between the Company and you (as defined
below).
“Good Reason Process” shall mean that (i) you reasonably determine in good faith
that one of the foregoing “Good Reason” conditions has occurred; (ii) you notify
the Company in writing of the first occurrence of the Good Reason condition
within thirty (30) days of the first occurrence of such condition; (iii) you
cooperate in good faith with the Company’s efforts, for a period not less than
thirty (30) days following such notice (the “Cure Period”) to remedy the
condition; (iv) notwithstanding such efforts, the Good Reason condition
continues to exist; and (v) you terminate your employment within thirty (30)
days after the end of the Cure Period. If the Company cures the Good Reason
condition during the Cure Period, Good Reason shall be deemed not to have
occurred.
“Disability” shall mean your inability (as determined by the Company in good
faith) to perform the essential functions of your position due to physical or
mental disability (after taking into account the Company’s obligation to provide
reasonable accommodations in accordance with the Americans with Disabilities Act
of 1990 or analogous state law), which continues for a period of 90 days
(whether or not consecutive) during any 12-month period. In connection with any
determination regarding your possible Disability, you shall have the right to
provide to the Company, and the Company shall consider in good faith, any
physical or mental evaluation performed by a competent physician of your
selection.
11.    Modified Section 280G Cutback: Notwithstanding any other provision of
this Letter Agreement, except as set forth in Section 11.B, in the event that
the Company undergoes a “Change in Ownership or Control” (as defined below), the
following provisions shall apply:
A.The Company shall not be obligated to provide to you any portion of any
“Contingent Compensation Payments” (as defined below) that you would otherwise
be entitled to receive to the extent necessary to eliminate any “excess
parachute payments” (as defined in Section 280G(b)(1) of the Code) for you. For
purposes of this Section 11, the Contingent Compensation Payments so eliminated
shall be referred to as the “Eliminated Payments” and the aggregate amount
(determined in accordance with Treasury Regulation Section 1.280G-1, Q/A-30 or
any successor provision) of the Contingent Compensation Payments so eliminated
shall be referred to as the “Eliminated Amount.”
B.Notwithstanding the provisions of Section 11.A, no such reduction in
Contingent Compensation Payments shall be made if (1) the Eliminated Amount
(computed without regard to this sentence) exceeds (2) 100% of the aggregate
present value (determined in accordance with Treasury Regulation Section
1.280G-1, Q/A-31 and Q/A-32 or any successor provisions) of the amount of any
additional taxes that would be incurred by you if the Eliminated Payments
(determined without regard to this sentence) were paid to you (including, state
and federal income taxes on the Eliminated Payments, the excise tax imposed by
Section 4999 of the Code payable with respect to all of the Contingent
Compensation Payments in excess of your “base amount” (as defined in Section
280G(b)(3) of the Code), and any withholding taxes). The override of such
reduction in Contingent Compensation Payments pursuant to this Section 11.B
shall be referred to as a “Section 11.B Override.” For purpose of this
paragraph, if any federal or state income taxes would be attributable to the
receipt of any Eliminated Payment, the amount of such taxes shall be computed by
multiplying the amount of the Eliminated Payment by the maximum combined federal
and state income tax rate provided by law.
C.For purposes of this Section 11 the following terms shall have the following
respective meanings:
i.“Change in Ownership or Control” shall mean a change in the ownership or
effective control of the Company or in the ownership of a substantial portion of
the assets of the Company determined in accordance with Section 280G(b)(2) of
the Code.
ii.“Contingent Compensation Payment” shall mean any payment (or benefit) in the
nature of compensation that is made or made available (under this Letter
Agreement or otherwise) to a “disqualified individual” (as defined in Section
280G(c) of the Code) and that is contingent (within the meaning of Section
280G(b)(2)(A)(i) of the Code) on a Change in Ownership or Control of the
Company.
D.Any payments or other benefits otherwise due to you following a Change in
Ownership or Control that could reasonably be characterized (as determined by
the Company) as Contingent Compensation Payments (the “Potential Payments”)
shall not be made until the dates provided for in this Section 11.D. Within 30
days after each date on which you first become entitled to receive (whether or
not then due) a Contingent Compensation Payment relating to such Change in
Ownership or Control, the Company shall determine and notify you (with
reasonable detail regarding the basis for its determinations) (1) which
Potential Payments constitute Contingent Compensation Payments, (2) the
Eliminated Amount and (3) whether the Section 11.B Override is applicable.
