Document:

EX-10.72

 Exhibit 10.72 

EXECUTIVE EMPLOYMENT 

AGREEMENT BY AND BETWEEN 

HORIZON PHARMA, INC., HORIZON PHARMA USA, INC. AND 

DAVID A. HAPPEL 
 This
Executive Employment Agreement (hereinafter referred to as the “Agreement”), is entered into by and between Horizon Pharma, Inc., a Delaware corporation, and its wholly owned subsidiary, Horizon Pharma USA, Inc., a Delaware
corporation, each having a principal place of business at 150 S. Saunders Road, Lake Forest, IL 60045 (hereinafter referred to together as the “Company”) and David A. Happel (hereinafter referred as to the
“Executive”). The terms of this Agreement shall be effective commencing October 25, 2016 (the “Effective Date”). 

RECITALS 
 WHEREAS,
the Executive previously entered into an amended and restated employment agreement with Raptor Pharmaceuticals Corp. (“Raptor”) on October 13, 2014 and a Change in Control Severance Agreement with Raptor dated March 8, 2016
(together, the “Prior Agreement”); 
 WHEREAS, the Company’s parent entity, Horizon Pharma Public
Limited Company (“Horizon plc”) acquired Raptor on October 25, 2016, and Raptor became a wholly owned subsidiary of Horizon plc; 

WHEREAS, the Company desires assurance of the continued association and services of the Executive in order to continue to retain the
Executive’s experience, skills, abilities, background and knowledge, and is willing to continue to engage the Executive’s services on the terms and conditions set forth in this Agreement, which as of the Effective Date shall replace
supersede in its entirety the terms of the Prior Agreement; and 
 WHEREAS, Executive desires to be in the employ of the Company, and
is willing to accept such employment on the terms and conditions set forth in this Agreement and the letter agreement by and between the Executive and Raptor dated October 13, 2016 (the “Transition Services Agreement”) the
terms of which will continue in full force and effect following the Effective Date. 
 WHEREAS, nothing herein is intended to alter
Executive’s right to receive the retention bonus amount of $196,219 that was approved for Executive by Raptor’s compensation committee in September 2016. 

AGREEMENT 
  

	1.	Employment. 

 1.1 Term. Executive’s employment will be transferred from
Raptor to the Company as of the Effective Date. The Company hereby agrees to employ the Executive, and the Executive hereby accepts employment by the Company, upon the terms and conditions set forth in this Agreement. Executive’s employment
shall be 

 
governed under the terms set forth in this Agreement beginning on the Effective Date and shall continue until it is terminated pursuant to Section 4 herein (hereinafter referred to as the
“Term”). 
 1.2 Title. From and after the Effective Date the Executive will have the title of Executive Vice
President, Global Orphan Business (such position held by Executive during such period is hereinafter referred to as “EVP GOB”) and Executive shall continue to serve in such other capacity or capacities commensurate
with his position as EVP GOB as the President and CEO of the Company may from time to time prescribe. 
 1.3 Duties. The Executive
shall do and perform all services, acts or things necessary or advisable to manage and conduct the business of the Company and shall have the authority and responsibilities which are generally associated with the position of EVP GOB including being
responsible for the Company’s international operations and the U.S. orphan business unit. The Executive shall report to the President and CEO. 

1.4 Policies and Practices. The employment relationship between the parties shall be governed by this Agreement and the policies and
practices established by the Company and the Board of Directors (hereinafter referred to as the “Board”). In the event that the terms of this Agreement differ from or are in conflict with the Company’s policies or
practices or the Company’s Employee Handbook, this Agreement shall control. 
 1.5 Location. The Executive shall perform the
services the Executive is required to perform pursuant to this Agreement in Novato California. The Company may from time to time require the Executive to travel temporarily to other locations outside of the Novato California area in connection with
the Company’s business. 
  

	2.	Loyalty of Executive. 

 2.1 Loyalty. During the Executive’s employment by the
Company, the Executive shall devote the Executive’s business energies, interest, abilities and productive time to the proper and efficient performance of Executive’s duties under this Agreement. Subject to the prior written consent of the
President and CEO, the Executive is permitted to serve on the board of directors of one other company, so long as the other company does not compete with the Company. 

2.2 Exclusive Employment. Except with the prior written consent of the Chief Executive Officer, Executive shall not, during the term of
this Agreement, undertake or engage in any other employment, occupation or business enterprise, other than ones in which Executive is a passive investor. Executive may engage in any civic and not-for-profit activities so long as such activities do not materially interfere with the performance of his duties hereunder or present a conflict of interest with the Company. 

2.3 Agreement not to Participate in Company’s Competitors. During the Term of this Agreement, the Executive agrees not to acquire,
assume or participate in, directly or indirectly, any position, investment or interest known by Executive to be adverse or antagonistic to the Company, its business or prospects, financial or otherwise or in any company, person or entity that is,
directly or indirectly, in competition with the business of the Company or any of its affiliates. Notwithstanding the foregoing, 

 
Executive may invest and/or maintain investments in any public or private entity up to an amount of 2% of an entity’s fully diluted shares and on a passive basis. 

 

	3.	Compensation to Executive. 

 3.1 Base Salary. The Company shall pay the Executive
a base salary at the initial annualized rate of five hundred thousand dollars ($500,000) per year, subject to standard deductions and withholdings, or such higher rate as may be determined from time to time by the Board or the compensation committee
thereof (hereinafter referred to as the “Base Salary”). Such Base Salary shall be paid in accordance with the Company’s standard payroll practice. Payments of salary installments shall be made no less frequently than
once per month. Executive’s Base Salary will be reviewed annually each December and Executive shall be eligible to receive a salary increase (but not decrease) annually in an amount to be determined by the Board or the compensation committee
thereof in its sole and exclusive discretion. Once increased, the new salary shall become the Base Salary for purposes of this Agreement and shall not be reduced without the Executive’s written consent. Any material reduction in the Base Salary
of the Executive, without his written consent, may be deemed Good Reason as set forth in and subject to Section 4.5.2 of this Agreement. 

3.2 Discretionary Bonus. Executive’s eligibility to receive a bonus for the 2016 calendar year will be governed by the terms of
Transition Services Agreement. Provided the Executive meets the conditions stated in this Section 3.2, commencing with the 2017 calendar year the Executive shall be eligible for an annual discretionary bonus (hereinafter referred to as the
“Bonus”) with a target amount of fifty percent (50%) of the Executive’s Base Salary, subject to standard deductions and withholdings, based on the Board’s determination, in good faith, and based upon the
Executive’s individual achievement and company performance objectives as set by the Board or the compensation committee thereof, of whether the Executive has met such performance milestones as are established for the Executive by the Board or
the compensation committee thereof, in good faith, in consultation with the Executive (hereinafter referred to as the “Performance Milestones”). The Performance Milestones will be based on certain factors including, but not
limited to, the Executive’s performance and the Company’s financial performance. The Executive’s Bonus target will be reviewed annually and may be adjusted by the Board or the compensation committee thereof in its discretion, provided
however, that the Bonus target may only be materially reduced upon Executive’s written consent. The Executive must be employed on the date the Bonus is awarded to be eligible for the Bonus, subject to the termination provisions thereof. The
Bonus shall be paid during the calendar year following the performance calendar year. 
 3.3 Horizon Retention Agreement.
Concurrently with the execution of this Agreement, the Executive shall execute the Retention Agreement, a copy of which is attached as Exhibit D (the “Horizon Retention Agreement”). Subject to Executive’s timely
acceptance and execution of this Agreement and the Horizon Retention Agreement, Executive will be eligible to earn a retention bonus on the terms and conditions set forth in the Horizon Retention Agreement. 

