EXHIBIT 10.11

EMPLOYMENT AGREEMENT

This EMPLOYMENT AGREEMENT (the "Agreement"), dated and entered into as of the
29th day of September, 2017 ("Effective Date"), by and between Nightstar, Inc.,
a Delaware corporation and wholly owned subsidiary of Nightstar Therapeutics
Limited, a company incorporated under the laws of England and Wales (hereinafter
referred to together as the "Company"), and Seokho Bryan Yoon (the "Employee").

WHEREAS, the Company desires to engage the full-time services of the Employee;
and WHEREAS, the Employee desire to be so employed by the Company; and

WHEREAS, the Company desires to be assured that the unique and expert services
of the Employee will be available solely to the Company on such full-time basis,
and that the Employee is willing and able to render such services on the terms
and conditions hereinafter set forth;

WHEREAS, the Company desires to be assured that the confidential information and
good will of the Company will be preserved for the exclusive benefit of the
Company.

NOW, THEREFORE, in consideration of such employment and the mutual covenants and
promises herein contained, and for other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the Company and the
Employee agree as follows:

Section 1.Employment. The Company hereby continues to employ the Employee as
General Counsel, and the Employee hereby accepts such continued employment
subject to the terms and conditions hereinafter set forth.

Section 2.Term. The Term of employment under this Agreement shall begin on
November 6, 2017 or such date as may be otherwise agreed upon with the Company
(the "Commencement Date"), and shall conclude pursuant to Section 7.

Section 3.Duties. The Employee shall be responsible for the duties of a General
Counsel and shall have such additional duties as the Company may assign to him
from time to time. The Employee shall perform services in a managerial capacity
subject to the general supervision of the Chief Executive Officer. The Employee
hereby agrees to devote his full business time and best efforts to the faithful
performance of such duties and to the business and affairs of the Company for
the Term.

Section 4.Compensation.

(a)Salary. In consideration of the services rendered by the Employee under this
Agreement, the Company shall pay the Employee a base salary (the "Base Salary")
at the annualized rate of three hundred and fifty thousand dollars ($350,000)
per calendar year. The Base Salary shall be paid in such installments and at
such times as the Company pays its regular, salaried employees, and the Company
may review and revise the Base Salary annually in a manner that is consistent
with the Company's policies.

 

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(b)Equity. On the Commencement Date, the Company shall grant Employee a stock
option under its 2017 Equity Incentive Plan to purchase 160,000 shares of the
Company's common stock at a per share exercise price equal to the closing price
of the common stock on the date of grant. Subject to approval by the Board or
the Compensation Committee thereof, the Employee may be eligible to receive
additional equity awards on terms to be determined by the Board or the
Compensation Committee (as applicable) at the time of any such grant. The
determination whether to grant any such equity award(s) to the Employee is in
the sole discretion of the Board or the Compensation Committee (as applicable).

Section 5.Bonus Compensation. The Employee shall be eligible to earn an annual
bonus of up to 35% of his Base Salary, to be determined at the sole discretion
of the Company, and payable in accordance with the terms and conditions of the
applicable bonus plan(s) of the Company. In order to receive an annual bonus,
Employee must remain employed through the date such bonus is paid. A one-time
sign on bonus will be paid to the Employee in the first payroll period after he
starts employment in the gross sum of $40,000, less applicable withholdings upon
hiring.

Section 6.Fringe Benefits. The Employee will be eligible to participate in the
Company's health insurance plans (including medical, dental, and vision
coverage, for which the Company will pay 75% of the premium). The Employee will
also be entitled to take up to twenty days paid vacation per year accrued at the
rate of 1.66 days per month: such days must be taken in the year accrued and may
not be carried over to subsequent years, without the prior consent of the CEO.
In addition, the Employee will also receive paid holidays subject to the
Company's holiday schedule. The benefits made available by the Company, and the
rules, terms, and conditions for participation in such benefit plans, may be
changed by the Company at any time without advance notice.

Section 7.Termination. The parties acknowledge that the Employee's employment
with the Company is at-will. The provisions of Sections 7 and 8 govern the
amount of compensation and continued benefits, if any, to be provided to the
Employee upon termination of employment and do not alter this at-will status.
This Agreement and Employee's employment hereunder shall be terminated as
follows:

Section 7.01Death. This Agreement shall terminate upon the death of the
Employee, except that the compensation provided in Section 4(a) shall continue
through the end of the month in which the Employee's death occurs.

Section 7.02Permanent Disability. In the event of any physical or mental
disability or incapacity of the Employee rendering the Employee unable to
perform the essential functions of his position with or without reasonable
accommodation for a period of at least ninety (90) consecutive days and the
further determination that such disability is permanent, this Agreement shall
terminate automatically. Any determination of disability shall be made by the
Company in consultation with a qualified physician or physicians selected by the
Company and reasonably acceptable to the Employee. The failure of the Employee
to submit to a reasonable examination by such physician or physicians shall
preclude any objection by the Employee to the determination of disability by the
Company.

