UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

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Horizon Pharma Public Limited Company

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PRELIMINARY PROXY STATEMENT

DATED MARCH 22, 2019 — SUBJECT TO COMPLETION

HORIZON PHARMA PUBLIC LIMITED COMPANY

ANNUAL GENERAL MEETING OF SHAREHOLDERS

May 3, 20182, 2019

NOTICE AND PROXY STATEMENT

April 2, 2018                    , 2019

Dear Fellow Shareholder:

2018 was an exceptional year for Horizon.  In addition to generating record net sales of $1.2 billion, an increase of 14 percent over 2017, and adjusted EBITDA of $451 million¹, an increase of 16 percent, we made tremendous progress executing our strategy to build a robust and differentiated pipeline and maximize the growth of KRYSTEXXA^®, our biologic medicine for uncontrolled gout².  We also generated strong results for our shareholders with aone-year total shareholder return of 34 percent in a year when the Nasdaq Biotechnology Index (NBI) declined 9 percent. 

KRYSTEXXA, with its 65 percent year-over-year growth, was the key driver of our net sales performance for the year.  It was a year of significant progressexpansion and investment in our flagship medicine to accelerate its growth potential.  We doubled the commercial team and our addressable patient population and supported the expansion with investment in the commercial infrastructure.  Strong demand for this medicine based on the clinical conviction physicians have for KRYSTEXXA was the driving force behind its growth to $259 million in net sales for the year – more than four times the annual sales when we acquired it three years ago.  We are confident in the long-term potential of KRYSTEXXA, the only approved medicine for uncontrolled gout, and continue to project peak U.S. net sales of more than $750 million. 

At Horizon, Pharma.  Having rapidly transformed the Company into one focused primarily on rare and rheumatic diseases over the past five years, we launched the next stage ofdo things differently.  Our commercial execution in transforming KRYSTEXXA from an underperforming, underutilized medicine is a great example.  So is our evolution –to the rare disease biopharma company we are today.  Instead of the typical biopharma model, starting out with a pipeline and raising capital to finance development opportunities, we started by developing a robustsuccessful business, using our business development capabilities and strong commercial execution to build our foundation.  Using the resulting cash flows and growth, we built our rare disease medicine portfolio. Then we moved to where we are today – investing in a pipeline of clinically meaningfulrobust and differentiated medicines to drive sustainedsustainable growth over the long term.  longer-term – and to make even more of a difference to patients in need of innovative therapies for disease areas many others won’t address. 

We added several new programs toare making a great deal of progress with our pipeline in 2017, includingHZN-001 (teprotumumab), a– particularly with teprotumumab, our late-stage fully human monoclonal antibody (mAb) insulin-like growth factorfactor-11-receptor(IFG-1R), receptor(IGF-1R) inhibitor, which isand a candidate for the treatment ofmoderate-to-severe active thyroid eye disease (TED), a rare eye disease.  Enrollmentdisease with no approved treatment.  In 2018, we completed enrollment in teprotumumab’s Phase 3 confirmatory trial ahead of schedule.  We also presented48-weekoff-treatment data from its breakthrough Phase 2 trial that demonstrated durability of response.  More recently, we were pleased to announce that the Phase 3 trial met its primary endpoint, demonstrating a dramatic, highly significant 82.9 percent response rate in the confirmatory Phase 3 clinical trial beganreduction in proptosis – or bulging of the fourth quartereye – in patients treated with teprotumumab compared to 9.5 percent for placebo patients (p<0.001), paving the way for the potential approval of 2017this medicine by the U.S. Food and Drug Administration (FDA).  We are very excited about teprotumumab’s prospects – for the many patients suffering the painful, debilitating effects of TED, and for you, our shareholders, as we projectbelieve that if approved, teprotumumabit could achieve U.S. peak annual U.S. net sales of more than $750 million.  We also added two otherpre-clinical rheumatology programs designed to enhance our leadership in the treatment of uncontrolled gout¹, a position which we hold today with our rare-disease biologic KRYSTEXXA^®, one of our key growth drivers.  We continued to invest in KRYSTEXXA in 2017 by doubling its commercial organization and expanding its targeted patient population to include uncontrolled gout patients treated by nephrologists.  As a result, we recently increased our estimate of KRYSTEXXA peak annual net sales to moregreater than $750 million. 

These developments exemplifyNew to our pipeline in 2018 was our MIRROR trial, a clinical program designed to evaluate the effectiveness of combining KRYSTEXXA with the immunomodulator methotrexate, which, if successful, executioncould increase the number of patients who benefit from KRYSTEXXA.  We also advanced our two next-generation programs for uncontrolled gout, designed to sustain our leadership position well into the future.  More recently, we added a new program to discover novel therapies for the treatment of gout. 

To support our expanding pipeline, we considerably enhanced our research and development (R&D) organization in 2018. Shao-Lee Lin, M.D., Ph.D., joined Horizon early in 2018 to accelerate the development of our strategy overR&D portfolio, bringing an impressive record of developing new medicines.  She soon transformed the past five years.  leadership team, adding scientific expertise and to enhance our R&D capabilities and business development process. 

In 2013, Horizon Pharma had two medicines with net sales of $74 million.  Today,addition to building our pipeline, we are a biopharmaceutical company focused primarily on rare diseases, with 11 medicines, sixaligning our capital structure to be closer to that of them for rare diseases, and ourR&D-focused rare disease medicines making upbiopharma companies, which generally have lower debt levels.  We recently announced plans to pay down approximately 60 percent$550 million of our 2017 net sales.  This rapid, transformational growth has resulted in a five-year total shareholder return of 527 percent, significantly outperformingoutstanding debt, which was $2.0 billion at December 31, 2018, using available cash and proceeds from our peer group² and the Nasdaq Biotechnology Index (NBI). 

Our net sales of $1.06 billion in 2017 represented a year-over-year increase of 8 percent on a GAAP basis and 1 percent on anon-GAAP basis³, driven primarily by strong growth in our orphan and rheumatology business units.  Impacting our net sales performance were challenges we experienced early in the year in our primary care business unit related to the implementation of a new contracting model with pharmacy benefit managers (PBMs), which we effected primarily in response to the increasing level of control in the managed care environment.  Despite the resulting negative impact of approximately $230 million to our primary care business unit net sales, our diversification strategy over the past three years proved successful, as the growth in net sales of our rare disease medicines of 60 percent more than offset that decrease, resulting in year-over-year net sales growth.  Our 2017 net loss,non-GAAP net income and adjusted EBITDA⁴ were $411 million, $195 million and $390 million⁵, respectively.  We ended 2017 with a cash balance of $751 million, providing us with the financial flexibility to continue to execute our strategy. 

Overall, I am very pleased with our team’s performance.  We remained diligently focused on strong execution and driving the business forward.  We demonstrated the commitment that underscores everything we do at Horizon Pharma:  making a powerful difference for the patients, caregivers and physicians through the innovative medicines we commercialize and develop to address unmet treatment needs.  The dedication and purpose of our talented team of employees is reflected in the recognition Horizon Pharma continues to receive, including threeFortune Magazine 2017 surveys – One of the Best Workplaces in Health Care, 100 Best Small & Medium Workplaces and 2017 Best Work Places to Work in Chicago – as well as the 2017Crain’s Chicago Business Best Places to Work andChicago Tribune’s 2017 TopMedium-Sized Workplaces.  Our ongoing efforts to diversify our employee base has helped us achieve our goals.  To drive our continued growth and evolution in this regard, Irina Konstantinovsky, an accomplished human resources professional, joined us in September 2017 as executive vice president, chief human resources officer.

More recently,recent $345 million underwritten public offering. This initiative will lower our outstanding debt and leverage ratio, and at the same time allow us the flexibility to take advantage of business development opportunities.  We subsequently paid down $300 million of the debt.  Our current outstanding debt is now $1.7 billion, and we were very pleasedare on track to welcomeShao-Lee Lin, M.D.pay down the remaining $250 million of our $550 million target. 

Transformation describes our journey over the last several years.  Horizon today is much different than it was when we started out as a public company in 2011.  Today, we are a biopharma company focused primarily on rare diseases.  Our disciplined business development strategy, along with our strong commercial execution, has driven rapid, transformational growth and delivered a five-year total shareholder return of 156 percent, significantly ahead of our peer group³ and the NBI.  And importantly for the future, we are building a robust pipeline of innovative medicines.  That is why the Board is recommending changing the name of the Company toHorizon Therapeutics plc, Ph.D.to better reflect who we are today and our vision for the future.  We are transforming health by building healthier communities, urgently and responsibly.  As a company, we are going to incredible lengths to impact incredible lives. 

One way we do this is ensuring that patients have access to our medicines, regardless of their ability to pay.  In 2018, we provided nearly $2.0 billion in patient assistance.  But our dedication goes well beyond our medicines.  We help our patients and their caregivers better manage and live with their disease, and we help their treating physicians as well, through the services we offer, our awareness campaigns and disease advocacy efforts – a holistic approach. 

It’s personal for us.  We are a company of dedicated, engaged people making a difference every day – whether in the results we achieve, the commitments we make or the recognition we receive.  In 2018,PEOPLE Magazine cited us as one of its “50 Companies That Care,” andFortune Magazine named us the Number One Best Workplace in BioPharma – in addition to several other workplace awards.  We joined Pledge 1%, who joined Horizon Pharma earlier this year as executive vice president, heada corporate philanthropy movement that empowers companies to donate 1% of research and development (R&D) and chief scientific officer. Shao-Lee brings exceptional experience and a proven track recordproduct, 1% of developing new medicinesequity, 1% of profit or 1% of employee time to improve communities around the world – and she shares our focus on improving patient outcomes. Shao-Lee is focused on drivingwe are among the accelerated development of a R&D portfolio of medicines for Horizon Pharma, leading the next phase of growthfirst biopharma companies to make this commitment. 

We also received recognition for the Company.value we place on diversity, withCrain’s Chicago Business recognizing us as one of the Best Places for Women to Work in Chicago.  We firmly believe that people from different backgrounds and life experiences greatly contributes to our success and the contributions we make to the patients and diverse communities we serve.  I am proud to be a signatory of the CEOAction for Diversity and Inclusion pledge, aCEO-driven business commitment to advance diversity and inclusion within the workplace.  And our Board recognizes the importance and value of diversity as well, formally instituting its policy on diversity to publicly affirm the Board’s belief that maintaining a diverse membership enhances its deliberations and enables the Board to better represent all of our constituents. 

In sum, we made significant progress in 2018 on multiple fronts.  We are deliveringbuilding on that momentum in 2019, continuing to deliver on our core principles – strong commercial execution, a disciplined business development strategy, clinical development of innovative medicines for patients in need and expanding patient access – while also increasing affordability ofall aimed at making a difference and creating value for our medicines.  Moving forward, we will continue to drivepatients, for our employees and motivatefor you, our growing organization with the goal of delivering strong financial performance that creates long-term market-leading shareholder value.shareholders. 