 3.4 Equity Awards. 

3.4.1 Equity Grants. Subject to Executive’s timely acceptance and execution of this Agreement, on the Effective Date the Executive
was granted the following equity awards pursuant to and subject to the terms of the Horizon Pharma Public Limited Company 2014 Equity Incentive Plan (“2014 Equity Incentive Plan”) and its form of stock option and restricted
stock unit award agreements, in the forms provided to Executive concurrently with this Agreement (collectively the “Equity Plan Documents”) and compliance with applicable securities laws: 

(i) Option. A stock option to purchase up to 50,674 ordinary shares of Horizon plc (the “Option”). The Option
has an exercise price equal to the fair market value of Horizon plc’s ordinary shares on the applicable date of grant, which is October 25, 2016. The Option will be an incentive stock option to the maximum extent permitted by applicable tax
laws. Any portion of the Option that does not qualify as an incentive stock option will be a nonstatutory stock option. Subject to Executive’s continued provision of services to the Company through the applicable vesting dates, the Option shall
vest as follows: 25% of the total number of shares subject to the Option shall vest on the first anniversary of the date of grant (the “Vesting Commencement Date”) and 1/36 of the remaining number of shares subject to the
Option shall vest on each monthly anniversary thereafter so that the Option would fully vest on the four (4) year anniversary of the Vesting Commencement Date subject to Executive’s continued services with the Company through such date.

 (ii) Restricted Stock Unit Award. A restricted stock unit award in respect of 31,813 ordinary shares of Horizon plc (the
“RSU Award”). Subject to Executive’s continued provision of services to the Company through the applicable vesting dates, the RSU Award shall vest as follows: 25% of the total number of units subject to the RSU Award
shall vest on the first anniversary of the Vesting Commencement Date, and thereafter 25% of the total number of units subject to the RSU Award shall vest on each anniversary thereafter, so that the RSU Award would fully vest on the fourth
anniversary of the Vesting Commencement Date, subject to Executive’s continued services with the Company through such date. 
 3.4.2
Legal Review. Upon the Executive’s submission of appropriate itemized proof and verification of reasonable and customary legal fees incurred by the Executive in obtaining legal advice associated with the review, preparation, approval, and
execution of this Agreement, the Company shall pay for up to $10,000.00 of such legal fees subject to receipt of appropriate proof and verification of such legal fees no later than sixty (60) days of receipt of an invoice for legal services
from the Executive and/or his attorneys. To be eligible for reimbursement, the invoice must be submitted no later than ninety (90) days after the legal fees are incurred. 

3.5 Changes to Compensation. The Executive’s compensation may be changed from time to time by mutual agreement of the Executive
and the Company. In the event that the Executive’s base salary is materially decreased without his written consent, said decrease will be Good Reason for the Executive to terminate the Agreement as set forth in and subject to Section 4.5.2
of this Agreement. 
 3.6 Taxes. All amounts paid under this Agreement to the Executive by the Company will be paid less applicable
tax withholdings and any other withholdings required by law or authorized by the Executive. 

 3.7 Benefits. The Executive shall, in accordance with Company policy and the terms of the
applicable plan documents, be eligible to participate in benefits under any executive benefit plan or arrangement which may be in effect from time to time and made available to the Company’s executives or key management employees, provided,
however, that the Executive shall be entitled to at least four (4) weeks of paid vacation annually. 
  

	4.	Termination. 

 4.1 Termination by the Company. The Executive’s
employment with the Company may be terminated only under the following conditions: 
 4.1.1 Termination for Death or Disability. The
Executive’s employment with the Company shall terminate effective upon the date of the Executive’s death or “Complete Disability” (as defined in Section 4.5.1), provided, however, that this Section 4.1.1 shall in no way
limit the Company’s obligations to provide such reasonable accommodations to the Executive and/or his heirs as may be required by law. 

4.1.2 Termination by the Company For Cause. The Company may terminate the Executive’s employment under this Agreement for
“Cause” (as defined in Section 4.5.3) by delivery of written notice to the Executive specifying the Cause or Causes relied upon for such termination, provided that such notice is delivered within two (2) months following the
occurrence or discovery of any event or events constituting “Cause”. Any notice of termination given pursuant to this Section 4.1.2 shall effect termination as of the date of the notice or such date as specified in the notice. The
Executive shall have the right to appear before the CEO before any termination for Cause becomes effective and binding upon the Executive. 

4.1.3 Termination by the Company Without Cause. The Company may terminate the Executive’s employment under this Agreement at any
time and for any reason or no reason subject to the requirements set out in Section 4.4 of this Agreement. Such termination shall be effective on the date the Executive is so informed or as otherwise specified by the Company, pursuant to notice
requirements set forth in Section 6 of this Agreement. 
 4.2 Termination By The Executive. The Executive may terminate his
employment with the Company at any time and for any reason or no reason, including, but not limited, to the following conditions: 

4.2.1 Good Reason. The Executive may terminate his employment under this Agreement for “Good Reason” (as defined below in
Section 4.5.2) by delivery of written notice to the Company specifying the Good Reason relied upon by the Executive for such termination in accordance with the requirements of such section. 

4.2.2 Without Good Reason. The Executive may terminate the Executive’s employment hereunder for other than Good Reason upon thirty
(30) days written notice to the Company. 

 4.3 Termination by Mutual Agreement of the Parties. The Executive’s employment
pursuant to this Agreement may be terminated at any time upon a mutual agreement in writing of the parties. Any such termination of employment shall have the consequences specified in such mutual agreement. 

4.4 Compensation to Executive Upon Termination. In connection with any termination of the Executive’s employment for any reason,
the Executive or the Executive’s estate, as applicable, shall be entitled to any amounts payable to the Executive or the Executive’s beneficiaries subject to and accordance with the terms of the Company’s employee welfare benefit
plans or policies (excluding any severance pay). 
 4.4.1 Death or Complete Disability. If the Executive’s employment shall be
terminated by death or Complete Disability as provided in Section 4.1.1, the Company shall pay to Executive, and/or Executive’s heirs, all earned but unpaid Base Salary, any earned but unpaid discretionary bonuses for any prior period at
such time as bonuses would have been paid if the Executive remained employed, all accrued but unpaid business expenses, and all accrued but unused vacation time earned through the date of termination at the rate in effect at the time of termination
(hereinafter referred to as the “Accrued Amounts”), less standard deductions and withholdings. The Executive shall also be eligible to receive a pro-rated bonus for the year of
termination, as determined by the Board or the Compensation Committee of the Board based on actual performance and the period of the year he was employed (hereinafter referred to as the “Pro-rata
Bonus”), less standard deductions and withholdings, to be paid as a lump sum within thirty (30) days after the date of termination. 

4.4.2 With Cause or Without Good Reason. If the Executive’s employment shall be terminated by the Company for Cause, or if the
Executive terminates employment hereunder without Good Reason, the Company shall pay the Executive’s Base Salary, accrued but unpaid business expenses and accrued and unused vacation benefits earned through the date of termination at the rate
in effect at the time of termination, less standard deductions and withholdings. 
 4.4.3 Without Cause or For Good Reason. 

