Ownership Submission
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 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
OMB APPROVAL
OMB Number: 3235-0287
Expires: January 31, 2005
Estimated average burden hours per response... 0.5

(Print or Type Responses)
1. Name and Address of Reporting Person *
Marchington Allan P
  2. Issuer Name and Ticker or Trading Symbol
AMBIT BIOSCIENCES CORP [AMBI]
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 AMBIT BIOSCIENCES CORPORATION, 11080 ROSELLE STREET
3. Date of Earliest Transaction (Month/Day/Year)
05/21/2013
(Street)

SAN DIEGO, CA 92121
4. If Amendment, Date Original Filed(Month/Day/Year)
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 (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 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 05/21/2013   C   281,624 A (1) 281,847 I See Footnote (2)
Common Stock 05/21/2013   C   307,051 A (3) 588,898 I See Footnote (2)
Common Stock 05/21/2013   C   306,619 A (4) 895,517 I See Footnote (2)
Common Stock 05/21/2013   P   431,527 (6) A $ 8 1,327,044 I See Footnote (2)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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 control number. SEC 1474 (9-02)

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 (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 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
(Month/Day/Year)
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
Series D Preferred Stock (1) 05/21/2013   C     3,058,909   (1)   (1) Common Stock 281,624 $ 0 0 I See Footnote (2)
Series D-2 Preferred Stock (3) 05/21/2013   C     7,369,222   (3)   (3) Common Stock 307,051 $ 0 0 I See Footnote (2)
Series E Preferred Stock (4) 05/21/2013   C     7,358,848   (4)   (4) Common Stock 306,619 $ 0 0 I See Footnote (2)
Stock Option (right to buy) $ 6.66 05/21/2013   A     7,085   (5) 05/20/2023 Common Stock 7,085 $ 0 7,085 D  

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
Marchington Allan P
C/O AMBIT BIOSCIENCES CORPORATION
11080 ROSELLE STREET
SAN DIEGO, CA 92121
  X      

Signatures

 /s/ Allan P. Marchington   05/21/2013
**Signature of Reporting Person Date

Explanation of Responses:

* 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).
(1) Upon the closing of the Issuer's initial public offering, every 10.86166 shares of Series D Preferred Stock automatically converted into 1 share of Common Stock for no additional consideration and had no expiration date. The conversion ratio was incorrectly stated in the Reporting Person's Form 3.
(2) The securities are held by Apposite Healthcare Fund LP, or Apposite. Apposite Healthcare (GP) Limited, the general partner of Apposite, has appointed Apposite Capital LLP as the manager of Apposite. The Reporting Person is a designated member of Apposite Capital LLP and, together with F. David Porter and Stephen Adkin, the other designated members of Apposite Capital LLP, shares voting and investment control over the securities held by Apposite; however, each disclaims beneficial ownership, except to the extent of their pecuniary interests therein.
(3) Upon the closing of the Issuer's initial public offering, every 24 shares of Series D-2 Preferred Stock automatically converted into 1 share of Common Stock for no additional consideration and had no expiration date.
(4) Upon the closing of the Issuer's initial public offering, every 24 shares of Series E Preferred Stock automatically converted into 1 share of Common Stock for no additional consideration and had no expiration date.
(5) One-third of the shares will vest on the first, second and third year anniversaries of the date of grant, such that the stock option is fully vested on May 21, 2016, subject to the optionee's continuous service with the Issuer through such vesting date.
(6) The shares were purchased by Apposite in a private placement concurrent with the closing of the Issuers' initial public offering.

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

Potential persons who are to respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB number.