You are cordially invited to attend the Annual General Meeting of Shareholders on Thursday, May 3, 2018,2, 2019, at 3:00 p.m. local time at our corporate headquarters located at Connaught House, 1st Floor, 1 Burlington Road, Dublin 4, D04 C5Y6, Ireland. 

WhetherIt is important that your shares be represented and voted, whether or not you plan to attend the Annual General Meeting, it is important that your shares be represented and voted.Meeting.  Please take a moment now to vote your shares by internet, by toll-free telephone call or by signing, dating and returning the enclosed proxy card. 

Thank you for your continued support. 

Sincerely,
Timothy P. Walbert
Chairman, President and Chief Executive Officer

Important Notice Regarding the Availability of Proxy Materials for the Annual General Meeting of

Shareholders to Be Held on Thursday, May 3, 2018,2, 2019, at 3:00 p.m. Local Time at Our Corporate

Headquarters Located at Connaught House, 1st Floor, 1 Burlington Road, Dublin 4, D04 C5Y6, Ireland. 

Dear Shareholder:

We will be holding the Annual General Meeting of Shareholders of Horizon Pharma plc on Thursday, May 3, 2018,2, 2019, at 3:00 p.m. local time at our corporate headquarters located at Connaught House, 1st Floor, 1 Burlington Road, Dublin 4, D04 C5Y6, Ireland for the following purposes:

The Board recommends that you vote FOR each of the nominees for director named herein for ONE YEAR as the preferred frequency of advisory votes to approve executive compensation and FOR Proposals 2, 3, 4, 5, 6, 7, 8, 9, 10 and 6.11. 

Our Irish statutory financial statements for the fiscal year ended December 31, 2017,2018, including the reports of the directors and statutory auditors thereon, will be presented at the Annual General Meeting.  There is no requirement under Irish law that such statements be approved by the shareholders and no such approval will be sought at the Annual General Meeting. 

For the purposes of our Articles of Association, Proposals 1 and 2 and the receipt and consideration of the Irish statutory financial statements by us at the Annual General Meeting are deemed to be ordinary business and Proposals 3, 4, 5, 6, 7, 8, 9, 10 and 611 are deemed to be special business.  The Annual General Meeting will also include a review of the Company’s affairs.  Shareholders of record as of March 23, 2018,13, 2019, the record date for the Annual General Meeting, are entitled to notice of the Annual General Meeting and to vote at the Annual General Meeting or any adjournment or postponement thereof. 

We ask that you review the Proxy Statement carefully and complete, sign, date and return the enclosed proxy card in the envelope provided or vote over the internet or by telephone as instructed in these materials, as promptly as possible in order to ensure your representation at the meeting.  A return envelope (which is postage prepaid if mailed in the United States) has been provided for your convenience.  Even if you have voted by proxy, you may still vote in person if you attend the meeting.  Please note, however, that if your shares are held of record by a broker, bank or other nominee and you wish to vote at the meeting, you must obtain a proxy issued in your name from that record holder. 

The Proxy Statement and Annual Report to shareholders are available atwww.edocumentview.com/hznp. www.proxyvote.com.

By Order of the Board of Directors

David G. KellyAnne-Marie Dempsey

Company Secretary

Dublin 4, Ireland

April 2, 2018                    , 2019

TABLE OF CONTENTS

PROXY STATEMENT SUMMARY

This summary highlights certain information contained elsewhere in this Proxy Statement and does not contain all of the information that you should consider.  You should read the entire Proxy Statement carefully before voting.  For more complete information regarding our business and 20172018 performance, please review our Annual Report on Form10-K for the year ended December 31, 2017.2018 and our subsequent filings with the Securities and Exchange Commission (SEC). 

Meeting and Voting Information Time and Date: 3:00 p.m. local time on May 2, 2019 Place: Our corporate headquarters located at Connaught House, 1st Floor, 1 Burlington Road, Dublin 4, D04 C5Y6, Ireland Record Date: March 13, 2019 How to Vote: Shareholders as of the record date are entitled to vote and may do so in person at the Annual General Meeting, by returning the completed enclosed proxy card, via the internet at www.proxyvote.com or by telephone at 1-800-690-6903 within the United States, U.S. territories and Canada.

Voting Items and Board Recommendations

2018 at a Glance

A Year of Strong Performance Generating Record Net Sales and Strong Shareholder Return

Except for5-year total shareholder return, growth percentages represent comparison to full-year 2017. 

A Year of Significant Progress

Business Overview

We made significant progress in 2018 on our strategy to build a robust and differentiated pipeline and maximize the growth of KRYSTEXXA, our biologic medicine for uncontrolled gout, and our flagship medicine.  As a result, we generated record full-year net sales of $1.2 billion, an increase of 14 percent over 2017, andone-year total shareholder return of 34 percent in a year when the Nasdaq Biotechnology Index (NBI) declined 9 percent.  In addition to advancing our existing pipeline programs, we added several new programs designed to enhance our leadership position in uncontrolled gout.  We also transformed our research and development (R&D) organization, augmenting its scientific expertise with a new leadership team.  We accelerated the growth of KRYSTEXXA by investing in its commercial infrastructure — doubling its commercial team and our addressable patient population. 

Our Strategy

We are constantly driving toward our aspiration, which is to be a leading rare disease biopharma company that delivers innovative therapies to patients and generates high returns for our shareholders.  We have made a great deal of progress in that regard and are building on the resulting momentum. 

We have taken a different approach, however, from typical biopharma companies.  Instead of starting out with a pipeline only, raising capital to finance development opportunities, we first developed a successful commercial business, generating cash flows and significant growth.  We then deployed our cash flows and access to capital to the development of leading-edge therapeutic products for rare diseases. 

Our Evolution to a Rare Disease Biopharma Company:  A Different Approach

Horizon today has a growing pipeline of development programs, 11on-market medicines and total net sales of $1.2 billion — a significant transformation from our beginnings as a public company in 2011, when we had two medicines and total net sales of $7 million.  Today, our medicines for rare and rheumatic diseases make up nearly 70 percent of our total net sales. 

Our strategy is to build a robust and differentiated pipeline and to maximize growth of KRYSTEXXA, ouron-market medicine for uncontrolled gout. 

We are also aligning our capital structure to be closer to that of R&D-focused rare disease biopharma companies, which generally have lower debt levels.  We recently announced plans to pay down approximately $550 million of our outstanding debt, which was $2.0 billion at December 31, 2018, using available cash and proceeds from our recent $345 million underwritten public offering.  This initiative which will lower our outstanding debt and leverage ratio, and at the same time allow us the flexibility to take advantage of business development opportunities.  We subsequently paid down $300 million of the debt.  Our current outstanding debt is now $1.7 billion, and we are on track to pay down the remaining $250 million of our $550 million target.  This initiative exemplifies our disciplined approach to debt and efficient use of capital, which together with our strong cash balance enable continued investment in our pipeline and KRYSTEXXA. 

Our Future:  Our Expanding Pipeline

Expanding our pipeline to drive long-term sustainable growth is a strategic priority. 

Our lead pipeline candidate,teprotumumab, which we acquired in 2017, is a fully human monoclonal antibody insulin-like growth factor1-receptor(IGF-1R) for the treatment of active thyroid eye disease (TED).  TED is a rare, autoimmune inflammatory eye disease in which local inflammation and tissue expansion behind the eye can lead to proptosis (eye bulging).  Proptosis can result in double vision, misalignment of the eyes, and an inability to close the eyelids, making the tasks of daily life challenging.  Currently, there are no U.S. Food and Drug Administration (FDA) approved treatments available for treating TED.  Following the presentation of breakthrough Phase 2 results in 2017, in February 2019 we announced the Phase 3 trial topline data, which demonstrated a highly statistically significant reduction in proptosis, with 82.9 percent of teprotumumab patients meeting the primary endpoint versus 9.5 percent of placebo patients.  We continue to expect to submit a biologics license application to the FDA inmid-2019. We are also conducting an extension study, known asOPTIC-X, which will help inform us if patients would benefit from longer treatment or retreatment with teprotumumab. 

Inuncontrolled gout, our R&D strategy is to maximize the benefits ofKRYSTEXXA, as well as to enhance and sustain our leadership position through the development of new medicines.  For KRYSTEXXA, which is the only approved treatment for uncontrolled gout, we are investigating ways to improve the patient response rate so that it can benefit more patients.  (Uncontrolled gout is chronic gout that is refractory to conventional therapies.)  Our MIRROR trial is evaluating the combination of KRYSTEXXA and methotrexate, which is the immunomodulator most commonly used by rheumatologists, with the goal to increase the number of patients that can benefit from KRYSTEXXA.  Based on recent positive external case series data, we are adapting the trial to support the potential for registration, with enrollment expected to begin in the second quarter of 2019.  We will also be initiating a clinical trial in the second half of 2019 to study the effect of KRYSTEXXA on serum uric acid levels in kidney transplant patients with uncontrolled gout.  In addition, we are working on three preclinical programs designed to build on and sustain our leadership position in uncontrolled gout well into the future:  two next-generation biologics for uncontrolled gout and the other a long-term collaboration to discover and develop novel therapeutics for gout. 

In support of our expanding pipeline and the value-maximization of ouron-market medicines, in 2018, we considerably augmented the scientific expertise and acumen of ourR&D organization. Shao-Lee Lin, M.D., Ph.D., joined Horizon in January 2018 in the new role of chief scientific officer and head of R&D.  Dr. Lin is an immunologist, rheumatologist and allergist with more than 20 years of academic and industry experience.  She has established a new leadership team that oversees our R&D programs, partners with business development on pipeline opportunities and manages the therapeutic area development strategies and portfolios. 

Our Pipeline

Driving Growth Today and Tomorrow:  Our Orphan and Rheumatology Segment

We have two segments:  orphan and rheumatology, and primary care.  The orphan and rheumatology segment is the strategic driver of our growth today.  Its compound annual growth rate from 2014 to 2018 of 101 percent underscores the value of our focus on rare disease medicines. 

The orphan and rheumatology segment includes KRYSTEXXA, our flagshipon-market medicine.  In addition, if approved, teprotumumab, our late-stage development biologic candidate, will be part of this segment’s portfolio.  The segment also includes a durable base of rare disease medicines:  RAVICTI^®, for the treatment of urea cycle disorders; PROCYSBI^®, for the treatment of nephropathic cystinosis and ACTIMMUNE^®, for the treatment of chronic granulomatous disease. 

We believe the orphan and rheumatology segment offers tremendous potential for future growth.  KRYSTEXXA and teprotumumab, if approved, both offer significant growth potential, and we estimate peak annual net sales of more than $750 million for each. 

Our Orphan and Rheumatology Segment: 

Driving Growth Now and In the Future

Teprotumumab is an investigational candidate and its safety and efficacy have not been established. 

CAGR: compound annual growth rate.

The Foundation of Our Success:  Strong Business Development and Commercial Execution

The foundation of our success since we launched as a public company in 2011 lies in our strong business development capabilities and commercial execution. 

