CONVERSION AND AMENDMENT AGREEMENT

Exhibit 4.14

CONVERSION AND AMENDMENT AGREEMENT

THIS CONVERSION AND AMENDMENT AGREEMENT (this “Agreement”) is made and entered into as of June 16, 2011, by and among HORIZON PHARMA, INC., a Delaware corporation (the “Company”), and the undersigned stockholders of the Company (the “Stockholders”).

RECITALS

WHEREAS, the Company is contemplating the consummation of a firm commitment underwritten initial public offering of its common stock (the “IPO”);

WHEREAS, the Stockholders are holders of shares of the Company’s outstanding Series A Preferred Stock (the “Series A Preferred”) and Series B Preferred Stock (the “Series B Preferred”, together with the Series A Preferred, the “Series Preferred”), and/or shares of the Company’s Common Stock (“Common Stock”);

WHEREAS, pursuant to the Company’s Amended and Restated Certificate of Incorporation, as amended and as may be amended from time to time (the “Restated Certificate”), each share of Series Preferred shall automatically be converted into shares of Common Stock, based on the then-effective Conversion Price (as defined in the Restated Certificate) applicable to such share of Series Preferred, immediately upon the earlier of (A) the Company’s sale of its Common Stock in a firm commitment underwritten public offering pursuant to a registration statement under the Securities Act of 1933, as amended, provided: (i) such offering results in aggregate gross cash proceeds of not less than $50,000,000 (prior to underwriting discounts and commissions) and (ii) the shares of Common Stock so sold are listed on the NYSE, the NASDAQ Global Select Market, or the NASDAQ Global Market (a “Qualified IPO”); or (B) the date specified by written consent or agreement of the holders of at least 66 ²/3% of the then outstanding shares of Series Preferred, voting together as a single class on an as-converted basis;

WHEREAS, the Stockholders constitute the holders of at least 66 ²/3% of the outstanding shares of the Series Preferred, voting together as a single class on an as-converted basis;

WHEREAS, the Company and certain of the undersigned Stockholders, among others, are parties to that certain Investors’ Rights Agreement dated as of April 1, 2010 (the “Investors’ Rights Agreement”) and that certain Voting Agreement dated as of April 1, 2010 (the “Voting Agreement”);

WHEREAS, the Investors’ Rights Agreement contains certain provisions the termination of which are triggered by the closing of a Qualified IPO;

WHEREAS, the Voting Agreement terminates upon the consummation of a firm commitment underwritten public offering by the Company of shares of its Common Stock in connection with which all of the outstanding shares of Series Preferred are converted into shares of Common Stock, pursuant to the Restated Certificate;

1.

WHEREAS, any term of the Investors’ Rights Agreement may be amended or waived with the written consent of the Company and the holders of at least 66 ²/3% of the Registrable Securities (as defined in the Investors’ Rights Agreement) then outstanding;

WHEREAS, the undersigned stockholders have the requisite percentages of the applicable securities required to amend the provisions of the Investors’ Rights Agreement;

WHEREAS, the undersigned Stockholders desire to assist the Company in proceeding with an IPO and, in connection therewith, desire to amend certain provisions of the Investors’ Rights Agreement and to confirm the termination of the Voting Agreement; and

WHEREAS, in order to eliminate any uncertainty or delay with respect to the conversion of the Series Preferred in connection with the IPO the undersigned Stockholders desire to: (A) approve the conversion, effective immediately prior to the closing of the IPO, of each share of Series Preferred then outstanding into Common Stock at the then-effective applicable Conversion Price, provided that the price per share of the Common Stock sold in the IPO to the public is approved by the Board of Directors of the Company (the “Board”) or the Pricing Committee of the Board (an “Approved IPO”), and (B) amend the Investors’ Rights Agreement and confirm the termination of the Voting Agreement, all as more fully set forth herein.

AGREEMENT

NOW, THEREFORE, the parties to this Agreement, for good and valuable consideration, the receipt and sufficiency of which are acknowledged and agreed, hereby agree as follows:

1. CONVERSION. Each undersigned Stockholder, with respect to all shares of Series Preferred held by it, hereby agrees and consents that, effective immediately prior to the closing of an Approved IPO, whether or not such Approved IPO also constitutes a Qualified IPO, all outstanding shares of the Series Preferred shall automatically be converted into shares of Common Stock at the applicable Conversion Price (each as defined in the Restated Certificate) then in effect.

2. AMENDMENT OF INVESTORS’ RIGHTS AGREEMENT. The Company and the undersigned Stockholders that are holders of Registrable Securities, with respect to all shares of Registrable Securities held thereby, on behalf of themselves and all other holders of Registrable Securities, hereby amend the Investors’ Rights Agreement as follows:

The following defined term in Section 1.1(i) of the Investors’ Rights Agreement is hereby amended in its entirety as follows:

“Qualified IPO” means the Company’s sale of its Common Stock in a firm commitment underwritten public offering pursuant to a registration statement under the Securities Act, provided: (i) the price per share of the Common Stock sold in the IPO to the public is approved by the Board or a Pricing Committee of the Board and (ii) the shares of Common Stock so sold are listed on the NYSE, the NASDAQ Global Select Market, or the NASDAQ Global Market.

2.

3. TERMINATION OF VOTING AGREEMENT. The Company and the undersigned Stockholders, on behalf of themselves and all other parties to the Voting Agreement, hereby acknowledge that, effective immediately prior to the closing of an Approved IPO, the Voting Agreement shall terminate in its entirety and be of no further force or effect pursuant to its terms.