(i) Not in Connection With a Change in Control. If the Company terminates the Executive’s employment without Cause or the
Executive terminates his employment for Good Reason, and Section 4.4.3(ii) below does not apply, the Company shall pay the Accrued Amounts subject to standard deductions and withholdings, to be paid as a lump sum no later than thirty (30) days
after the date of termination. In addition, subject to the limitations stated in this Agreement and upon the Executive’s furnishing to the Company an executed waiver and release of claims (the form of which is attached hereto as Exhibit A) (the
“Release”) within the applicable time period set forth therein, but in no event later than forty-five days following termination of employment and permitting such Release to become effective in accordance with its terms (the
“Release Effective Date”), and subject to Executive entering into no later than the Release Effective Date a non-competition agreement to be effective during the 

 Severance Period (as defined below), substantially similar to Section 2.3, and continuing to
abide by its terms during the Severance Period, the Executive shall be entitled to: 
 (a) the equivalent of the Executive’s
Base Salary in effect at the time of termination will continue to be paid for a period of twelve (12) months following the date of termination (hereinafter referred to as the “Severance Period”), less standard deductions
and withholdings, to be paid during the Severance Period according to the Company’s regular payroll practices, subject to any delay in payment required by Section 4.6 in connection with the Release Effective Date; and 

(b) in the event the Executive timely elects continued coverage under COBRA, the Company will continue to pay the same portion of
Executive’s COBRA health insurance premium as the percentage of health insurance premiums that it paid during the Executive’s employment, including any amounts that Company paid for benefits to the qualifying family members of the
Executive, following the date of termination up until the earlier of either (i) the last day of the Severance Period or, (ii) the date on which the Executive begins full-time employment with another company or business entity which offers
comparable health insurance coverage to the Executive (such period, the “COBRA Payment Period”). Notwithstanding the foregoing, if the Company determines, in its sole discretion, that the Company cannot provide the COBRA
premium benefits without potentially incurring financial costs or penalties under applicable law (including, without limitation, Section 2716 of the Public Health Service Act), the Company shall in lieu thereof pay Executive a taxable cash
amount, which payment shall be made regardless of whether the Executive or his qualifying family members elect COBRA continuation coverage (the “Health Care Benefit Payment”). The Health Care Benefit Payment shall be paid in
monthly or bi-weekly installments on the same schedule that the COBRA premiums would otherwise have been paid to the insurer. The Health Care Benefit Payment shall be equal to the amount that the Company
otherwise would have paid for COBRA insurance premiums (which amount shall be calculated based on the premium for the first month of coverage), and shall be paid until the expiration of the COBRA Payment Period. 

(ii) In Connection With a Change in Control. If the Company (or its successor) terminates the Executive’s employment without
Cause or the Executive terminates his employment for Good Reason within the period commencing ninety (90) days immediately prior to a Change in Control of the Company and ending eighteen (18) months immediately following a Change in
Control of the Company (as defined in Section 4.5.4 of this Agreement), the Executive shall receive the Accrued Amounts subject to standard deductions and withholdings, to be paid as a lump sum no later than thirty (30) days after the date
of termination. In addition, subject to the limitations stated in this Agreement and upon the Executive’s furnishing to the Company (or its successor) an executed Release within the applicable time period set forth therein, but in no event
later than forty-five days following termination of employment and permitting such Release to become effective in accordance with its terms, and subject to Executive entering into no later than the Release Effective Date a non-competition agreement to be effective during the Severance Period, substantially similar to Section 2.3, and continuing to abide by its terms during the Severance Period, then in lieu of (and not additional
to) the benefits provided pursuant to Section 4.4.3(i) above, the 

 
Executive shall be entitled to: 
 (a) the equivalent of the Executive’s
Base Salary in effect at the time of termination will continue to be paid during the Severance Period, less standard deductions and withholdings, to be paid during the Severance Period according to the Company’s regular payroll practices,
subject to any delay in payment required by Section 4.6 in connection with the Release Effective Date; 
 (b) Executive’s
target Bonus in effect at the time of termination, or if none, the last target Bonus in effect for Executive, less standard deductions and withholdings, to be paid in a lump sum within ten (10) days following the later of (i) the Release
Effective Date, or (ii) the effective date of the Change in Control; and 
 (c) in the event the Executive timely elects
continued coverage under COBRA, the Company will continue to pay the same portion of Executive’s COBRA health insurance premium as the percentage of health insurance premiums that it paid during the Executive’s employment, including any
amounts that Company paid for benefits to the qualifying family members of the Executive, following the date of termination until the expiration of the COBRA Payment Period. Notwithstanding the foregoing, if the Company determines, in its sole
discretion, that the Company cannot provide the COBRA premium benefits without potentially incurring financial costs or penalties under applicable law (including, without limitation, Section 2716 of the Public Health Service Act), the Company
shall in lieu thereof pay Executive the Health Care Benefit Payment, which payment shall be made regardless of whether the Executive or his qualifying family members elect COBRA continuation coverage. The Health Care Benefit Payment shall be paid in
monthly or bi-weekly installments on the same schedule that the COBRA premiums would otherwise have been paid to the insurer. The Health Care Benefit Payment shall be equal to the amount that the Company
otherwise would have paid for COBRA insurance premiums (which amount shall be calculated based on the premium for the first month of coverage), and shall be paid until the expiration of the COBRA Payment Period. 

(iii) No Duplication of Benefits. For the avoidance of doubt, in no event will Executive be entitled to benefits under Section
4.4.3(i) and Section 4.4.3(ii). If Executive commences to receive benefits under Section 4.4.3(i) due to a qualifying termination prior to a Change in Control and thereafter becomes entitled to benefits under Section 4.4.3(ii), any benefits
previously provided to Executive under Section 4.4.3(i) shall offset the benefits to be provided to Executive under Section 4.4.3(ii) and shall be deemed to have been provided to Executive pursuant to Section 4.4.3(ii). 

4.4.4 Equity Award Acceleration. 

(i) In Connection With a Change in Control. In the event that the Executive’s employment is terminated without Cause or for Good
Reason within the ninety (90) days immediately preceding or during the eighteen (18) months immediately following a Change in Control of the Company (as defined in Section 4.5.4 of this Agreement), the vesting of the Option, the RSU
Award and any other time-based vesting Company equity awards granted to Executive shall be fully accelerated such that 

 
on the effective date of such termination (or, if later, the date of the Change in Control) one hundred percent (100%) of the equity award shares granted to Executive prior to such termination
shall be fully vested and immediately exercisable, if applicable, by the Executive. 
 (ii) Release and Waiver. Any equity vesting
acceleration pursuant to this Section 4.4.4 shall be conditioned upon and subject to the Executive’s delivery to the Company of a fully effective Release in accordance with the terms specified by Section 4.4.3 hereof and such vesting
acceleration benefit shall be in addition to the benefits provided by Section 4.4.3 hereof. 
 4.5 Definitions. For purposes of
this Agreement, the following terms shall have the following meanings: 
 4.5.1 Complete Disability. “Complete
Disability” shall mean the inability of the Executive to perform the Executive’s duties under this Agreement, whether with or without reasonable accommodation, because the Executive has become permanently disabled within the
meaning of any policy of disability income insurance covering employees of the Company then in force. In the event the Company has no policy of disability income insurance covering employees of the Company in force when the Executive becomes
disabled, the term “Complete Disability” shall mean the inability of the Executive to perform the Executive’s duties under this Agreement, whether with or without reasonable accommodation, by reason of any incapacity, physical or
mental, which the Board, based upon medical advice or an opinion provided by a licensed physician, determines to have incapacitated the Executive from satisfactorily performing all of the Executive’s usual services for the Company, with or
without reasonable accommodation, for a period of at least one hundred eighty (180) days during any twelve (12) month period that need not be consecutive. 

4.5.2 Good Reason. “Good Reason” for the Executive to terminate the Executive’s employment hereunder shall
mean the occurrence of any of the following events without the Executive’s consent: 
 (i) a material reduction in the
Executive’s duties, authority, or responsibilities relative to the duties, authority, or responsibilities in effect immediately prior to such reduction, including by way of example, having the same title, duties, authority and responsibilities
at a subsidiary level following a Change in Control; 
 (ii) the relocation of the Executive’s primary work location to a point
more than fifty (50) miles from the Executive’s current work location set forth in Section 1.5 that requires a material increase in Executive’s one-way driving distance; 

(iii) a material reduction by the Company of the Executive’s base salary or annual target Bonus opportunity, without the written
consent of the Executive, as initially set forth herein or as the same may be increased from time to time pursuant to this Agreement; and 

(iv) a material breach by the Company of Section 1.2 of this Agreement. 