Business development is an integral factor in our success — both since launch and going forward — and was a key component of our transformation into a biopharma company focused on rare disease medicines.  In 2014, we began rapidly diversifying our portfolio with rare disease medicines through key transactions that brought us ACTIMMUNE, RAVICTI, KRYSTEXXA and PROCYSBI over the next three years.  In 2017, we made our first acquisition of a development-stage candidate medicine — teprotumumab — beginning the expansion of our pipeline, which is a current strategic priority. 

Being able to quickly take advantage of strategic opportunities is one of our business development strengths, and it has served us well with the many acquisitions we have completed that have performed above and beyond our expectations.  Given the importance of acquisitions to our strategy, it is important that we retain the flexibility to efficiently raise capital going forward, particularly since many acquisitions are highly competitive. 

We Have Transformed to Become a Biopharma Company Focused on Rare Disease Medicines

Through Our Business Development Capabilities

Rare Disease Medicine Acquisitions 2014-2019

Commercial execution — Acquiring assets is not a guarantee of success.  We, however, have a strong record of successfully commercializing our medicines and improving the performance of the medicines we acquire.  We attribute our successful results to the deep expertise and knowledge of our commercial teams, coupled with the holistic approach we employ supporting our patient and physician communities. KRYSTEXXA is a prime example of the value of our approach:  it was an underperforming asset when we acquired it in 2016.  In only two years we transformed it into the flagship growth driver it is for us today — more than quadrupling its net sales to $259 million in 2018.  Our commercial team understands the market for KRYSTEXXA, and we invested in 2018 to accelerate the potential we see for the medicine — more than $750 million in peak annual net sales. 

Our Purpose:  To Help Build Healthier Communities, Urgently and Responsibly

At Horizon, we are making the world a better place — one patient, one medicine, one community at a time.  That’s why we go to incredible lengths to impact incredible lives — to make health a priority, not a privilege.  That’s what drives our insistence that patients have access to our medicines, regardless of their ability to pay, supporting patients in 2018 with nearly $2.0 billion in assistance, representing 46 percent of our full-year gross sales.  We are transforming health by building healthier communities both urgently and responsibly.  As a company we are going to incredible lengths to impact incredible lives.  It’s in our DNA — who we are as a company and who we are as individuals.  For us, it’s personal — we want to make a difference.  Our social responsibility programs, patient advocacy support and awareness, dedication to individual employee volunteerism — all reflect our ideals, a commitment to our patients and the communities we serve. 

Our dedication and commitment are evident in the recognition we receive.  We were honored in 2018 to be spotlighted byPEOPLE Magazine as one of the“50 Companies That Care” — companies that succeed in business while also demonstrating respect, compassion and concern for their communities, employees and the environment.  This distinction is a realization of what we strive for — to be a positive force for good amid a constantly changing health care system.  We also became a member ofPledge 1%, a corporate philanthropy movement that empowers companies to donate 1% of product, 1% of equity, 1% of profit or 1% of employee time to improve communities around the world.  We are one of the first biopharma companies to join the initiative, which includes6,000-plus organizations across 100 countries. 

Horizon is a great place to work and our employees tell us so.  We continue to place in multiple third-party workplace recognition surveys, including being named byFORTUNE Magazine as theNumber One “Best Workplace in BioPharma.” We are also proud to have been named byCrain’s Chicago Business as one of the “Best Places to Work for Women in Chicago” in 2018.  The percentage of women of our total employee population is above the industry standard for all levels in the Company, including upper management levels, reflecting the value we place on diversity.  But diversity encompasses more than gender:  we believe that people from different backgrounds and life experiences fuel innovation, which helps provide life-changing solutions for our patients — fostering healthier communities and making the world a better place. 

Consistently Recognized as One of the Best Places to Work —

And as a Company That Cares

Total Shareholder Return

Our disciplined approach, with our clear strategy, business development acumen and strong commercial execution, has driven rapid transformational growth.  As a result, we have outperformed both our peer group and the NBI over theone-, three- and five-year periods ended December 31, 2018.  With our durable base of rare disease medicines, our high-growth KRYSTEXXA medicine and the pipeline we are building for future growth, including our late-stage development candidate teprotumumab, we believe Horizon is well positioned for sustainable long-term growth. 

Note:  The peer group used for the TSR calculations for the1-,3- and5-year periods ended December 31, 2018 is our peer group shown on page 44. 

Director Nominees and Continuing Directors

Board Highlights

The Nominating and Corporate Governance Committee of our Board examines multiple factors when evaluating directors, including their knowledge, skills and experience, including experience in our industry and with respect to clinical development, business, finance, management and public service.  The Committee believes in an expansive definition of diversity that includes differences of experience, education, talents, gender and race, among other things.  The table below highlights the extensive experience of our directors as well as a balance of skills on our Board: 

Our Board, which is predominantly independent, includes a range of expertise, experience, diversity, as well as newer and longer-tenured directors.  The Board values diversity, believing that maintaining a diverse membership enhances the Board’s deliberations and enables the Board to better represent all of the Company’s constituents.  In this respect, the goal of the Nominating and Corporate Governance Committee is to ensure that the Board has diversity of experience and perspectives, as well as race, gender, geography and areas of expertise — as is set forth in theDiversity Policy the Board instituted in 2018, which is available on our website atwww.horizonpharma.com. 

Corporate Governance Highlights

Executive Compensation Overview

Our executive compensation program emphasizes three major pay considerations, and this is how we currently achieve them:

With a strategic focus on growing the business over the long term, it is imperative that our executive compensation program motivates our talented management team in such a manner as to encourage — and reward — successful execution of this business strategy.  We utilize the following compensation elements to achieve this: 

Shareholder Engagement

We value the views of our shareholders.  During the governance outreach we have conducted over the past five years, we have had significant and meaningful dialogue with our shareholders regarding our compensation and governance.  Feedback from our outreach informs the Compensation Committee’s thinking when evaluating our current compensation program and considering potential modifications going forward. 

Changes to our compensation program and corporate governance over the past several years that were heavily influenced by shareholder feedback include: 

In 2018, during our spring engagement cycle before the Annual General Meeting, we offered engagement opportunities to 67 percent of our shareholders, and dialogued with 32 percent of our shareholders.  At our 2018 Annual General Meeting of Shareholders, oursay-on-pay proposal received the support of 95 percent of the shares voted.  We believe this high level of support is a result of our comprehensive shareholder outreach and engagement program to solicit feedback, understand investor viewpoints and incorporate their feedback into further discussions of our compensation programs and corporate governance. 

In addition, our shareholder engagement provides a forum for educating shareholders on key issues of importance to the Company.  For example, during our 2018 fall engagement cycle, we had discussions with 31 percent of our shareholders on the share-issuance authority we are required to receive from our investors as part of being an Irish plc, as well other governance- and compensation-related topics.  Given that not all of our holders were familiar with the share-issuance authority requirements, we wanted to provide them with the opportunity to learn about the requirements and understand the nuances of our situation as an Irish plc listed on The Nasdaq Stock Market LLC (Nasdaq), a U.S. stock exchange.  Our shareholders appreciated the outreach, and the feedback from this engagement was very positive.

We value the dialogue we have with our shareholders and remain committed to conducting consistent engagement going forward. 

Please see our Compensation Discussion and Analysis on page 32 for additional information on our compensation philosophy. 

QUESTIONS AND ANSWERS ABOUT THESE PROXY MATERIALS AND VOTING

Why am I receiving these materials?

We have sent you these proxy materials because our Board is soliciting your proxy to vote at the Annual General Meeting, including at any adjournments or postponements of the meeting.  You are invited to attend the Annual General Meeting to vote on the proposals described in this Proxy Statement.  However, you do not need to attend the meeting to vote your shares.  Instead, you may simply complete, sign and return the enclosed proxy card, or follow the instructions below to submit your proxy over the telephone or through the internet. 

How do I attend the Annual General Meeting?

The meeting will be held on Thursday, May 2, 2019, at 3:00 p.m. local time at our corporate headquarters located at Connaught House, 1^st Floor, 1 Burlington Road, Dublin 4, D04 C5Y6, Ireland.  Directions to the Annual General Meeting may be found athttps://www.google.com/maps/place/Connaught+House,+Burlington+Rd,+Dublin+4,+Ireland.  Information on how to vote in person at the Annual General Meeting is provided below.  However, you do not need to attend the Annual General Meeting to vote your ordinary shares. 

Who can vote at the Annual General Meeting?

Only shareholders of record at the close of business on March 13, 2019 will be entitled to vote at the Annual General Meeting.  On this record date, there were 184,433,612 of our ordinary shares outstanding and entitled to vote. 

Shareholder of Record (shares registered in your name). If on March 13, 2019, your shares were registered in your name in our Register of Members, which is maintained by our transfer agent, Computershare Shareowner Services LLC, then you are a shareholder of record.  As a shareholder of record, you may vote in person at the meeting or vote by proxy.  Whether or not you plan to attend the meeting, we urge you to fill out and return the enclosed proxy card or vote by proxy over the telephone or on the internet as instructed below to ensure your vote is counted. 

Beneficial Owner (shares registered in the name of a broker or bank). If on March 13, 2019, your shares were not registered in your name in our Register of Members, but rather held in an account at a brokerage firm, bank, dealer or other similar organization, then you are the beneficial owner of shares held in “street name” and these proxy materials are being forwarded to you by that organization.  The organization holding your account is considered to be the shareholder of record for purposes of voting at the Annual General Meeting.  As a beneficial owner, you have the right to direct your broker or other agent regarding how to vote the shares in your account.  You are also invited to attend the Annual General Meeting.  However, since you are not the shareholder of record, you may not vote your shares in person at the meeting unless you request and obtain a valid proxy from your broker or other agent. 

What am I voting on?

There are 11 matters scheduled for a vote:

What if another matter is properly brought before the meeting?

The Board knows of no other matters that will be presented for consideration at the Annual General Meeting.  If any other matters are properly brought before the meeting, it is the intention of the persons named in the accompanying proxy to vote on those matters in accordance with their best judgment. 

How do I vote?

You may vote “For” or “Against” each Class II director nominee or you may abstain from voting for all or any of the nominees.  For each of the other matters to be voted on, you may vote “For” or “Against” or abstain from voting. 

The procedures for voting are fairly simple:

Shareholder of Record. If you are a shareholder of record, you may vote in person at the Annual General Meeting, vote by proxy using the enclosed proxy card, vote by proxy over the telephone or vote by proxy through the internet.  Whether or not you plan to attend the meeting, we urge you to vote by proxy to ensure your vote is counted.  You may still attend the meeting and vote in person even if you have already voted by proxy. 

Beneficial Owner. If you are a beneficial owner of shares registered in the name of your broker, bank or other agent, you should have received a voting instruction form with these proxy materials from that organization rather than from us.  Simply complete and mail the voting instruction form to ensure that your vote is counted.  Alternatively, you may vote by telephone or through the internet as instructed by your broker or bank.  To vote in person at the Annual General Meeting, you must obtain a valid proxy from your broker, bank or other agent.  Follow the instructions from your broker or bank included with these proxy materials or contact your broker or bank to request a proxy form. 

