Exhibit 10.1

SEPARATION AGREEMENT

This Separation Agreement (this “Agreement”) by and between Tara Nickerson
(“Executive”) and Prothena Biosciences Inc, a Delaware corporation (the
“Company”) is made effective as of the date that the Company and Executive sign
this Agreement (the “Effective Date”), with reference to the following facts:
 
A.    Executive’s employment with the Company and status as an officer, director
and employee of the Company and as an officer of its ultimate parent entity
Prothena Corporation plc (“Prothena”) will end on the Separation Date (as
defined below).

B.    Executive and the Company want to end their relationship amicably and also
to establish the obligations of the parties including, without limitation, all
amounts due and owing to Executive.

NOW, THEREFORE, in consideration of the mutual covenants and agreements
hereinafter set forth, the parties agree as follows:

1.Separation Date. Executive acknowledges and agrees that Executive’s status as
an officer, director and employee of the Company, and as an officer of Prothena,
will end effective as of the close of business on July 1, 2018 (the “Separation
Date”). Executive will execute such documents as are determined by the Company
to be necessary or desirable to give effect to the termination of Executive’s
status as an officer and director of the Company and as an officer of Prothena.
2.Final Paycheck; Reimbursement of Expenses.
(a)Final Paycheck. On the Separation Date, the Company will pay to Executive all
accrued but unpaid wages and all accrued and unused vacation earned through the
Separation Date (subject to standard payroll deductions and withholdings).
Executive is entitled to and will receive these payments regardless of whether
Executive executes this Agreement or the Release of Claims (as defined below).
(b)    Business Expenses. On or as soon as administratively practicable after
the Separation Date, the Company will reimburse Executive for all outstanding
business expenses incurred by Executive prior to the Separation Date that are
consistent with the Company’s policies in effect from time to time with respect
to travel, entertainment and other business expenses, subject to the Company’s
standard procedures with respect to reporting and documenting such expenses.
Executive is entitled to and will receive these reimbursements regardless of
whether Executive executes this Agreement.
1.    Separation Payments and Benefits. Without admission of any liability, fact
or claim, the Company hereby agrees, subject to the execution of this Agreement
and the General Release of Claims attached hereto as Exhibit A (the “Release of
Claims”) and Executive’s performance of Executive’s continuing obligations
pursuant to this Agreement and the Employee

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Proprietary Information and Invention Assignment Agreement between Executive and
the Company (the “Confidentiality Agreement”), to provide Executive the
following payments and benefits as consideration for Executive’s promises in
this Agreement:
(a)    Severance Payment. In accordance with and subject to the terms of the
Company’s Amended and Restated Severance Plan (the “Severance Plan”), Executive
is entitled to receive from the Company, and the Company hereby confirms it will
pay to Executive, a lump-sum payment in the amount of $496,534 (before
applicable tax and other withholdings), which is the sum of (i) the amount equal
to 100% of Executive’s annual base salary, and (ii) the amount equal to 100% of
Executive’s target annual cash bonus, in each case as in effect on the
Separation Date (collectively, the “Severance Payment”). The Company will pay
the Severance Payment, less applicable withholdings, to Executive within ten
(10) business days after the date the Release of Claims becomes effective and
irrevocable.
(b)    COBRA Continuation Coverage. Under the Consolidated Omnibus Budget
Reconciliation Act of 1985, as amended (“COBRA”), if Executive participates in a
Company-maintained healthcare (medical, dental and/or vision) plan as of the
Separation Date, Executive will be entitled to elect COBRA continuation coverage
under each such plan in which Executive (and any of Executive’s eligible
dependents) is enrolled as of the Separation Date. In accordance with and
subject to the terms of the Severance Plan, if Executive timely elects to
receive continued healthcare coverage pursuant COBRA, from the Separation Date
until the six-month anniversary of the Separation Date, Executive will only be
required to pay the same share of the applicable premium that would apply if
Executive were participating in the applicable health plan(s) as an active
employee, and following the six-month anniversary of the Separation Date until
the 12-month anniversary of the Separation Date, Executive will be required to
pay the full monthly COBRA premium provided that, on a monthly basis, the
Company will reimburse Executive for the cost of COBRA premiums paid, less the
amount that would apply if Executive were participating in the applicable health
plan(s) as an active employee. Notwithstanding the foregoing, the Company will
cease to directly pay or reimburse Executive for COBRA premiums in accordance
with the previous sentence upon the earlier of (i) the date that Executive
and/or Executive’s covered dependents, as applicable, become no longer eligible
for COBRA, or (ii) the date Executive becomes eligible for new healthcare
coverage (other than through Executive’s spouse). Notwithstanding anything to
the contrary in this Section 3(b), (x) if any plan pursuant to which such
benefits are provided is not, or ceases prior to the expiration of the period of
continuation coverage to be, exempt from the application of Section 409A of the
Code under Treasury Regulation Section l.409A-l(a)(5), or (ii) the Company is
otherwise unable to continue to cover Executive under its group health plans
without penalty under applicable law (including without limitation, Section 2716
of the Public Health Service Act), then, in either case, an amount equal to each
remaining COBRA subsidy, subject to the limitations set forth above, shall
thereafter be paid to Executive in substantially equal monthly installments.
(c)    Outplacement Services. In accordance with and subject to the terms of the
Severance Plan, the Company will provide career transition assistance to
Executive, at the Company’s cost through a provider of the Company’s choosing,
for a period of 12 months following the Separation Date. To receive this
benefit, Executive must commence use of that

