[Form 4] Amphastar Pharmaceuticals, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Amphastar Pharmaceuticals director reports option exercise and share sale. A director of Amphastar Pharmaceuticals, Inc. (AMPH) exercised a stock option for 4,179 shares of common stock on 11/25/2025 at an exercise price of $16.69 per share. On the same date, the director sold 4,179 shares of common stock in an open-market transaction at a weighted average price of $27.1006 per share, with individual sale prices ranging from $27.10 to $27.125. After these transactions, the director beneficially owns 35,183 shares of Amphastar common stock held directly. The option exercised covered fully vested, immediately exercisable shares and now has a remaining balance of zero derivative securities.

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
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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^*

PRINS RICHARD K

(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
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
11/25/2025

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	11/25/2025		M		4,179	A	$16.69	39,362	D
Common Stock	11/25/2025		S		4,179	D	$27.1006(1)	35,183	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
Stock Option (right to buy)	$16.69	11/25/2025		M			4,179	(2)	06/07/2026	Common Stock	4,179	$0	0	D

Explanation of Responses:

1. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $27.10 to $27.125, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price.

2. Shares subject to the option are fully vested and immediately exercisable.

	/s/ Eva Wen, by power of attorney	11/25/2025
	** 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 Amphastar Pharmaceuticals (AMPH) report on this Form 4?

The filing reports that a director of Amphastar Pharmaceuticals, Inc. (AMPH) exercised a stock option for 4,179 shares of common stock on 11/25/2025 and sold 4,179 shares of common stock on the same date in an open-market transaction.

At what prices were the Amphastar (AMPH) stock option exercised and the shares sold?

The director exercised a stock option at an exercise price of $16.69 per share and sold the resulting 4,179 shares at a weighted average price of $27.1006 per share, with individual sale prices ranging from $27.10 to $27.125.

How many Amphastar (AMPH) shares does the reporting person own after this transaction?

Following the reported option exercise and share sale, the director beneficially owns 35,183 shares of Amphastar common stock, held with direct ownership.

What type of derivative security was involved in this Amphastar (AMPH) Form 4 filing?

The derivative security was a stock option (right to buy) covering 4,179 shares of Amphastar common stock at an exercise price of $16.69 per share, which was fully vested and immediately exercisable and was exercised in full.

Were the Amphastar (AMPH) shares sold in a single trade or multiple trades?

The 4,179 shares of Amphastar common stock were sold in multiple transactions on 11/25/2025 at prices ranging from $27.10 to $27.125, resulting in a weighted average sale price of $27.1006 per share.

What is the relationship of the reporting person to Amphastar Pharmaceuticals (AMPH)?

The reporting person is identified as a Director of Amphastar Pharmaceuticals, Inc. and filed this Form 4 as a single reporting person.

Is the reported ownership in Amphastar (AMPH) direct or indirect?

The 35,183 shares of Amphastar common stock held after the transactions are reported with direct (D) ownership, with no indirect beneficial ownership specified.