EX-10.10





 Exhibit 10.10 

EMPLOYMENT AGREEMENT 

This Employment Agreement (“Agreement”) is made between Fusion Pharmaceuticals Inc. (“Parent Company”), Fusion
Pharmaceuticals US, Inc., a Delaware corporation and US subsidiary of the Parent Company (the “Company”), and James O’Leary (the “Executive”) and is effective as of the closing of the first underwritten public offering of
the equity securities of the Parent Company pursuant to an effective registration statement under the Securities Act of 1933, as amended (the “Effective Date”). Except with respect to the Restrictive Covenants Agreement and the Equity
Documents (each as defined below), this Agreement supersedes in all respects all prior agreements between the Executive and the Parent Company and/or the Company regarding the subject matter herein, including without limitation (i) the
Employment Agreement between the Executive and the Parent Company dated March 11, 2020 (the “Prior Agreement”), provided that the Executive’s repayment obligation with respect to the Signing Bonus in Section 6 of the Prior
Agreement shall remain in effect until March 16, 2021, and (ii) any offer letter, employment agreement or severance agreement. 

WHEREAS, the Company desires to continue to employ the Executive and the Executive desires to continue to be employed by the Company on the
new terms and conditions contained herein. 
 NOW, THEREFORE, in consideration of the mutual covenants and agreements herein
contained and other good and valuable consideration, the receipt and sufficiency of which is hereby acknowledged, the parties agree as follows: 

1.    Employment. 

(a)    Term. The Company shall employ the Executive and the Executive shall be employed by the Company pursuant to
this Agreement commencing as of the Effective Date and continuing until such employment is terminated in accordance with the provisions hereof (the “Term”). The Executive’s employment with the Company will continue to be “at
will,” meaning that the Executive’s employment may be terminated by the Company or the Executive at any time and for any reason subject to the terms of this Agreement. 

(b)    Position and Duties. The Executive shall serve as the Chief Medical Officer of the Parent Company and shall
have such powers and duties commensurate with the position of Chief Medical Officer and as may from time to time be prescribed by the Chief Executive Officer (the “CEO”) or the “CEO’s Designate” (as defined below). At all
times during the Term, the Executive shall report to the CEO or the CEO’s Designate. For purposes of this Agreement, “CEO’s Designate” shall mean such other person discharging the duties of the CEO. The Executive shall devote the
Executive’s full working time and efforts to the business and affairs of the Company. Notwithstanding the foregoing, the Executive may serve on other boards of directors, with the approval of the Board of Directors of the Parent Company
(the “Board”), or engage in religious, charitable or other community activities as long as such services and activities are disclosed to the Board and do not interfere with the Executive’s performance of the Executive’s
duties to the Company. 












 2.    Compensation and Related Matters. 

(a)    Base Salary. The Executive’s initial base salary shall be paid at the rate of $438,300 per year. The
Executive’s base salary shall be subject to periodic review by the Board or the Compensation Committee of the Board (the “Compensation Committee”). The base salary in effect at any given time is referred to herein as “Base
Salary.” The Base Salary shall be payable in a manner that is consistent with the Company’s usual payroll practices for executive officers. 

(b)    Incentive Compensation. The Executive shall be eligible to receive an annual discretionary bonus of up to
forty percent (40%) of the Executive’s Base Salary (the “Target Bonus”) as determined by the Board or the Compensation Committee from time to time. The actual amount of the Executive’s annual incentive compensation, if any, shall
be determined in the sole discretion of the Board or the Compensation Committee. Any bonus pursuant to this Section that the Executive may receive may vary significantly from year to year. There is no representation that a bonus in one year will be
comparable to another year. There is no implied term that, if the amount of any bonus is lower in any subsequent year, the Company will compensate the Executive for such difference. Under no circumstances is the bonus to be considered part of the
Base Salary or other regular employment income. The bonus, if any, will be paid when the Company normally pays such bonuses and is not earned or accrued until the bonus payout date. Except as otherwise provided herein, to earn incentive
compensation, the Executive must be employed by the Company on the day such incentive compensation is paid. 

(c)    Expenses. The Executive shall be entitled to receive prompt reimbursement for all reasonable expenses
incurred by the Executive during the Term in performing services hereunder, in accordance with the policies and procedures then in effect and established by the Company for its executive officers. 

(d)    Other Benefits. The Executive shall be eligible to participate in or receive benefits under the
Company’s employee benefit plans in effect from time to time, subject to the terms of such plans. 

(e)    Vacation. Subject to the terms and conditions of the Company’s vacation policy in effect from time to
time, the Executive will be eligible to accrue up to four (4) weeks of paid vacation in each calendar year, accrued pro-rata on a monthly basis, to be taken at times agreed upon by the Executive and the
Company. Vacation time must accrue before the Executive may use it, except upon written approval of the Company, which approval will be at the sole discretion of the Company. The Company reserves the right to require the Executive to take some or
all of the accrued vacation days at any time during scheduled or unscheduled office shut-down periods, at its sole discretion. Forfeiture of unused vacation days will be subject to the Company’s vacation policy as in effect from time to time.

