Tax withholding trims Amphastar (NASDAQ: AMPH) exec's RSU shares

Rhea-AI Filing Summary

Amphastar Pharmaceuticals senior executive Rong Zhou reported a routine tax-withholding share disposition tied to restricted stock units. On March 15, 2026, 1,225 shares of common stock were withheld at $18.18 per share to satisfy tax liabilities from RSU vesting.

After this transaction, Zhou directly held 171,554 Amphastar shares. Footnotes show additional indirect holdings of 99,668 shares held by the Zhou Family Trust, where Zhou serves as trustee, and 5,000 shares held by Zhou’s spouse.

Insider Trade Summary

3 transactions reported

Mixed 3 txns

Insider Zhou Rong

Role SENIOR EVP, PRODUCTION CENTER

Type	Security	Shares	Price	Value
Tax Withholding	Common Stock	1,225	$18.18	$22K
holding	Common Stock	--	--	--
holding	Common Stock	--	--	--

Holdings After Transaction: Common Stock — 171,554 shares (Direct); Common Stock — 99,668 shares (Indirect, See footnote)

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

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^*

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)
03/15/2026

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	03/15/2026		F		1,225(1)	D	$18.18	171,554	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	03/17/2026
	** 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 did Amphastar (AMPH) executive Rong Zhou report in this Form 4 filing?

Rong Zhou reported a tax-related share disposition linked to restricted stock units. Amphastar withheld 1,225 common shares to cover taxes upon RSU vesting, a non-market transaction that does not represent an open-market sale or discretionary trading decision by the executive.

How many Amphastar (AMPH) shares were withheld for taxes in Rong Zhou’s filing?

The filing shows 1,225 Amphastar common shares were withheld to satisfy Rong Zhou’s RSU-related tax liability. These shares were valued at $18.18 each, reflecting a standard mechanism where the issuer retains shares instead of the executive paying cash for the associated tax obligation.

How many Amphastar (AMPH) shares does Rong Zhou hold directly after the transaction?

Following the reported tax withholding, Rong Zhou directly holds 171,554 Amphastar common shares. This figure reflects his direct ownership after the RSU-related disposition and indicates that the withholding affected only a small portion of his overall directly held equity position in the company.

What indirect Amphastar (AMPH) holdings related to Rong Zhou are disclosed?

The Form 4 discloses 99,668 Amphastar shares held by the Zhou Family Trust, for which Rong Zhou serves as trustee. It also notes 5,000 shares held by his spouse. These positions are reported as indirect ownership interests associated with the executive’s household and trust arrangements.

Does Rong Zhou’s Amphastar (AMPH) Form 4 indicate open-market buying or selling?

No, the reported activity is a tax-withholding disposition, not an open-market trade. Shares were withheld by Amphastar to cover taxes on vesting RSUs, meaning there was no discretionary market purchase or sale by Rong Zhou reflected in this specific filing event.