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Section 7.03By The Company For Cause. The employment of the Employee may be
terminated by the Company for Cause (as defined below) immediately at any time
effective upon written notice to the Employee. For purposes hereof, the term
"Cause" shall mean that the Company has determined that any one or more of the
following has occurred: (i) Employee's willful engagement in dishonesty, illegal
conduct or gross misconduct, which is, in each case, materially injurious to the
Company or any affiliate; (ii) Employee's willful and deliberate
insubordination; (iii) Employee's substantial malfeasance or nonfeasance of
duty; (iv) Employee's deliberate unauthorized disclosure of confidential
information; (v) Employee's embezzlement, misappropriation or fraud, whether or
not related to Employee's employment with the Company; (vi) Employee's material
breach of Section 10 or 11 of this Agreement; (vii) the Employee's repeated,
substantial and material breach of another material provision of this Agreement,
which causes actual and material harm to the Company; or (viii) the Employee
shall have been convicted of, or shall have pleaded guilty or nolo contendere
to, any felony or a crime involving moral turpitude. In all cases, the Company
shall provide Employee with a description of the specific conduct or events that
the Company believes constitutes Cause and, in case of (ii), (iii), (vi) (for
the avoidance of doubt, clause (iv) of this Section 7.03 shall independently
apply from clause (vi) in relation to this sentence) or (vii) above. Employee
shall have thirty (30) days to effect a cure of the claimed conduct or events.

Section 7.04By The Company Without Cause. The Company may terminate the
Employee's employment at any time without Cause effective upon written notice to
the Employee.

Section 7.05By the Employee Voluntarily. The Employee may terminate this
Agreement at any time effective upon at least thirty (30) business days' prior
written notice to the Company.

Section 7.06By the Employee For Good Reason. The Employee may terminate this
Agreement for Good Reason. As used herein. "Good Reason" shall mean: (i)
relocation of Employee's principal business location to a location more than
fifty (50) miles from Employee's then-current business location; (ii) a material
diminution in Employee's duties, authority or responsibilities; or (iii) a
material reduction in the Employee's Base Salary without the Employee's consent
(other than a reduction generally applicable to all executive employees of the
Company); provided that (A) Employee provides Company with written notice that
Employee intends to terminate Employee-s employment hereunder for one of the
circumstances set forth in this Section 7.06 within ten (10) days of such
circumstance occurring, (B) if such circumstance is capable of being cured, the
Company has failed to cure such circumstance within a period of thirty (30) days
from the date of such written notice, and (C) Employee terminates Employee's
employment within forty-five days from the date that Good Reason first occurs.
For purposes of clarification, the above-listed conditions shall apply
separately to each occurrence of Good Reason and failure to adhere to such
conditions in the event of Good Reason shall not disqualify Employee from
asserting Good Reason for any subsequent occurrence of Good Reason. For purposes
of this Agreement, "Good Reason" shall be interpreted in a manner, and limited
to the extent necessary, so that it shall not cause, to the extent possible,
adverse tax consequences for either party with respect to Section 409A ("Section
409A") of the U.S. Internal Revenue Code of 1986, as amended (the "Code"), and
any successor statute, regulation and guidance thereto.

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Section 8.Termination Payments and Benefits.

Section 8.01Voluntary Termination by Employee without Good Reason, Termination
For Cause By Company, Death, Permanent Disability. Upon any termination of this
Agreement and Employee's employment hereunder: (1) voluntarily by the Employee
without Good Reason, (2) upon the Employee's Death or Permanent Disability, or
(3) by the Company for Cause, all payments, salary and other benefits hereunder
shall cease at the effective date of termination, except that in the case of the
Employee's Death, the compensation provided in Section 4(a) shall continue
through the end of the month in which the Employee's death occurs.

Section 8.02Termination By the Company Without Cause, Termination by Employee
for Good Reason. In the event that this Agreement and Employee's employment is
terminated by the Company without Cause or by the Employee for Good Reason, and
the Employee executes a separation agreement and general release of legal claims
in a form provided by the Company (the "Release") and such release becomes
effective within sixty (60) days following the Employee's date of termination,
then:

(a)the Company shall pay the Employee's Base Salary as is in effect at the
effective date of termination for twelve (12) months (the "Termination
Payment"). The Termination Payment shall be paid according to the Company's
regular payroll schedule, provided that the Termination Payment shall commence
to be paid on the first regular payroll date of the Company that occurs sixty
(60) days after the effective date of such termination, and the first payment
thereof shall include a include a catch-up payment to cover amounts retroactive
to the day immediately following the date of such termination. The Termination
Payment shall be reduced by any statutorily-mandated severance,
change-of-control, plant closing, or similar payment to the Employee by the
Company or its stockholders; and

