Ownership Submission
FORM 3
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

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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(Print or Type Responses)
1. Name and Address of Reporting Person *
  Haines Timothy
2. Date of Event Requiring Statement (Month/Day/Year)
10/28/2014
3. Issuer Name and Ticker or Trading Symbol
Sientra, Inc. [SIEN]
(Last)
(First)
(Middle)
C/O ABINGWORTH LLP,, 38 JERMYN STREET
4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
__X__ Director __X__ 10% Owner
_____ Officer (give title below) _____ Other (specify below)
5. If Amendment, Date Original Filed(Month/Day/Year)
(Street)

LONDON, X0 SW1Y 6DN
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 Beneficially Owned
1.Title of Security
(Instr. 4)
2. Amount of Securities Beneficially Owned
(Instr. 4)
3. Ownership Form: Direct (D) or Indirect (I)
(Instr. 5)
4. Nature of Indirect Beneficial Ownership
(Instr. 5)
Common Stock 1,704,012
I
refer to footnotes 1 and 2 (1) (2)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly. SEC 1473 (7-02)
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Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 4)
2. Date Exercisable and Expiration Date
(Month/Day/Year)
3. Title and Amount of Securities Underlying Derivative Security
(Instr. 4)
4. Conversion or Exercise Price of Derivative Security 5. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 5)
6. Nature of Indirect Beneficial Ownership
(Instr. 5)
Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address Relationships
Director 10% Owner Officer Other
Haines Timothy
C/O ABINGWORTH LLP,
38 JERMYN STREET
LONDON, X0 SW1Y 6DN
  X   X    

Signatures

/s/ Joel Smith, Attorney-in-fact for Timothy Haines 10/28/2014
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 5(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).
(1) Consists of (i) 852,006 shares held of record by Abingworth Bioventures V LP, or ABV V, and (ii) 852,006 shares held of record by Abingworth Bioventures V Co-Invest Growth Equity Fund LP., or AGE. ABV V and AGE are collectively referred to as the "Abingworth Funds." The investment manager of the Abingworth Funds is Abingworth LLP, or Abingworth. Abingworth Bioventures V GP LP or "Abingworth GP", a Scottish limited partnership, serves as the general partner of each of the Abingworth Funds. Abingworth General Partner V LLP, a Scottish limited liability partnership, serves as the general partner of Abingworth GP. Abingworth GP (acting by its general partner Abingworth General Partner V LLP) has delegated to Abingworth all investment and dispositive power over the shares held by the Abingworth Funds. The reporting person holds the reported securities indirectly through Abingworth.
(2) The reporting person is part of an investment committee of Abingworth, which approves investment and voting decisions by a majority vote, and no individual member has the sole control or voting power over the shares held by the Abingworth Funds. The reporting person disclaims beneficial ownership of all shares held of record by the Abingworth Funds. This report shall not be deemed an admission that the reporting person, Abingworth or any other person is the beneficial owner of the securities reported herein for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or for any other purpose.
 
Remarks:
Exhibit 24- Power of Attorney for Timothy Haines.

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, See Instruction 6 for procedure.

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