Sec Form 4 Filing - QVT Associates GP LLC @ ACHILLION PHARMACEUTICALS INC - 2013-12-20

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

OMB APPROVAL OMB Number: 3235-0287 Expires: November 30, 2011 Estimated average burden hours per response... 0.5

1. Name and Address of Reporting Person QVT Associates GP LLC 2. Issuer Name and Ticker or Trading Symbol ACHILLION PHARMACEUTICALS INC [ ACHN] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 1177 AVENUE OF THE AMERICAS, 9TH FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 12/20/2013 (Street) NEW YORK, NY10036 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, $0.001 par value 12/20/2013 S 32,155 D $ 3.16 11,365,383 I Through QVT Fund IV LP, QVT Fund V LP and Quintessence Fund L.P. Common Stock, $0.001 par value 12/20/2013 S 75,000 D $ 3.16 11,290,383 I Through QVT Fund IV LP, QVT Fund V LP and Quintessence Fund L.P. Common Stock, $0.001 par value 12/23/2013 S 75,000 D $ 3.25 11,215,383 I Through QVT Fund IV LP, QVT Fund V LP and Quintessence Fund L.P. Common Stock, $0.001 par value 12/23/2013 S 75,000 D $ 3.3 11,140,383 I Through QVT Fund IV LP, QVT Fund V LP and Quintessence Fund L.P. Common Stock, $0.001 par value 12/23/2013 S 31,986 D $ 3.37 11,108,397 I Through QVT Fund IV LP, QVT Fund V LP and Quintessence Fund L.P.

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 QVT Associates GP LLC 1177 AVENUE OF THE AMERICAS 9TH FLOOR NEW YORK, NY10036 X Signatures /s/ Arthur Chu, Managing Member 12/24/2013 Signature of Reporting Person Date

Explanation of Responses:

Remarks: On December 20, 2013, QVT Fund IV LP sold 13,761 shares of Common Stock, Quintessence Fund L.P. sold 11,872 shares of Common Stockand QVT Fund V LP sold 81,522 shares of Common Stock. On December 23, 2013, QVT Fund IV LP sold 23,373 shares of Common Stock,Quintessence Fund L.P. sold 20,162 shares of Common Stock and QVT Fund V LP sold 138,451 shares of Common Stock. As a result, QVTFund IV LP directly beneficially owns 1,426,760 shares of Common Stock, Quintessence Fund L.P. directly beneficially owns 1,230,738 sharesof Common Stock and QVT Fund V LP directly beneficially owns 8,450,899 shares of Common Stock. QVT Associates GP LLC is the generalpartner of QVT Fund IV LP, QVT Fund V LP and Quintessence Fund L.P. (together with QVT Fund IV LP, and QVT Fund V LP, the"Funds"). QVT Financial LP is the investment manager for the Funds and therefore may be deemed the beneficial owner of the Common Stockheld by the Funds. QVT Financial GP LLC is the general partner of QVT Financial LP and therefore may be deemed the beneficial owner ofCommon Stock beneficially owned by QVT Financial LP. The reporting person disclaims beneficial ownership of the reported securities exceptto the extent of its pecuniary interest therein.

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).

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.