Joint Holders. In the case of joint holders of record, any one of such holders may vote either in person or by proxy in respect thereof as if he or she were the sole holder thereof, but the vote of the senior holder who tenders a vote, whether in person or by proxy, shall be accepted to the exclusion of the votes of the other joint holders, and for this purpose seniority shall be determined by the order in which the names stand in our Register of Members. 

How many votes do I have?

On each matter to be voted upon, you have one vote for each ordinary share you own as of March 13, 2019. 

What happens if I do not vote?

Shareholder of Record. If you are a shareholder of record and do not vote by completing your proxy card, by telephone, through the internet or in person at the Annual General Meeting, your shares will not be voted. 

Beneficial Owner. If you are a beneficial owner and do not instruct your broker, bank, or other agent how to vote your shares, the question of whether your broker or nominee will still be able to vote your shares depends on whether the New York Stock Exchange (NYSE) deems the particular proposal to be a “routine” matter.  Brokers and nominees can use their discretion to vote “uninstructed” shares with respect to matters that are considered to be “routine,” but not with respect to“non-routine” matters.  Under the rules and interpretations of the NYSE,“non-routine” matters are matters that may substantially affect the rights or privileges of shareholders, such as mergers, shareholder proposals, elections of directors (even if not contested), executive compensation (including any advisory shareholder votes on executive compensation) and certain corporate governance proposals, even if management-supported.  We have been advised by the NYSE that your broker or nominee may not vote your shares on Proposals 1, 3, 10 or 11 without your instructions, but may vote your shares on Proposals 2, 4, 5, 6, 7, 8 and 9. 

What if I return a proxy card or otherwise vote but do not make specific choices?

If you return a signed and dated proxy card or otherwise vote without marking voting selections, then our designated proxy holders (one of the individuals named on your proxy card) will vote your shares in the manner recommended by our Board on all matters presented in this Proxy Statement and as the proxy holders may determine in their discretion regarding any other matters properly presented for a vote at the meeting.  If any other matter is properly presented at the meeting, your proxy holder will vote your shares using his or her best judgment. 

Who is paying for this proxy solicitation?

We have retained Alliance Advisors, a proxy solicitation firm, to solicit proxies in connection with the Annual General Meeting at a cost of approximately $35,000 plus expenses.  The cost of soliciting proxies incurred by us and Alliance Advisors, including the preparation, assembly and mailing of the proxies and soliciting material, as well as the cost of forwarding such material to beneficial owners of our ordinary shares, will be borne by us.  Our directors, officers and other employees may, without compensation other than their regular remuneration, solicit proxies personally or by telephone. 

What does it mean if I receive more than one set of proxy materials?

If you receive more than one set of proxy materials, your shares may be registered in more than one name or in different accounts.  Please follow the voting instructions on the proxy cards in each set of proxy materials to ensure that all of your shares are voted. 

Can I change my vote after submitting my proxy?

Shareholder of Record. Yes, you may revoke your proxy at any time before the final vote at the meeting.  If you are the record holder of your shares, you may revoke your proxy in any one of the following ways:

Your most current proxy card or telephone or internet proxy is the one that is counted. 

Beneficial Owner.  If your shares are held by your broker or bank as a nominee or agent, you should follow the instructions provided by your broker or bank. 

Do I need a ticket to attend the Annual General Meeting?

You will need an admission ticket or proof of ownership of ordinary shares to enter the Annual General Meeting.  If you are a shareholder of record, your admission ticket is the top half of the proxy card sent to you.  If you plan to attend the Annual General Meeting, please so indicate when you vote and bring the ticket with you to the Annual General Meeting.  If your shares are held in the name of a bank, broker or other holder of record, you do not need an admission ticket, but you will need proof of ownership to be admitted to the Annual General Meeting.  A recent brokerage statement or letter from a bank or broker is an example of proof of ownership.  If you arrive at the Annual General Meeting without an admission ticket or proof of ownership of ordinary shares, we will admit you only if we are able to verify that you are one of our shareholders. 

How are votes counted?

Votes will be counted by the inspector of election appointed for the meeting, who will separately count, with respect to the proposal to elect directors, votes “For,” “Against,” abstentions and brokernon-votes; and, with respect to other proposals, votes “For” and “Against,” abstentions and, as applicable, brokernon-votes. Abstentions and brokernon-votes will be treated as shares present for the purpose of determining the presence of a quorum for the transaction of business at the Annual General Meeting.  Abstentions and brokernon-votes will not, however, be considered votes cast at the Annual General Meeting.  Because the approval of all of the proposals is based on the votes cast at the Annual General Meeting, abstentions and brokernon-votes will not have any effect on the outcome of voting on the proposals. 

What are “brokernon-votes”?

As discussed above, when a beneficial owner of shares held in “street name” does not give instructions to the broker or nominee holding the shares as to how to vote on matters deemed by the NYSE to be“non-routine,” the broker or nominee cannot vote the shares.  Theseun-voted shares are counted as “brokernon-votes.”

What is the quorum requirement?

A quorum of shareholders is necessary to hold a valid meeting.  A quorum will be present if shareholders holding a majority of the issued and outstanding ordinary shares entitled to vote are present at the meeting in person or represented by proxy.  On the record date, there were 184,433,612 ordinary shares outstanding and entitled to vote.  Thus, the holders of 92,216,807 ordinary shares must be present in person or represented by proxy at the meeting to have a quorum. 

Your shares will be counted towards the quorum only if you submit a valid proxy (or one is submitted on your behalf by your broker, bank or other nominee) or, provided that you are a shareholder of record, if you vote in person at the meeting.  Abstentions and brokernon-votes will be counted towards the quorum requirement.  If there is no quorum, within one hour of the time appointed for the Annual General Meeting, the Annual General Meeting will stand adjourned to May 9, 2019, at 3:00 p.m. local time at the same location, or such other time or place as the Board may determine. 

Assuming there is a quorum of shares present at the Annual General Meeting, how many votes are needed to approve each proposal?

Proposal 7 will be redundant in the event Proposal 6 is not approved. 

How can I find out the results of the voting at the Annual General Meeting?

Preliminary voting results will be announced at the Annual General Meeting.  In addition, final voting results will be published in a current report on Form8-K that we expect to file within four business days after the Annual General Meeting.  If final voting results are not available to us in time to file a Form8-K within four business days after the meeting, we intend to file a Form8-K to publish preliminary results and, within four business days after the final results are known to us, file an additional Form8-K to publish the final results. 

What are the Irish statutory financial statements?

We are presenting our Irish statutory financial statements, including the reports of the directors and the statutory auditors thereon, at the Annual General Meeting, and we are making a copy of them available for download in PDF format in the Investors section (see Annual Reports subsection) of our website (www.horizonpharma.com) on or before April 11, 2019.  Since we are an Irish company, we are required to prepare Irish statutory financial statements under applicable Irish company law and to deliver those accounts to shareholders of record in connection with our Annual General Meetings of Shareholders.  The Irish statutory financial statements cover the results of operations and financial position of Horizon Pharma plc for the year ended December 31, 2018.  Irish law requires the directors to prepare financial statements for each financial year giving a true and fair view of the state of the group’s and parent company’s affairs at the end of the financial year and of the group’s profit or loss for the financial year.  Under that law, the directors have prepared the group’s consolidated financial statements in accordance with U.S. accounting standards, as defined in Section 279 of the Irish Companies Act 2014, to the extent that the use of those accounting standards in the preparation of the consolidated financial statements does not contravene any provision of the Irish Companies Act 2014 or of any regulations made thereunder and have prepared the Irish statutory financial statements in accordance with accounting standards issued by the Financial Reporting Council and promulgated by the Institute of Chartered Accountants in Ireland (Generally Accepted Accounting Practice in Ireland). 

We will mail without charge, upon written request, a copy of the Irish statutory financial statements to shareholders of record or beneficial owners of our ordinary shares.  Requests should be sent to: Horizon Pharma plc, Attention: Company Secretary, Connaught House, 1^st Floor, 1 Burlington Road, Dublin 4, D04 C5Y6, Ireland. 

What proxy materials are available on the internet?

The Proxy Statement and the Annual Report to shareholders are available atwww.proxyvote.com. 

PROPOSAL 1

ELECTION OF DIRECTORS

The Board is divided into three classes.  Each class consists, as nearly as possible, ofone-third of the total number of directors and each class has a three-year term.  The Board currently consists of nine members, as follows:

The authorized number of directors may be changed only by resolution of the Board.  Any additional directorships resulting from an increase in the number of directors will be distributed between the three classes so that, as nearly as possible, each class will consist ofone-third of the directors.  This classification of the Board may have the effect of delaying or preventing changes in our control or management.  Our directors may be removed by ordinary resolution with majority vote of our shareholders at a general meeting provided that notice of such resolution has been given in accordance with Section 146 of the Irish Companies Act 2014.  Vacancies on the Board may be filled only by persons elected by a majority of the directors then in office, provided that a quorum is present.  A director elected by the Board to fill a vacancy in a class, including vacancies created by an increase in the number of directors, shall serve for the remainder of the full term of that class and until the director’s successor is duly elected and qualified. 

There are currently three directors in Class  II whose term of office expires in 2019, one of whom, Ronald Pauli, will not be subject tore-election at the 2019 Annual General Meeting.  Each of the nominees listed below in Class  II is currently one of our directors who was nominated for election by the Board, upon the recommendation of the Nominating and Corporate Governance Committee. In order to be elected as a director, each nominee must receive the affirmative vote of a majority of the votes cast by the holders of ordinary shares represented at the Annual General Meeting in person or by proxy.  If elected, each of these nominees would serve until the 2022 Annual General Meeting of Shareholders and until his or her successor has been duly elected and qualified, or, if sooner, until the director’s death, resignation, disqualification or removal. 

THE BOARD RECOMMENDS

A VOTE IN FAVOR OF EACH NAMED NOMINEE

THE BOARD OF DIRECTORS AND ITS COMMITTEES

In 2018, the Board held six meetings and did not act by unanimous written consent without a meeting.  Each Board member attended 93% or more of the aggregate number of meetings of the Board and of the committees on which he or she served.  It is our policy to encourage directors and nominees for director to attend annual general meetings of shareholders.  All our current directors attended our 2018 Annual General Meeting of Shareholders. 

The Board is committed to exercising good corporate governance practices.  As part of this commitment, the Board regularly monitors developments in corporate governance and reviews processes, policies and procedures in light of such developments.  Key information regarding our corporate governance initiatives can be found on our website,www.horizonpharma.com, including our Memorandum and Articles of Association, Code of Business Conduct and Ethics, and the charters for the Audit, Compensation, Nominating and Corporate Governance and Transaction Committees.  The Board believes that its strong corporate governance policies and practices, including the substantial percentage of independent directors on the Board and the robust duties of its lead independent director, empower the Board to effectively oversee our Chief Executive Officer and provide an effective and appropriately balanced Board governance structure. 

