Option Award Agreement, dated March 2, 2020, between Prothena Corporation plc and Brandon S. Smith under the Prothena Corporation plc 2020 Employment Inducement Incentive Plan

You acknowledge that the Plan and any Awards granted thereunder are intended to conform with the requirements of the rules promulgated by The Nasdaq Stock Market, including without limitation, Nasdaq Listing Rule 5635(c)(4). Accordingly, you acknowledge that you have not been previously employed in any capacity by the Company or any Subsidiary, or if previously employed, are commencing employment following a bona-fide period of non-employment with the Company and its Subsidiaries, and that the grant of this Option is an inducement material to your agreement to enter into employment with the Company or a Subsidiary.

This Option is intended to be a Nonqualified Stock Option and not an Incentive Stock Option (ISO), and will be interpreted accordingly.

Your right to exercise this Option vests in increments over the four-year (4-year) period, commencing on the Vesting Start Date, as shown on the cover sheet. The percentage of the total number of Shares for which this Option will vest and become exercisable is as follows:

•    25% on the first anniversary of the Vesting Start Date, and

•    1/36 of the remaining grant will vest on each monthly anniversary thereafter for 36 months

The vesting will be cumulative and will not exceed 100% of the Shares subject to the Option. If the vesting results in fractional Shares, the number of Shares that vests on the relevant vesting date will be rounded down to the nearest whole number.

Except as otherwise provided in the Plan, the entire Option vests and becomes exercisable if (i) within twenty-four (24) months following a Change in Control, your employment with the Company or one of its Subsidiaries is terminated for any reason other than Cause (as defined below) or you resign for Good Reason (as defined below) (such a resignation or termination being hereinafter referred to as an “Involuntary Termination”); (ii) you die while you are still an employee of the Company or a Subsidiary, as applicable; or (iii) your service as an employee of the Company or a Subsidiary, as applicable, terminates because of your Total and Permanent Disability (as defined below). In addition, except as otherwise provided above or in the Plan, the number of Shares subject to the Option that would have vested and become exercisable had you remained employed for the twelve-month (12) period following an Involuntary Termination shall become vested and exercisable as of the date of your Involuntary Termination.

As used herein, and except as otherwise defined in an employment agreement between you and the Company or one of its Subsidiaries to the extent applicable, “Cause” shall mean any of the following: (a) your willful breach, habitual neglect, or poor performance of your job duties and responsibilities, as determined by the Company in its sole discretion; (b) your conviction (or the entry of a guilty plea or plea of nolo contendre) of any crime, excluding minor traffic offenses; (c) your commission of an act of dishonesty or breach of fiduciary duty; (d) your commission of a material violation of any of the personnel policies of the Company or a Subsidiary, as applicable, including but not limited to, violations of the Company’s confidentiality or stock trading policies or its policies against any form of harassment; or (e) any action or omission by you, which, as reasonably determined by the Company, is contrary to the business interest, reputation or goodwill of the Company or a Subsidiary.

As used herein, and except as otherwise defined in an employment agreement between you and the Company or one of its Subsidiaries to the extent applicable, “Good Reason” means (a) a material diminution in your authority, duties or responsibilities or a material diminution in your total base compensation (in each case, as determined by the Company in its sole discretion), or (b) that your primary job site is relocated and your new location increases your commute between home and work by at least thirty (30) miles (however, this does not apply to field-based sales representatives or similar field-based positions) or in the Company’s reasonable opinion, the new location requires that you move your home to a new location at least thirty (30) miles away from your home immediately prior to the change.

In order to receive the benefits of a resignation for “Good Reason”, you must provide your employer with written notice within ninety (90) days after the occurrence of such event and the employer shall then have thirty (30) days to cure such event. If the employer does not cure the event giving rise to Good Reason, your employment will terminate on the first day immediately following the end of thirty (30) day cure period.

Except as provided above or as otherwise provided in a written employment agreement between you and the Company or one of its Subsidiaries, all Shares will cease vesting as of the date your service with the Company or a Subsidiary, as applicable, has terminated for any reason.

Your Option will expire in any event at the close of business at the Company’s registered office on the tenth anniversary of the Grant Date, as shown on the cover sheet. (It will expire earlier if your service with the Company or a Subsidiary, as applicable, terminates – as described below.)

If you die prior to expiration of this Option, then your right to purchase vested Shares under this Option will expire at the close of business at the Company’s registered office on the date that is twelve (12) months after the date of death (or on the tenth anniversary of the Grant Date, if earlier). During that twelve-month (12) period, your estate or heirs may exercise this Option.

If your service as an employee of the Company or a Subsidiary, as applicable, terminates because of your Total and Permanent Disability, then your right to purchase vested Shares under this Option will expire at the close of business at the Company’s registered office on the date that is twelve (12) months after your termination date (or on the tenth anniversary of the Grant Date, if earlier). “Total and Permanent Disability” means that you are unable to engage in any substantial gainful activity by reason of any medically determinable physical or mental impairment which can be expected to result in death or which has lasted, or can be expected to last, for a continuous period of not less than one year.