 Provided, however that, such termination by the Executive shall only be deemed for Good Reason pursuant to the
foregoing definition if (i) the Company is given written notice from the Executive within sixty (60) days following the first occurrence of the condition that he considers to constitute Good Reason describing the condition and the Company
fails to satisfactorily remedy such condition within thirty (30) days following such written notice, and (ii) the Executive terminates employment within thirty (30) days following the end of the period within which the Company was
entitled to remedy the condition constituting Good Reason but failed to do so. 
 4.5.3 Cause. “Cause” for
the Company to terminate Executive’s employment hereunder shall mean the occurrence of any of the following events, as determined reasonably and in good faith by the Board or a committee designated by the Board: 

(i) the Executive’s gross negligence or willful failure to substantially perform his duties and responsibilities to the Company
or willful and deliberate violation of a Company policy; 
 (ii) the Executive’s conviction of a felony or the Executive’s
commission of any act of fraud, embezzlement or dishonesty against the Company or involving moral turpitude that is likely to inflict or has inflicted material injury on the business of the Company, to be determined by the sole discretion of the
Company; 
 (iii) the Executive’s unauthorized use or disclosure of any proprietary information or trade secrets of the Company
or any other party that the Executive owes an obligation of nondisclosure as a result of the Executive’s relationship with the Company; and 

(iv) the Executive’s willful and deliberate breach of the obligations under this Agreement that causes material injury to the
business of the Company. 
 4.5.4 Change in Control. For purposes of this Agreement, “Change in Control”
means: (i) a sale of all or substantially all of the assets of the Company; (ii) a merger or consolidation in which the Company is not the surviving entity and in which the holders of the Company’s outstanding voting stock
immediately prior to such transaction own, immediately after such transaction, securities representing less than fifty percent (50%) of the voting power of the entity surviving such transaction or, where the surviving entity is a wholly-owned
subsidiary of another entity, the surviving entity’s parent; (iii) a reverse merger in which the Company is the surviving entity but the shares of Common Stock outstanding immediately preceding the merger are converted by virtue of the
merger into other property, whether in the form of securities of the surviving entity’s parent, cash or otherwise, and in which the holders of the Company’s outstanding voting stock immediately prior to such transaction own, immediately
after such transaction, securities representing less than fifty percent (50%) of the voting power of the Company or, where the Company is a wholly-owned subsidiary of another entity, the Company’s parent; or (iv) an acquisition by any
person, entity or group (excluding any employee benefit plan, or related trust, sponsored or maintained by the Company or subsidiary of the Company or other entity controlled by the Company) of the beneficial

 
ownership of securities of the Company representing at least seventy-five percent (75%) of the combined voting power entitled to vote in the election of Directors; provided, however, that nothing
in this paragraph shall apply to a sale of assets, merger or other transaction effected exclusively for the purpose of changing the domicile of the Company. 

4.6 Application of Internal Revenue Code Section 409A. Notwithstanding anything to the contrary set forth herein, any payments and
benefits provided under this Agreement (the “Severance Benefits”) that constitute “deferred compensation” within the meaning of Section 409A of the Internal Revenue Code of 1986, as amended (the
“Code”) and the regulations and other guidance thereunder and any state law of similar effect (collectively “Section 409A”) shall not commence in connection with Executive’s termination of
employment unless and until Executive has also incurred a “separation from service” (as such term is defined in Treasury Regulation Section 1.409A-1(h) (“Separation From
Service”), unless the Company reasonably determines that such amounts may be provided to Executive without causing Executive to incur the additional 20% tax under Section 409A. 

It is intended that each installment of the Severance Benefits payments provided for in this Agreement is a separate “payment” for
purposes of Treasury Regulation Section 1.409A-2(b)(2)(i). For the avoidance of doubt, it is intended that payments of the Severance Benefits set forth in this Agreement satisfy, to the greatest extent
possible, the exemptions from the application of Section 409A provided under Treasury Regulation Sections 1.409A-1(b)(4), 1.409A-1(b)(5) and 1.409A-1(b)(9). However, if the Company (or, if applicable, the successor entity thereto) determines that the Severance Benefits constitute “deferred compensation” under Section 409A and Executive is, on
the termination of service, a “specified employee” of the Company or any successor entity thereto, as such term is defined in Section 409A(a)(2)(B)(i) of the Code, then, solely to the extent necessary to avoid the incurrence of the adverse
personal tax consequences under Section 409A, the timing of the Severance Benefit payments shall be delayed until the earlier to occur of: (i) the date that is six months and one day after Executive’s Separation From Service, or
(ii) the date of Executive’s death (such applicable date, the “Specified Employee Initial Payment Date”), the Company (or the successor entity thereto, as applicable) shall (A) pay to Executive a lump sum
amount equal to the sum of the Severance Benefit payments that Executive would otherwise have received through the Specified Employee Initial Payment Date if the commencement of the payment of the Severance Benefits had not been so delayed pursuant
to this Section and (B) commence paying the balance of the Severance Benefits in accordance with the applicable payment schedules set forth in this Agreement. 

 Notwithstanding anything to the contrary set forth herein, Executive shall receive the Severance
Benefits described above, if and only if Executive duly executes and returns to the Company within the applicable time period set forth therein, but in no event more than forty-five days following Separation From Service, the Company’s standard
form of release of claims in favor of the Company (attached to this Agreement as Exhibit A) (the “Release”) and permits the release of claims contained therein to become effective in accordance with its terms (such latest
permitted date, the “Release Deadline”). If the severance benefits are not covered by one or more exemptions from the application of Section 409A and the Release could become effective in the calendar year
following the calendar year in which Executive separates from service, the Release will not be deemed effective any earlier than the Release Deadline. Notwithstanding any other payment schedule set forth in this Agreement, none of the Severance
Benefits will be paid or otherwise delivered prior to the effective date (or deemed effective date) of the Release. Except to the extent that payments may be delayed until the Specified Employee Initial Payment Date pursuant to the preceding
paragraph, on the first regular payroll pay day following the effective date of the Release, the Company will pay Executive the Severance Benefits Executive would otherwise have received under the Agreement on or prior to such date but for the delay
in payment related to the effectiveness of the Release, with the balance of the Severance Benefits being paid as originally scheduled. 

The severance benefits are intended to qualify for an exemption from application of Section 409A 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. 

4.7 Application of Internal Revenue Code Section 280G. If any payment or benefit Executive would receive pursuant to a Change in
Control from the Company or otherwise (“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 such 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 being subject to the Excise Tax or (y) the largest portion, up to and including the total, of the Payment, whichever amount, 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 Executive’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 payments or benefits constituting “parachute payments” is necessary so that the Payment equals the Reduced Amount, reduction shall occur in the manner that results
in the greatest economic benefit for Executive. If more than one method of reduction will result in the same economic benefit, the items so reduced will be reduced pro rata. 

In the event it is subsequently determined by the Internal Revenue Service that some portion of the Reduced Amount as determined pursuant to
clause (x) in the preceding paragraph is subject to the Excise Tax, Executive agrees to promptly return to 

 
the Company a sufficient amount of the Payment so that no portion of the Reduced Amount is subject to the Excise Tax. For the avoidance of doubt, if the Reduced Amount is determined pursuant to
clause (y) in the preceding paragraph, Executive will have no obligation to return any portion of the Payment pursuant to the preceding sentence. 