Other than Mr. Walbert, our chairman, president and chief executive officer, all members of the Board are independent and all members of committees of the Board are independent.  The Board has affirmatively determined that the following eight directors are independent directors within the meaning of the applicable Nasdaq Stock Market (Nasdaq) listing standards:  Mr. Daniel, Mr. Grey, Dr. Himawan, Mr. Pauli, Mr. Santini, Dr. Shannon, Mr. Watkins and Ms. Witz.  In making this determination, the Board found that none of these directors or nominees for director had a material or other disqualifying relationship with us.  Mr. Walbert is not an independent director by virtue of his current employment with us.  To determine independence, the Board reviewed all relevant identified transactions or relationships between each director, or any of his or her family members, and us, our senior management and our independent registered public accounting firm. 

As required under applicable Nasdaq listing standards, in fiscal year 2018, our independent directors met four times in regularly scheduled executive sessions at which only independent directors were present. 

We have adopted a Code of Business Conduct and Ethics (the Code) that applies to all officers, directors and employees, including our principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions.  The Code is available on our website atwww.horizonpharma.com.  If we make any substantive amendments to the Code or grants any waiver from a provision of the Code to any executive officer or director, we will promptly disclose the nature of the amendment or waiver on its website or in a current report on Form8-K. 

The Board has determined that the current leadership structure, in which the offices of Chairman and Chief Executive Officer are held by one individual and an independent director acts as lead independent director, ensures that the appropriate level of oversight, independence, and responsibility is applied to all Board decisions, including risk oversight, and is in our best interests and those of our shareholders. 

Chairman/Chief Executive Officer

The Board is currently chaired by our President and Chief Executive Officer, Mr. Walbert.  We believe that combining the positions of Chief Executive Officer and Chairman of the Board helps to ensure that the Board and management act with a common purpose for the following reasons:

Lead Independent Director

We require the election, by the independent directors of the Board, of a lead independent director to serve during any period when there is no independent Chairman of the Board.  Because Mr. Walbert is currently serving as Chief Executive Officer and Chairman of the Board, the independent directors of the Board elected Mr. Grey as the lead independent director.  The lead independent director serves as the liaison between the Chairman of the Board and the independent directors and his responsibilities include:

One of the Board’s key functions is informed oversight of our risk management process.  The Board does not have a standing risk management committee, but rather administers this oversight function directly through the Board as a whole, as well as through various Board standing committees that address risks inherent in their respective areas of oversight.  In particular, the Board is responsible for monitoring and assessing strategic risk exposure, including a determination of the nature and level of risk appropriate for the Company.  Our Audit Committee has the responsibility to consider and discuss our major financial risk exposures and the steps our management has taken to monitor and control these exposures, including guidelines and policies to govern the process by which risk assessment and management is undertaken and provides oversight of the performance of our internal audit function and external auditors.  The Audit Committee also reviews and receives regular briefings concerning information security and technology risks (including cybersecurity), including discussions of our information security and risk management programs.  Our Nominating and Corporate Governance Committee monitors the effectiveness of our corporate governance guidelines, including whether they are successful in preventing illegal or improper liability-creating conduct, and monitors compliance with legal, regulatory and ethical requirements.  Our Compensation Committee assesses and monitors whether any of our compensation policies and programs has the potential to encourage excessive risk-taking.  Our Transaction Committee evaluates potential strategic transactions and financing opportunities, including the risks that such transactions could pose to the Company. 

The Nominating and Corporate Governance Committee will consider candidates for the Board who are recommended by shareholders, directors, third-party search firms engaged by the Board and other sources.  When selecting candidates for recommendation to the Board, the Nominating and Corporate Governance Committee will consider the attributes of the candidates and the needs of the Board and will review all candidates in the same manner, regardless of the source of the recommendation.  In evaluating director nominees, a candidate should have certain minimum qualifications, including being able to read and understand basic financial statements, having familiarity with our business and industry, having high moral character and mature judgment and being able to work collegially with others.  In addition, factors such as the following may be considered:

During 2018, we paid a fee to one third-party search firm that was retained by the Board to identify potential nominees and assist our Nominating and Corporate Governance Committee in evaluating such potential nominees. 

Diversity Policy

The Board believes that maintaining a diverse membership enhances the Board’s deliberations and enables the Board to better represent all of the Company’s constituents, and as such has a formal diversity policy.  As part of the policy, the Nominating and Corporate Governance Committee annually reviews the tenure, performance, and contributions of existing Board members to the extent they are candidates forre-election and considers all aspects of each candidate’s qualifications and skills with the goal of ensuring the Board has diversity of experience and perspectives as well as race, gender, geography, and areas of expertise. 

To further this goal, the Board is committed to including in each director search highly qualified candidates who reflect diverse experiences and backgrounds, including diversity of gender and race.  The diversity policy is available on our website atwww.horizonpharma.com. 

Shareholders who wish to recommend individuals for consideration by the Nominating and Corporate Governance Committee to become nominees for election to the Board at an Annual General Meeting of Shareholders must do so by delivering a written recommendation to the Nominating and Corporate Governance Committee.  See “Other Information — Shareholder Proposals” in this Proxy Statement for additional information. 

The Board has four standing committees: the Audit Committee, Compensation Committee, Nominating and Corporate Governance Committee, and Transaction Committee.  All committees are comprised of independent directors within the meaning of the applicable Nasdaq listing standards.  A description of each committee of the Board is described below. 

The following table provides membership and meeting information for fiscal year 2018 for each of the Board committees:

		Audit		Compensation		Nominating and        Corporate Governance		Transaction
Timothy P. Walbert
Michael Grey
William F. Daniel
Jeff Himawan, Ph.D.
Ronald Pauli(1)
Gino Santini
James Shannon, M.D.(2)
H. Thomas Watkins
Pascale Witz(3)
Total meetings in fiscal year 2018		5		6		4		7

= Chair		= Member		= Lead Independent Director

(1)

Mr. Pauli has served on the Nominating and Corporate Governance Committee since February 2018.  Mr. Pauli will not be subject tore-election at the 2019 Annual General Meeting and will no longer serve on any committees of the Board after the 2019 Annual General Meeting.

(2)

Dr. Shannon has served on the Compensation Committee since February 2018.

(3)

Ms. Witz has served on the Audit Committee since February 2018.

Audit Committee

The Audit Committee assists the Board in fulfilling its oversight responsibility with respect to, among other things: (i) our corporate accounting and financial reporting practices, (ii) the system of internal control over financial reporting, (iii) the audit

process, (iv) the quality and integrity of our financial statements, (v) the qualifications, independence and performance of our independent registered public accounting firm, (vi) the qualifications, independence and performance of our internal audit function and (vii) enterprise risk management.  Each of the independent registered public accounting firm, internal audit and management periodically meet privately with the Audit Committee. 

The Board has determined that Mr. Daniel qualifies as an “audit committee financial expert,” within the meaning of applicable SEC rules.  In making this determination, the Board has considered Mr. Daniel’s formal education, the nature and scope of his previous experience and his financial and corporate governance expertise. 

Report of the Audit Committee of the Board of Directors

The material in this report is not “soliciting material,” is not deemed “filed” with the SEC and is not to be incorporated by reference in any of our filings under the Securities Act of 1933, as amended (the Securities Act), or the Securities Exchange Act of 1934, as amended (Exchange Act), whether made before or after the date hereof and irrespective of any general incorporation language in any such filing.  

The Audit Committee has reviewed and discussed the audited financial statements for the fiscal year ended December 31, 2018 with management of the Company.  The Audit Committee has discussed with the independent registered public accounting firm the matters required to be discussed by Auditing Standard No. 1301, Communications with Audit Committees, as adopted by the Public Company Accounting Oversight Board (PCAOB).  The Audit Committee has also received the written disclosures and the letter from the independent registered public accounting firm required by applicable requirements of the PCAOB regarding the independent registered public accounting firm’s communications with the Audit Committee concerning independence, and has discussed with the independent registered public accounting firm the accounting firm’s independence.  Based on the foregoing, the Audit Committee has recommended to the Board that the audited financial statements be included in the Company’s Annual Report on Form10-K for the fiscal year ended December 31, 2018. 

Audit Committee

William F. Daniel,Chairman

Ronald Pauli

H. Thomas Watkins

Pascale Witz

Compensation Committee

The Compensation Committee oversees, reviews and approves or recommends for adoption our compensation policies, plans and programs, reviews and approves or recommends to the full Board, as appropriate, the compensation to be paid to our executive officers and directors, and prepares and reviews the Compensation Committee report included in our annual proxy statement.  In making its compensation decisions and recommendations, the Compensation Committee may take into account the recommendations of the Chief Executive Officer and other senior management.  Other than giving such recommendations, however, the Chief Executive Officer and other senior management have no formal role and no authority to determine the amount or form of executive and director compensation.  The processes and procedures used for the consideration and determination of executive compensation are described in the section of this Proxy Statement captioned, ‘‘Compensation Discussion and Analysis.’’

The Compensation Committee may, at our expense, retain legal counsel (which may, but need not be, our regular corporate counsel) and other consultants and advisors, other thanin-house legal counsel and certain other types of advisors, to assist it with its functions only after taking into consideration six factors, prescribed by the SEC and Nasdaq, that bear upon the advisor’s independence; however, there is no requirement that any advisor be independent.  The Compensation Committee has authority to approve such advisors’ fees and other retention terms and to terminate its relationship with any advisor that it retains.  In addition, the Compensation Committee has authority to delegate its responsibilities to subcommittees or individual committee members. 

In October 2016, our Compensation Committee engaged Radford, an Aon Hewitt Company (Radford), as its independent consultant.  For additional information regarding our processes and procedures for the consideration and determination of executive compensation, including the role of Radford in determining and recommending executive compensation, the aggregate cost of Radford’s executive and director compensation consulting services during 2018, see the section of this Proxy Statement entitled “Compensation Discussion and Analysis — Compensation Determination Process.” With respect to director compensation matters, our Compensation Committee recommends to our Board and our Board determines and setsnon-employee director compensation.  Our compensation arrangements for ournon-employee directors are described under the section of this Proxy Statement entitled“Non-Employee Director Compensation.”

Compensation Committee Interlocks and Insider Participation

No member of our Compensation Committee has ever been an executive officer or employee of the Company.  None of our executive officers currently serves, or has served during the last completed year, on the compensation committee or board of directors of any other entity that has one or more officers serving as a member of our Board or Compensation Committee. 

Nominating and Corporate Governance Committee

The Nominating and Corporate Governance Committee oversees all aspects of our corporate governance functions on behalf of the Board, including, but not limited to, (i) making recommendations to the Board regarding corporate governance issues; (ii) identifying, reviewing and evaluating candidates to serve as our directors consistent with criteria approved by the Board and reviewing and evaluating incumbent directors; (iii) serving as a focal point for communication between such candidates,non-committee directors and our management; (iv) nominating candidates to serve as directors; (v) making other recommendations to the Board regarding affairs relating to our directors; and (vi) providing oversight assistance in connection with our legal, regulatory and ethical compliance programs, policies and procedures as established by management and the Board.