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career transition assistance within sixty (60) days after the Separation Date.
Details on this program will be provided to Executive in a separate
communication after the Separation Date.
(d)    Option Vesting Acceleration. In accordance with and subject to the terms
of the Nonstatutory Stock Option Agreements between Prothena and Executive (the
“Option Agreements”), the vesting of Executive’s nonqualified stock options
thereunder to purchase ordinary shares of Prothena (the “Options”) shall
accelerate upon the Separation Date in respect of that number of ordinary shares
that would have vested had Executive’s employment with the Company continued
through the first anniversary of the Separation Date. The unvested portion of
the Options, after giving effect to the accelerated vesting described in the
preceding sentence, shall be forfeited as of the Separation Date. The vested
portion of the Options shall remain exercisable through the one-year anniversary
of the Separation Date (or if earlier, the original expiration date of such
Options). Any vested Options not exercised during such period shall then
terminate.
(e)    Supplemental Cash Payment. Although Executive is not eligible for or
entitled to receive a bonus under the Prothena Corporation plc Incentive
Compensation Plan (the “Incentive Plan”) for the 2018 performance period, the
Company will pay to Executive a lump-sum amount of $50,717 (before applicable
tax and other withholdings) (the “Supplemental Cash Payment”). Executive
acknowledges and agrees that the Supplemental Cash Payment (i) is not required
to be made by the Company, including without limitation under the Severance Plan
or the Incentive Plan, (ii) is being made solely in connection with this
Agreement, and (iii) constitutes adequate and valuable consideration, in and of
itself, for the promises contained in this Agreement. The Company will pay the
Supplemental Cash Payment to Executive within ten (10) business days after the
date the Release of Claims becomes effective and irrevocable.
All payments under this Agreement will be subject to applicable tax and other
withholdings. To the extent any taxes may be payable by Executive for the
benefits provided to Executive under this Agreement beyond those taxes withheld
by the Company, Executive will pay them and indemnify and hold the Company and
the other Releasees (defined below) harmless for and against any tax claims or
penalties, and associated attorneys’ fees and costs, resulting from any failure
by Executive to make required payments.
2.    Full Payment. Executive acknowledges that the payments and arrangements
provided for herein shall constitute full and complete satisfaction of any and
all amounts properly due and owing to Executive as a result of Executive’s
employment with the Company and the termination thereof. Executive further
acknowledges that, other than the Confidentiality Agreement, the Option
Agreements, the Deed of Indemnification by and between Prothena and Executive
(the “Indemnification Agreement”) and the Release of Claims, this Agreement
shall supersede each agreement entered into between Executive and the Company or
Prothena regarding Executive’s employment, including, without limitation, any
offer letter, employment agreement, severance and/or change in control
agreement, and each such agreement shall be deemed terminated and of no further
effect as of the Separation Date.
3.    Executive’s Release of the Company. Executive understands that by agreeing
to the release provided by this Section 5, Executive is agreeing not to sue, or
otherwise file any

