Amphastar executive covers taxes with 1,357 AMPH shares

Amphastar Pharmaceuticals senior executive Rong Zhou reported a routine tax-related share disposition.

Rhea-AI Filing Summary

Amphastar Pharmaceuticals senior executive Rong Zhou reported a routine tax-related share disposition. On March 6, 2026, 1,357 shares of common stock were withheld at $19.34 per share to cover taxes from vesting restricted stock units. After this withholding, Zhou directly held 135,562 shares, with additional indirect holdings of 99,668 shares through the Zhou Family Trust and 5,000 shares held by the spouse, as noted in the footnotes. This filing reflects compensation- and tax-driven activity rather than an open-market trade.

Insider Trade Summary

Exercise Price or Tax Liability: 1,357 shares

Exercise Price or Tax Liability 3 txns

Insider Zhou Rong

Role SENIOR EVP, PRODUCTION CENTER

Type	Security	Shares	Price	Value
Exercise Price or Tax Liability	Common Stock	1,357	$19.34	$26K
holding	Common Stock	--	--	--
holding	Common Stock	--	--	--

Holdings After Transaction: Common Stock — 135,562 shares (Direct); Common Stock — 104,668 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 shares are held of record by the Zhou Family Trust for which the reporting person serves as a trustee.
3. F3. The shares are held of record by the reporting person's spouse.

FAQ

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

What insider transaction did Amphastar (AMPH) executive Rong Zhou report?

Rong Zhou reported a tax-withholding disposition of shares. On March 6, 2026, 1,357 Amphastar common shares were withheld at $19.34 each to satisfy tax obligations from vesting restricted stock units, rather than through an open-market sale.

How many Amphastar (AMPH) shares does Rong Zhou hold after this Form 4 filing?

After the reported transaction, Rong Zhou directly holds 135,562 Amphastar shares. Footnotes show additional indirect holdings of 99,668 shares in the Zhou Family Trust and 5,000 shares held by the spouse, reflecting a sizable ongoing equity position.

Was the Amphastar (AMPH) insider transaction an open-market sale?

No, the transaction was not an open-market sale. The 1,357 shares were withheld by the company to cover Rong Zhou’s tax liability related to vesting restricted stock units, a routine compensation-related event rather than a discretionary stock sale.

What do the footnotes in Rong Zhou’s Amphastar (AMPH) Form 4 explain?

The footnotes clarify that the disposed shares covered tax liabilities on RSU vesting. They also explain that 99,668 shares are held by the Zhou Family Trust, where Zhou serves as trustee, and 5,000 shares are held by the reporting person’s spouse as additional indirect ownership.

Does this Amphastar (AMPH) Form 4 indicate changes to derivative or option holdings?

The Form 4 data show no derivative transactions or option exercises in this filing. The only reported activity is the withholding of 1,357 common shares for taxes on vesting RSUs, while derivativeSummary indicates no remaining derivative positions disclosed here.

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

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Accepted by SEC EDGAR 03/10/2026 - 05:44 PM EDT 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^*

Zhou Rong

(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)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	SENIOR EVP, PRODUCTION CENTER

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)

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	03/06/2026		F		1,357(1)	D	$19.34	135,562	D
Common Stock								99,668	I	See footnote(2)
Common Stock								5,000	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

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 shares are held of record by the Zhou Family Trust for which the reporting person serves as a trustee.

3. The shares are held of record by the reporting person's spouse.

	/s/ Eva Wen, by power of attorney	03/10/2026
	** 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.