The process used by the Nominating and Corporate Governance Committee to identify a nominee to serve as a member of the Board depends on the qualities being sought.  From time to time, the Board engages an executive search firm to assist the Nominating and Corporate Governance Committee in identifying individuals qualified to be Board members.  The process used by the Nominating and Corporate Governance Committee to identify nominees is described in the section of this Proxy Statement captioned, ‘‘Director Selection.’’

Transaction Committee

The functions of the Transaction Committee include, but are not limited to:

Description of Our Short-Term Shareholder Rights Agreement

In February 2019, we entered into a short-term shareholder rights agreement, commonly referred to as a poison pill.  In general terms, the shareholder rights agreement works by causing significant dilution to any person or group that acquires 10% (or 15% in the case of an existing “13G Investor” as defined in the shareholder rights agreement) or more of our outstanding ordinary shares without the prior approval of the Board.  The shareholder rights agreement, which has a limited12-month term expiring in February 2020, is not intended to prevent an acquisition of the company on terms that the Board considers favorable to and in the best interests of all shareholders.  Rather, the shareholder rights agreement aims to provide the Board with adequate time to fully assess any takeover proposal in full compliance with its fiduciary duties and to encourage anyone seeking to acquire us to negotiate with the Board prior to attempting a takeover.

Irish Takeover Rules Preclude a“Wait-and-See” Approach Under an“On-the-Shelf” Strategy

As an Irish public company, we are subject to the Irish Takeover Panel Act 1997, as amended, and the Irish Takeover Rules made thereunder.  Under the Irish Takeover Rules, we are precluded from adopting a shareholder rights agreement in the event that we receive an offer to acquire our company or we have reason to believe that such an offer is or may be imminent.  Many U.S.-incorporated companies, particularly those companies incorporated in Delaware, generally have the ability to design, prepare and draft a shareholder rights agreement in advance and put it“on-the-shelf,” with the actual adoption of the shareholder rights agreement delayed until a takeover proposal develops or becomes imminent.  However, as a result of the application of the Irish Takeover Rules, we do not have the ability to“wait-and-see” under this“on-the-shelf” shareholder rights agreement strategy available to U.S.-incorporated companies. 

Rationale for Adoption of Our Short-Term Shareholder Rights Agreement

The Board decided to adopt the shareholder rights agreement in response to the takeover environment in general and the Board’s belief that we face a heightened risk of receiving takeover proposals at inadequate prices, given several factors: our evolution into a biopharma company focused on rare disease medicines; the highly positive Phase 3 clinical trial results of our rare disease drug candidate teprotumumab for the treatment of active thyroid eye disease (TED) announced on February 28, 2019; the strong financial performance we delivered in 2018; the expected $750 million in peak sales for each of KRYSTEXXA and teprotumumab; and the investments we are making in 2019, all of which are discussed in our letter to shareholders at the beginning of this Proxy Statement, as well as the summary to this Proxy Statement beginning on page 2.  In addition, in making the determination, the Board considered our balance sheet cash, our debt levels and our capacity to continue to invest in building a pipeline of rare disease medicines.

Furthermore, as a result of our strong financial performance and our evolution into a rare disease-focused biopharma company, our stock-trading multiples as a percentage of net sales and adjusted EBITDA have increased to be more aligned with biopharma companies we view as comparable.  However, we do not believe analysts and investors have fully valued us as a biopharma company.  Instead, they continue to value us as a specialty pharma company, and we believe this adds to the risk of receiving an inadequately priced takeover proposal.

The adoption of the plan is not in response to any specific approach; as explained above, under the Irish Takeover Rules, we are precluded from adopting a shareholder rights agreement in such a case. 

In consideration of these factors, and due to the application of the Irish Takeover Rules, which preclude a“wait-and-see” approach under an“on-the-shelf” shareholder rights agreement strategy available to U.S.-incorporated companies, explained above, the Board determined that it was necessary and advisable to adopt the shareholder rights agreement in order to guard against attempts to acquire control of the Company at an inadequate price that would be unfair to our shareholders.  The Board balanced its assessment of that risk with what it believed was an appropriately limited term of the shareholder rights agreement, concluding that a short,12-month term was an adequate response to that risk.  Ultimately, the Board adopted the shareholder rights agreement to enable all of our shareholders to realize the long-term value of their investment in the Company.  During recent discussions with investors, our shareholders have generally been supportive of our strategy and the Board’s decision to adopt our shareholder rights agreement.

Shareholders who wish to communicate with the Board may do so by sending written communications addressed to the Company Secretary of Horizon Pharma at Connaught House, 1^st Floor, 1 Burlington Road, Dublin 4, D04 C5Y6, Ireland or by communicating online to the Board as a group.  This information and an online communications form are available on our website atwww.horizonpharma.com.  Each communication will be reviewed by our Company Secretary to determine whether it is appropriate for presentation to the Board or such director on a periodic basis.  Examples of inappropriate communications include advertisements, solicitations or hostile communications. 

EXECUTIVE OFFICERS

The following table sets forth information regarding executive officers as of March 1, 2019:

The following is biographical information as of March 1, 2019 for our executive officers other than Mr. Walbert, whose biographical information is included in Proposal 1.

Brian K. Beeler.  Mr. Beeler has served as our executive vice president, general counsel since May 2015.  Mr. Beeler previously served as our senior vice president, legal and chief compliance officer from January 2015 until May 2015 and as our associate general counsel and chief compliance officer from January 2013 until January 2015.  Prior to joining Horizon, Mr. Beeler served as associate general counsel for Fenwal, Inc., a global blood technology company, from December 2008 until December 2012.  Before that, Mr. Beeler was senior counsel, business development, commercial and research and development at TAP Pharmaceuticals and Takeda Pharmaceuticals North America and also previously served as chief compliance officer at Schwartz Pharma.  Mr. Beeler received a bachelor’s degree in history from Purdue University, a master’s degree in business administration from the Kellogg School of Management at Northwestern University and a JD from the Indiana University School of Law.

Robert F. Carey.  Mr. Carey has served as our executive vice president, chief business officer since March 2014.  Prior to that, Mr. Carey spent more than 11 years as managing director and head of the life sciences investment banking group at JMP Securities LLC, a full-service investment bank.  Prior to JMP, Mr. Carey was a managing director in the healthcare groups at Dresdner Kleinwort Wasserstein and Vector Securities.  Mr. Carey also has held roles at Shearson Lehman Hutton and Ernst & Whinney.  Mr. Carey serves on the board of directors of Sangamo Therapeutics, Inc., a public pharmaceutical company, and AIT Therapeutics, Inc., a public medical device and biopharmaceutical company.  Mr. Carey previously served on the board of directors of Argos Therapeutics Inc., a public pharmaceutical company, from 2014 to 2018.  Mr. Carey received his bachelor of business administration degree in accounting from the University of Notre Dame.

Geoffrey M. Curtis. Mr. Curtis has served as our executive vice president, corporate affairs and chief communications officer since August 2018.  Prior to that, from May 2017 he served as our senior vice president of corporate affairs and chief communications officer, and as group vice president of corporate communications from December 2015, when he joined the Company.  From May 2012 until April 2015, Mr. Curtis served as senior vice president at Edelman Public Relations and, as part of its National Health Media Team, he led media strategy and execution for a large portfolio of pharmaceutical, biotech and medical device clients.  Prior to that, Mr. Curtis was group director of the media practice at WCG, a marketing and communications firm and part of W20 Group, from July 2006 until May 2012 and held a similar role at GCI Group from March 2004 until July 2006.  Prior to joining GCI, Mr. Curtis served as a public affairs manager in the Pharmaceutical Products Division at Abbott, where he led internal and external communications programs for the immunology, neuroscience and oncology franchises.  Mr. Curtis has a bachelor’s degree in English from Lake Forest College in Lake Forest, Illinois.

Michael A. DesJardin.  Mr. DesJardin has served as our executive vice president, technical operations since February 2017.  Mr. DesJardin previously served as our senior vice president, technical operations from October 2016 to November 2016 and as our senior vice president, life cycle management from December 2016 to January 2017.  Mr. DesJardin joined Horizon from Raptor in October 2016 as part of the Raptor acquisition.  While at Raptor, Mr. DesJardin was the senior vice president of technical operations from April 2015 to October 2016.  Prior to that, Mr. DesJardin served as senior vice president of product development at Jazz Pharmaceuticals Public Limited Company (formerly Jazz Pharmaceuticals, Inc.) (Jazz) from July 2004 to March 2015.  Mr. DesJardin spent nine years as an executive director and engineering fellow at ALZA Corporation and spent 15 years at the Dow Chemical Company working in pharmaceutical and agricultural chemical development for Marion Merrill Dow.  Mr. DesJardin has over 38 years of experience in pharmaceutical development.  Mr. DesJardin received a bachelor of science

degree in chemical engineering from the University of California, Berkeley and is a registered professional engineer in the State of California.

Paul W. Hoelscher. Mr. Hoelscher has served as our executive vice president, chief financial officer since October 2014.  Previously, Mr. Hoelscher was our executive vice president, finance from June 2014 through September 2014.  Prior to joining Horizon, Mr. Hoelscher served as senior vice president, finance-treasury and corporate development of OfficeMax, Inc., from August 2013 to May 2014, and as vice president, finance-treasury and corporate development of OfficeMax from August 2012 to July 2013.  Prior to that, Mr. Hoelscher served in various finance roles at Alberto Culver Company from 1992 to 2012 and in various positions in the audit practice at KPMG LLP from 1986 to 1993.  He currently serves on the board of trustees of the Illinois Chapter of the Leukemia and Lymphoma Society.  Mr. Hoelscher received his bachelor of science degree in accountancy from the University of Illinois at Urbana-Champaign and is a certified public accountant.

Vikram Karnani.  Mr. Karnani has served as our executive vice president, chief commercial officer since March 2018.  Prior to that, he served as our senior vice president, rheumatology business unit from February 2017 to March 2018, and before that, from July 2014 until February 2017, he served as our general manager, specialty business unit.  Prior to joining Horizon, Mr. Karnani was with Fresenius Kabi, a global health care company, where he served as vice president of the therapeutics and cell therapy business, from October 2011 to July 2014.  Mr. Karnani also held various positions in business development, corporate strategy and strategic marketing within Fenwal Inc., a global blood technology company that was acquired by Fresenius Kabi, from November 2008 to October 2011.  Mr. Karnani brings nearly 16 years of cross-functional expertise across a multitude of industries, including medical devices, management consulting, semiconductors and cellular telecommunications.  Mr. Karnani has a master’s degree from the Kellogg School of Management at Northwestern University, a master’s degree in electrical engineering from Case Western Reserve University and a bachelor of science degree in electrical engineering from University of Bombay, India.