(b)for a period of up to twelve (12) months following Employee's Termination
Date, Employee and where applicable, Employee's spouse and eligible dependents,
will continue to be eligible to receive reimbursement for medical coverage
premiums, on the same basis as when Employee was employed, under the Company's
medical plans in accordance with the terms of the applicable plan documents;
provided, that in order to receive such continued coverage at such rates,
Employee will be required to pay the applicable premiums to the plan provider.
Notwithstanding the foregoing, if Employee obtains full-time employment during
this twelve (12) month period that entitles him and his spouse and eligible
dependents to comprehensive medical coverage, Employee must notify the Company
and no further reimbursements will be paid by the Company to the Employee
pursuant to this subsection. In addition, if Employee does not pay the
applicable monthly premium for a particular month at any time during the twelve
(12) month period and coverage is lost as a result, no further reimbursements
will be paid by the Company to the Employee pursuant to this subsection.
Further, notwithstanding the foregoing, if the Company determines, in its sole
discretion, that it cannot pay the such premiums without potentially incurring
financial costs or penalties under applicable law (including, without
limitation, Section 2716 of the U.S. Public Health Service Act), regardless of
whether Employee or Employee's dependents elect or are eligible for COBRA
coverage, the Company instead shall pay to Employee, on the first day of each
calendar month following the termination date, a fully taxable cash payment
equal to the applicable premium

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amount for that month, subject to applicable tax withholdings (such amount, the
"Special Cash Payment"), for the remainder of the applicable period specified
above.

Section 8.03Termination By the Company Without Cause or Termination by Employee
for Good Reason following a Change in Control. In the event that this Agreement
and Employee's employment is terminated by the Company (or its successor)
without Cause or by the Employee for Good Reason, in each case, upon or within
twelve (12) months following a Change in Control (as such term is defined in the
Nightstar Therapeutics plc 2017 Equity Incentive Plan), then, in addition to the
payments and benefits described in Section 8.02, above, subject to the
Employee’s execution of the Release and the Release becoming effective within
sixty (60) days following the Employee's date of termination:

(a)the Company shall pay the Employee a lump-sum amount equal to the Employee's
target annual cash bonus for the year of termination, pro-rated based on the
number of days from the beginning of the calendar year through the date of such
termination, payable on the first regular payroll date of the Company that is
sixty (60) days following the date of such termination; and

(b)the vesting and exercisability of all then unvested time-based vesting equity
awards then held by the Employee shall accelerate such that all shares become
immediately vested and exercisable, if applicable, by Employee upon such
termination and shall remain exercisable, if applicable, following the
Employee's termination as set forth in the applicable equity award documents.
With respect to any performance-based vesting equity award, such award shall
continue to be governed in all respects by the terms of the applicable equity
award documents.

Section 8.04Other Benefits. Except as specifically provided in this Section, the
Employee shall not be entitled to any compensation, severance or other benefits
from the company or any of its subsidiaries or affiliates upon the termination
of this Agreement for any reason whatsoever.

Section 9.Merger Clause. The Company shall not consolidate merge or transfer all
or a substantial portion of its assets without requiring the transferee to
assume this Agreement and the obligations hereunder.

Section 10.Confidentiality, Ownership and Assignment.

Section 10.01Licensed Property; Reservation of Rights. The Company and its
respective licensors hereby reserve all rights not specifically and expressly
granted hereunder.

Section 10.02Intellectual Property Rights. "Intellectual Property Rights" shall
mean. collectively, worldwide Patents, Trade Secrets, Copyrights, Moral Rights,
trade names, Trademarks, rights in trade dress and all other intellectual
property rights and proprietary rights, whether arising under the laws of the
United States or any other state, country or jurisdiction, including all rights
or causes of action for infringement or misappropriation of any of the
foregoing. "Patents" shall mean all patent rights and all right, title and
interest in all letters patent or equivalent rights and applications for letters
patent or rights and any reissuing division, continuation or continuation in
part application throughout the world. "Trade Secrets" shall

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mean all right, title and interest in all trade secrets and trade secret rights
arising under the common law, state law, U.S. federal law or laws of foreign
countries. "Copyrights" shall mean all copyright rights, neighboring and
derivative rights, and all other literary property and author rights and all
right, title and interest in all copyrights, copyright registrations,
certificates of copyright and copyrighted interests throughout the world.
"Trademarks" shall mean all trademark and service mark rights arising under the
common law, state law, U.S. federal law and laws of foreign countries and all
right, title and interest in all trademarks, service marks, trademark and
service mark applications and registrations and trademark and service mark
interests throughout the world. "Moral Rights" shall mean any rights of
paternity or integrity, any right to claim authorship of a work or to object to
any distortion, mutilation or other modification of, or other derogatory action
in relation to, any work, whether or not such would be prejudicial to the
Employee's honor or reputation, and any similar rights existing under judicial
or statutory law of any country in the world, or under any treaty, regardless of
whether or not such right is denominated or generally referred to as a "moral"
right, and shall include the right of an author to be known as the author of a
work; to prevent others from being named as the author of a work; to prevent
others from falsely attributing to an author the authorship of a work which
he/she has not in fact created; to prevent others from making deforming changes
in an author's work; to withdraw a published work from distribution if it no
longer represents the views of the author; and to prevent others from using the
work or the author's name in such a way as to reflect on his/her professional
standing.