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claim against, the Company or any of the other Releases (defined below) for any
reason whatsoever based on anything that has occurred as of the date Executive
signs this Agreement.
(a)    On behalf of Executive and Executive’s heirs, assigns, executors,
administrators, trusts, spouse and estate, Executive hereby releases and forever
discharges the “Releasees” hereunder, consisting of the Company, and each of its
owners, affiliates, subsidiaries, predecessors, successors, assigns, agents,
directors, officers, partners, employees, and insurers, and all persons acting
by, through, under or in concert with them, or any of them, of and from any and
all manner of action or actions, cause or causes of action, in law or in equity,
suits, debts, liens, contracts, agreements, promises, liability, claims,
demands, damages, loss, cost or expense, of any nature whatsoever, known or
unknown, fixed or contingent (“Claims”), which Executive now has or may
hereafter have against the Releasees, or any of them, by reason of any matter,
cause, or thing whatsoever from the beginning of time to the date hereof,
including, without limiting the generality of the foregoing, any Claims arising
out of, based upon, or relating to Executive’s hire, employment, remuneration or
resignation by the Releasees, or any of them, Claims arising under federal,
state, or local laws relating to employment, Claims of any kind that may be
brought in any court or administrative agency, including any Claims for:
(i)any pay, compensation, or benefits (whether under the Fair Labor Standards
Act or otherwise) including bonuses, commissions, equity, expenses, incentives,
insurance, paid/unpaid leave, profit sharing or separation or severance
pay/benefits;
(ii)    any compensatory, emotional or distress damages, punitive or liquidated
damages, attorneys’ fees, costs, interest or penalties;
(iii)    any violation of express or implied employment contracts, covenants,
promises or duties, intellectual property or other proprietary rights;
(iv)    any unlawful or tortious conduct such as assault or battery, background
check violations, defamation, detrimental reliance, fiduciary breach, fraud,
indemnification, intentional or negligent infliction of emotional distress,
interference with contractual or other legal rights, invasion of privacy, loss
of consortium, misrepresentation, negligence (including negligent hiring,
retention, or supervision), personal injury, promissory estoppel, public policy
violation, retaliatory discharge, safety violations, posting or records-related
violations, wrongful discharge, or other federal, state or local statutory or
common law matters;
(v)    any benefit entitlement, citizenship, color, concerted activity,
disability, ethnicity, gender, genetic information, immigration status, leave
rights, military status, national origin, parental status, protected off-duty
conduct, race, religion, retaliation, sexual orientation, union activity,
veteran status, whistleblower activity (including under the Sarbanes-Oxley,
Dodd-Frank and False Claims Acts), other legally protected status or activity,
or any allegation that payment under this Agreement was affected by any such
discrimination; and
(vi)    any participation in any class or collective action against the Company.

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(b)    Notwithstanding the generality of the foregoing, Executive does not
release the following claims:
(i)    Claims that cannot be waived, such as for unemployment compensation or
any state disability insurance benefits pursuant to the terms of applicable
state law;
(ii)    Claims for workers’ compensation insurance benefits under the terms of
any worker’s compensation insurance policy or fund of the Company;
(iii)    Claims to continued participation in certain of the Company’s group
benefit plans pursuant to the terms and conditions of COBRA;
(iv)    Claims for any benefit entitlement vested as the date of Executive’s
employment termination, pursuant to written terms of any Company employee
benefit plan;
(v)    Claims for breach of this Agreement; and
(vi)    Claims for indemnification under the Indemnification Agreement, the
Company’s Bylaws, Prothena’s Constitution, California Labor Code Section 2802 or
any other applicable law.
(c)    Rights with Respect to Administrative Agencies. Neither the release
section(s) above nor anything else in this Agreement limit Executive’s rights to
file a charge with any administrative agency, such as the U.S. Equal Employment
Opportunity Commission (the “EEOC”) or a state fair employment practices agency,
communicate directly with or provide information to an agency, or otherwise
participate in an agency investigation or other administrative proceeding.
However, Executive does give up all rights to any money or other individual
relief based on any agency or judicial decision, including class or collective
action rulings; provided, however, that Executive may receive money properly
awarded to Executive by the U.S. Securities and Exchange Commission as a reward
for providing information to that agency.
(d)    Whistleblower Protection; Trade Secrets. For the avoidance of doubt,
nothing in this Agreement will be construed to prohibit Executive from filing a
charge with, reporting possible violations to, or participating or cooperating
with any governmental agency or entity, including but not limited to the EEOC,
the U.S. Department of Justice, the U.S. Securities and Exchange Commission, the
U.S. Congress, or any federal agency Inspector General, or making other
disclosures that are protected under the whistleblower, anti-discrimination, or
anti-retaliation provisions of federal, state or local law or regulation;
provided, however, that Executive may not disclose information of the Company or
Prothena that is protected by the attorney-client privilege, except as otherwise
required by law. Executive does not need the prior authorization of the Company
to make any such reports or disclosures, and Executive is not required to notify
the Company that Executive has made such reports or disclosures. Furthermore, in
accordance with 18 U.S.C. § 1833, notwithstanding anything to the contrary in
this Agreement: (i) Executive shall not be in breach of this Agreement, and
shall not be held criminally or civilly