Within 30 days after delivery of such notice to you, you shall deliver a
response to the Company (the “Executive Response”) stating either (A) that you
agree with the Company’s determination pursuant to the preceding sentence or (B)
that you disagrees with such determination, in which case you shall set forth
(x) which Potential Payments should be characterized as Contingent Compensation
Payments, (y) the Eliminated Amount, and (z) whether the Section 11.B Override
is applicable. In the event that you fail to deliver an Executive Response on or
before the required date, the Company’s initial determination shall be final. If
you state in the Executive Response that you agree with the Company’s
determination, the Company shall make the Potential Payments to you within three
(3) business days following delivery to the Company of the Executive Response
(except for any Potential Payments which are not due to be made until after such
date, which Potential Payments shall be made on the date on which they are due).
If you state in the Executive Response that you disagree with the Company’s
determination, then, for a period of sixty (60) days following delivery of the
Executive Response, you and the Company shall use good faith efforts to resolve
such dispute. If such dispute is not resolved within such 60-day period, such
dispute shall be settled exclusively by arbitration in Pennsylvania, in
accordance with the rules of the American Arbitration Association then in
effect. Judgment may be entered on the arbitrator’s award in any court having
jurisdiction. The Company shall, within three (3) business days following
delivery to the Company of the Executive Response, make to you those Potential
Payments as to which there is no dispute between the Company and you regarding
whether they should be made (except for any such Potential Payments which are
not due to be made until after such date, which Potential Payments shall be made
on the date on which they are due). The balance of the Potential Payments shall
be made within three (3) business days following the resolution of such dispute.
E.The Contingent Compensation Payments to be treated as Eliminated Payments
shall be determined by the Company by determining the “Contingent Compensation
Payment Ratio” (as defined below) for each Contingent Compensation Payment and
then reducing the Contingent Compensation Payments in order beginning with the
Contingent Compensation Payment with the highest Contingent Compensation Payment
Ratio. For Contingent Compensation Payments with the same Contingent
Compensation Payment Ratio, such Contingent Compensation Payment shall be
reduced based on the time of payment of such Contingent Compensation Payments
with amounts having later payment dates being reduced first. For Contingent
Compensation Payments with the same Contingent Compensation Payment Ratio and
the same time of payment, such Contingent Compensation Payments shall be reduced
on a pro rata basis (but not below zero) prior to reducing Contingent
Compensation Payment with a lower Contingent Compensation Payment Ratio. The
term “Contingent Compensation Payment Ratio” shall mean a fraction the numerator
of which is the value of the applicable Contingent Compensation Payment that
must be taken into account by you for purposes of Section 4999(a) of the Code,
and the denominator of which is the actual amount to be received by you in
respect of the applicable Contingent Compensation Payment. For example, in the
case of an equity grant that is treated as contingent on the Change in Ownership
or Control because the time at which the payment is made or the payment vests is
accelerated, the denominator shall be determined by reference to the fair market
value of the equity at the acceleration date, and not in accordance with the
methodology for determining the value of accelerated payments set forth in
Treasury Regulation Section 1.280G-1Q/A-24(b) or (c)).
F.    The provisions of this Section 11 are intended to apply to any and all
payments or benefits available to you under this Letter Agreement or any other
agreement or plan of the Company under which you receive Contingent Compensation
Payments.
12.    General: By signing below, you represent that you are not bound by any
employment contract, restrictive covenant or other restriction preventing or
limiting you from entering into employment with or performing your duties or
responsibilities for the Company, or which is in any way inconsistent with the
terms of this Letter Agreement. You also agree that you do not have in your
possession, and will not disclose to anyone at the Company, bring onto Company
premises, or use in the course of your employment at the Company at any time,
any confidential information or trade secrets belonging to any former employer
or to any other entity. You further agree that you will not, as a Sesen Bio
employee, engage in any conduct that would constitute a breach of any obligation
you may have to a former employer, including but not limited to any covenants
not to solicit or compete.
After the Effective Date, this Letter Agreement (and Employee Non-Competition,
Non-Solicitation, Confidentiality and Assignment Agreement, the plans,
documents, and policies referenced herein) shall constitute our entire agreement
regarding the terms and conditions of your employment with the Company and shall
supersede any prior agreements or other promises or statements (whether oral or
written) regarding the terms of your employment, including, without limitation,
your Employment Agreement with the Company dated July 26, 2019 . The terms
described herein cannot be modified except in writing by you and the Company.
Failure of either party to this Letter Agreement to insist upon strict
compliance with any of the terms, covenants or conditions hereof will not be
deemed a waiver of such terms, covenants or conditions. In the event of any
inconsistency between this Letter Agreement and any other contract between the
Company and you, including the Employee Non-Competition, Non-Solicitation,
Confidentiality and Assignment Agreement, the provisions of this Letter
Agreement will prevail.
We are thrilled to have you join the leadership team at Sesen Bio. Please
contact me if you have any questions or need more information.
Sincerely

/s/ Thomas R. Cannell            
Thomas R. Cannell, DVM
President and Chief Executive Officer
I accept the above terms of employment as stated:
/s/ Monica Forbes     August 26, 2019    
Monica Forbes    Date

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