Amphastar Pharmaceuticals (AMPH) CFO reports 1,744-share tax withholding

Rhea-AI Filing Summary

Amphastar Pharmaceuticals CFO William J. Peters had 1,744 shares of common stock withheld at $19.96 per share to cover taxes from vesting restricted stock units. After this tax-withholding disposition, he directly owns 123,786 shares, which include 545 shares acquired under the company’s 2014 Employee Stock Purchase Plan.

Insider Trade Summary

1 transaction reported

Mixed 1 txn

Insider PETERS WILLIAM J

Role CFO, EVP & TREASURER

Type	Security	Shares	Price	Value
Tax Withholding	Common Stock	1,744	$19.96	$35K

Holdings After Transaction: Common Stock — 123,786 shares (Direct)

Footnotes (1)

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. Includes 545 shares acquired on May 31, 2025 under the Issuer's 2014 Employee Stock Purchase Plan.

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Form 4 Insider Transactions: What Each Field Means →

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^*

PETERS WILLIAM J

(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		10% Owner
X	Officer (give title below)		Other (specify below)
	CFO, EVP & TREASURER

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)

X	Form filed by One Reporting Person
	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		1,744(1)	D	$19.96	123,786(2)	D

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

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. Includes 545 shares acquired on May 31, 2025 under the Issuer's 2014 Employee Stock Purchase Plan.

	/s/ William J. Peters	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.

FAQ

What insider transaction did AMPH CFO William J. Peters report on this Form 4?

William J. Peters reported a tax-withholding disposition of 1,744 shares of Amphastar common stock. The shares were withheld by the company to satisfy his tax liability arising from the vesting of restricted stock units, rather than being sold in an open-market transaction.

At what price were the AMPH shares withheld for William J. Peters’ tax obligations?

The 1,744 Amphastar shares withheld for William J. Peters’ tax liability were valued at $19.96 per share. This price reflects the value used to cover taxes triggered by the vesting of his restricted stock units, as disclosed in the Form 4 filing.

How many Amphastar (AMPH) shares does William J. Peters own after this Form 4 transaction?

Following the tax-withholding disposition, William J. Peters directly owns 123,786 shares of Amphastar common stock. This total includes 545 shares he previously acquired under Amphastar’s 2014 Employee Stock Purchase Plan, as noted in the Form 4 footnotes.

Was the AMPH Form 4 transaction an open-market sale by William J. Peters?

No, the Form 4 transaction was not an open-market sale. The 1,744 shares were withheld by Amphastar to satisfy William J. Peters’ tax liability related to vesting restricted stock units, which is reported as a tax-withholding disposition under transaction code F.

What do the Form 4 footnotes reveal about William J. Peters’ AMPH holdings?

The footnotes explain that the 1,744 shares were withheld to cover taxes on RSU vesting and that his direct holdings include 545 shares acquired on May 31, 2025 under Amphastar’s 2014 Employee Stock Purchase Plan, clarifying the composition of his total share ownership.