Amphastar (AMPH) CEO logs 10,850-share RSU tax withholding, retains large stake

Rhea-AI Filing Summary

Amphastar Pharmaceuticals director and CEO Jack Y. Zhang reported routine tax-related share withholdings tied to restricted stock unit vesting. On March 6, 2026, a total of 10,850 shares of common stock were withheld to satisfy tax liabilities, rather than sold on the open market.

After these withholdings, Zhang holds 2,834,117 shares directly. Additional indirect holdings include 1,179,966 shares held of record by his spouse, Mary Z. Luo, and 6,827,679 shares held through Applied Physics and Chemistry Laboratories, Inc. and a related family trust.

SEC Form 4

FORM 4

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
or Section 30(h) of the Investment Company Act of 1940

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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Zhang Jack Y.

(Last) (First) (Middle)

C/O AMPHASTAR PHARMACEUTICALS, INC.

11570 6TH STREET

(Street)

RANCHO CUCAMONGA CA 91730

(City) (State) (Zip)

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 SCIENTIFIC OFFICER

3. Date of Earliest Transaction (Month/Day/Year)
03/06/2026

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

	Form filed by One Reporting Person
X	Form filed by More than One Reporting Person

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	03/06/2026		F		7,773(1)	D	$19.34	2,834,117	D
Common Stock	03/06/2026		F		3,077(1)	D	$19.34	1,179,966	I	See footnote(2)
Common Stock								6,827,679	I	See footnote(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 (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 Securities Underlying Derivative Security (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: 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

1. Name and Address of Reporting Person^*

Zhang Jack Y.

(Last) (First) (Middle)

C/O AMPHASTAR PHARMACEUTICALS, INC.

11570 6TH STREET

(Street)

RANCHO CUCAMONGA CA 91730

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

X	Director	X	10% Owner
X	Officer (give title below)		Other (specify below)
	CEO & CHIEF SCIENTIFIC OFFICER

1. Name and Address of Reporting Person^*

Luo Mary Z.

(Last) (First) (Middle)

C/O AMPHASTAR PHARMACEUTICALS, INC.

11570 6TH STREET

(Street)

RANCHO CUCAMONGA CA 91730

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

X	Director	X	10% Owner
X	Officer (give title below)		Other (specify below)
	COO, Chief Scientist, Chairman

Explanation of Responses:

1. The reported shares were withheld to satisfy the reporting person's tax liability in connection with the vesting of restricted stock units, or RSUs.

2. The securities are held of record by Mary Z. Luo. The reporting persons are husband and wife.

3. The shares are held of record by Applied Physics and Chemistry Laboratories, Inc., of which the reporting persons and The Bill Luobei Zhang 2004 Irrevocable Trust are the sole owners.

	/s/ Eva Wen, by power of attorney for Mary Z. Luo	03/10/2026
	/s/ Eva Wen, by power of attorney for Jack Y. Zhang	03/10/2026
	** Signature of Reporting Person	Date
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FAQ

What insider transactions did AMPH executives report on March 6, 2026?

Amphastar Pharmaceuticals executives reported tax-withholding dispositions on March 6, 2026. A total of 10,850 common shares were withheld to cover tax liabilities arising from vesting restricted stock units, rather than being sold in open-market transactions.

Were the AMPH Form 4 transactions open-market sales or tax withholdings?

The reported AMPH Form 4 transactions were tax withholdings, not open-market sales. Shares were surrendered to satisfy tax obligations triggered by restricted stock unit vesting, categorized under transaction code F for payment of tax liability by delivering securities.

How many Amphastar (AMPH) shares does Jack Y. Zhang hold after this Form 4?

After the reported tax-withholding transactions, Jack Y. Zhang directly holds 2,834,117 Amphastar common shares. He also reports indirect beneficial interests in 1,179,966 shares held by his spouse and 6,827,679 shares held through Applied Physics and Chemistry Laboratories, Inc. and a related trust.

What does the 10,850-share tax withholding mean for AMPH shareholders?

The 10,850-share withholding reflects routine tax payments on executive equity awards, not discretionary selling. Shares were delivered to cover tax liabilities from restricted stock unit vesting, so the event is administrative compensation-related rather than a traditional buy or sell signal.

How are Mary Z. Luo’s Amphastar (AMPH) holdings reflected in this Form 4?

The filing notes that certain securities are held of record by Mary Z. Luo, who is Zhang’s spouse. One indirect position of 1,179,966 shares is attributed to her holdings, while both spouses are also owners of Applied Physics and Chemistry Laboratories, Inc., which holds 6,827,679 shares.

What entity holds 6,827,679 Amphastar (AMPH) shares mentioned in the filing?

According to the footnotes, 6,827,679 Amphastar common shares are held of record by Applied Physics and Chemistry Laboratories, Inc. The reporting persons and The Bill Luobei Zhang 2004 Irrevocable Trust are identified as the sole owners of this entity.