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liable under any federal or state trade secret law (x) for the disclosure of a
trade secret that is made in confidence to a federal, state, or local government
official or to an attorney solely for the purpose of reporting or investigating
a suspected violation of law, or (y) for the disclosure of a trade secret that
is made in a complaint or other document filed in a lawsuit or other proceeding,
if such filing is made under seal; and (ii) if Executive files a lawsuit for
retaliation by the Company for reporting a suspected violation of law, Executive
may disclose the trade secret to Executive’s attorney, and may use the trade
secret information in the court proceeding, if Executive files any document
containing the trade secret under seal, and does not disclose the trade secret,
except pursuant to court order.
(e)    EXECUTIVE ACKNOWLEDGES THAT EXECUTIVE HAS BEEN ADVISED OF AND IS FAMILIAR
WITH THE PROVISIONS OF CALIFORNIA CIVIL CODE SECTION 1542, WHICH PROVIDES AS
FOLLOWS:
“A GENERAL RELEASE DOES NOT EXTEND TO CLAIMS WHICH THE CREDITOR DOES NOT KNOW OR
SUSPECT TO EXIST IN HIS OR HER FAVOR AT THE TIME OF EXECUTING THE RELEASE,
WHICH, IF KNOWN BY HIM OR HER, MUST HAVE MATERIALLY AFFECTED HIS OR HER
SETTLEMENT WITH THE DEBTOR.”
BEING AWARE OF SAID CODE SECTION, EXECUTIVE HEREBY EXPRESSLY WAIVES ANY RIGHTS
EXECUTIVE MAY HAVE THEREUNDER, AS WELL AS UNDER ANY OTHER STATUTES OR COMMON LAW
PRINCIPLES OF SIMILAR EFFECT.
4.    Promise Not To Sue. A “promise not to sue” means Executive promises not to
sue any Releasee in court. This is different from the release in Section 5. In
addition to releasing claims covered by that release, Executive agrees never to
sue any Releasee for any reason covered by that release; provided, however, that
Executive may file a suit to enforce this Agreement or to challenge its validity
under the Age Discrimination in Employment Act. If Executive sues a Releasee in
violation of this Agreement Executive will be required to pay that Releasee’s
attorneys’ fees and other litigation costs incurred in defending against
Executive’s suit, or alternatively the Company can require Executive to return
all but $1,000 of the payments and benefits provided to Executive under this
Agreement; in addition, the Company will be excused from any remaining
obligations that exist solely because of this Agreement. This Section 6 shall
not affect the validity of this Agreement and any payment provided for in this
Section 6 shall not be deemed to be a penalty or forfeiture.
5.    Non-Admission. Neither the Company’s offer of this Agreement nor any
payment or benefit provided for in this Agreement are an admission that
Executive has a viable claim against the Company or any other Releasee. Each
Releasee denies all liability to Executive.
6.    Non-Disparagement, Transition, Transfer of Company Property.
(a)    Non-Disparagement. Executive will not disparage, criticize or defame the
Company or Prothena, or their respective affiliates or their directors,
officers, employees, agents, partners, shareholders or businesses, either
publicly or privately. Prothena’s current directors and officers will not
disparage, criticize or defame Executive, either publicly or

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privately. Nothing in this Section 8(a) shall have application to any evidence
or testimony required by any court, arbitrator or government agency.
(b)    Transition. Each of the Company and Executive will use their respective
reasonable efforts to cooperate with each other in good faith to facilitate a
smooth transition of Executive’s duties to other employees of the Company or its
affiliates.
(c)    Return of Company Property. On or before the Separation Date, Executive
will turn over to the Company all files, memoranda, records and other documents,
and any other physical or personal property which are the property of the
Company and which Executive had in Executive’s possession, custody or control at
the time Executive signed this Agreement.
7.    Executive Representations. Executive warrants and represents that (a)
Executive has not filed or authorized the filing of any complaints, charges or
lawsuits against the Company, Prothena or any affiliate of either with any
governmental agency or court, and that if, unbeknownst to Executive, such a
complaint, charge or lawsuit has been filed on Executive’s behalf, Executive
will immediately cause it to be withdrawn and dismissed, (b) Executive has been
paid all compensation, wages, paid time off, bonuses, commissions and/or
benefits to which Executive may be entitled and no other compensation, wages,
paid time off, bonuses, commissions and/or benefits are due to Executive, except
as provided in this Agreement, (c) Executive has no known workplace injuries or
occupational diseases and has been provided and/or has not been denied any leave
requested under the Family and Medical Leave Act or any similar state law, (d)
Executive has had the opportunity to negotiate this Agreement with the Company,
Executive has had the opportunity seek the advice of Executive’s attorney,
Executive has relied on Executive’s own informed judgment and/or that of
Executive’s attorney in deciding whether to enter into this Agreement, Executive
understands the terms of this Agreement, Executive has not relied upon any
promises or representations not set forth in this Agreement in deciding to enter
into this Agreement, and Executive is signing this Agreement knowingly and
voluntarily, (e) the execution, delivery and performance of this Agreement by
Executive does not and will not conflict with, breach, violate or cause a
default under any agreement, contract or instrument to which Executive is a
party or any judgment, order or decree to which Executive is subject, and (f)
upon the execution and delivery of this Agreement by the Company and Executive,
this Agreement will be a valid and binding obligation of Executive, enforceable
in accordance with its terms.
8.    Maintaining Confidential Information. Executive reaffirms Executive’s
obligations under the Confidentiality Agreement. Executive acknowledges and
agrees that the payments provided for in Section 3 above shall be subject to
Executive’s continued compliance with Executive’s obligations under the
Confidentiality Agreement.
9.    Executive’s Cooperation.  After the Separation Date, Executive will
cooperate with the Company, Prothena and their respective affiliates, upon their
reasonable request, with respect to any internal investigation or
administrative, regulatory or judicial proceeding involving matters within the
scope of Executive’s duties and responsibilities to the Company, Prothena or
their respective affiliates during Executive’s employment with the Company
(including, without limitation, Executive being available to the Company upon
reasonable notice for interviews and factual investigations, appearing at the
Company’s reasonable request to give testimony without requiring service of a
subpoena or other legal process, and turning over to the Company all