Section 10.03Ownership. Ownership of the Intellectual Property Rights in and to
the services, Deliverable Items, Milestones, and all derivatives thereof and
improvements thereto, including, without limitation, any objects, scenes,
artwork, models, textures, names, rules, products, materials, files, effects,
reports, data, and any other audio or visual elements associated with each of
the foregoing, and compilations or contributions to a collective work
(collectively referred to as the "Work") hereby automatically vests in and is
transferred and assigned to the Company in perpetuity as its sole and exclusive
property upon and as of the creation, conception, reduction to practice thereof
(i.e., from the moment that the applicable Intellectual Property Right first
comes into being), or if such events took place prior to the Effective Date, as
of the Effective Date. The Employee hereby appoints the Company (or its
designee) as its attorney-in-fact to execute any and all documents to effectuate
such assignment. Through the Company's ownership of such Intellectual Property
Rights under this Agreement, the Company may make or have made, and accordingly
will own all right, title and interest in any other work product and any other
derivative works or improvements of any Deliverable items. The Employee agrees
and acknowledges that the Company may utilize the Work in any other software
program or printed material or visual representation or license or sell the Work
for incorporation into or as a basis for producing other products or otherwise
exploiting the Work at the sole discretion of the Company without the payment of
any royalty or other fee to the Employee, except for the compensation
specifically set forth in this Agreement. Furthermore, the Company may, in its
sole discretion, adapt, reproduce, add to, delete from, edit, modify, duplicate,
license, display, provide to third parties and otherwise use and exploit the
Deliverable Items for any purpose.

Section 10.04Work Made For Hire. The Employee agrees and acknowledges that the
Work completed hereunder shall be considered "works made for hire," that the
Employee has no claim to any right, title or interest in the Work supplied to
the Company pursuant to the terms

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of this Agreement or otherwise, and that the Employee will make no claims that
the Work infringes upon the copyright or other right, title or interest of the
Employee and that the Work shall, upon creation, be owned exclusively by the
Company and be and hereby is assigned to the Company.

Section 10.05Retained Rights. If and to the extent the Employee may, under
applicable law, the Employee is deemed to have retained any right, title or
interest in or to any portion of the Work notwithstanding the other provisions
of this Section 10, the Employee hereby transfers, grants, conveys, assigns and
relinquishes solely and exclusively to the Company all of the Employee's right,
title and interest in and to the Work, without reservation and without
additional consideration, under applicable Patent, Copyright, Trade Secret,
Trademark and other similar laws or rights, in perpetuity, and in the
alternative to the extent such assignment is ineffective under applicable law,
the Employee hereby grants to the Company, its successors and assigns, a sole
and exclusive, irrevocable, worldwide, paid-up license to reproduce, fix, adapt,
modify, translate, create derivative works from, manufacture, introduce into
circulation, publish, distribute, sell, license, sublicense, transfer, rent,
lease, transmit or provide access electronically, broadcast, display, perform,
enter into computer memory, and use and practice the Work, all modified and
derivative works thereof, all portions and copies thereof in any form, all
inventions, designs, and marks embodied therein, and all Intellectual Property
Rights in and to the Work.

Section 10.06Moral Rights. The Employee hereby irrevocably transfers and assigns
to the Company any and all Moral Rights that the Employee may have in the Work.
To the extent such Moral Rights cannot be assigned under applicable law and to
the extent the following is allowed by the laws in the various countries where
Moral Rights exist, the Employee also hereby forever waives and agrees never to
assert any and all Moral Rights it may have in the Work, even after termination
of the Employee's work on behalf of the Company or this Agreement.

Section 10.07Execution of Documents. The Employee will cooperate with the
Company, at the Company's expense, in obtaining Patent, Copyright, Trademark or
other statutory protections for the Work, in each country in which it, or
derivatives thereof or improvements thereto, is sold, distributed or licensed
and in taking any enforcement action including any public or private
prosecution, to protect the Company's Intellectual Property Rights in and to the
Work. the Employee hereby grants the Company the exclusive right, and appoints
the Company (or its designee) as attorney-in-fact, to execute and prosecute in
the Employee's name as author or inventor or in the Company's (or its
designee's) name as assignee any application for registration or recordation of
any Copyright, Trademark, Patent or other right in or to the Work, and to
undertake any enforcement action with respect to the Work. The Employee will
execute such other documents of registration and recordation as may be necessary
to perfect in the Company, or protect, the rights assigned to the Company
hereunder in each country in which the Company reasonably determines to be
prudent.

Section 10.08Survival. The provisions of this Section 10 shall survive any
expiration or termination of this Agreement.

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Section 10.09Nondisclosure. Except as may be required by law, and
notwithstanding anything contained herein to the contrary, the Employee shall
not be permitted to disclose the existence of or deal terms applicable to this
Agreement or the subject matter of this Agreement. All work related to the Work
is deemed confidential proprietary information belonging exclusively to the
Company.