Unless Executive 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 in Control 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 in Control, 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 Executive and the Company within fifteen (15) calendar days after the date on which Executive’s right to a Payment is triggered (if
requested at that time by Executive or the Company) or such other time as requested by Executive or the Company. 
 4.8 Indemnification
Agreements. Concurrently with the execution of this Agreement, the Company and the Executive shall enter into indemnification agreements, copies of which are attached hereto as Exhibit B-1 and Exhibit B-2. 
 4.9 Confidential Information and Invention Assignment Agreement. Concurrently with the
execution of this Agreement, the Executive shall execute the Company’s Confidential Information and Invention Assignment Agreement, a copy of which is attached as Exhibit C. 

4.10 No Mitigation or Offset. The Executive shall not be required to seek or accept other employment, or otherwise to mitigate damages,
as a condition to receipt of the Severance Benefits, and the Severance Benefits shall not be offset by any amounts received by the Executive from any other source, except to the extent that the Executive’s rights to the benefits described in
Sections 4.4.3(i)(b) or 4.4.3(ii)(c), as applicable, are terminated by reason of the Executive obtaining full-time employment with another company or business entity which offers comparable health insurance coverage. 

 

	5.	Assignment and Binding Effect. 

 This Agreement shall be binding upon the
Executive and the Company and inure to the benefit of the Executive and the Executive’s heirs, executors, personal representatives, assigns, administrators and legal representatives. Because of the unique and personal nature of the
Executive’s duties under this Agreement, neither this Agreement nor obligations under this Agreement shall be assignable by the Executive. This Agreement shall be binding upon and inure to the benefit of the Company and its successors, assigns
and legal representatives, provided that the Agreement may only be assigned to an acquirer of all or substantially all of the Company’s assets. Any such 

 
successor of the Company will be deemed substituted for the Company under the terms of this Agreement for all purposes. For this purpose, “successor” means any person, firm, corporation
or other business entity which at any time, whether by purchase, merger or otherwise, directly or indirectly acquires all or substantially all of the assets or business of the Company. 

 

	6.	Notice. 

 For the purposes of this Agreement, notices, demands, and all other
forms of communication provided for in this Agreement shall be in writing and shall be deemed to have been duly given when delivered or (unless otherwise specified) mailed by registered mail, return receipt requested, postage prepaid, or by
confirmed facsimile, addressed as set forth below, or to such other address as any party may have furnished to the other in writing in accordance herewith, except that notices of address shall be effective only upon receipt, as follows: 

If to the Company: 
 Horizon
Pharma, Inc. 
 150 S. Saunders Road 

Lake Forest, IL 60045 
 Attention:
Timothy P. Walbert, Chairman, President & CEO 
 Fax:
847-572-1372 
 If to the Executive: 

David A. Happel 
 2362 Caballo
Ranchero Drive 
 Diablo, CA 94528 

Any such written notice shall be deemed given on the earlier of the date on which such notice is personally delivered or five (5) days
after its deposit in the United States mail as specified above. Either Party may change its address for notices by giving written notice to the other Party in the manner specified in this section. 

 

	7.	Choice of Law. 

 This Agreement shall be governed by the laws of the State of
Illinois, without regard to any conflicts of law principals thereof that would call for the application of the laws of any other jurisdiction. The parties consent to the exclusive jurisdiction and venue of the federal court in the Northern District
of Illinois, and state courts located in the state of Illinois, county of Cook. Nothing in this Section 7 limits the rights of the parties to seek appeal of a decision of an Illinois court outside of Illinois that has proper jurisdiction over
the decision of a court sitting in Illinois. 

	8.	Integration. 

 This Agreement, including Exhibit A, Exhibit B, Exhibit C, Exhibit D, the
2014 Equity Incentive Plan, and the Transition Services Agreement contains the complete, final and exclusive agreement of the parties relating to the terms and conditions of the Executive’s employment and the termination of Executive’s
employment, and supersedes all prior and contemporaneous oral and written employment agreements or arrangements between the parties, including but not limited to the Prior Agreement. By executing this Agreement, Executive hereby agrees that
Executive’s Prior Agreement is terminated and superseded in its entirety by this Agreement as of the Effective Date and that Executive waives any right that Executive may have and/or is not entitled to severance benefits under the Prior
Agreement. 
  

	9.	Amendment. 

 This Agreement cannot be amended or modified except by a written
agreement signed by the Executive and the Company. 
  

	10.	Waiver. 

 No term, covenant or condition of this Agreement or any breach thereof
shall be deemed waived, except with the written consent of the party against whom the wavier is claimed, and any waiver or any such term, covenant, condition or breach shall not be deemed to be a waiver of any preceding or succeeding breach of the
same or any other term, covenant, condition or breach. 
  

	11.	Severability. 

 The finding by a court of competent jurisdiction of the
unenforceability, invalidity or illegality of any provision of this Agreement shall not render any other provision of this Agreement unenforceable, invalid or illegal. Such court shall have the authority to modify or replace the invalid or
unenforceable term or provision with a valid and enforceable term or provision, which most accurately represents the parties’ intention with respect to the invalid, unenforceable, or illegal term or provision. 

 

	12.	Interpretation; Construction. 

 The headings set forth in this Agreement are for
convenience of reference only and shall not be used in interpreting this Agreement. This Agreement has been drafted and negotiated by legal counsel representing the Company and the Executive. The parties acknowledge that each party and its counsel
has reviewed and revised, or had an opportunity to review and revise, this Agreement, and any rule of construction to the effect that any ambiguities are to be resolved against the drafting party shall not be employed in the interpretation of this
Agreement. 
  

	13.	Execution by Facsimile Signatures and in Counterparts. 

 The parties agree that
facsimile signatures shall have the same force and effect as original signatures. This Agreement may be executed in one or more counterparts, each 

 
of which shall be deemed an original but all of which together shall constitute one and the same instrument. 
  

	14.	Survival. 

 The provisions of this Agreement, and of all other agreements referenced
herein, shall survive the termination of this Agreement, and of the Executive’s employment by the Company for any reason, to the extent necessary to enable the parties to enforce their respective rights hereunder. 

[Remainder of Page Intentionally Left Blank] 

 IN WITNESS WHEREFORE, the parties have signed this Agreement on the date
first written above. 
  

					
	COMPANY:
	
	HORIZON PHARMA, INC.
	HORIZON PHARMA USA, INC.
			
		 	 By:
	 	
		 	 Title:
	 	Chairman, President & CEO
		 	 Print Name: Timothy P. Walbert

		
		 	 /s/ Timothy P. Walbert

		
		 	 Signature:

			
		 		 	As authorized agent of the Company
		
		 	 November 4, 2016

		
		 	 Date

		
		 	EXECUTIVE:
		
		 	David A. Happel
		
		 	 /s/ David A. Happel

		 	 David A. Happel, individually

		
		 	 November 4, 2016

		
		 	 Date

 EXHIBIT A 

RELEASE AND WAIVER OF CLAIMS 
 In
consideration of the payments and other benefits set forth in Section 4.4 of the Executive Employment Agreement dated October 25, 2016, (the “Employment Agreement”), to which this form is attached, I, David A. Happel,
hereby furnish Horizon Pharma, Inc. and Horizon Pharma USA, Inc. (together the “Company”), with the following release and waiver (“Release and Waiver”). 