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relevant Company documents which are or may have come into Executive’s
possession during Executive’s employment); provided, however, that any such
request by the Company shall not be unduly burdensome or interfere with
Executive’s ability to engage in gainful employment. 
10.    SEC Requirements Under Section 16.
(a)    Section 16(a) Reporting. Executive hereby certifies that Executive has
reported to the Company all ownership of and transactions in Prothena securities
(including any change in the nature of Executive’s ownership in such securities,
such as by moving such securities from direct ownership into a trust account)
that are required to be reported on a Form 3, Form 4 and/or Form 5 pursuant
Section 16(a) of the Securities Exchange Act of 1934, as amended (the “Exchange
Act”).
(b)    Section 16(b) Short-Swing Profit Liability. Executive acknowledges that
to the extent Executive engaged in any transaction in Prothena securities during
the six-month period prior to the Separation Date, Executive will have
continuing obligations under Section 16(b) of the Exchange Act to disgorge
profits on any “matchable” transaction in Prothena securities for up to six (6)
months following the Separation Date. Following the Separation Date, Executive
will not undertake, directly or indirectly, any such transaction in Prothena
securities that would be “matchable” under Section 16(b).
11.    Section 409A of the Code. This Agreement is intended, to the greatest
extent permitted under applicable law, to comply with the short-term deferral
exemption and the separation pay exemption provided in Section 409A of the
Internal Revenue Code of 1986, as amended, and the regulations and other
interpretative guidance issued thereunder (“Section 409A”) such that no payments
or benefits provided under this Agreement are subject to Section 409A.
Notwithstanding anything herein to the contrary, the timing of any payments
under this Agreement shall be made consistent with such exemption. Executive’s
right to receive a series of installment payments under this Agreement, if any,
shall be treated as a right to receive a series of separate payments. To the
extent applicable, this Agreement shall be interpreted in accordance with
Section 409A, including without limitation any such regulations or other
guidance that may be issued after the Separation Date. Notwithstanding any
provision of this Agreement to the contrary, in the event that the Company
determines that any amounts payable hereunder may be subject to Section 409A,
the Company may, to the extent permitted under Section 409A cooperate in good
faith to adopt such amendments to this Agreement or adopt other appropriate
policies and procedures, including amendments and policies with retroactive
effect, that the Company determines are necessary or appropriate to avoid the
imposition of taxes under Section 409A; provided, however, that this Section 13
shall not create an obligation on the part of the Company to adopt any such
amendment, policy or procedure or take any such other action, nor shall the
Company have any liability for failing to do so. To the extent that any
reimbursements payable pursuant to this Agreement are subject to the provisions
of Section 409A, such reimbursements shall be paid to Executive no later than
December 31 of the year following the year in which the expense was incurred,
the amount of expenses reimbursed in one year shall not affect the amount
eligible for reimbursement in any subsequent year, and Executive’s right to
reimbursement under this Agreement will not be subject to liquidation or
exchange for another benefit.

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12.    No Assignment by Executive. Executive warrants and represents that no
portion of any of the matters released herein, and no portion of any recovery or
settlement to which Executive might be entitled, has been assigned or
transferred to any other person, firm or corporation not a party to this
Agreement, in any manner, including by way of subrogation or operation of law or
otherwise. If any claim, action, demand or suit should be made or instituted
against the Company or any other Releasee because of any actual assignment,
subrogation or transfer by Executive, Executive will indemnify and hold harmless
the Company and all other Releasees against such claim, action, suit or demand,
including necessary expenses of investigation, attorneys’ fees and costs. In the
event of Executive’s death, this Agreement will inure to the benefit of
Executive and Executive’s executors, administrators, heirs, distributees,
devisees and legatees. None of Executive’s rights or obligations under this
Agreement may be assigned or transferred by Executive, other than Executive’s
rights to payments hereunder, which may be transferred only upon Executive’s
death by will or operation of law.
13.    Company Assignment and Successors. The Company may assign its rights and
obligations under this Agreement to any successor to all or substantially all of
the business or assets of the Company (by merger or otherwise). This Agreement
shall be binding upon and inure to the benefit of the Company and its
affiliates, successors, assigns, personnel and legal representatives.
14.    Enforceability. If any court or arbitrator(s) determines that any part of
this Agreement is invalid unenforceable, (a) the application of such provision
shall be interpreted so as best to effect the intent of the parties to this
Agreement, (b) the parties shall replace such provision with a valid and
enforceable provision that will achieve, to the greatest extent possible, the
purposes of such provision, and (c) the remainder of this Agreement shall be
enforceable.
15.    Injunctive Relief. Executive acknowledges that Executive’s breaches this
Agreement would cause the Company irreparable harm for which money would not be
adequate compensation. Executive therefore agrees that, in the event of
Executive’s breach of this Agreement, the Company shall be entitled to
preliminary and permanent injunctive relief, in addition to any other relief
determined to be appropriate, as well as recovery of attorneys’ fees and other
costs incurred by the Company to enforce this Agreement.
16.    Waivers. Any waiver by the Company or by the Executive of any of right
under this Agreement must be in writing and signed by both parties to this
Agreement. No waiver by the Company or Executive of any right shall be construed
as a waiver of any other right. No waiver or indulgence by the Company of any
failure by Executive to keep or perform any promise or condition of this
Agreement shall be a waiver of any preceding or succeeding breach of the same or
any other promise or condition.
17.    Miscellaneous. This Agreement, together with the Confidentiality
Agreement, the Option Agreements, the Indemnification Agreement and the Release
of Claims, comprise the entire agreement between the parties with regard to the
subject matter hereof and supersedes, in their entirety, any other agreements
between Executive and the Company or Prothena with regard to the subject matter
hereof, including without limitation, the Severance Plan and the Incentive Plan.
Executive acknowledges and agrees that there are no other agreements, written,
oral or implied, and that Executive may not rely on any prior negotiations,
discussions, representations