Section 10.10Confidentiality. In the course of performing this Agreement, the
Employee may learn (or may have previously learned of) non-public, confidential
or proprietary information of the Company (including their respective licensors
or business partners), and their respective businesses, including, but not
limited to, information developed and relating to products and services of the
Company, customers, pricing, know-how, processes, and practices (collectively
"Confidential Information"). The Employee will keep confidential and not
disclose to third parties the Confidential Information, and shall not use any
such Confidential Information for its own benefit or for the benefit of any
third party, and shall use such Confidential Information solely for purposes of
performing its obligations under this Agreement. It is understood, however, that
the restrictions listed above shall not apply to any portion of the Confidential
Information which: (a) was previously known to the Employee without obligations
of confidentiality; (b) is obtained by the Employee after the effective date of
this Agreement from a third party which is lawfully in possession of such
information and not in violation of any contractual or legal obligation to the
Company with respect to such information; or (c) is or becomes part of the
public domain through no fault of the Employee. The Employee may disclose
Confidential Information if and to the extent it is approved for release by
written authorization of the Company or it is required to do so by
administrative or judicial action (provided that the Employee immediately after
receiving notice of such action notifies the Company of such action to give it
the opportunity to seek any other legal remedies to maintain such Confidential
Information in confidence). Should the Company need to enforce this provision,
it shall not be required to post a bond before obtaining an injunction. At the
termination of this Agreement, or earlier upon the completion of the services
hereunder or the written request of the Company, and subject to the other
provisions of this Agreement, the Employee shall return or destroy all drawings,
specifications, manuals and other printed or reproduced material (including
information stored on machine readable media) related to any Work created
hereunder as well as all other materials embodying any Confidential Information
in its possession. Any and all Work produced under this Agreement by the
Employee shall be deemed to be Confidential Information of the Company.

Section 10.11Publicity. No publicity or public announcements by the Employee
regarding this Agreement, the Work or the business relationship set forth herein
shall be made without the prior written consent of the Company.

Section 11.Restrictions on Activities of the Employee.

Section 11.01Acknowledgements. The Employee agrees that he is being employed
hereunder in a key capacity with the Company and that the Company is engaged in
a highly competitive business and that the success of the Company's business in
the marketplace depends upon its goodwill and reputation for quality and
dependability. The Employee agrees that reasonable limits may be placed on his
ability to compete against the Company as provided herein so as to protect and
preserve the legitimate business interests and good will of the

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Company. The Employee further agrees that the Employee's responsibilities,
duties, position. compensation, title and/or other terms and conditions of
employment may change from time to time and, notwithstanding any change in any
terms and conditions of employment, this Agreement, including but not limited to
this Section 11, shall remain in full force and effect.

Section 11.02General Restrictions.

(a)During the Term and the Non-Competition Period (as defined below), the
Employee will not (anywhere in the world where the Company or any of its
subsidiaries or affiliates then conducts business) engage or participate in,
directly or indirectly, as principal, agent, employee, employer, consultant,
investor or partner, or assist in the management of, or own any stock or any
other ownership interest in, any business which is Competitive with the Company
(as defined below). For purposes of this Agreement, a business shall be
considered "Competitive with the Company" if it is engaged in the business of
developing ophthalmic gene therapies for inherited retinal diseases and the
manufacture of adeno-associated virus products. Notwithstanding the foregoing,
the Employee may own, directly or indirectly, less than 1% of the capital stock
of any public corporation.

(b)For purposes of this Agreement the "Non-Competition Period” shall mean the
period of six (6) consecutive months after the Employee's employment terminates
for any reason.

Section 11.03Employees, Customers and Suppliers.

(a)During the Term and the Non-Solicitation Period, the Employee will not
solicit, or attempt to solicit, any officer, director, consultant, executive or
employee of the Company or any of its subsidiaries or affiliates to leave his or
her engagement with the Company or such subsidiary or affiliate, or hire or
engage any officer, director, consultant, executive or employee of the Company
or any of its subsidiaries or affiliates in any capacity, nor will he call upon,
solicit, divert or attempt to solicit or divert from the Company or any of its
affiliates or subsidiaries any of their customers or suppliers, or potential
customers or suppliers, or of whose names he was aware during his employment
with the Company; provided, however, that nothing in this Section shall be
deemed to prohibit the Employee from calling upon or soliciting a customer or
supplier during the Non- Solicitation Period if such action relates solely to a
business which is not competitive with the Company.

(b)For purposes of this Agreement the "Non-Solicitation Period" shall mean the
period of twelve (12) consecutive months after the Employee's employment
terminates for any reason.

Section 11.04THE EMPLOYEE REPRESENTS AND WARRANTS THAT THE KNOWLEDGE, SKILLS AND
ABILITIES HE POSSESSES AT THE TIME OF COMMENCEMENT OF EMPLOYMENT HEREUNDER ARE
SUFFICIENT TO PERMIT HIS EMPLOYMENT HEREUNDER, TO EARN A LIVELIHOOD SATISFACTORY
TO HIMSELF WITHOUT VIOLATING ANY PROVISION OF SECTION 10 OR 11 HEREOF, FOR
EXAMPLE, BY USING SUCH KNOWLEDGE, SKILLS AND ABILITIES, OR SOME OF THEM, IN THE
SERVICE OF A NON-COMPETITOR. THE EMPLOYEE FURTHER

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REPRESENTS AND WARRANTS THAT HIS ABILITY SO TO EARN A LIVELIHOOD SATISFACTORY TO
HIMSELF DOES NOT DEPEND UPON HIS SERVICES AT, OR IN EXCESS OF, THE LEVEL AT
WHICH HE IS COMPENSATED BY THE COMPANY.

