Sec Form 4 Filing - VITULLO NICOLE @ ACHILLION PHARMACEUTICALS INC - 2015-05-21

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 VITULLO NICOLE 2. Issuer Name and Ticker or Trading Symbol ACHILLION PHARMACEUTICALS INC [ ACHN] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O DOMAIN ASSOCIATES, LLC, ONE PALMER SQUARE 3. Date of Earliest Transaction (MM/DD/YY) 05/21/2015 (Street) PRINCETON, NJ08542 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 05/21/2015 J( 1 ) 1,700,000 D $ 0 ( 1 ) 2,872,968 I By Domain Partners VIII, L.P. ( 2 ) Common Stock 05/21/2015 J( 1 ) 222,630 A $ 0 ( 1 ) 483,521 I By One Palmer Square Associates VIII, LLC ( 2 ) Common Stock 59,161 I By DP VIII Associates, L.P. ( 2 ) Common Stock 25,000 I By Domain Associates, LLC ( 2 )

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

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other VITULLO NICOLE C/O DOMAIN ASSOCIATES, LLC ONE PALMER SQUARE PRINCETON, NJ08542 X Signatures /s/Kathleen K. Schoemaker, Attorney-in-Fact 05/22/2015 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Distribution of shares in kind by Domain Partners VIII, L.P. pro rata to its partners, including 222,630 shares to One Palmer Square Associates VIII, LLC, the general partner of Domain Partners VIII, L.P. ( 2 )The Reporting Person is a Managing Member of Domain Associates, LLC and a Managing Member of One Palmer Square Associates VIII, LLC, which is the sole general partner of Domain Partners VIII, L.P. and DP VIII Associates, L.P. Pursuant to Instruction 4(b)(iv) of Form 4, the Reporting Person has elected to report as indirectly beneficially owned the entire number of securities beneficially owned by each such entity. The Reporting Person disclaims beneficial ownership of any securities, and any proceeds thereof, that exceed his or her pecuniary interest therein and/or that are not actually distributed to him or her.

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).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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