In exchange for the consideration provided to me by the Employment Agreement that I am not otherwise entitled to receive, I hereby generally
and completely release the Company and its directors, officers, employees, shareholders, partners, agents, attorneys, predecessors, successors, parent and subsidiary entities, insurers, Affiliates, and assigns from any and all claims, liabilities
and obligations, both known and unknown, that arise out of or are in any way related to events, acts, conduct, or omissions occurring relating to my employment or the termination thereof prior to my signing this Release and Waiver. This general
release includes, but is not limited to: (1) all claims arising out of or in any way related to my employment with the Company or the termination of that employment; (2) all claims related to my compensation or benefits from the Company,
including, but not limited to, salary, bonuses, commissions, vacation pay, expense reimbursements, severance pay, fringe benefits, stock, stock options, or any other ownership interests in the Company; (3) all claims for breach of contract,
wrongful termination, and breach of the implied covenant of good faith and fair dealing; (4) all tort claims, including, but not limited to, claims for fraud, defamation, emotional distress, and discharge in violation of public policy; and
(5) all federal, state, and local statutory claims, including, but not limited to, claims for discrimination, harassment, retaliation, attorneys’ fees, or other claims arising under the federal Civil Rights Act of 1964 (as amended), the
federal Americans with Disabilities Act of 1990, the federal Age Discrimination in Employment Act of 1967 (as amended) (“ADEA”), the California Labor Code (as amended), the California Family Rights Act, and the California
Fair Employment and Housing Act (as amended). Notwithstanding the foregoing, this Release and Waiver, shall not release or waive my rights: to indemnification under the articles and bylaws of the Company or applicable law; to payments under Sections
of the Employment Agreement; under any provision of the Employment Agreement that survives the termination of that agreement; under any applicable workers’ compensation statute; under any option, restricted share or other agreement
concerning any equity interest in the Company; as a shareholder of the Company or any other right that is not waivable under applicable law. 

I acknowledge that, among other rights, I am waiving and releasing any rights I may have under ADEA, that this Release and Waiver is knowing
and voluntary, and 

 that the consideration given for this Release and Waiver is in addition to anything of value to which I was
already entitled as an executive of the Company. If I am 40 years of age or older upon execution of this Release and Waiver, I further acknowledge that I have been advised, as required by the Older Workers Benefit Protection Act, that: (a) the
release and waiver granted herein does not relate to claims under the ADEA which may arise after this Release and Waiver is executed; (b) I should consult with an attorney prior to executing this Release and Waiver; and (c) I have twenty-one (21) days from the date of termination of my employment with the Company in which to consider this Release and Waiver (although I may choose voluntarily to execute this Release and Waiver earlier);
(d) I have seven (7) days following the execution of this Release and Waiver to revoke my consent to this Release and Waiver; and (e) this Release and Waiver shall not be effective until the seven (7) day revocation period has expired
unexercised. If I am less than 40 years of age upon execution of this Release and Waiver, I acknowledge that I have the right to consult with an attorney prior to executing this Release and Waiver (although I may choose voluntarily not to do so);
and (c) I have five (5) days from the date of termination of my employment with the Company in which to consider this Release and Waiver (although I may choose voluntarily to execute this Release and Waiver earlier). 

I acknowledge my continuing obligations under my Confidential Information and Inventions Agreement
dated             ,        . Pursuant to the Confidential Information and Inventions Agreement I understand that among other things, I must not use
or disclose any confidential or proprietary information of the Company and I must immediately return all Company property and documents (including all embodiments of proprietary information) and all copies thereof in my possession or control. I
understand and agree that my right to the payments and other benefits I am receiving in exchange for my agreement to the terms of this Release and Waiver is contingent upon my continued compliance with my Confidential Information and Inventions
Agreement. 
 This Release and Waiver, including my Confidential Information and Inventions Agreement dated
            ,         , constitutes the complete, final and exclusive embodiment of the entire agreement between the Company and me with regard to
the subject matter hereof. I am not relying on any promise or representation by the Company that is not expressly stated herein. This Release and Waiver may only be modified by a writing signed by both me and a duly authorized officer of the
Company. 
 Date: 
 By: 

David A. Happel 

 EXHIBIT D 

HORIZON RETENTION AGREEMENT 

 

 
  

 October 28, 2016 

David Happel 
  

	RE:	Retention Agreement 

 Dear David: 

As you know, Horizon Pharma PLC (“Horizon”) and Misneach Corporation have executed an Agreement and Plan of Merger (the
“Merger Agreement”) with Raptor Pharmaceutical Corp. (“Raptor”), pursuant to which Raptor has become a wholly-owned subsidiary of Horizon effective as of October 25, 2016 (the “Merger
Closing Date”). In connection with the closing of this transaction, your employment was transferred from Raptor to Horizon Pharma, Inc., a Delaware corporation, and its wholly owned subsidiary, Horizon Pharma USA, Inc., a Delaware
corporation, (together “the Company”) as of October 25, 2016. Certain capitalized terms used in this Retention Agreement have the meanings set forth in Section III below. 

 

	I.	Eligibility for Retention Bonus 

 As you know, under your Transition Services Agreement with
Raptor dated October 13, 2016 you are eligible to earn a retention bonus of $335,000 subject to your continued employment through May 15, 2017 (the “Initial Retention Date”) and the other terms and conditions set
forth in the Transition Services Agreement, which remains in full force and effect. As an incentive for you to continue to contribute your efforts, talents and services to the Company and its Affiliates for the period following the Initial Retention
Date through and including the Earn Date (as defined below) Horizon is pleased to announce your eligibility to earn a one-time retention bonus in the aggregate amount of 150% of your annual base salary
($750,000) (the “Retention Bonus”), less applicable taxes and withholdings, pursuant to the terms and conditions set forth in this Retention Agreement. 

In order to earn the Retention Bonus, you must remain employed by the Company or any other Affiliate (together, the “Horizon
Employer”) regularly working at least 30 hours per week and in good performance standing for the period following the Initial Retention Date through and including November 1, 2017 (the “Earn Date”). The
period from the Initial Retention Date through and including the Earn Date is the “Retention Bonus Period.” If earned, the Retention Bonus will be paid in a lump sum by the Company or its Affiliate, less
applicable taxes and withholdings, on the first administratively practicable payroll pay date after the Earn Date. 
  

	II.	Employment Termination 

 Notwithstanding the foregoing, if during the Retention Bonus Period, the
Horizon Employer terminates your employment without Cause, or your employment with the Horizon Employer is terminated due to your death or Disability (as defined below), you will be eligible for the following benefits, subject to your satisfaction
of the additional conditions specified below: 
  

	 	•	 	If the Horizon Employer terminates your employment without Cause during the Retention Bonus Period, you will be eligible for the full amount of the Retention Bonus. 

 

	 	•	 	If your employment with the Horizon Employer is terminated due to your death or Disability during the Retention Bonus Period, you will be eligible for a pro-rata portion of the
Retention 

  
 Connaught House, 1st
Floor, 1 Burlington Road, Dublin 4, D04 C5Y6, Ireland 

 

 
  

	 	 
Bonus, with such pro-rata portion determined by dividing the number of days you were actually employed by the Horizon Employer during the Retention Bonus
Period by the total number of days in the Retention Bonus Period (the “Pro-Rata Retention Bonus”). 

In order to earn the full Retention Bonus or Pro-Rata Retention Bonus in connection with your employment termination,
you (or your estate or legal guardian, if applicable) must execute and deliver to Horizon a general release of all known and unknown claims in a form acceptable to Horizon (the “Release”), and such Release must become
effective in accordance with its terms, but in no event later than sixty (60) days following your employment termination date. If earned, such bonus payment will be paid in a lump sum by the Horizon Employer or its Affiliate, less applicable
taxes and withholdings, on the first administratively practicable payroll pay date after the Release becomes effective. 
 For the avoidance of doubt, if
prior to expiration of the Retention Bonus Period: (i) you provide notice of your employment resignation, or actually sever the employment relationship by resignation (for any reason, including retirement), or (ii) the Horizon Employer
terminates your employment for Cause; then you will not be eligible for and will not earn the full Retention Bonus or any Pro-Rata Retention Bonus. Under no circumstances will you be eligible to receive both
the full Retention Bonus and a Pro-Rata Retention Bonus. 
  

