Amphastar insiders report RSU tax share withholdings

Amphastar Pharmaceuticals insiders reported tax-related share withholdings tied to equity compensation, not open-market sales.

Rhea-AI Filing Summary

Amphastar Pharmaceuticals insiders reported tax-related share withholdings tied to equity compensation, not open-market sales. CEO and Chief Scientific Officer Jack Y. Zhang had 5,769 shares of common stock withheld at $19.96 per share to satisfy tax liabilities from vesting restricted stock units, leaving 2,841,890 shares held directly.

Additional tax-withholding dispositions of 2,432 common shares at $19.96 per share were reported as indirectly owned, with 1,183,043 indirect shares remaining. Footnotes state that some securities are held of record by Mary Z. Luo and that 6,827,679 shares are held of record by Applied Physics and Chemistry Laboratories, Inc., which is owned by the reporting persons and The Bill Luobei Zhang 2004 Irrevocable Trust.

Insider Trade Summary

Exercise Price or Tax Liability: 8,201 shares

Exercise Price or Tax Liability 3 txns

Insider Zhang Jack Y., Luo Mary Z.

Role CEO & CHIEF SCIENTIFIC OFFICER | COO, Chief Scientist, Chairman

Type	Security	Shares	Price	Value
Exercise Price or Tax Liability	Common Stock	5,769	$19.96	$115K
Exercise Price or Tax Liability	Common Stock	2,432	$19.96	$49K
holding	Common Stock	--	--	--

Holdings After Transaction: Common Stock — 2,841,890 shares (Direct); Common Stock — 8,010,722 shares (Indirect, See footnote)

Footnotes (3)

1. F1. 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. F2. The securities are held of record by Mary Z. Luo. The reporting persons are husband and wife.
3. F3. 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.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What did Amphastar (AMPH) insiders report in this Form 4 filing?

Amphastar insiders reported shares withheld to cover tax liabilities from vesting restricted stock units. These Form 4 entries reflect tax-withholding dispositions rather than open-market stock sales, while the insiders continue to hold substantial direct and indirect positions in Amphastar common stock.

How many Amphastar (AMPH) shares did Jack Y. Zhang have withheld for taxes?

Jack Y. Zhang had 5,769 Amphastar common shares withheld at $19.96 per share to satisfy tax obligations on vesting restricted stock units. After this tax-withholding disposition, he continued to hold 2,841,890 shares directly, according to the reported post-transaction ownership figures.

What indirect Amphastar (AMPH) share holdings are disclosed for the insiders?

The filing shows 1,183,043 Amphastar common shares indirectly owned after a small tax-withholding disposition. It also notes 6,827,679 shares held of record by Applied Physics and Chemistry Laboratories, Inc., owned by the reporting persons and The Bill Luobei Zhang 2004 Irrevocable Trust.

Were the Amphastar (AMPH) insider transactions open-market stock sales?

The reported Amphastar insider transactions were not open-market sales. They are coded as tax-withholding dispositions, meaning shares were withheld to pay tax liabilities arising from restricted stock unit vesting, while the insiders maintained large continuing direct and indirect shareholdings.

How is Mary Z. Luo referenced in the Amphastar (AMPH) Form 4 footnotes?

One footnote explains that certain Amphastar securities are held of record by Mary Z. Luo and that the reporting persons are husband and wife. This clarifies part of the indirect ownership structure associated with the reported holdings in Amphastar common stock.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 03/06/2026 - 09:58 PM EST Learn about SEC filing dates

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

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

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)
03/04/2026

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	03/04/2026		F		5,769(1)	D	$19.96	2,841,890	D
Common Stock	03/04/2026		F		2,432(1)	D	$19.96	1,183,043	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 Jack Y. Zhang	03/06/2026
	/s/ Eva Wen, by power of attorney for Mary Z. Luo	03/06/2026
	** Signature of Reporting Person	Date
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).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
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 Number.