If your service as an employee of the Company or a Subsidiary, as applicable, terminates by reason of an Involuntary Termination, then your right to purchase vested Shares under this Option will expire at the close of business at the Company’s registered office on the date that is twelve (12) months after your termination date (or on the tenth anniversary of the Grant Date, if earlier).

If your service as an employee of the Company or a Subsidiary, as applicable, terminates for any reason other than those set forth in the immediately preceding three paragraphs, then your right to purchase vested Shares under this Option will expire at the close of business at the Company’s registered office on the 90th day after your termination date (or on the tenth anniversary of the Grant Date, if earlier).

The Company determines when your service with the Company or a Subsidiary, as applicable, terminates for this purpose.

For purposes of this Option, your service does not terminate when you go on a military leave, a sick leave or another bona fide leave of absence, if the leave was approved by the Company in writing. But your service will be treated as terminating ninety (90) days after you went on leave, unless your right to return to active work is guaranteed by law or by a contract. Your service terminates, in any event, when the approved leave ends, unless you immediately return to active work.

The Company determines which leaves count for this purpose.

The Company will not permit you to exercise this Option if the issuance of Shares at that time would violate any law, regulation or Company policy.

When you wish to exercise this Option, you must complete and execute such documents, if any, and complete such processes, that the Company or a securities broker approved by the Company may require to accomplish the Option exercise (“Notice of Exercise”).

If someone else wants to exercise this Option after your death, that person must prove to the Company’s satisfaction that he or she is entitled to do so.

When you submit your Notice of Exercise, you must include payment of the exercise price for the Shares you are purchasing. Payment may be made in one (or a combination of both) of the following forms:

•    Your personal check, a cashier’s check or a money order.

•    Irrevocable directions to a securities broker approved by the Company to sell your Shares subject to the Option and to deliver all or a portion of the sale proceeds to the Company in payment of the exercise price. (The balance of the sale proceeds, if any, less withholding taxes, will be delivered to you.) The directions must be given by signing forms, if any, provided by the Company or the securities broker.

With the consent of the Administrator, payment may also be made by any other method set forth in Section 6.5 of the Plan.

You will not be allowed to exercise this Option unless you make acceptable arrangements to pay any taxes that may be due as a result of the Option exercise.

By signing this Agreement, you agree not to sell any Shares received upon exercise of the Option at a time when applicable laws, regulations or Company policies prohibit a sale.

Prior to your death, only you may exercise this Option. You cannot transfer or assign this Option. For instance, you may not sell this Option or use it as security for a loan. If you attempt to do any of these things, this Option will immediately become invalid. You may, however, dispose of this Option in your will.

Regardless of any marital property settlement agreement, the Company or a securities broker, as applicable, is not obligated to honor a Notice of Exercise from your former spouse, nor is the Company or the securities broker obligated to recognize your former spouse’s interest in your Option in any other way.

Neither your Option nor this Agreement gives you the right to be retained by the Company or any Subsidiary in any capacity. The Company and its Subsidiaries reserve the right to terminate your service at any time, with or without Cause.

You, or your estate or heirs, have no rights as a shareholder of the Company with respect to any Shares subject to the Option until a proper Notice of Exercise has been submitted, the exercise price has been tendered and you, or your estate or heirs, become a holder of such Shares. No adjustments are made for dividends or other rights if the applicable record date occurs before a proper Notice of Exercise has been submitted and the exercise price has been tendered, except as described in the Plan.

In the event of a stock split, a stock dividend or a similar change in Company stock, the number of Shares covered by this Option and the exercise price per Share may be adjusted pursuant to the Plan. In the event where the Company is a party to a merger, this Option will be handled in accordance with the Plan.

You agree to contract electronically regarding your participation in the Plan and to the receipt of electronic notifications, documents, payments or other communications from the Company in connection with the Plan, to the normal electronic mail address used by you for the purposes of your employment or such other address as may be from time to time notified for that purpose by you to the Company.

All the terms and provisions of this Agreement are distinct and severable, and if any term or provision is held unenforceable, illegal or void in whole or in part by any court, regulatory authority or other competent authority it shall to that extent be deemed not to form part of this Agreement, and the enforceability, legality and validity of the remainder of this Agreement will not be affected; if any invalid, unenforceable or illegal provision would be valid, enforceable or legal if some part of it were deleted, the provision shall apply with whatever modification is necessary to make it valid, enforceable and legal.

This Agreement will be interpreted and enforced under the laws of Ireland.

The text of the Plan and any amendments thereto are incorporated in this Agreement by reference.

This Agreement and the Plan constitute the entire understanding between you and the Company regarding this Option. Any prior agreements, commitments or negotiations concerning this Option are superseded.