Sec Form 3 Filing - G1 EXECUTION SERVICES, LLC @ ACHILLION PHARMACEUTICALS INC - 2020-01-27

FORM 3 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 G1 EXECUTION SERVICES, 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) 175 W. JACKSON BLVD., SUITE 1700, 501 PLAZA 2 3. Date of Earliest Transaction (MM/DD/YY) 01/27/2020 (Street) CHICAGO, IL60604 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ 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 10,917 D ( 1 ) ( 3 ) Common Stock 14,115,498 D ( 2 ) ( 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 Call Option (right to buy) $ 7 ( 4 ) 12/18/2020 Common Stock 454,900 D ( 2 ) ( 3 ) Total Return Swap ( 5 ) ( 5 ) ( 6 ) 07/29/2020 Common Stock 8,000 D ( 3 ) Total Return Swap ( 5 ) ( 5 ) ( 6 ) 07/30/2020 Common Stock 8,000 D ( 3 ) Total Return Swap ( 5 ) ( 5 ) ( 6 ) 07/31/2020 Common Stock 8,000 D ( 3 ) Total Return Swap ( 5 ) ( 5 ) ( 6 ) 08/03/2020 Common Stock 7,100 D ( 3 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other G1 EXECUTION SERVICES, LLC 175 W. JACKSON BLVD., SUITE 1700 501 PLAZA 2 CHICAGO, IL60604 X SUSQUEHANNA FUNDAMENTAL INVESTMENTS, LLC 401 CITY AVENUE, SUITE 220 BALA CYNWYD, PA19004 X SUSQUEHANNA SECURITIES, LLC 401 CITY AVENUE, SUITE 220 BALA CYNWYD, PA19004 X Signatures G1 Execution Services, LLC By: /s/ Brian Sopinsky Name: Brian Sopinsky Title: Secretary 01/30/2020 Signature of Reporting Person Date Susquehanna Fundamental Investments, LLC By: /s/ Brian Sopinsky Name: Brian Sopinsky Title: Assistant Secretary 01/30/2020 Signature of Reporting Person Date Susquehanna Securities, LLC By: /s/ Brian Sopinsky Name: Brian Sopinsky Title: Secretary 01/30/2020 Signature of Reporting Person Date

Explanation of Responses:

( 1 )These securities are directly owned by G1 Execution Services, LLC ("G1X"). ( 2 )These securities are directly owned by Susquehanna Securities, LLC ("SS"). ( 3 )G1X, Susquehanna Fundamental Investments, LLC ("SFNDI") and SS are affiliated entities under common ownership. G1X, SFNDI and SS each disclaim beneficial ownership of the reported securities except to the extent of their respective pecuniary interest therein, and this report shall not be deemed an admission that any of them are the beneficial owners of the securities for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or for any other purpose. ( 4 )These options are exercisable at any time prior to their expiration. ( 5 )SFNDI has entered into cash-settled total return swaps with an unaffiliated third party financial institution, under which SFNDI acquired an aggregate of 31,100 "notional" shares of Achillion Pharmaceuticals, Inc. ("Achillion") common stock at prices ranging from $2.12 to $2.24 per share. The swap agreements provide that, upon settlement of the swaps, SFNDI will pay the applicable purchase price to the counterparty, and the counterparty will pay to SFNDI an amount equal to the then market price of the applicable number of shares of Achillion common stock. These swaps provide SFNDI with economic results that are comparable to the economic results of ownership of, but do not provide SFNDI with the power to vote or direct the voting of, or dispose of or direct the disposition of, the shares of common stock that are the subject of such swap. ( 6 )Each of these total return swaps may be settled at any time prior to its expiration in SFNDI's discretion.

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