 (f)    Retention Bonus. The Executive shall be provided with a
one-time retention bonus in the amount of $1,000 as consideration for entering into the Restrictive Covenants Agreement (as defined below). 












 (g)    Equity. The equity awards held by the Executive shall
continue to be governed by the terms and conditions of the Parent Company’s applicable equity incentive plan(s) and the applicable award agreement(s) governing the terms of such equity awards held by the Executive (collectively, the
“Equity Documents”); provided, however, and notwithstanding anything to the contrary in the Equity Documents, Section 6(a)(ii) of this Agreement shall apply in the event of a termination by the Company without Cause or by the
Executive for Good Reason in either event within the Change in Control Period (as such terms are defined below). 

(h)    Indemnification. During and after the Term, the Executive shall be entitled to indemnification pursuant to
the Parent Company’s and Company’s articles of organization and/or by-laws, as applicable, and applicable state law. 

3.    Termination. In the event Executive’s employment is terminated, the Executive shall be deemed to have
resigned from all officer and board member positions that the Executive holds with the Parent Company or any of its respective subsidiaries and affiliates upon the termination of the Executive’s employment for any reason. The Executive shall
execute any documents in reasonable form as may be requested to confirm or effectuate any such resignations. The Executive’s employment hereunder may be terminated without any breach of this Agreement under the following circumstances: 

(a)    Death. The Executive’s employment hereunder shall terminate upon death. 

(b)    Disability. The Company may terminate the Executive’s employment if the Executive is disabled and
unable to perform or expected to be unable to perform the essential functions of the Executive’s then existing position or positions under this Agreement with or without reasonable accommodation for a period of 180 days (which need not be
consecutive) in any 12-month period. If any question shall arise as to whether during any period the Executive is disabled so as to be unable to perform the essential functions of the Executive’s then
existing position or positions with or without reasonable accommodation, the Executive may, and at the request of the Company shall, submit to the Company a certification in reasonable detail by a board-certified physician selected by the Company to
whom the Executive or the Executive’s guardian has no reasonable objection as to whether the Executive is so disabled or how long such disability is expected to continue, and such certification shall for the purposes of this Agreement be
conclusive of the issue. The Executive shall cooperate with any reasonable request of the physician in connection with such certification. If such question shall arise and the Executive shall fail to submit such certification, the Company’s
determination of such issue shall be binding on the Executive. Nothing in this Section 3(b) shall be construed to waive the Executive’s rights, if any, under existing law including, without limitation, the Family and Medical Leave Act of
1993, 29 U.S.C. §2601 et seq. and the Americans with Disabilities Act, 42 U.S.C. §12101 et seq. 












 (c)    Termination by Company for Cause. The Company may
terminate the Executive’s employment hereunder for Cause. For purposes of this Agreement, “Cause” shall mean any of the following: 

(i)    conduct by the Executive constituting a material act of misconduct in connection with the performance of the
Executive’s duties that would reasonably be expected to result in injury or reputational harm to the Company or any of its subsidiaries or affiliates if the Executive were to continue to be employed in the same position, including, without
limitation, (A) willful failure or refusal to perform material responsibilities that have been requested by the CEO; (B) dishonesty with respect to any material matter; or (C) misappropriation of funds or property of the
Company or any of its subsidiaries or affiliates other than the occasional, customary and de minimis use of Company property for personal purposes; 

(ii)    the commission by the Executive of acts satisfying the elements of (A) any felony or (B) a misdemeanor
involving moral turpitude, deceit, dishonesty or fraud; 
 (iii)    any misconduct by the Executive, regardless of
whether or not in the course of the Executive’s employment, that would reasonably be expected to result in material injury or reputational harm to the Company or any of its subsidiaries or affiliates if the Executive were to continue to be
employed in the same position; 
 (iv)    a breach by the Executive of any of the material provisions contained in
Section 8 of this Agreement or the Restrictive Covenants Agreement (as defined below); 
 (v)    a material
violation by the Executive of any of the Company’s written policies that would reasonably be expected to result in material injury or reputational harm to the Company or any of its subsidiaries or affiliates if the Executive were to continue to
be employed in the same position; or 
 (vi)    the Executive’s failure to cooperate with a bona fide internal
investigation or an investigation by regulatory or law enforcement authorities, after being instructed by the Parent Company or Company to cooperate, or the willful destruction or failure to preserve documents or other materials known to be relevant
to such investigation or the inducement of others to fail to cooperate or to produce documents or other materials in connection with such investigation. 

Notwithstanding anything to the contrary in the foregoing, any purported termination for Cause under subsections (i), (iii), (iv), (v) or (vi) above
shall not be effective unless and until (A) the Company has provided Executive with Notice of Termination that describes in reasonable detail the facts and circumstances giving rise to the termination for Cause and (B) to the extent the
Executive’s action (or inaction) is curable as reasonably determined in the Company’s discretion, the Executive has been afforded an opportunity of not less than fourteen (14) days in which to cure the
complained-of action (or inaction) described in the Notice of Termination. 