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or agreements. This Agreement may be modified only in writing, and such writing
must be signed by both parties and recited that it is intended to modify this
Agreement. This Agreement may be executed in separate counterparts, each of
which is deemed to be an original and all of which taken together constitute one
and the same agreement.
18.    Governing Law. This Agreement shall be construed and enforced in
accordance with, and the rights of the parties shall be governed by, the laws of
the State of California or, where applicable, United States federal law, in each
case, without regard to any conflicts of laws provisions or those of any state
other than California.
IN WITNESS WHEREOF, the undersigned have caused this Separation Agreement to be
duly executed and delivered as of the date indicated next to their respective
signatures below.

/s/ Tara Nickerson                         May 23, 2018    
Tara Nickerson                            Date

PROTHENA BIOSCIENCES INC                

By:     /s/ A. W. Homan                         May 23, 2018    
Name: A. W. Homan                        Date
Title: Secretary

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Exhibit A
General Release of Claims

This General Release of Claims (“Release”) is entered into as of
_________________, 2018, between Tara Nickerson (“Executive”) and Prothena
Biosciences Inc, a Delaware corporation (the “Company”) (collectively referred
to herein as the “Parties”), effective eight (8) days after Executive’s
signature hereto, unless Executive revokes Executive’s acceptance of this
Release as provided in Paragraph 1(e) below.
1.Executive’s Release of the Company. Executive understands that by agreeing to
this Release, Executive is agreeing not to sue, or otherwise file any claim
against, the Company or any of the other Releasees (defined below) for any
reason whatsoever based on anything that has occurred as of the date Executive
signs this Release.
(a)    On behalf of Executive and Executive’s heirs, assigns, executors,
administrators, trusts, spouse and estate, Executive hereby releases and forever
discharges the “Releasees” hereunder, consisting of the Company, and each of its
owners, affiliates, subsidiaries, predecessors, successors, assigns, agents,
directors, officers, partners, employees, and insurers, and all persons acting
by, through, under or in concert with them, or any of them, of and from any and
all manner of action or actions, cause or causes of action, in law or in equity,
suits, debts, liens, contracts, agreements, promises, liability, claims,
demands, damages, loss, cost or expense, of any nature whatsoever, known or
unknown, fixed or contingent (“Claims”), which Executive now has or may
hereafter have against the Releasees, or any of them, by reason of any matter,
cause, or thing whatsoever from the beginning of time to the date hereof,
including, without limiting the generality of the foregoing, any Claims arising
out of, based upon, or relating to Executive’s hire, employment, remuneration or
resignation by the Releasees, or any of them, Claims arising under federal,
state, or local laws relating to employment, Claims of any kind that may be
brought in any court or administrative agency, including any Claims for:
(i)    any pay, compensation, or benefits (whether under the Fair Labor
Standards Act or otherwise) including bonuses, commissions, equity, expenses,
incentives, insurance, paid/unpaid leave, profit sharing or separation or
severance pay/benefits;
(ii)    any compensatory, emotional or distress damages, punitive or liquidated
damages, attorneys’ fees, costs, interest or penalties;
(iii)    any violation of express or implied employment contracts, covenants,
promises or duties, intellectual property or other proprietary rights;
(iv)    any unlawful or tortious conduct such as assault or battery, background
check violations, defamation, detrimental reliance, fiduciary breach, fraud,
indemnification, intentional or negligent infliction of emotional distress,
interference with contractual or other legal rights, invasion of privacy, loss
of consortium, misrepresentation, negligence (including negligent hiring,
retention, or supervision), personal injury, promissory estoppel, public policy
violation, retaliatory discharge, safety violations, posting or records-

