Sec Form 4 Filing - FORMELA JEAN FRANCOIS @ HORIZON PHARMA, INC. - 2012-03-02

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person FORMELA JEAN FRANCOIS 2. Issuer Name and Ticker or Trading Symbol HORIZON PHARMA, INC. [ HZNP] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 25 FIRST STREET, SUITE 303 3. Date of Earliest Transaction (MM/DD/YY) 03/02/2012 (Street) CAMBRIDGE, MA02141 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price COMMON STOCK 03/02/2012 P 828,443 ( 1 ) A $ 3.6212 ( 2 ) 3,688,294 ( 3 ) I See Footnote ( 3 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Warrants to Purchase Common Stock $ 4.308 03/02/2012 P 207,110 ( 4 ) 03/02/2012 03/02/2017 Com mon Stock 207,110 ( 4 ) $ 3.6212 ( 2 ) 207,110 ( 4 ) I See Footnote ( 4 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other FORMELA JEAN FRANCOIS 25 FIRST STREET, SUITE 303 CAMBRIDGE, MA02141 X X Signatures /s/ Jean-Francois Formela, By Kristen Laguerre, as attorney-in-fact 03/06/2012 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Includes 789,828 shares of common stock purchased by Atlas Venture Fund VI, L.P., 14,462 shares of common stock purchased by Atlas Venture Fund VI GmbH & Co. KG and 24,153 shares of common stock purchased by Atlas Venture Entrepreneurs' Fund VI, L.P. Atlas Venture Associates VI, L.P. is the general partner of Atlas Venture Fund VI, L.P. and Atlas Venture Entrepreneurs' Fund VI, L.P. and the managing limited partner of Atlas Venture Fund VI GmbH & Co. KG. Each of the Filing Persons disclaims beneficial ownership of such shares except to the extent of its pecuniary interest therein. Mr. Formela disclaims beneficial ownership of the shares except to the extent of his pecuniary interest therein. Mr. Formela is a director of Issuer. ( 2 )Purchase price consists of the sum of (i) $3.59 (the closing bid price of the Issuer's common stock on 2/28/2012) and (ii) $0.03125. ( 3 )Includes 3,516,377 shares of common stock held by Atlas Venture Fund VI, L.P., 64,385 shares of common stock held by Atlas Venture Fund VI GmbH & Co. KG and 107,532 shares of common stock held by Atlas Venture Entrepreneurs' Fund VI, L.P. Atlas Venture Associates VI, L.P. is the general partner of Atlas Venture Fund VI, L.P. and Atlas Venture Entrepreneurs' Fund VI, L.P. and the managing limited partner of Atlas Venture Fund VI GmbH & Co. KG. Each of the Filing Persons disclaims beneficial ownership of such shares except to the extent of its pecuniary interest therein. Mr. Formela disclaims beneficial ownership of the shares except to the extent of his pecuniary interest therein. Mr. Formela is a director of Issuer. ( 4 )For each share of common stock of the Issuer purchased in the financing, a purchaser received a warrant to purchase 0.25 of a share of common stock of the Issuer. Includes warrants to purchase 197,456 shares of common stock purchased by Atlas Venture Fund VI, L.P., warrants to purchase 3,616 shares of common stock purchased by Atlas Venture Fund VI GmbH & Co. KG and warrants to purchase 6,038 shares of common stock purchased by Atlas Venture Entrepreneurs' Fund VI, L.P. Atlas Venture Associates VI, L.P. is the general partner of Atlas Venture Fund VI, L.P. and Atlas Venture Entrepreneurs' Fund VI, L.P. and the managing limited partner of Atlas Venture Fund VI GmbH & Co. KG. Each of the Filing Persons disclaims beneficial ownership of such shares except to the extent of its pecuniary interest therein. Mr. Formela disclaims beneficial ownership of the shares except to the extent of his pecuniary interest therein. Mr. Formela is a director of Issuer.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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