(d)    Termination by the Company without Cause. The Company may terminate the Executive’s employment
hereunder at any time without Cause. Any termination by the Company of the Executive’s employment under this Agreement which does not constitute a termination for Cause under Section 3(c) and does not result from the death or disability of
the Executive under Section 3(a) or (b) shall be deemed a termination without Cause. 












 (e)    Termination by the Executive. The Executive may terminate
employment hereunder at any time for any reason, including but not limited to, Good Reason. For purposes of this Agreement, “Good Reason” shall mean that the Executive has completed all steps of the Good Reason Process (hereinafter
defined) following the occurrence of any of the following events without the Executive’s consent (each, a “Good Reason Condition”): 

(i)    an adverse change in the Executive’s position or a material diminution in the Executive’s
responsibilities, authority or duties; 
 (ii)    a reduction of twenty percent (20%) or more to the
Executive’s Base Salary or Target Bonus except for across-the-board salary or compensation reductions based on the Company’s financial performance similarly
affecting all or substantially all senior management employees of the Company; 
 (iii)    a material
change in the geographic location at which the Executive provides services to the Company, such that there is an increase of at least thirty (30) miles of driving distance to such location from the Executive’s principal residence as of
such change; 
 (iv)    a material breach of this Agreement by the Company; or 

(v)    the failure of any successor to the Company or Parent Company to fully assume this Agreement. 

The “Good Reason Process” consists of the following steps: 

(i)    the Executive reasonably determines in good faith that a Good Reason Condition has occurred; 

(ii)    the Executive notifies the Company in writing of the first occurrence of the Good Reason Condition
within ninety (90) days of the first occurrence of such condition; 
 (iii)    the Executive
cooperates in good faith with the Company’s efforts, for a period of 30 days following such notice (the “Cure Period”), to remedy the Good Reason Condition; 

(iv)    notwithstanding such efforts, the Good Reason Condition continues to exist; and 

(v)    the Executive terminates 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. 

If the Executive’s employment with the Company is terminated for any reason, the Company shall pay or provide to the Executive (or to the
Executive’s authorized representative or estate) 












 
(i) any Base Salary earned through the Date of Termination; (ii) unpaid expense reimbursements (subject to, and in accordance with, Section 2(c) of this Agreement); (iii) accrued but
unused vacation pay through the Date of Termination; and (iv) any vested benefits the Executive may have under any employee benefit plan of the Company through the Date of Termination, which vested benefits shall be paid and/or provided in
accordance with the terms of such employee benefit plans (collectively, the “Accrued Obligations”). 

4.    Notice and Date of Termination. 

(a)    Notice of Termination. Except for termination as specified in Section 3(a), any termination of the
Executive’s employment by the Company or any such termination by the Executive shall be communicated by written Notice of Termination to the other party hereto. For purposes of this Agreement, a “Notice of Termination” shall mean a
notice which shall indicate the specific termination provision (by subsection) in this Agreement relied upon. 

(b)    Date of Termination. “Date of Termination” shall mean: (i) if the Executive’s employment
is terminated by death, the date of death; (ii) if the Executive’s employment is terminated on account of disability under Section 3(b), the date on which Notice of Termination is given; (iii) if the Executive’s employment
is terminated by the Company for Cause under Section 3(c), and the Company determines that the Executive’s action or inaction is curable, the date which is fourteen (14) days after the date on which the Notice of Termination is given,
and if the Company determines that the Executive’s action or inaction is not curable, or if a cure period is not required under Section 3(c), the date on which the Notice of Termination is given; (iv) if the Executive’s
employment is terminated by the Company without Cause under Section 3(d), the date on which a Notice of Termination is given or the date otherwise specified by the Company in the Notice of Termination; (v) if the Executive’s
employment is terminated by the Executive under Section 3(e) other than for Good Reason, thirty (30) days after the date on which a Notice of Termination is given, and (vi) if the Executive’s employment is terminated by the
Executive under Section 3(e) for Good Reason, the date on which a Notice of Termination is given after the end of the Cure Period. Notwithstanding the foregoing, in the event that the Executive gives a Notice of Termination to the Company, the
Company may unilaterally accelerate the Date of Termination and such acceleration shall not result in a termination by the Company for purposes of this Agreement. 

5.    Severance Pay and Benefits Upon Termination by the Company without Cause or by the Executive for Good Reason
Outside the Change in Control Period. If the Executive’s employment is terminated by the Company without Cause as provided in Section 3(d), or the Executive terminates employment for Good Reason as provided in Section 3(e), each
outside of the Change in Control Period (as defined below), then, in addition to the Accrued Obligations, and subject to (i) the Executive signing a separation agreement and release in a form and manner satisfactory to the Company, which
shall include, without limitation, a general release of claims against the Company and all related persons and entities, a reaffirmation of all of the Executive’s Continuing Obligations (as defined below), and, in the Company’s sole
discretion, a one-year post-employment noncompetition agreement substantially similar to or the same as the noncompetition provision in Section 8(c) of the Restrictive Covenant Agreement, and shall
provide that if the Executive breaches any of the Continuing Obligations, all payments of the Severance Amount shall immediately cease (the “Separation Agreement and Release”), and (ii) 












 
the Separation Agreement and Release becoming irrevocable, all within 60 days after the Date of Termination (or such shorter period as set forth in the Separation Agreement and Release), which
shall include a seven (7) business day revocation period: 
 (a)    the Company shall pay the Executive an amount
equal to twelve (12) months of the Executive’s Base Salary (the “Severance Amount”); provided in the event the Executive is entitled to any payments pursuant to the Restrictive Covenants Agreement, the Severance Amount
received in any calendar year will be reduced by the amount the Executive is paid in the same such calendar year pursuant to the Restrictive Covenants Agreement (the “Restrictive Covenants Agreement Setoff”); and 