	III.	Definitions 

 For purposes of this Retention Agreement, “Affiliates” means
Horizon Pharma plc and each of its majority owned subsidiaries and “Affiliate” means any of the Affiliates. 
 For purposes of this
Retention Agreement, “Cause” means the occurrence of any one or more of the following: (i) your conviction of, or plea of no contest with respect to, any felony, or of any misdemeanor involving dishonesty or moral
turpitude; (ii) your participation in a fraud or act of dishonesty (or an attempted fraud or act of dishonesty) that results in (or could result in) material harm to the Horizon Employer or any Affiliate, including but not limited to
material harm to reputational interests; (iii) your violation of a fiduciary duty owed to the Horizon Employer or any Affiliate; (iv) your material breach of any fully executed agreement between you and the Horizon Employer
or any Affiliate; (v) persistent, unsatisfactory performance or neglect of your job duties, which is not cured within ten (10) business days after you are provided written notice by the Horizon Employer (provided, that, such
written notice and opportunity to cure are not required if your performance or neglect is not reasonably susceptible to being cured); or (vi) your gross misconduct or material failure to comply with a written instruction of the Horizon
Employer or any Affiliate. 
 For purposes of this Retention Agreement, “Disability” means you are eligible for long-term disability
benefits under the Horizon Employer’s long-term disability benefit plan. 
  

	IV.	IRS Code Section 409A 

 It is intended that any bonus amount payable under this Retention
Agreement satisfies, to the greatest extent possible, the exemption from the application of Section 409A of the Internal Revenue Code of 1986, as amended (the “Code”) provided under Treasury Regulations Section 1.409A-1(b)(4) and in all cases will be paid not later than March 15 of the year following the year in which your right to such amount became vested. To the extent that such bonus is deferred compensation
under Section 409A of the Code, and is not otherwise exempt from the application of Section 409A, then, if the period during which you may consider and sign the Release spans two calendar years, the payment of such bonus will not be made to you
until the later calendar year. 

  
 Connaught House, 1st
Floor, 1 Burlington Road, Dublin 4, D04 C5Y6, Ireland 

 

 
  

	V.	Miscellaneous 

 The Retention Agreement is intended to provide a financial incentive to you and is
not intended to confer any rights to continued employment upon you. Nothing in this Retention Agreement is intended to alter your at-will employment relationship with the Horizon Employer, and your employment
remains terminable by either you or the Horizon Employer with or without Cause or advanced notice. This Agreement also does not change or modify any other benefits that you may be eligible to receive from the Horizon Employer. 

This Retention Agreement is the complete, final and exclusive embodiment of the entire agreement between you and Horizon with regard to the Retention Bonus
and Pro-Rata Retention Bonus, and it supersedes and replaces any other agreements (whether written or unwritten) you may have with the Horizon Employer concerning these matters. This Retention Agreement is
entered into without reliance on any promise or representation (written or unwritten), other than those expressly contained herein, and it supersedes any other such promises, warranties or representations. The terms of this Retention Agreement may
not be modified or amended except in a written agreement signed by you and a duly authorized officer of Horizon. 
 Please sign and return this agreement to
Keith Swenson on or before November 4, 2016. 
 Sincerely, 

/s/ Timothy P. Walbert 
 Timothy P. Walbert 

Chairman, President & CEO 

ACKNOWLEDGMENT AND ACCEPTANCE 
  

	
	Accepted and Agreed:
	
	  

	David Happel
	
	 /s/ David Happel

	Signature
	
	 11/04/16

	Date

  
 Connaught House, 1st
Floor, 1 Burlington Road, Dublin 4, D04 C5Y6, IrelandEX-10.73

 Exhibit 10.73 
  

					
	

	 		 	 ***Text Omitted and Filed Separately

with the Securities and Exchange Commission.

Confidential Treatment Requested

Under 17 C.F.R. Sections 200.80(b)(4)

and 240.24b-2.
  

 October 13, 2016 

David A. Happel 
 CONFIDENTIAL 

Dear Mr. Happel, 
 As you are aware, on September 12,
2016, Raptor Pharmaceutical Corp. (the “Company”) entered into a definitive agreement to be acquired by Horizon Pharma plc. (“Parent”). We expect the acquisition to close by the end of October of this year (the date the
acquisition closes, the “Closing”). 
 We are committed to a seamless and smooth transition and in order to promote these goals, we have adopted a
transition services program pursuant to which you are eligible to earn a retention bonus for your continued service from the Closing through December 31, 2016 ( or earlier termination by the Company or Horizon without Cause), subject to certain
conditions described in more detail below. As a participant in the program, you will be eligible to earn and receive an amount equal to $128,000 (the “2016 Retention Bonus”), less any applicable state, federal and local income taxes as
well as any applicable employment or excise taxes, subject to your continued employment with the Company through December 31, 2016 (or earlier termination by the Company or Horizon without Cause) and your compliance with the terms of this
letter agreement. 
 As a condition to your participation in this program and eligibility to earn the 2016 Retention Bonus and in consideration therewith,
you hereby expressly waive any right that you may have to be paid the target amount of your 2016 performance bonus under the Company’s 2016 bonus program at the Closing. You will instead have the opportunity to earn a 2016 performance bonus
under the Company’s 2016 bonus program (the “2016 Performance Bonus”) subject to your continued employment with the Company through December 31, 2016 (or earlier termination by the Company or Horizon without Cause) and your
compliance with the terms of this letter agreement. If earned, the amount of your 2016 Performance Bonus awarded to you will be equal to the lesser of: (i) your target 2016 bonus amount, and (ii) the amount of 2016 bonus determined
pursuant to the applicable performance criteria previously established for the Company’s 2016 bonus program for you, as specified on the attached Exhibit A, based on the actual performance levels attained through December 31, 2016,
as determined by Parent in its sole discretion. In no event will you be eligible to earn more than your target 2016 bonus amount as specified on the attached Exhibit A. Parent’s determination of your actual 2016 Performance Bonus amount
awarded to you will be final and binding. Your 2016 Performance Bonus will be paid to you less any applicable state, federal and local income taxes as well as any applicable employment or excise taxes. 

  
 1 

 If you satisfy this continued service requirement through December 31 , 2016 (the “2016 Transition
Period End Date”) or are earlier terminated by the Company or Horizon without Cause, and comply with the terms of this letter agreement, your 2016 Retention Bonus will be payable in a lump-sum on the first regular payroll in January 2017. If
you satisfy this continued service requirement through the 2016 Transition Period End Date or are earlier terminated by the Company or Horizon without Cause, and comply with the terms of this letter agreement, your 2016 Performance Bonus will be
payable in a lump-sum as soon as practicable following the determination by Parent’ of the applicable level of attainment of the performance goals, but in no event will be paid later than March 15, 2017. 

We have also adopted an additional transition services bonus program pursuant to which you are eligible to earn an additional bonus for your continued service
from January 1, 2017 through May 15, 2017 (the “2017 Transition Period End Date”), subject to certain conditions described in more detail below. As a participant in this program, you will be eligible to earn and receive an
additional amount equal to $335,000 (the “2017 Retention Bonus”), less any applicable state, federal and local income taxes as well as any applicable employment or excise taxes, subject to your continued employment with the Company through
the 2017 Transition Period End Date or earlier termination by the Company or Horizon without Cause and your compliance with the terms of this letter agreement. If earned, your 2017 Retention Bonus will be paid to you in a single lump sum on the
first regular payroll following the 2017 Transition Period End Date. You will not be eligible to receive the 2017 Retention Bonus if your employment terminates prior to the 2017 Transition Period End Date due to your resignation for any reason,
death or disability (within the meaning of Section 22(e) of the Code). 
 The period from the Closing through the 2017 Transition Period End Date (or,
if earlier, the date of your termination by the Company or Horizon without Cause) is the “Transition Period.” During the Transition Period you shall continue to provide services in your area of expertise and responsibility including as
related to the following goals: assisting with the Quinsair launch in Canada and preparation for U.S. and assisting in Procysbi and Quinsair commercial transition outside the U.S. and Procybi in the U.S. (your “Responsibilities”). You
agree to continue to devote your best efforts and substantially all of your business time and attention to the business of the Company during this period and keep the Company regularly apprised of your activities in order to facilitate this process.