Section 12.Remedies. It is specifically understood and agreed that any breach of
the provisions of Sections 10 or 11 of this Agreement is likely to result in
irreparable injury to the Company and that the remedy at law alone will be an
inadequate remedy for such breach, and that in addition to any other remedy it
may have, the Company shall be entitled to enforce the specific performance of
this Agreement by the Employee and to seek both temporary and permanent
injunctive relief (to the extent permitted by law) without the necessity of
proving actual damages.

Section 13.Severable Provisions. The provisions of this Agreement are severable
and the invalidity of any one or more provisions shall not affect the validity
of any other provision. In the event that a court of competent jurisdiction
shall determine that any provision of this Agreement or the application thereof
is unenforceable in whole or in part because of the duration or scope thereof,
the parties hereto agree that said court in making such determination shall have
the power to reduce the duration and scope of such provision to the extent
necessary to make it enforceable, and that the Agreement in its reduced form
shall be valid and enforceable to the full extent permitted by law.

Section 14.Notices. All notices hereunder, to be effective, shall be in writing
and shall be delivered by hand or mailed by certified mail, postage and fees
prepaid, as follows:

If to the Company:

Nightstar Therapeutics Limited

215 Euston Road

London, UK NW1 2BE

Attn: David Fellows

 

 

Copy to:

Marc Recht, Esq.

Cooley LLP

500 Boylston Street

Boston, MA 02116-3736

 

 

If to the Employee:

Seokho Bryan Yoon

Address

or to such other address as a party may notify the other pursuant to a notice
given in accordance with this Section 14.

Section 15.Mediation and Arbitration.

Section 15.01Mediation. In the event of a dispute regarding any of the terms and
conditions of this Agreement, or otherwise relating to the Employee's employment
with the Company, either party may request that the other party engage in a
mediation to resolve such dispute. If such request is made, the other party
shall respond in writing by no later than seven (7) business days thereafter,
stating whether such other party is willing to participate in such

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mediation, and such mediation shall occur within thirty (30) days following such
notification. If the parties are unable to agree to a mediator, then the matter
shall be submitted to the mediation program conducted by the American
Arbitration Association in Boston, Massachusetts, and a mediator shall be
selected pursuant to the rules applicable to such program.

Section 15.02Arbitration.

(a)In the event that the other party declines to participate in a mediation, if
no mediation has been requested, or if mediation has not resulted in resolution
of the dispute, either party may require that the dispute be submitted to
binding arbitration, and in such event the dispute shall be settled by
arbitration in accordance with the National Rules for the Resolution of
Employment Disputes of the American Arbitration Association, except that both
parties agree that the matter shall be submitted to and resolved by a single
arbitrator. Such arbitration shall occur in Boston, Massachusetts. Each party
hereby agrees to a speedy hearing upon the matter in dispute and the judgment
upon the award rendered by the arbitrator may be entered in a court as set forth
in this Section. Notwithstanding the foregoing, nothing in this Agreement shall
be deemed to limit the Company's right to seek immediate judicial relief in the
event of a claimed breach by the Employee of his obligations in Sections 10
and/or 11 of this Agreement.

(b)Each party shall pay its own costs for the arbitration including, but not
limited to, arbitrator or adjudication fees (arbitrator fees to be split equally
between the parties), attorneys' fees, witnesses' fees, transcripts and other
expenses. The prevailing party in any arbitration shall be entitled to recover
its reasonable attorneys' fees and costs where authorized by contract or
statute.

(c)The Employee understands that by signing this Agreement, the Employee agrees
to submit any claims arising out of, relating to, or in connection with this
Agreement, or the interpretation, validity, construction, performance, breach or
termination thereof, or his employment or the termination thereof, to binding
arbitration, and that this arbitration provision constitutes a waiver of the
Employee's right to a jury trial and relates to the resolution of all disputes
relating to all aspects of the employer/employee relationship, including but not
limited to the following:

(i)Any and all claims for wrongful discharge of employment, breach of contract,
both express and implied; breach of the covenant of good faith and fair dealing,
both express and implied; negligent or intentional infliction of emotional
distress; negligent or intentional misrepresentation; negligent or intentional
interference with contract or prospective economic advantage; and defamation;

(ii)Any and all claims for violation of any federal, state or municipal statute,
including, without limitation, Title VII of the Civil Rights Act of 1964, as
amended. the Civil Rights Act of 1991, the Equal Pay Act, the Employee
Retirement Income Security Act, as amended, the Age Discrimination in Employment
Act of 1967, the Americans with Disabilities Act of 1990, the Family and Medical
Leave Act of 1993, the Fair Labor Standards Act, and the Massachusetts Fair
Employment Practices Act; and

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(iii)Any and all claims arising out of any other federal, state or local laws or
regulations relating to employment or employment discrimination.