(b)    subject to the Executive’s copayment of premium amounts at the applicable active employees’ rate and the
Executive’s proper election to receive benefits under the Consolidated Omnibus Budget Reconciliation Act of 1985, as amended (“COBRA”), the Company shall pay to the group health plan provider, the COBRA provider or the
Executive a monthly payment equal to the monthly employer contribution that the Company would have made to provide health insurance to the Executive if the Executive had remained employed by the Company until the earliest of (A) the 12-month anniversary of the Date of Termination; (B) the Executive’s eligibility for group medical plan benefits under any other employer’s group medical plan; or (C) the cessation of the
Executive’s continuation rights under COBRA; provided, however, if the Company determines that it cannot pay such amounts to the group health plan provider or the COBRA provider (if applicable) without potentially violating applicable law
(including, without limitation, Section 2716 of the Public Health Service Act), then the Company shall convert such payments to payroll payments directly to the Executive for the time period specified above. Such payments shall be subject to tax-related deductions and withholdings and paid on the Company’s regular payroll dates; and 

(c)    the Company shall pay the Executive an amount equal to (i) any incentive compensation pursuant to
Section 2(b) of this Agreement awarded in respect of the year preceding the year of termination but not yet paid (the “Prior Year’s Bonus”), and (ii) a pro-rated Target Bonus up to the
Date of Termination. 
 The amounts payable under Section 5, to the extent taxable, shall be paid out in substantially equal installments in accordance
with the Company’s payroll practice over twelve (12) months commencing within 60 days after the Date of Termination; provided, however, that if the 60-day period begins in one calendar year
and ends in a second calendar year, the Severance Amount, to the extent it qualifies as “non-qualified deferred compensation” within the meaning of Section 409A of the Internal Revenue Code of
1986, as amended (the “Code”), shall begin to be paid in the second calendar year by the last day of such 60-day period; provided, further, that the initial payment shall include a catch-up payment to cover amounts retroactive to the day immediately following the Date of Termination. Each payment pursuant to this Agreement is intended to constitute a separate payment for purposes of Treasury
Regulation Section 1.409A-2(b)(2). 
 6.    Severance Pay and Benefits
Upon Termination by the Company without Cause or by the Executive for Good Reason within the Change in Control Period. The provisions of this Section 6 shall apply in lieu of, and expressly supersede, the provisions of Section 5 if
(i) the Executive’s employment is terminated either (a) by the Company without Cause as provided in 












 
Section 3(d), or (b) by the Executive for Good Reason as provided in Section 3(e), and (ii) the Date of Termination is within 12 months after the occurrence of the first event
constituting a Change in Control (such period, the “Change in Control Period”). These provisions shall terminate and be of no further force or effect after a Change in Control Period. 

(a)    If the Executive’s employment is terminated by the Company without Cause as provided in Section 3(d) or
the Executive terminates employment for Good Reason as provided in Section 3(e) and in each case the Date of Termination occurs during the Change in Control Period, then, in addition to the Accrued Obligations, and subject to the signing of the
Separation Agreement and Release by the Executive and the Separation Agreement and Release becoming fully effective, all within the time frame set forth in the Separation Agreement and Release but in no event more than 60 days after the Date of
Termination: 
 (i)    the Company shall pay the Executive a lump sum in cash in an amount equal to the
Executive’s then current Base Salary (or the Executive’s Base Salary in effect immediately prior to the Change in Control, if higher) (the “Change in Control Payment”); provided the Change in Control Payment shall be reduced by
the amount of the Restrictive Covenants Agreement Setoff, if applicable; and 
 (ii)    notwithstanding
anything to the contrary in any applicable option agreement or other stock-based award agreement, all time-based stock options and other stock-based awards subject to time-based vesting held by the Executive (the “Time-Based Equity
Awards”) shall immediately accelerate and become fully exercisable or nonforfeitable as of the later of (i) the Date of Termination or (ii) the effective date of the Separation Agreement and Release (the “Accelerated Vesting
Date”); provided that any termination or forfeiture of the unvested portion of such Time-Based Equity Awards that would otherwise occur on the Date of Termination in the absence of this Agreement will be delayed until the effective date
of the Separation Agreement and Release and will only occur if the vesting pursuant to this subsection does not occur due to the absence of the Separation Agreement and Release becoming fully effective within the time period set forth therein.
Notwithstanding the foregoing, no additional vesting of the Time-Based Equity Awards shall occur during the period between the Executive’s Date of Termination and the Accelerated Vesting Date; and 