4. SUNSET. Notwithstanding anything to the contrary set forth herein, this Agreement and all obligations hereunder shall terminate and this Agreement shall have no force or effect retrospectively or prospectively if the closing of an Approved IPO has not occurred prior to September 30, 2011.

5. MISCELLANEOUS.

(a) Entire Agreement; Binding Effect. This Agreement constitutes the entire agreement of the parties hereto related to the matters set forth herein, and supersedes all prior agreements between such parties, whether written or oral, related to such subject matter. The terms and conditions of this Agreement shall inure to the benefit of and be binding upon the respective successors and assigns of the parties hereto. Except as amended or expressly provided hereby, the terms of the Investors’ Rights Agreement and the Voting Agreement shall remain in full force and effect.

(b) Amendment; Waiver. Neither this Agreement nor any term hereof may be amended, waived, discharged or terminated other than by a written instrument signed by the Company and each party against whom enforcement of such amendment, waiver, discharge or termination is sought.

(c) Governing Law. This Agreement shall be governed by and construed in accordance with the laws of the State of California as applied to contracts among California residents entered into and performed entirely within California.

(d) Counterparts; Facsimile. This Agreement may be executed in one or more counterparts, each of which shall be deemed an original, but all of which together shall constitute one and the same instrument. Facsimile signatures shall be as effective as original signatures.

(e) Further Assurances. Each party hereto agrees to execute and deliver, or cause to be executed and delivered, such further instruments or documents or take such other actions as may be reasonably necessary to consummate the transactions contemplated by this Agreement.

3.

IN WITNESS WHEREOF, the parties hereto have executed this CONVERSION AND AMENDMENT AGREEMENT as of the date first written above.

[SIGNATURE PAGE TO CONVERSION AMENDMENT AGREEMENT]

IN WITNESS WHEREOF, the parties hereto have executed this CONVERSION AND AMENDMENT AGREEMENT as of the date first written above.

[SIGNATURE PAGE TO CONVERSION AMENDMENT AGREEMENT]

IN WITNESS WHEREOF, the parties hereto have executed this CONVERSION AND AMENDMENT AGREEMENT as of the date first written above.

[SIGNATURE PAGE TO CONVERSION AMENDMENT AGREEMENT]

IN WITNESS WHEREOF, the parties hereto have executed this CONVERSION AND AMENDMENT AGREEMENT as of the date first written above.

[SIGNATURE PAGE TO CONVERSION AMENDMENT AGREEMENT]

IN WITNESS WHEREOF, the parties hereto have executed this CONVERSION AND AMENDMENT AGREEMENT as of the date first written above.

[SIGNATURE PAGE TO CONVERSION AMENDMENT AGREEMENT]

IN WITNESS WHEREOF, the parties hereto have executed this CONVERSION AND AMENDMENT AGREEMENT as of the date first written above.

[SIGNATURE PAGE TO CONVERSION AND AMENDMENT AGREEMENT]

IN WITNESS WHEREOF, the parties hereto have executed this CONVERSION AND AMENDMENT AGREEMENT as of the date first written above.

[SIGNATURE PAGE TO CONVERSION AND AMENDMENT AGREEMENT]

IN WITNESS WHEREOF, the parties hereto have executed this CONVERSION AND AMENDMENT AGREEMENT as of the date first written above.

[SIGNATURE PAGE TO CONVERSION AND AMENDMENT AGREEMENT]

IN WITNESS WHEREOF, the parties hereto have executed this CONVERSION AND AMENDMENT AGREEMENT as of the date first written above.

[SIGNATURE PAGE TO CONVERSION AND AMENDMENT AGREEMENT]

IN WITNESS WHEREOF, the parties hereto have executed this CONVERSION AND AMENDMENT AGREEMENT as of the date first written above.

[SIGNATURE PAGE TO CONVERSION AND AMENDMENT AGREEMENT]

IN WITNESS WHEREOF, the parties hereto have executed this CONVERSION AND AMENDMENT AGREEMENT as of the date first written above.

[SIGNATURE PAGE TO CONVERSION AND AMENDMENT AGREEMENT]

IN WITNESS WHEREOF, the parties hereto have executed this CONVERSION AND AMENDMENT AGREEMENT as of the date first written above.

[SIGNATURE PAGE TO CONVERSION AND AMENDMENT AGREEMENT]

IN WITNESS WHEREOF, the parties hereto have executed this CONVERSION AND AMENDMENT AGREEMENT as of the date first written above.

[SIGNATURE PAGE TO CONVERSION AND AMENDMENT AGREEMENT]

IN WITNESS WHEREOF, the parties hereto have executed this CONVERSION AND AMENDMENT AGREEMENT as of the date first written above.

[SIGNATURE PAGE TO CONVERSION AND AMENDMENT AGREEMENT]

IN WITNESS WHEREOF, the parties hereto have executed this CONVERSION AND AMENDMENT AGREEMENT as of the date first written above.

[SIGNATURE PAGE TO CONVERSION AND AMENDMENT AGREEMENT]

IN WITNESS WHEREOF, the parties hereto have executed this CONVERSION AND AMENDMENT AGREEMENT as of the date first written above.

[SIGNATURE PAGE TO CONVERSION AND AMENDMENT AGREEMENT]

IN WITNESS WHEREOF, the parties hereto have executed this CONVERSION AND AMENDMENT AGREEMENT as of the date first written above.

[SIGNATURE PAGE TO CONVERSION AND AMENDMENT AGREEMENT]

IN WITNESS WHEREOF, the parties hereto have executed this CONVERSION AND AMENDMENT AGREEMENT as of the date first written above.

[SIGNATURE PAGE TO CONVERSION AND AMENDMENT AGREEMENT]