Jeffrey D. Kent, M.D., FACG.  Dr. Kent has served as our senior vice president, head of medical affairs and outcomes research since joining Horizon in May 2012.  Before that Dr. Kent was executive director, medical affairs at Astellas Pharmaceuticals, a public Japanese biopharmaceutical company, from 2011 to 2012.  Prior to Astellas, he spent more than eight years as global project head for medical affairs in immunology within Abbott Laboratories, then a public health care and pharmaceutical company.  Dr. Kent also worked at G.D. Searle & Company (now Pfizer) from 1999 to 2003, and served in various capacities in research and development, including global director for valdecoxib (Bextra) development.  A Fellow of the American College of Gastroenterology (FACG), Dr. Kent received his M.D. from the Jefferson Medical College in Philadelphia, Pennsylvania.  He completed a residency in Internal Medicine at Thomas Jefferson University Hospital and a fellowship in gastroenterology and hepatology at Rush Presbyterian St. Luke’s Hospital in Chicago.

Irina P. Konstantinovsky.  Ms. Konstantinovsky has served as our executive vice president, chief human resources officer since September 2017.  Prior to Horizon, from August 2012 to September 2017, she was vice president of global talent at Baxter International Inc. a healthcare products company, where she led a team of talent professionals worldwide and oversaw organizational effectiveness, leadership development, inclusion and diversity and talent acquisition.  She and her team were responsible for talent management strategies, programs and systems for more than 50,000 employees worldwide.  Prior to Baxter, Ms. Konstantinovsky spent 15 years in senior partner and director roles at Towers Watson (currently Willis Towers Watson), a global human-resources consulting firm serving Fortune 1000 companies.  While in these roles, she served as the interim chief human resource officer at Capital BlueCross for two years.  Ms. Konstantinovsky has a bachelor of arts in education from the University of Buenos Aires and two master’s degrees, one in higher education and one in industrial and labor relations from Cornell University.  In addition, she serves on the board of the Human Resource Management Association of Chicago and the YWCA of Metropolitan Chicago.

Shao-Lee Lin, M.D., Ph.D.  Dr. Lin has served as our executive vice president, head of research and development and chief scientific officer since January 2018.  Prior to Horizon, Dr. Lin was a corporate officer and vice president, therapeutic areas, development excellence and international development at AbbVie, Inc., a pharmaceutical company, from March 2015 to December 2017.  In that role, she led immunology, virology, neuroscience and general medicine, acrosson-market and pipeline compounds as well as international development across all therapeutic areas.  Prior to AbbVie, Dr. Lin was vice president, inflammation and respiratory development at Gilead Sciences, Inc., a biopharmaceutical company, from July 2012 to February 2015.  She also held leadership positions in immunology and other therapeutic areas while at Amgen Inc., a biotechnology company.  Dr. Lin received her medical degree and doctorate at the Johns Hopkins University School of Medicine and completed fellowships and post-doctoral work in rheumatology, allergy and immunology at the University of California San Diego and The Scripps Clinic and Research Institute.  She has a bachelor of science in biochemistry and chemical engineering from Rice University.  Dr. Lin is currently adjunct faculty at Northwestern University.  She has previously been on the faculty of Rockefeller University as a Clinical Scholar and also served as adjunct faculty at Cornell, University of California Los Angeles (UCLA) and Stanford medical schools. 

Barry J. Moze. Mr. Moze has served as our executive vice president, chief administrative officer since February 2017.  Prior to that, Mr. Moze was our executive vice president, chief operating officer from February 2016 to January 2017 and was our executive vice president, corporate development from May 2014 to January 2016.  Prior to joining Horizon, Mr. Moze spent more than 28 years as a partner of Crystal Clear Communications, a consulting firm focused on the development and execution of corporate strategies.  Prior to Crystal Clear, Mr. Moze was a founder and president of Review Services and Asset Management Group, a licensed investment advisory firm. 

COMPENSATION DISCUSSION AND ANALYSIS

This Compensation Discussion and Analysis (CD&A) discusses the compensation philosophy, policies and principles underlying our executive compensation decisions made for 2018 compensation.  This CD&A provides qualitative information on the factors relevant to these decisions and the manner in which compensation is awarded to the following executive officers who have been named in the Summary Compensation Table included in this Proxy Statement and whom we refer to as our named executive officers (NEOs).

Quick CD&A Reference Guide

2018 at a Glance

A Year of Strong Performance Generating Record Net Sales and Strong Shareholder Return

Except for5-year total shareholder return, growth percentages represent comparison to full-year 2017.

A Year of Significant Progress

Business Overview

We made significant progress in 20172018 on our strategy to build a robust and differentiated pipeline and maximize the growth of KRYSTEXXA, our biologic medicine for uncontrolled gout, and our flagship medicine.  As a result, we generated record full-year net sales of $1.2 billion, an increase of 14 percent over 2017, andone-year total shareholder return of 34 percent in a year when the Nasdaq Biotechnology Index (NBI) declined 9 percent.  In addition to advancing our existing pipeline programs, we added several new programs designed to enhance our leadership position in uncontrolled gout.  We also transformed our research and development (R&D) organization, augmenting its scientific expertise with a new leadership team.  We accelerated the growth of KRYSTEXXA by investing in its commercial infrastructure – doubling its commercial team and our addressable patient population.

Our Strategy

We are constantly driving toward our aspiration, which is to be a leading rare disease biopharma company that delivers innovative therapies to patients and generates high returns for our shareholders.  We have made a great deal of progress in that regard and are building on the resulting momentum.

We have taken a different approach, however, from typical biopharma companies.  Instead of starting out with a pipeline only, raising capital to finance development opportunities, we first developed a successful commercial business, generating cash flows and significant growth.  We then deployed our cash flows and access to capital to the development of leading-edge therapeutic products for rare diseases. 

Our Evolution to a Rare Disease Biopharma Company: A Different Approach

Horizon today has a growing pipeline of development programs, 11 on-market medicines and total net sales of $1.2 billion – a significant transformation from our beginnings as a public company in 2011, when we had two medicines and total net sales of $7 million.  Today, our medicines for rare and rheumatic diseases make up nearly 70 percent of our total net sales.

Our strategy is to build a robust and differentiated pipeline and to maximize growth of KRYSTEXXA, our on-market medicine for uncontrolled gout.

We are also aligning our capital structure to be closer to that of R&D-focused rare disease biopharma companies, which generally have lower debt levels.  We recently announced plans to pay down approximately $550 million our outstanding debt, which was $2.0 billion at December 31, 2018, using available cash and proceeds from our recent $345 million underwritten public offering.  This initiative will lower our outstanding debt and leverage ratio, and at the same time allow us the flexibility to take advantage of business development opportunities.  We subsequently paid down $300 million of the debt.  Our current outstanding debt is now $1.7 billion, and are on track to pay down the remaining $250 million of our $550 million target.  This initiative exemplifies our disciplined approach to debt and efficient use of capital, which together with our strong cash balance enable continued investment in our pipeline and KRYSTEXXA.

Our Future: Our Expanding Pipeline

Expanding our pipeline to drive long-term sustainable growth is a strategic priority.

Our lead pipeline candidate,teprotumumab, which we acquired in 2017, is a fully human monoclonal antibody insulin-like growth factor 1-receptor (IGF-1R) for the treatment of active thyroid eye disease (TED).  TED is a rare, autoimmune inflammatory eye disease in which local inflammation and tissue expansion behind the eye can lead to proptosis (eye bulging).  Proptosis can

result in double vision, misalignment of the eyes, and an inability to close the eyelids, making the tasks of daily life challenging.  Currently, there are no U.S. Food and Drug Administration (FDA) approved treatments available for treating TED.  Following the presentation of breakthrough Phase 2 results in 2017, in February 2019 we announced the Phase 3 trial topline data, which demonstrated a highly statistically significant reduction in proptosis, with 82.9 percent of teprotumumab patients meeting the primary endpoint versus 9.5 percent of placebo patients.  We continue to expect to submit a biologics license application to the FDA in mid-2019.  We are also conducting an extension study, known as OPTIC-X, which will help inform us if patients would benefit from longer treatment or retreatment with teprotumumab.

Inuncontrolled gout, our R&D strategy is to maximize the benefits ofKRYSTEXXA, as well as to enhance and sustain our leadership position through the development of buildingnew medicines.  For KRYSTEXXA, which is the only approved treatment for uncontrolled gout, we are investigating ways to improve the patient response rate so that it can benefit more patients.  (Uncontrolled gout is chronic gout that is refractory to conventional therapies.) Our MIRROR trial is evaluating the combination of KRYSTEXXA and methotrexate, which is the immunomodulator most commonly used by rheumatologists, with the goal to increase the number of patients that can benefit from KRYSTEXXA.  Based on recent positive external case series data, we are adapting the trial to support the potential for registration, with enrollment expected to begin in the second quarter of 2019.  We will also be initiating a diversifiedclinical trial in the second half of 2019 to study the effect of KRYSTEXXA on serum uric acid levels in kidney transplant patients with uncontrolled gout.  In addition, we are working on three preclinical programs designed to build on and durable, high-growth biopharmaceutical company focusedsustain our leadership position in uncontrolled gout well into the future: two next-generation biologics for uncontrolled gout and the other a long-term collaboration to discover and develop novel therapeutics for gout.

In support of our expanding pipeline and the value-maximization of ouron-market medicines, in 2018, we considerably augmented the scientific expertise and acumen of ourR&D organization. Shao-Lee Lin, M.D., Ph.D., joined Horizon in January 2018 in the new role of chief scientific officer and head of R&D.  Dr. Lin is an immunologist, rheumatologist and allergist with more than 20 years of academic and industry experience.  She has established a new leadership team that oversees our R&D programs, partners with business development on pipeline opportunities and manages the therapeutic area development strategies and portfolios.

Our Pipeline

Driving Growth Today and Tomorrow: Our Orphan and Rheumatology Segment

We have two segments: orphan and rheumatology, and primary care.  The orphan and rheumatology segment is the strategic driver of our growth today.  Its compound annual growth rate from 2014 to 2018 of 101 percent underscores the value of our focus on rare disease medicines.

The orphan and rheumatology segment includes KRYSTEXXA, our flagshipon-market medicine.  In addition, if approved, teprotumumab, our late-stage development biologic candidate, will be part of this segment’s portfolio.  The segment also includes a durable base of rare disease medicines: RAVICTI^®, for the treatment of urea cycle disorders; PROCYSBI^®, for the treatment of nephropathic cystinosis and ACTIMMUNE^®, for the treatment of chronic granulomatous disease.

We generated full-yearbelieve the orphan and rheumatology segment offers tremendous potential for future growth.  KRYSTEXXA and teprotumumab, if approved, both offer significant growth potential, and we estimate peak annual net sales of $1.06 billion, with our rare disease medicines, now representing approximately 60 percent of our net sales, increasing 60 percent year-over-year.  In addition to expanding the commercial efforts for our key growth driver KRYSTEXXA, which we now believe has peak net sales potential of more than $750 million we augmented our pipeline with the addition ofHZN-001 (teprotumumab), a late-stage development fully human monoclonal antibody (mAb) insulin-like growthfactor-1 receptor(IGF-1R) inhibitor candidate for the treatment ofmoderate–to-severe thyroid eye disease (TED), as well as several new rheumatology pipeline programs. 