(iii)    subject to the Executive’s copayment of premium amounts at the applicable active
employees’ rate and the Executive’s proper election to receive benefits under COBRA, the Company shall pay to the group health plan provider, the COBRA provider or the Executive a monthly payment equal to the monthly employer contribution
that the Company would have made to provide health insurance to the Executive if the Executive had remained employed by the Company until the earliest of (A) the 12-month anniversary of the Date of
Termination; (B) the Executive’s eligibility for group medical plan benefits under any other employer’s group medical plan; or (C) the cessation of the Executive’s continuation rights under COBRA; provided, however, if the
Company determines that it cannot pay such amounts to the group health plan provider or the COBRA provider (if applicable) without potentially violating applicable law (including, without limitation, Section 2716 of the Public Health Service
Act), then the Company shall convert such payments to payroll payments directly to the Executive for the time period specified above. Such payments shall be subject to tax-related deductions and withholdings
and paid on the Company’s regular payroll dates; and 












 (iv)    the Company shall pay the Executive an amount
equal to (i) the Prior Year’s Bonus, and (ii) the Executive’s Target Bonus for the then-current year. 
 The amounts payable under this
Section 6(a), to the extent taxable, shall be paid or commence to be paid within 60 days after the Date of Termination; provided, however, that if the 60-day period begins in one calendar year and ends in
a second calendar year, such payments to the extent they qualify as “non-qualified deferred compensation” within the meaning of Section 409A of the Code, shall be paid or commence to be paid in
the second calendar year by the last day of such 60-day period. 

(b)    Additional Limitation. 

(i)    Anything in this Agreement to the contrary notwithstanding, in the event that the amount of any
compensation, payment or distribution by the Company to or for the benefit of the Executive, whether paid or payable or distributed or distributable pursuant to the terms of this Agreement or otherwise, calculated in a manner consistent with
Section 280G of the Code, and the applicable regulations thereunder (the “Aggregate Payments”), would be subject to the excise tax imposed by Section 4999 of the Code, then the Aggregate Payments shall be reduced (but not below
zero) so that the sum of all of the Aggregate Payments shall be $1.00 less than the amount at which the Executive becomes subject to the excise tax imposed by Section 4999 of the Code; provided that such reduction shall only occur if it would
result in the Executive receiving a higher After Tax Amount (as defined below) than the Executive would receive if the Aggregate Payments were not subject to such reduction. In such event, the Aggregate Payments shall be reduced in the following
order, in each case, in reverse chronological order beginning with the Aggregate Payments that are to be paid the furthest in time from consummation of the transaction that is subject to Section 280G of the Code: (1) cash payments not
subject to Section 409A of the Code; (2) cash payments subject to Section 409A of the Code; (3) equity-based payments and acceleration; and (4) non-cash forms of benefits; provided
that in the case of all the foregoing Aggregate Payments all amounts or payments that are not subject to calculation under Treas. Reg. §1.280G-1, Q&A-24(b) or
(c) shall be reduced before any amounts that are subject to calculation under Treas. Reg. §1.280G-1, Q&A-24(b) or (c). 

(ii)    For purposes of this Section 6(b), the “After Tax Amount” means the amount of the
Aggregate Payments less all federal, state, and local income, excise and employment taxes imposed on the Executive as a result of the Executive’s receipt of the Aggregate Payments. For purposes of determining the After Tax Amount, the Executive
shall be deemed to pay federal income taxes at the highest marginal rate of federal income taxation applicable to individuals for the calendar year in which the determination is to be made, and state and local income taxes at the highest marginal
rates of individual taxation in each applicable state and locality, net of the maximum reduction in federal income taxes which could be obtained from deduction of such state and local taxes. 












 (iii)    The determination as to whether a reduction in
the Aggregate Payments shall be made pursuant to Section 6(b)(i) shall be made by a nationally recognized accounting firm selected by the Company (the “Accounting Firm”), which shall provide detailed supporting calculations both to
the Company and the Executive within 15 business days of the Date of Termination, if applicable, or at such earlier time as is reasonably requested by the Company or the Executive. Any determination by the Accounting Firm shall be binding upon the
Company and the Executive. The Company shall pay the Accounting Firm’s fees. 
 (c)    Definitions. For
purposes of this Section 6, the following terms shall have the following meanings: 
 “Change in Control” shall mean any of
the following: 
 (i)    any “person,” as such term is used in Sections 13(d) and 14(d) of the
Securities Exchange Act of 1934, as amended (the “Act”) (other than the Company, any of its subsidiaries, or any trustee, fiduciary or other person or entity holding securities under any employee benefit plan or trust of the Company or any
of its subsidiaries), together with all “affiliates” and “associates” (as such terms are defined in Rule 12b-2 under the Act) of such person, shall become the “beneficial owner”
(as such term is defined in Rule 13d-3 under the Act), directly or indirectly, of securities of the Company representing 50 percent or more of the combined voting power of the Company’s then
outstanding securities having the right to vote in an election of the Board (“Voting Securities”) (in such case other than as a result of an acquisition of securities directly from the Company); or 

(ii)    the date a majority of the members of the Board is replaced during any 12-month period by directors whose appointment or election is not endorsed by a majority of the members of the Board before the date of the appointment or election; or 

(iii)    the consummation of (A) any consolidation or merger of the Company where the stockholders of
the Company, immediately prior to the consolidation or merger, would not, immediately after the consolidation or merger, beneficially own (as such term is defined in Rule 13d-3 under the Act), directly or
indirectly, shares representing in the aggregate more than 50 percent of the voting shares of the Company issuing cash or securities in the consolidation or merger (or of its ultimate parent corporation, if any), or (B) any sale or other
transfer (in one transaction or a series of transactions contemplated or arranged by any party as a single plan) of all or substantially all of the assets of the Company. 