 If, after the Closing but prior to the 2017 Transition Period End Date, (1) your employment with the Company is terminated by the Company or Horizon
for reasons other than for Cause, or (2) the Company or Horizon provides you with written direction not to devote all of your business time and attention to the business of the Company during this period, then if any payment or benefit you
receive in connection with the acquisition or otherwise (“Payment”) would (A) constitute a “parachute payment” within the meaning of Section 280G of the Code, and (B) as such, is subject to the excise tax imposed
by Section 4999 of the Code (the “Excise Tax”), then the Company shall pay to you an additional cash amount (the “Gross-Up Payment”) with respect to each such Payment. The amount of each Gross-Up Payment shall be sufficient
that, after paying (A) any Excise Tax on the Payment, (B) any federal, state or local income or employment taxes and Excise Tax on the Gross-Up Payment, and (C) any interest and penalties imposed in respect of the Excise Tax, you will
retain an amount equal to the full amount of the Payment. Any Gross-Up Payment, as determined in accordance with this letter agreement, shall be paid by the Company to you at the same time withholding taxes for the related excise tax is due. You
will not be eligible to receive the Gross-Up 

  
 2 

 
Payment if your employment terminates prior to the 2017 Transition Period End Date due to your resignation for any reason, death or disability (within the meaning of Section 22(e) of the
Code). 
 If you are not entitled to a Gross-Up Payment and any payment or benefit you would receive from the Company or otherwise pursuant to the
acquisition of the Company by Parent (“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 such 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 being subject to the Excise Tax or (y) the largest portion, up to and including the total, of the Payment, whichever amount, 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 your 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 payments or benefits constituting “parachute payments” is necessary so that the Payment equals the Reduced Amount, reduction shall occur in the following order: (1) reduction of cash payments; (2) cancellation of
accelerated vesting of equity awards other than stock options; (3) cancellation of accelerated vesting of stock options; and (4) reduction of other benefits payable to you. 

If you are not entitled to a Gross-Up Payment and it is subsequently determined by the U.S. Internal Revenue Service that some portion of the Reduced Amount
as determined pursuant to clause (x) in the preceding paragraph is subject to the Excise Tax, you agree to promptly return to the Company a sufficient amount of the Payment so that no portion of the Reduced Amount is subject to the Excise Tax.
For the avoidance of doubt, if the Reduced Amount is determined pursuant to clause (y) in the preceding paragraph, you will have no obligation to return any portion of the Payment pursuant to the preceding sentence. 

For the avoidance of doubt, the benefits provided by this letter agreement shall not be in lieu of or in any way amend any rights to base salary, severance or
other benefits under your employment agreement or change in control severance agreement with the Company. You hereby reaffirm your commitment to remain in compliance with the Employee Invention Assignment and Confidentiality Agreement entered into
between you and the Company (the “Confidentiality Agreement”). You acknowledge and agree that the benefits described in this letter agreement are subject to all of the terms and conditions set forth above, including your agreement to
remain in compliance with the Confidentiality Agreement and that if you fail to do so, any right you may have to receive the bonuses and other benefits described in this letter will be forfeited. Please indicate your acceptance of and agreement to,
the terms and conditions of this letter agreement by signing and returning a copy of this letter agreement to Justin Ford. 
 Yours sincerely, 

Julie Anne Smith 
 President and CEO 

Raptor Pharmaceutical Corp. 

  
 3 

 Acknowledged, agreed and accepted: 

 

			
	 /s/ David A. Happel

	David A. Happel
	Date:	 	10/13/16

  
 4 

 APPENDIX 

“Cause” means (i) your commission of a felony or other crime involving moral turpitude; (ii) any willful act or acts
of dishonesty, embezzlement or fraud you undertake that are intended to result in substantial gain or personal enrichment for you, your family or any third party at the expense of the Company or Horizon; (iii) your commission of any willful act
of gross misconduct which is materially and demonstrably injurious to the Company or Horizon; (iv) your material breach of the letter agreement to which this Appendix is attached, your employment, severance or other similar written agreement
with the Company or the Confidentiality Agreement, (v) your unauthorized use or disclosure of any proprietary information or trade secrets of the Company, Horizon or any other party that you owe an obligation of nondisclosure as a result of
your relationship with the Company; and/or (vi) your gross negligence or willful failure to substantially perform your Responsibilities to the Company or willful and deliberate violation of a material Company policy. For the avoidance of doubt,
the termination of your employment as a result of your death or your inability to perform the essential functions of your job due to permanent disability (within the meaning of Section 22(e) of the Internal Revenue Code of 1986, as amended)
will not be deemed to constitute a termination without Cause. 

  

 EXHIBIT A 

2016 BONUS PERFORMANCE CRITERIA 

Target 2016 Bonus Amount: $156,975 
 Horizon will determine the
level of attainment of the corporate goals and your individual performance level and applicable amount of 2016 bonus payments in accordance with the following criteria, which are set forth in Raptor’s proxy statement and are consistent with the
Raptor Compensation Committee’s stated policy and historical practice: 
  

	 	•	 	After evaluation of performance, achievement scores may be awarded which recognize partial performance of a goal or recognize additional score points for exceptional performance due to unanticipated challenges or
superior performance. 

  

	 	•	 	Awards can vary to up to 125% of the target percentage based on assessment of achievement above the targeted levels, of meaningful additional goals or sustained superior performance in the conduct of duties and
responsibilities in the employee’s position. 

 In determining your 2016 bonus award, corporate goals are weighted at 80% and your
individual 2016 performance is weighted at 20%. 
 The corporate goals established for the 2016 bonus program are: 

 

			
	    Weight    	  	2016 Corporate Goals
	 	 
	
    30%
	  	Achieve WW net sales revenue of $120M
	 	 
	
    15%
	  	Launch QUINSAIR in Europe by 1st half of 2016
	 	 
	
    20%
	  	Acceptance of QUINSAIR NDA for CF in the U.S.
	 	 
	
    15%
	  	End 2016 with sufficient cash to provide planned funded runway through June 30, 2018
	 	 
	
    20%
	  	 Advance pipeline by achieving certain internal
and external development.
 a) 10% First patient dosed for MP-376 P2 in BE;

b) 10% Generate data from clinical and/or non-clinical studies to inform dose selection, advance discussions with FDA and EMA regarding the full development
plan including the pivotal Phase 3 HD study and make substantial progress to partner or out-license the RP-103 HD program.

 The individual goals established for the 2016 bonus program are: 

 

			
	    Weight    	  	2016 Individual Goals
	 	 
	
    35%
	  	[...***...]
	 	 
	
    20%
	  	[...***...]
	 	 
	
    25%
	  	[...***...]

  
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Treatment Requested 
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    10%
	  	[...***...]
	 	 
	
    5%
	  	[...***...]
	 	 
	
    5%
	  	[...***...]

 Horizon’s determination of your 2016 bonus award will be final and binding on you and all other parties. Regardless of
performance levels, in no event are you eligible to be awarded more than your Target 2016 Bonus Amount. 

  
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Treatment Requested 
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