Amphastar (AMPH) exec granted RSUs, options and reports tax share withholding

Rhea-AI Filing Summary

Amphastar Pharmaceuticals, Inc. senior executive Rong Zhou reported routine equity compensation and related tax withholding. On March 9, 2026, Zhou received 39,432 restricted stock units (RSUs) and an option for 81,341 shares of common stock at $19.21 per share, both vesting in four equal annual installments beginning on March 9, 2027. A separate entry on March 10, 2026 shows 2,215 common shares withheld at $18.91 per share to cover taxes on RSU vesting, which is characterized as a tax-withholding disposition rather than an open-market sale. After these transactions, Zhou holds 172,779 common shares directly, in addition to indirect holdings of 99,668 shares through the Zhou Family Trust and 5,000 shares held by a spouse, plus the newly granted option for 81,341 shares.

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^*

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)
03/09/2026

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 Srock	03/09/2026		A		39,432(1)	A	$0	174,994	D
Common Stock	03/10/2026		F		2,215(2)	D	$18.91	172,779	D
Common Stock								99,668	I	See footnote(3)
Common Stock								5,000	I	See footnote(4)

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
Employee Stock Option (right to buy)	$19.21	03/09/2026		A		81,341		(5)	03/09/2036	Common Stock	81,341	$0	81,341	D

Explanation of Responses:

1. The reported shares are represented by restricted stock units, or RSUs, which vest in four equal annual installments beginning on March 9, 2027.

2. The reported shares were withheld to satisfy the reporting person's tax liability in connection with the vesting of RSUs.

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

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

5. The shares subject to the option vest in four equal annual installments beginning on March 9, 2027.

	/s/ Eva Wen, by power of attorney	03/11/2026
	** Signature of Reporting Person	Date
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FAQ

What insider transactions did Amphastar (AMPH) executive Rong Zhou report on this Form 4?

Rong Zhou reported new equity awards and tax withholding. The filing shows grants of 39,432 restricted stock units, a stock option for 81,341 shares, and 2,215 shares withheld to cover taxes on RSU vesting.

How many Amphastar (AMPH) shares were granted to Rong Zhou in RSUs and options?

Zhou received 39,432 restricted stock units and an option covering 81,341 shares of common stock. Both awards are scheduled to vest in four equal annual installments beginning on March 9, 2027, subject to continued service and plan terms.

What was the exercise price and expiration date of Rong Zhou’s Amphastar (AMPH) stock option grant?

The newly granted employee stock option covers 81,341 shares at an exercise price of $19.21 per share. The option expires on March 9, 2036 and vests in four equal annual installments starting March 9, 2027.

Did Rong Zhou sell Amphastar (AMPH) shares in the open market in this Form 4?

The filing does not show any open-market sales. Instead, 2,215 shares of common stock were withheld to satisfy Zhou’s tax liability related to RSU vesting, which is recorded as a tax-withholding disposition, not a discretionary sale.

What are Rong Zhou’s Amphastar (AMPH) shareholdings after the reported transactions?

After the transactions, Zhou directly owns 172,779 common shares. In addition, 99,668 shares are held through the Zhou Family Trust, and 5,000 shares are held by a spouse, both reported as indirect ownership interests in the filing.

How do the new equity awards for Rong Zhou in Amphastar (AMPH) vest over time?

Both the 39,432 RSUs and the option for 81,341 shares vest in four equal annual installments. Vesting begins on March 9, 2027, meaning one-quarter of each award is scheduled to vest on that date and annually thereafter.