We Have Transformed to Become a Biopharma Company Focused on Rare Disease Medicines

Through Our Business Development Capabilities

Rare Disease Medicine Acquisitions 2014-2019

Commercial execution – Acquiring assets is not a guarantee of success.  We, however, have a strong record of successfully commercializing our medicines and improving the performance of the medicines we acquire.  We attribute our successful results to the deep expertise and knowledge of our commercial teams, coupled with the holistic approach we employ supporting our patient and physician communities. KRYSTEXXA is a prime example of the value of our approach: it was an underperforming asset when we acquired it in 2016.  In only two years we transformed it into the flagship growth driver it is for us today – more than quadrupling its net sales to $259 million in 2018.  Our commercial team understands the market for KRYSTEXXA, and we invested in 2018 to accelerate the potential we see for the medicine – more than $750 million in peak annual net sales. 

Our Purpose: To Help Build Healthier Communities, Urgently and Responsibly

At Horizon, we are making the world a better place – one patient, one medicine, one community at a time.  That’s why we go to incredible lengths to impact incredible lives – to make health a priority, not a privilege.  That’s what drives our insistence that patients have access to our medicines, regardless of their ability to pay, supporting patients in 2018 with nearly $2.0 billion in assistance, representing 46 percent of our full-year gross sales.  We are transforming health by building healthier communities both urgently and responsibly.  As a company we are going to incredible lengths to impact incredible lives.  It’s in our DNA – who we are as a company and who we are as individuals.  For us, it’s personal – we want to make a difference.  Our social responsibility programs, patient advocacy support and awareness, dedication to individual employee volunteerism – all reflect our ideals, a commitment to our patients and the communities we serve. 

Our dedication and commitment are evident in the recognition we receive.  We were honored in 2018 to be spotlighted byPEOPLE Magazine as one of the“50 Companies That Care” – companies that succeed in business while also demonstrating respect, compassion and concern for their communities, employees and the environment.  This distinction is a realization of what we strive for – to be a positive force for good amid a constantly changing health care system.  We also became a member ofPledge 1%, a corporate philanthropy movement that empowers companies to donate 1% of product, 1% of equity, 1% of profit or 1% of employee time to improve communities around the world.  We are one of the first biopharma companies to join the initiative, which includes6,000-plus organizations across 100 countries. 

Horizon is a great place to work and our employees tell us so.  We continue to place in multiple third-party workplace recognition surveys, including being named byFORTUNE Magazine as theNumber One “Best Workplace in BioPharma.” We are also proud to have been named byCrain’s Chicago Business as one of the “Best Places to Work for Women in Chicago” in 2018.  The percentage of women of our total employee population is above the industry standard for all levels in the Company, including upper management levels, reflecting the value we place on diversity.  But diversity encompasses more than gender: we believe that people from different backgrounds and life experiences fuel innovation, which helps provide life-changing solutions for our patients – fostering healthier communities and making the world a better place. 

Rare Disease Medicines Are Driving Our Sales GrowthConsistently Recognized as One of the Best Places to Work –

Net sales of our rare disease medicines grew 60 percent in 2017 compared to 2016.  Net sales of KRYSTEXXA alone, our medicine for the treatment of uncontrolled gout,And as a rare disease, grew 72 percent in 2017, following the implementation of our commercial strategy to maximize the medicine’s growth trajectory following its acquisition in January of 2016.  We believe KRYSTEXXA has significant future growth potential and invested substantially in its commercial organization in 2017, doubling its size to not only increase penetration in the rheumatology market, but also to expand into nephrology, a new market for KRYSTEXXA.  We estimate that the nephrology market has a similar addressable patient population as rheumatology, approximately 50,000 patients.  Our orphan business unit, which includes RAVICTI, PROCYSBI and ACTIMMUNE, provides us with a stable base of rare disease growth medicines. Company That Cares

CAGR:  compound annual growth rate

Expanding Our Pipeline to Drive Sustainable Long-Term Growth

In May 2017, we acquired River Vision Development Corp.  (River Vision), which added the first development-stage candidate to our pipeline – teprotumumab, a fully human monoclonal antibody (mAb) inhibitor ofIGF-1R. Teprotumumab, also known asHZN-001, demonstrated breakthrough efficacy in its Phase 2 trial in patients withmoderate-to-severe TED, a rare and debilitating eye disease with no approved therapies.  Enrollment in the Phase 3 confirmatory trial began in October 2017 and we expect to complete enrollment by the end of 2018.  We estimate the addressable population in the United States to be between 15,000 and 20,000 patients annually. 

We also expanded our rheumatology pipeline programs in 2017, adding two next-generation biologic development programs to support and sustain our leadership in the treatment of uncontrolled gout, as well asHZN-002, a novel dexamethasone conjugate, to augment our rheumatology portfolio.  In addition, two investigator-initiated immunomodulation studies are expected to start in 2018 to evaluate enhancing the response rate for KRYSTEXXA. 

Director NomineesHow are votes counted?

Votes will be counted by the inspector of election appointed for the meeting, who will separately count, with respect to the proposal to elect directors, votes “For,” “Against,” abstentions and Continuing Directorsbrokernon-votes; and, with respect to other proposals, votes “For” and “Against,” abstentions and, as applicable, brokernon-votes. Abstentions and brokernon-votes will be treated as shares present for the purpose of determining the presence of a quorum for the transaction of business at the Annual General Meeting.  Abstentions and brokernon-votes will not, however, be considered votes cast at the Annual General Meeting.  Because the approval of all of the proposals is based on the votes cast at the Annual General Meeting, abstentions and brokernon-votes will not have any effect on the outcome of voting on the proposals. 

What are “brokernon-votes”?

As discussed above, when a beneficial owner of shares held in “street name” does not give instructions to the broker or nominee holding the shares as to how to vote on matters deemed by the NYSE to be“non-routine,” the broker or nominee cannot vote the shares.  Theseun-voted shares are counted as “brokernon-votes.”

What is the quorum requirement?

A quorum of shareholders is necessary to hold a valid meeting.  A quorum will be present if shareholders holding a majority of the issued and outstanding ordinary shares entitled to vote are present at the meeting in person or represented by proxy.  On the record date, there were 184,433,612 ordinary shares outstanding and entitled to vote.  Thus, the holders of 92,216,807 ordinary shares must be present in person or represented by proxy at the meeting to have a quorum. 

Your shares will be counted towards the quorum only if you submit a valid proxy (or one is submitted on your behalf by your broker, bank or other nominee) or, provided that you are a shareholder of record, if you vote in person at the meeting.  Abstentions and brokernon-votes will be counted towards the quorum requirement.  If there is no quorum, within one hour of the time appointed for the Annual General Meeting, the Annual General Meeting will stand adjourned to May 9, 2019, at 3:00 p.m. local time at the same location, or such other time or place as the Board Highlightsmay determine. 

Assuming there is a quorum of shares present at the Annual General Meeting, how many votes are needed to approve each proposal?

Proposal 7 will be redundant in the event Proposal 6 is not approved. 

How can I find out the results of the voting at the Annual General Meeting?

Preliminary voting results will be announced at the Annual General Meeting.  In addition, final voting results will be published in a current report on Form8-K that we expect to file within four business days after the Annual General Meeting.  If final voting results are not available to us in time to file a Form8-K within four business days after the meeting, we intend to file a Form8-K to publish preliminary results and, within four business days after the final results are known to us, file an additional Form8-K to publish the final results. 

What are the Irish statutory financial statements?

We are presenting our Irish statutory financial statements, including the reports of the directors and the statutory auditors thereon, at the Annual General Meeting, and we are making a copy of them available for download in PDF format in the Investors section (see Annual Reports subsection) of our website (www.horizonpharma.com) on or before April 11, 2019.  Since we are an Irish company, we are required to prepare Irish statutory financial statements under applicable Irish company law and to deliver those accounts to shareholders of record in connection with our Annual General Meetings of Shareholders.  The Irish statutory financial statements cover the results of operations and financial position of Horizon Pharma plc for the year ended December 31, 2018.  Irish law requires the directors to prepare financial statements for each financial year giving a true and fair view of the state of the group’s and parent company’s affairs at the end of the financial year and of the group’s profit or loss for the financial year.  Under that law, the directors have prepared the group’s consolidated financial statements in accordance with U.S. accounting standards, as defined in Section 279 of the Irish Companies Act 2014, to the extent that the use of those accounting standards in the preparation of the consolidated financial statements does not contravene any provision of the Irish Companies Act 2014 or of any regulations made thereunder and have prepared the Irish statutory financial statements in accordance with accounting standards issued by the Financial Reporting Council and promulgated by the Institute of Chartered Accountants in Ireland (Generally Accepted Accounting Practice in Ireland). 

We will mail without charge, upon written request, a copy of the Irish statutory financial statements to shareholders of record or beneficial owners of our ordinary shares.  Requests should be sent to: Horizon Pharma plc, Attention: Company Secretary, Connaught House, 1^st Floor, 1 Burlington Road, Dublin 4, D04 C5Y6, Ireland. 

What proxy materials are available on the internet?

The Proxy Statement and the Annual Report to shareholders are available atwww.proxyvote.com. 

PROPOSAL 1

ELECTION OF DIRECTORS

The Board is divided into three classes.  Each class consists, as nearly as possible, ofone-third of the total number of directors and each class has a three-year term.  The Board currently consists of nine members, as follows:

The authorized number of directors may be changed only by resolution of the Board.  Any additional directorships resulting from an increase in the number of directors will be distributed between the three classes so that, as nearly as possible, each class will consist ofone-third of the directors.  This classification of the Board may have the effect of delaying or preventing changes in our control or management.  Our directors may be removed by ordinary resolution with majority vote of our shareholders at a general meeting provided that notice of such resolution has been given in accordance with Section 146 of the Irish Companies Act 2014.  Vacancies on the Board may be filled only by persons elected by a majority of the directors then in office, provided that a quorum is present.  A director elected by the Board to fill a vacancy in a class, including vacancies created by an increase in the number of directors, shall serve for the remainder of the full term of that class and until the director’s successor is duly elected and qualified. 

There are currently three directors in Class  II whose term of office expires in 2019, one of whom, Ronald Pauli, will not be subject tore-election at the 2019 Annual General Meeting.  Each of the nominees listed below in Class  II is currently one of our directors who was nominated for election by the Board, upon the recommendation of the Nominating and Corporate Governance Committee of our Board examines multiple factors when evaluating directors, including their knowledge, skills and experience, including experience in our industry and with respectCommittee. In order to clinical development, business, finance, management and public service.  The Committee believes in an expansive definition of diversity that includes differences of experience, education, talents, gender and race, among other things.  The table below highlights the extensive experience of our directors as wellbe elected as a balancedirector, each nominee must receive the affirmative vote of skills on our Board:

a majority of the votes cast by the holders of ordinary shares represented at the Annual General Meeting in person or by proxy.  If elected, each of these nominees would serve until the 2022 Annual General Meeting of Shareholders and until his or her successor has been duly elected and qualified, or, if sooner, until the director’s death, resignation, disqualification or removal. 

THE BOARD RECOMMENDS

A VOTE IN FAVOR OF EACH NAMED NOMINEE