Notwithstanding the foregoing, a “Change in Control” shall not be deemed to have occurred for purposes of the foregoing clause
(i) solely as the result of an acquisition of securities by the Company which, by reducing the number of shares of Voting Securities outstanding, increases the proportionate number of Voting Securities beneficially owned by any person to
50 percent or more of the combined voting power of all of the then outstanding Voting Securities; provided, however, that if any person referred to in this sentence shall thereafter become the beneficial owner of any additional shares of Voting
Securities (other than pursuant to 












 
a stock split, stock dividend, or similar transaction or as a result of an acquisition of securities directly from the Company) and immediately thereafter beneficially owns 50 percent or
more of the combined voting power of all of the then outstanding Voting Securities, then a “Change in Control” shall be deemed to have occurred for purposes of the foregoing clause (i). 

7.    Section 409A. 

(a)    Anything in this Agreement to the contrary notwithstanding, if at the time of the Executive’s separation from
service within the meaning of Section 409A of the Code, the Company determines that the Executive is a “specified employee” within the meaning of Section 409A(a)(2)(B)(i) of the Code, then to the extent any payment or benefit
that the Executive becomes entitled to under this Agreement or otherwise on account of the Executive’s separation from service would be considered deferred compensation otherwise subject to the 20 percent additional tax imposed pursuant to
Section 409A(a) of the Code as a result of the application of Section 409A(a)(2)(B)(i) of the Code, such payment shall not be payable and such benefit shall not be provided until the date that is the earlier of (A) six months and one
day after the Executive’s separation from service, or (B) the Executive’s death. If any such delayed cash payment is otherwise payable on an installment basis, the first payment shall include a
catch-up payment covering amounts that would otherwise have been paid during the six-month period but for the application of this provision, and the balance of the
installments shall be payable in accordance with their original schedule. 
 (b)    All
in-kind benefits provided and expenses eligible for reimbursement under this Agreement shall be provided by the Company or incurred by the Executive during the time periods set forth in this Agreement. All
reimbursements shall be paid as soon as administratively practicable, but in no event shall any reimbursement be paid after the last day of the taxable year following the taxable year in which the expense was incurred. The amount of in-kind benefits provided or reimbursable expenses incurred in one taxable year shall not affect the in-kind benefits to be provided or the expenses eligible for reimbursement
in any other taxable year (except for any lifetime or other aggregate limitation applicable to medical expenses). Such right to reimbursement or in-kind benefits is not subject to liquidation or exchange for
another benefit. 
 (c)    To the extent that any payment or benefit described in this Agreement constitutes “non-qualified deferred compensation” under Section 409A of the Code, and to the extent that such payment or benefit is payable upon the Executive’s termination of employment, then such payments
or benefits shall be payable only upon the Executive’s “separation from service.” The determination of whether and when a separation from service has occurred shall be made in accordance with the presumptions set forth in Treasury
Regulation Section 1.409A-1(h). 
 (d)    The parties intend that this
Agreement will be administered in accordance with Section 409A of the Code. To the extent that any provision of this Agreement is ambiguous as to its compliance with Section 409A of the Code, the provision shall be read in such a manner so
that all payments hereunder comply with Section 409A of the Code. Each payment pursuant to this Agreement or the Restrictive Covenants Agreement is intended to constitute a separate payment for purposes of Treasury Regulation Section 1.409A-2(b)(2). The parties agree that this 












 
Agreement may be amended, as reasonably requested by either party, and as may be necessary to fully comply with Section 409A of the Code and all related rules and regulations in order to
preserve the payments and benefits provided hereunder without additional cost to either party. 
 (e)    The Company
makes no representation or warranty and shall have no liability to the Executive or any other person if any provisions of this Agreement are determined to constitute deferred compensation subject to Section 409A of the Code but do not satisfy
an exemption from, or the conditions of, such Section. 
 8.    Continuing Obligations.  

(a)    Restrictive Covenants Agreement. As a condition of employment, the Executive’s eligibility for pay and
benefits in Sections 5 and 6 of this Agreement, and the one-time retention bonus provided for in Section 2(f), the Executive is required to enter into the Employee Confidentiality, Assignment,
Nonsolicitation and Noncompetition Agreement, attached hereto as Exhibit A (the “Restrictive Covenants Agreement”). For purposes of this Agreement, the obligations in this Section 8 and those that arise in the Restrictive
Covenants Agreement and any other agreement relating to confidentiality, assignment of inventions, or other restrictive covenants shall collectively be referred to as the “Continuing Obligations.” 