(d)This Agreement shall be governed by and construed in accordance with the
substantive laws of the Commonwealth of Massachusetts, without giving effect to
any choice or conflict of law provision or rule, and any legal action permitted
by this Agreement to enforce an award under this Section or for a claimed breach
by the Employee of his obligations in Sections 10 and/or 11 of this Agreement
shall be governed by the laws of the Commonwealth of Massachusetts and shall be
commenced and maintained solely in any state or federal court located in the
Commonwealth of Massachusetts, and both parties hereby submit to the
jurisdiction and venue of any such court.

Section 16.Section 409A of the Code.

Section 16.01The payments and benefits under this Agreement are intended to
qualify for an exemption from application of Section 409A of the Code or comply
with its requirements to the extent necessary to avoid adverse personal tax
consequences under Section 409A, and any ambiguities herein shall be interpreted
accordingly. For purposes of Section 409A of the Code (including, without
limitation, for purposes of Treasury Regulations Section 1.409A 2(b)(2)(iii)),
the Employee's right to receive any installment payments under this Agreement
(whether severance payments, if any, or otherwise) shall be treated as a right
to receive a series of separate payments and, accordingly, each installment
payment hereunder shall at all times be considered a separate and distinct
payment.

Section 16.02To the extent that any payment or benefit described in this
Agreement constitutes "non-qualified deferred compensation" under Section 409A,
and to the extent that such payment or benefit is payable upon the termination
of the Employee's employment, then such payments or benefits will be payable
only upon the Employee's "separation from service." The determination of whether
and when a separation from service has occurred will be made in accordance with
the presumptions set forth in Treasury Regulation Section 1.409A-1(h).

Section 16.03Anything in this Agreement to the contrary notwithstanding, if at
the time of the Employee's separation from service, the Company determines that
the Employee 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
Employee become entitled to under this Agreement on account of the Employee's
separation from service would be considered deferred compensation 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
will not be payable and such benefit will not be provided until the date that is
the earlier of (A) six months and one day after the Employee's separation from
service, (B) the Employee's death, or (C) such earlier date as permitted under
Section 409A without imposition of adverse taxation. If any such delayed cash
payment is otherwise payable on an installment basis, the first payment will
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 will be payable in accordance with their original
schedule. No interest shall be due on any amounts so deferred.

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Section 16.04All in-kind benefits provided and expenses eligible for
reimbursement under this Agreement shall be provided by the Company or incurred
by the Employee 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.

Section 17.Parachute Payments.

Section 17.01If any payment or benefit the Employee would receive from the
Company or otherwise in connection with a Change in Control or other similar
transaction (a "280G Payment") would (i) constitute a "parachute payment" within
the meaning of Section 280G of the Code, and (ii) but for this sentence, be
subject to the excise tax imposed by Section 4999 of the Code (the "Excise
Tax"), then any such 280G Payment (a "Payment") shall be equal to the Reduced
Amount. The "Reduced Amount" shall be either (x) the largest portion of the
Payment that would result in no portion of the Payment (after reduction) being
subject to the Excise Tax or (y) the largest portion, up to and including the
total, of the Payment, whichever amount (i.e., the amount determined by clause
(x) or by clause (y)), after taking into account all applicable federal, state
and local employment taxes, income taxes, and the Excise Tax (all computed at
the highest applicable marginal rate), results in the Employee's receipt, on an
after-tax basis, of the greater economic benefit notwithstanding that all or
some portion of the Payment may be subject to the Excise Tax. If a reduction in
a Payment is required pursuant to the preceding sentence and the Reduced Amount
is determined pursuant to clause (x) of the preceding sentence, the reduction
shall occur in the manner (the "Reduction Method") that results in the greatest
economic benefit for the Employee. If more than one method of reduction will
result in the same economic benefit, the items so reduced will be reduced pro
rata (the "Pro Rata Reduction Method").

Section 17.02Notwithstanding the foregoing, if the Reduction Method or the Pro
Rata Reduction Method would result in any portion of the Payment being subject
to taxes pursuant to Section 409A of the Code that would not otherwise be
subject to taxes pursuant to Section 409A of the Code, then the Reduction Method
and/or the Pro Rata Reduction Method, as the case may be, shall be modified so
as to avoid the imposition of taxes pursuant to Section 409A of the Code as
follows: (A) as a first priority, the modification shall preserve to the
greatest extent possible, the greatest economic benefit for the Employee as
determined on an after-tax basis; (B) as a second priority, Payments that are
contingent on future events (e.g., being terminated without cause), shall be
reduced (or eliminated) before Payments that are not contingent on future
events; and (C) as a third priority, Payments that are "deferred compensation"
within the meaning of Section 409A of the Code shall be reduced (or eliminated)
before Payments that are not deferred compensation within the meaning of Section
409A of the Code.

