Sec Form 4 Filing - Zhang Jack Y. @ Amphastar Pharmaceuticals, Inc. - 2015-06-15

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 Zhang Jack Y. 2. Issuer Name and Ticker or Trading Symbol Amphastar Pharmaceuticals, Inc. [ AMPH] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director X __ 10% Owner X __ Officer (give title below) _____ Other (specify below) CEO & Chief Science Officer (Last) (First) (Middle) C/O AMPHASTAR PHARMACEUTICALS, INC., 11570 6TH STREET 3. Date of Earliest Transaction (MM/DD/YY) 06/15/2015 (Street) RANCHO CUCAMONGA, CA91730 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 06/15/2015 M 50,061 A $ 12.97 961,697 D Common Stock 06/15/2015 S( 1 ) 45,382 D $ 16.2938 ( 2 ) 916,315 D Common Stock 06/15/2015 F 4,679 ( 3 ) D $ 16.2938 911,636 D Common Stock 661,666 I See footnote ( 4 ) Common Stock 7,631,594 I See footnote ( 5 ) Common Stock 5,000 I See footnote ( 6 ) Common Stock 200,000 I See footnote ( 7 )

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 Employee Stock Option (right to buy) $ 12.97 06/15/2015 M 50,061 ( 8 ) 09/28/2015 Common Stock 50,061 $ 0 8,481 D Employee Stock Option (right to buy) $ 12.97 ( 8 ) 09/28/2015 Common Stock 8,481 8,481 I See footnote ( 4 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Zhang Jack Y. C/O AMPHASTAR PHARMACEUTICALS, INC. 11570 6TH STREET RANCHO CUCAMONGA, CA91730 X X CEO & Chief Science Officer Luo Mary Z. C/O AMPHASTAR PHARMACEUTICALS, INC. 11570 6TH STREET RANCHO CUCAMONGA, CA91730 X X COO and Chief Scientist Signatures /s/ Ken Stupak, by power of attorney for Jack Y. Zhang 06/16/2015 Signature of Reporting Person Date /s/ Ken Stupak, by power of attorney for Mary Z. Luo 06/16/2015 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The sale reported in this Form 4 was effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on December 16, 2014. ( 2 )The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $16.00 to $16.45, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price. ( 3 )The reported securities were withheld to satisfy the Reporting Person's tax liability in connection with the reported reported option exercise. ( 4 )The securities are held of record by Mary Z. Luo. The reporting persons are husband and wife. ( 5 )The shares are held of record by Applied Physics & Chemistry Laboratories, Inc., of which the reporting persons are the sole owners. ( 6 )The shares are held of record in an account for the benefit of the reporting persons' son. The reporting persons disclaim beneficial ownership of these shares, and the inclusion of these shares in this report should not be deemed an admission of beneficial ownership of any such shares for purposes of Section 16, or for any other purpose. ( 7 )The shares are held of record by a trust for the benefit of the reporting persons' son. The reporting persons disclaim beneficial ownership of these shares, and the inclusion of these shares in this report should not be deemed an admission of beneficial ownership of any such shares for purposes of Section 16, or for any other purpose. ( 8 )Shares subject to the option are fully vested and immediately exercisable.

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).

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