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related violations, wrongful discharge, or other federal, state or local
statutory or common law matters;
(v)    any discrimination based on age (including under the Age Discrimination
in Employment Act, the “ADEA”), benefit entitlement, citizenship, color,
concerted activity, disability, ethnicity, gender, genetic information,
immigration status, leave rights, military status, national origin, parental
status, protected off-duty conduct, race, religion, retaliation, sexual
orientation, union activity, veteran status, whistleblower activity (including
under the Sarbanes-Oxley, Dodd-Frank and False Claims Acts), other legally
protected status or activity, or any allegation that payment under this Release
was affected by any such discrimination;
(vi)    any participation in any class or collective action against the Company.
(b)    Notwithstanding the generality of the foregoing, Executive does not
release the following claims:
(i)    Claims that cannot be waived, such as for unemployment compensation or
any state disability insurance benefits pursuant to the terms of applicable
state law;
(ii)    Claims for workers’ compensation insurance benefits under the terms of
any worker’s compensation insurance policy or fund of the Company;
(iii)    Claims to continued participation in certain of the Company’s group
benefit plans pursuant to the terms and conditions of COBRA;
(iv)    Claims for any benefit entitlement vested as the date of Executive’s
employment termination, pursuant to written terms of any Company employee
benefit plan;
(v)    Claims for breach of the Separation Agreement entered into between the
Parties as of May ___, 2018 (the “Separation Agreement”); and
(vi)    Claims for indemnification under the Deed of Indemnification by and
between Prothena and Executive, the Company’s Bylaws, the Constitution of
Prothena Corporation plc (“Prothena”), California Labor Code Section 2802 or any
other applicable law.
(c)    Rights with Respect to Administrative Agencies. Neither the release
section(s) above nor anything else in this Release limit Executive’s rights to
file a charge with any administrative agency, such as the U.S. Equal Employment
Opportunity Commission (the “EEOC”) or a state fair employment practices agency,
communicate directly with or provide information to an agency, or otherwise
participate in an agency investigation or other administrative proceeding.
However, Executive does give up all rights to any money or other individual
relief based on any agency or judicial decision, including class or collective
action rulings; provided, however, that Executive may receive money properly
awarded to Executive

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by the U.S. Securities and Exchange Commission as a reward for providing
information to that agency.
(d)    Whistleblower Protection; Trade Secrets. For the avoidance of doubt,
nothing in this Release will be construed to prohibit Executive from filing a
charge with, reporting possible violations to, or participating or cooperating
with any governmental agency or entity, including but not limited to the EEOC,
the U.S. Department of Justice, the U.S. Securities and Exchange Commission, the
U.S. Congress, or any federal agency Inspector General, or making other
disclosures that are protected under the whistleblower, anti-discrimination, or
anti-retaliation provisions of federal, state or local law or regulation;
provided, however, that Executive may not disclose information of the Company or
Prothena that is protected by the attorney-client privilege, except as otherwise
required by law. Executive does not need the prior authorization of the Company
to make any such reports or disclosures, and Executive is not required to notify
the Company that Executive has made such reports or disclosures. Furthermore, in
accordance with 18 U.S.C. § 1833, notwithstanding anything to the contrary in
this Release: (i) Executive shall not be in breach of this Release, and shall
not be held criminally or civilly liable under any federal or state trade secret
law (x) for the disclosure of a trade secret that is made in confidence to a
federal, state, or local government official or to an attorney solely for the
purpose of reporting or investigating a suspected violation of law, or (y) for
the disclosure of a trade secret that is made in a complaint or other document
filed in a lawsuit or other proceeding, if such filing is made under seal; and
(ii) if Executive files a lawsuit for retaliation by the Company for reporting a
suspected violation of law, Executive may disclose the trade secret to
Executive’s attorney, and may use the trade secret information in the court
proceeding, if Executive files any document containing the trade secret under
seal, and does not disclose the trade secret, except pursuant to court order.
(e)    Acknowledgement. In accordance with the Older Workers Benefit Protection
Act of 1990, Executive has been advised of the following:
(i)    Executive should consult with an attorney before signing this Release;
(ii)    Executive received a list of group program eligibility factors,
selection criteria and time limits, as well as job titles and ages of all
eligible/selected employees and non-eligible/non-selected employees in the same
job classification or organizational unit;
(iii)    Executive has been given at least forty-five (45) days to consider this
Release and Executive must sign and return this Release to the Company within
that time period if Executive wants to receive the payments or benefits provide
for in this Release; and
(iv)    Executive has seven (7) days after signing this Release to revoke it,
and Executive will not receive the severance benefits provided by Section 3 of
the Separation Agreement unless and until such seven (7) day period has expired.
If Executive wishes to revoke this Release, Executive must deliver notice of
Executive’s revocation in writing, no later than 5:00 p.m. Pacific Time on the
7th day following Executive’s execution of this Release to Kevin Hickey, the
Company’s Vice President, Human Resources, in person or by fax to (650)
745-2698.

