Sec Form 4 Filing - CDK ASSOCIATES, L.L.C. @ Strongbridge Biopharma plc - 2018-12-20

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

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1. Name and Address of Reporting Person CDK ASSOCIATES, L.L.C. 2. Issuer Name and Ticker or Trading Symbol Strongbridge Biopharma plc [ SBBP] 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) C/O CAXTON CORPORATION, 731 ALEXANDER ROAD, BLDG. 2 3. Date of Earliest Transaction (MM/DD/YY) 12/20/2018 (Street) PRINCETON, NJ08540 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 Ordinary Shares, $0.01 par value 12/20/2018 P 146,467 A $ 3.9967( 1 ) 6,441,296 D( 2 ) Ordinary Shares, $0.01 par value 12/21/2018 P 90,612 A $ 3.9508( 3 ) 6,531,908 D( 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 CDK ASSOCIATES, L.L.C. C/O CAXTON CORPORATION 731 ALEXANDER ROAD, BLDG. 2 PRINCETON, NJ08540 X CAXTON CORP 731 ALEXANDER ROAD BUILDING 2 PRINCETON, NJ08540 X Kovner Bruce C/O CAXTON CORPORATION 731 ALEXANDER ROAD, BLDG. 2 PRINCETON, NJ08540 X Signatures CDK Associates, L.L.C., By: Caxton Corporation, its Manager,By: /s/ Heath Weisberg, General Counsel 12/21/2018 Signature of Reporting Person Date Caxton Corporation, By: /s/ Heath Weisberg, General Counsel 12/21/2018 Signature of Reporting Person Date By: /s/ Heath Weisberg, Attorney-in-Fact 12/21/2018 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $3.85 to $4.22 per share, inclusive. The Reporting Persons undertake to provide to the staff of the Securities and Exchange Commission, the Issuer, or any security holder of the Issuer, upon request, full information regarding the number of shares purchased at each separate price. ( 2 )Following the transactions reported herein, these shares represent (a) 6,196,882 Ordinary Shares that are owned directly by CDK Associates, LLC, which is a reporting person, and may be deemed to be indirectly beneficially owned by (i) Caxton Corporation, the manager of CDK Associates, LLC, and (ii) Bruce Kovner, the chairman and sole shareholder of Caxton Corporation; and (b) 335,026 Ordinary Shares beneficially owned by employees of an affiliate of Caxton Corporation and may be deemed to be indirectly beneficially owned by (i) Caxton Corporation and (ii) Bruce Kovner, the chairman and sole shareholder of Caxton Corporation. ( 3 )The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $3.82 to $4.10 per share, inclusive. The Reporting Persons undertake to provide to the staff of the Securities and Exchange Commission, the Issuer, or any security holder of the Issuer, upon request, full information regarding the number of shares purchased at each separate price.Each Reporting Person disclaims beneficial ownership in the securities reported on this Form 4 except to the extent of its or his pecuniary interest, if any, therein, and this report shall not be deemed to be an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or for any other purpose.

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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