(b)    Third-Party Agreements and Rights. The Executive hereby confirms that the Executive is not bound by the
terms of any agreement with any previous employer or other party which restricts in any way the Executive’s use or disclosure of information, other than confidentiality restrictions (if any), or the Executive’s engagement in any business.
The Executive represents to the Company that the Executive’s execution of this Agreement, the Executive’s employment with the Company and the performance of the Executive’s proposed duties for the Company will not violate any
obligations the Executive may have to any such previous employer or other party. In the Executive’s work for the Company, the Executive will not disclose or make use of any information in violation of any agreements with or rights of any such
previous employer or other party, and the Executive will not bring to the premises of the Company any copies or other tangible embodiments of non-public information belonging to or obtained from any such
previous employment or other party. 
 (c)    Litigation and Regulatory Cooperation. During and after the
Executive’s employment, the Executive shall cooperate fully with the Company in (i) the defense or prosecution of any claims or actions now in existence or which may be brought in the future against or on behalf of the Company which relate
to events or occurrences that transpired while the Executive was employed by the Company, and (ii) the investigation, whether internal or external, of any matters about which the Company believes the Executive may have knowledge or information.
The Executive’s full cooperation in connection with such claims, actions or investigations shall include, but not be limited to, being available to meet with counsel to answer questions or to prepare for discovery or trial and to act as a
witness on behalf of the Company at mutually convenient times. During and after the Executive’s employment, the Executive also shall cooperate fully with the Company in connection with any investigation or review of any federal, state or local
regulatory authority as any such investigation or review relates to events or occurrences that transpired while the Executive was employed by the Company. The Company shall reimburse the Executive for any reasonable out-of-pocket expenses incurred in connection with such cooperation, and will compensate the Executive at an hourly rate for all time spent on such matters based on the Executive’s Base Salary on the
Date of Termination. 












 (d)    Non-Disparagement.
During the Executive’s employment and following the termination of the Executive’s employment for any reason, the Executive shall not, and will not cause any third party to, publish or communicate to any person, any Disparaging remarks,
comments or statements concerning the Company, its affiliated and related entities, and its and their present and former members, partners, directors, officers, shareholders, employees, agents, legal counsel, successors and assigns. For purposes of
this Agreement, “Disparaging” shall mean remarks, comments or statements that place the person or entity being disparaged in a false or negative light or that otherwise impugn the character, honesty, integrity, morality, acumen, abilities,
conduct or operations of the person or entity being disparaged. On or following the Executive’s Date of Termination, the Company shall instruct its then-current executive officers and then-current directors not to make Disparaging remarks,
comments or statements about the Executive during the then-current executive officers and then-current directors’ employment and/or engagement with the Company; provided, however, that the foregoing does not in any way limit or modify an
officer or director’s obligations or duties (fiduciary or otherwise) to any person. Notwithstanding anything to the contrary in the foregoing, nothing in this Agreement shall be construed to (a) preclude truthful disclosures in response to
lawful process as required by applicable law, regulation, or order or directive of a court, governmental agency or regulatory organization, (b) restrict or impede the exercise of rights under Section 7 of the National Labor Relations Act,
or (c) prevent the Executive, the Company, or any other person from making truthful statements as may be reasonably required to perform such person’s duties and responsibilities on behalf of the Company, such as (for example) offering
negative performance feedback in a personnel review. 
 (e)    Relief. The Executive agrees that it would be
difficult to measure any damages caused to the Company which might result from any breach by the Executive of the Continuing Obligations, and that in any event money damages would be an inadequate remedy for any such breach. Accordingly, the
Executive agrees that if the Executive breaches, or proposes to breach, any portion of the Continuing Obligations, the Company shall be entitled, in addition to all other remedies that it may have, to an injunction or other appropriate equitable
relief to restrain any such breach without showing or proving any actual damage to the Company and without the posting of a bond. 

9.    Consent to Jurisdiction. The parties hereby consent to the jurisdiction of the state and federal courts of
the Commonwealth of Massachusetts. Accordingly, with respect to any such court action, the Executive (a) submits to the exclusive personal jurisdiction of such courts; (b) consents to service of process; and (c) waives any
other requirement (whether imposed by statute, rule of court, or otherwise) with respect to personal jurisdiction or service of process. 

10.    Waiver of Jury Trial. Each of the Executive and the Company irrevocably and unconditionally WAIVES ALL RIGHT
TO TRIAL BY JURY IN ANY PROCEEDING (WHETHER BASED ON CONTRACT, TORT OR OTHERWISE) ARISING OUT OF OR RELATING TO THIS AGREEMENT OR THE EXECUTIVE’S EMPLOYMENT BY THE COMPANY OR ANY AFFILIATE OF THE COMPANY, INCLUDING WITHOUT LIMITATION THE
EXECUTIVE’S OR THE COMPANY’S PERFORMANCE UNDER, OR THE ENFORCEMENT OF, THIS AGREEMENT. 