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(f)    EXECUTIVE ACKNOWLEDGES THAT EXECUTIVE HAS BEEN ADVISED OF AND IS FAMILIAR
WITH THE PROVISIONS OF CALIFORNIA CIVIL CODE SECTION 1542, WHICH PROVIDES AS
FOLLOWS:
“A GENERAL RELEASE DOES NOT EXTEND TO CLAIMS WHICH THE CREDITOR DOES NOT KNOW OR
SUSPECT TO EXIST IN HIS OR HER FAVOR AT THE TIME OF EXECUTING THE RELEASE,
WHICH, IF KNOWN BY HIM OR HER, MUST HAVE MATERIALLY AFFECTED HIS OR HER
SETTLEMENT WITH THE DEBTOR.”
BEING AWARE OF SAID CODE SECTION, EXECUTIVE HEREBY EXPRESSLY WAIVES ANY RIGHTS
EXECUTIVE MAY HAVE THEREUNDER, AS WELL AS UNDER ANY OTHER STATUTES OR COMMON LAW
PRINCIPLES OF SIMILAR EFFECT.
1.    Promise Not To Sue. A “promise not to sue” means Executive promises not to
sue any Releasee in court. This is different from the release in Section 1. In
addition to releasing claims covered by that release, Executive agrees never to
sue any Releasee for any reason covered by that release; provided, however, that
Executive may file a suit to enforce this Release or to challenge its validity
under the ADEA. If Executive sues a Releasee in violation of this Release
Executive will be required to pay that Releasee’s attorneys’ fees and other
litigation costs incurred in defending against Executive’s suit, or
alternatively the Company can require Executive to return all but $1,000 of the
payments and benefits provided to Executive under this Release; in addition, the
Company will be excused from any remaining obligations that exist solely because
of this Release. This Section 2 shall not affect the validity of this Release
and any payment provided for in this Section 2 shall not be deemed to be a
penalty or forfeiture.
2.    Executive Representations. Executive represents and warrants that:
(a)    Executive has returned to the Company all Company property in Executive’s
possession;
(b)    Executive is not owed wages, commissions, bonuses or other compensation,
other than any payments that become due under Section 3 of the Separation
Agreement;
(c)    During the course of Executive’s employment Executive did not sustain any
injuries for which Executive might be entitled to compensation pursuant to
worker’s compensation law or Executive has disclosed any injuries of which he is
currently, reasonably aware for which he might be entitled to compensation
pursuant to worker’s compensation law;
(d)    From the date Executive executed the Separation Agreement through the
date Executive executes this Release, Executive has not made any disparaging
comments about the Company, nor will Executive do so in the future; and
(e)    Executive has not initiated any adversarial proceedings of any kind
against the Company or against any other person or entity released herein, nor
will Executive do so in the future, except as specifically allowed by this
Release.

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3.    Maintaining Confidential Information. Executive reaffirms his obligations
under the Employee Proprietary Information and Invention Assignment Agreement
between Executive and the Company (the “Confidentiality Agreement”). Executive
acknowledges and agrees that the payments provided in Section 3 of the
Separation Agreement shall be subject to Executive’s continued compliance with
Executive’s obligations under the Confidentiality Agreement.
4.    Cooperation with the Company. Executive reaffirms his obligations to
cooperate with the Company pursuant to Section 11 of the Separation Agreement.
5.    Severability. The provisions of this Release are severable. If any
provision is held to be invalid or unenforceable, it shall not affect the
validity or enforceability of any other provision.
6.    Governing Law. This Release shall be construed and enforced in accordance
with, and the rights of the parties shall be governed by, the laws of the State
of California or, where applicable, United States federal law, in each case,
without regard to any conflicts of laws provisions or those of any state other
than California.
7.    Miscellaneous. This Release and the Separation Agreement contain the
Parties’ entire agreement with regard to the separation of Executive’s
employment, and supersede and replace any prior agreements as to those matters,
whether oral or written, including without limitation, the Company’s Amended and
Restated Severance Plan. Executive acknowledges and agrees that there are no
other agreements, written, oral or implied, and that Executive may not rely on
any prior negotiations, discussions, representations or agreements. This Release
may be modified only in writing, and such writing must be signed by both parties
and recited that it is intended to modify this Release. This Release may be
executed in separate counterparts, each of which is deemed to be an original and
all of which taken together constitute one and the same agreement.
IN WITNESS WHEREOF, the undersigned have caused this Release to be duly executed
and delivered as of the date indicated next to their respective signatures
below.

__________________________________            ___________________________
Tara Nickerson                            Date

PROTHENA BIOSCIENCES INC                

By: _______________________________            ___________________________
Name: A. W. Homan                        Date
Title: Secretary

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