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Section 17.03Unless the Employee and the Company agree on an alternative
accounting firm, the accounting firm engaged by the Company for general tax
compliance purposes as of the day prior to the effective date of the change of
control transaction triggering the Payment shall perform the foregoing
calculations. If the accounting firm so engaged by the Company is serving as
accountant or auditor for the individual, entity or group effecting the change
of control transaction, the Company shall appoint a nationally recognized
accounting firm to make the determinations required hereunder. The Company shall
bear all expenses with respect to the determinations by such accounting firm
required to be made hereunder. The Company shall use commercially reasonable
efforts to cause the accounting firm engaged to make the determinations
hereunder to provide its calculations, together with detailed supporting
documentation, to the Employee and the Company within fifteen (15) calendar days
after the date on which the Employee's right to a 280G Payment becomes
reasonably likely to occur (if requested at that time by the Employee or the
Company) or such other time as requested by the Employee or the Company.

Section 17.04If the Employee receive a Payment for which the Reduced Amount was
determined pursuant to clause (x) of the first paragraph of this Section and the
Internal Revenue Service determines thereafter that some portion of the Payment
is subject to the Excise Tax, the Employee shall promptly return to the Company
a sufficient amount of the Payment (after reduction pursuant to clause (x) of
the first paragraph of this Section so that no portion of the remaining Payment
is subject to the Excise Tax. For the avoidance of doubt, if the Reduced Amount
was determined pursuant to clause (y) in the first paragraph of this Section,
the Employee shall have no obligation to return any portion of the Payment
pursuant to the preceding sentence.

Section 18.Miscellaneous.

Section 18.01Modification. This Agreement constitutes the entire Agreement
between the parties hereto with regard to the subject matter hereof, superseding
all prior understandings and agreements, whether written or oral. This Agreement
may not be amended or revised except by a writing signed by the parties.

Section 18.02Assignment and Transfer. This Agreement shall not be terminated by
the merger or consolidation of the Company with any corporate or other entity or
by the transfer of all or substantially all of the assets of the Company to any
other person, corporation, firm or entity. The provisions of this Agreement
shall be binding on and shall inure to the benefit of any such successor in
interest to the Company. Neither this Agreement nor any of the rights, duties or
obligations of the Employee shall be assignable by the Employee, nor shall any
of the payments required or permitted to be made to the Employee by this
Agreement be encumbered, transferred or in any way anticipated.

Section 18.03Captions. Captions herein have been inserted solely for the
convenience of reference and in no way define, limit or describe the scope or
substance of any provision of this Agreement.

Section 18.04Tax Treatment. In no event whatsoever shall the Company be liable
for any tax, interest or penalties that may be imposed on the Employee under
Section 409A

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(or otherwise) and the Company shall have no obligation to amend this Agreement
or to indemnify or otherwise hold the Employee harmless from any such taxes,
interest or penalties, or from liability for any damages related thereto. The
Employee is urged to consult his own tax adviser regarding the tax treatment of
this Agreement.

Section 18.05Defend Trade Secrets Act of 2016 Notice. Notwithstanding any
provision in this Agreement, an individual shall not be held criminally or
civilly liable under any federal or state trade secret law for the disclosure of
a trade secret that (A) is made (i) in confidence to a federal, state, or local
government official, either directly or indirectly, or to an attorney; and (ii)
solely for the purpose of reporting or investigating a suspected violation of
law; or (B) is made in a complaint or other document filed in a lawsuit or other
proceeding, provided that such filing is made under seal. Further, an individual
who files a lawsuit for retaliation by an employer for reporting a suspected
violation of law may disclose the trade secret to the attorney of the individual
and use the trade secret information in the court proceeding, provided that the
individual (A) files any document containing the trade secret under seal and (B)
does not disclose the trade secret, except pursuant to court order.

Section 18.06Governing Law. This Agreement shall be construed under and enforced
in accordance with the laws of the Commonwealth of Massachusetts.

Section 18.07Conditions. Employment is contingent upon the Employee providing
satisfactory documentation to the Company concerning his employment eligibility
as required by Congress under applicable immigration laws. This documentation
must be received by the Company within three (3) business days of the Effective
Date. Employment is also contingent upon the Company's completion of a
satisfactory investigation of the Employee's background. The Employee agrees to
release the Company, its employees and agents and any individuals who may
provide the Company with information regarding the Employee's background and
references from any liability in connection with this investigation.

[REMAINDER OF PAGE INTENTIONALLY LEFT BLANK;
SIGNATURE PAGE FOLLOWS]

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IN WITNESS WHEREOF, the parties hereto have duly executed this Agreement as a
sealed instrument as of the day and year first above written,

 

NIGHTSTAR THERAPEUTICS LIMITED

NIGHTSTAR, INC.

 

By:

 

 

/s/ David Fellows

 

David Fellows

 

Chief Executive Officer

 

EMPLOYEE

 

/s/ Seokho Bryan Yoon

Seokho Bryan Yoon

 

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