 11.    Integration. This Agreement constitutes the entire
agreement between the parties with respect to the subject matter hereof and supersedes all prior agreements between the parties concerning such subject matter, including the Prior Agreement (except for the Executive’s repayment obligation with
respect to the Signing Bonus in Section 6 of the Prior Agreement shall remain in effect until March 16, 2021), provided that the Continuing Obligations, Restrictive Covenants Agreement and the Equity Documents (as modified by
Section 2(g) in this Agreement) remain in full force and effect. 
 12.    Withholding; Tax Effect. All
payments made by the Company to the Executive under this Agreement shall be net of any tax or other amounts required to be withheld by the Company under applicable law. Nothing in this Agreement shall be construed to require the Company to make any
payments to compensate the Executive for any adverse tax effect associated with any payments or benefits or for any deduction or withholding from any payment or benefit. 

13.    Assignment. Neither the Executive nor the Company may make any assignment of this Agreement or any interest
in it, by operation of law or otherwise, without the prior written consent of the other; provided, however, that the Company may assign its rights and obligations under this Agreement (including the Restrictive Covenants Agreement) without the
Executive’s consent to any affiliate or to any person or entity with whom the Company shall hereafter effect a reorganization, consolidate with, or merge into or to whom it transfers all or substantially all of its properties or assets;
provided further that if the Executive remains employed or becomes employed by the Company, the purchaser or any of their affiliates in connection with any such transaction, then the Executive shall not be entitled to any payments, benefits or
vesting pursuant to Section 5 or pursuant to Section 6 of this Agreement solely as a result of such transaction. This Agreement shall inure to the benefit of and be binding upon the Executive and the Company, and each of the
Executive’s and the Company’s respective successors, executors, administrators, heirs and permitted assigns. 

14.    Enforceability. If any portion or provision of this Agreement (including, without limitation, any portion or
provision of any section of this Agreement) shall to any extent be declared illegal or unenforceable by a court of competent jurisdiction, then the remainder of this Agreement, or the application of such portion or provision in circumstances other
than those as to which it is so declared illegal or unenforceable, shall not be affected thereby, and each portion and provision of this Agreement shall be valid and enforceable to the fullest extent permitted by law. 

15.    Survival. The provisions of this Agreement shall survive the termination of this Agreement and/or the
termination of the Executive’s employment to the extent necessary to effectuate the terms contained herein. 

16.    Waiver. No waiver of any provision hereof shall be effective unless made in writing and signed by the
waiving party. The failure of any party to require the performance of any term or obligation of this Agreement, or the waiver by any party of any breach of this Agreement, shall not prevent any subsequent enforcement of such term or obligation or be
deemed a waiver of any subsequent breach. 












 17.    Notices. Any notices, requests, demands and other
communications provided for by this Agreement shall be sufficient if in writing and delivered in person or sent by a nationally recognized overnight courier service or by registered or certified mail, postage prepaid, return receipt requested, to
the Executive at the last address the Executive has filed in writing with the Company or, in the case of the Company, at its main offices, attention of the Board. 

18.    Amendment. This Agreement may be amended or modified only by a written instrument signed by the Executive
and by a duly authorized representative of the Company. 
 19.    Effect on Other Plans and Agreements. An
election by the Executive to resign for Good Reason under the provisions of this Agreement shall not be deemed a voluntary termination of employment by the Executive for the purpose of interpreting the provisions of any of the Company’s benefit
plans, programs or policies. Nothing in this Agreement shall be construed to limit the rights of the Executive under the Company’s benefit plans, programs or policies except as otherwise provided in this Agreement, and except that the Executive
shall have no rights to any severance benefits under any Company severance pay plan, offer letter or otherwise. Except for the Restrictive Covenants Agreement, in the event that the Executive is party to an agreement with the Company providing for
payments or benefits under such plan or agreement and under this Agreement, the terms of this Agreement shall govern and the Executive may receive payment under this Agreement only and not both. Further, Section 5 and Section 6 of this
Agreement are mutually exclusive and in no event shall the Executive be entitled to payments or benefits pursuant to both Section 5 and Section 6 of this Agreement. 

20.    Governing Law. This is a Massachusetts contract and shall be construed under and be governed in all respects
by the laws of the Commonwealth of Massachusetts, without giving effect to the conflict of laws principles thereof. With respect to any disputes concerning federal law, such disputes shall be determined in accordance with the law as it would be
interpreted and applied by the United States Court of Appeals for the First Circuit. 
 21.    Counterparts. This
Agreement may be executed in any number of counterparts, each of which when so executed and delivered shall be taken to be an original; but such counterparts shall together constitute one and the same document. 

22.    Legal Fees. The Company will reimburse Executive up to $5,000, inclusive of applicable taxes, in respect of
legal fees incurred by him in connection with the review and execution of this Agreement. The payment will be made directly to the firm retained by Executive upon submission to the Company of any invoice reflecting the total amount due. 












 IN WITNESS WHEREOF, the parties have executed this Agreement effective on the Effective
Date. 
  

			
	FUSION PHARMACEUTICALS, INC.


 
			
		
	By:	 	  

	Its:	 	  



 
			
	
	FUSION PHARMACEUTICALS US, INC.
		
	By:	 	
	Its:	 	
	
	EXECUTIVE
	
	  

	James O’Leary














 Exhibit A 

Restrictive Covenants Agreement