Amphastar officer plans $103K stock sale

Officer William J. Peters files a Rule 144 notice to resell Amphastar common stock, following an earlier sale in August 2026.

Rhea-AI Filing Summary

Amphastar Pharmaceuticals, Inc. (AMPH) has a notice of proposed resale of common stock under Rule 144 filed on behalf of officer William J. Peters. The notice covers 4,139 shares of common stock held at UBS Financial Services Inc., with an indicated aggregate value of $103,475.00 and a proposed sale date of September 21, 2026 on NASDAQ. The shares to be sold were acquired through RSU vesting on March 17, 2024, and the notice also reports a prior sale of 8,180 shares for $183,886.40 on August 7, 2026.

Key Figures

Planned shares to be sold: 4,139 shares Aggregate market value of planned sale: $103,475.00 Prior 3-month shares sold: 8,180 shares +3 more

6 metrics

Planned shares to be sold 4,139 shares Common stock resale under Rule 144 for William J. Peters

Aggregate market value of planned sale $103,475.00 Value of 4,139 Amphastar common shares to be sold

Prior 3-month shares sold 8,180 shares Common stock sold on August 7, 2026

Value of prior 3-month sale $183,886.40 Proceeds from sale of 8,180 shares on August 7, 2026

RSU vesting shares 4,139 shares Shares acquired via RSU vesting on March 17, 2024

Proposed sale date September 21, 2026 Planned date of Rule 144 resale on NASDAQ

Key Terms

Rule 144, RSU Vesting, attorney-in-fact

3 terms

Rule 144 regulatory

"notice of proposed resale of common stock under Rule 144 filed"

Rule 144 is a U.S. securities regulation that sets conditions under which restricted or insider-held shares can be legally resold to the public, such as required holding periods, availability of public information, limits on how much can be sold at once, and certain filing requirements. For investors it matters because it determines when previously locked-up shares can enter the market — like a release valve that can increase supply, affect share price, and signal insider intent.

RSU Vesting financial

"The shares to be sold were acquired through RSU Vesting"

RSU vesting is the process by which restricted stock units — a promise by a company to give shares to an employee — become actual, owned shares over time or when certain goals are met. Investors care because vested shares can dilute existing ownership when issued, and the timing of vesting affects when employees can sell shares, which can influence share supply, insider selling patterns, and company incentives.

attorney-in-fact regulatory

"UBS Financial Services Inc, as attorney-in-fact for William J Peters"

An attorney-in-fact is the person or entity given legal authority through a power of attorney to act on behalf of another for specific tasks, such as signing documents, voting shares, or handling transactions. For investors, this matters because it lets a trusted representative make timely decisions or complete paperwork when the owner cannot, much like handing keys to someone to run errands on your behalf—so checks on scope and limits of that authority are important.

FAQ

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

What does the Form 144 filing mean for Amphastar Pharmaceuticals, Inc. (AMPH)?

The filing reports a planned resale of 4,139 shares of Amphastar common stock under Rule 144 by officer William J. Peters through UBS Financial Services Inc., with an indicated value of $103,475.00 and a proposed sale date of September 21, 2026.

How many AMPH shares is William J. Peters planning to sell under this Form 144?

William J. Peters plans to sell 4,139 shares of Amphastar Pharmaceuticals, Inc. common stock. The notice lists an aggregate market value of $103,475.00 for these shares, with NASDAQ noted as the trading market.

When and how did William J. Peters acquire the AMPH shares to be sold?

The 4,139 shares covered by the notice were acquired on March 17, 2024 through RSU Vesting from the issuer, Amphastar Pharmaceuticals, Inc., as disclosed in the “Securities To Be Sold” section.

What prior AMPH stock sales by William J. Peters are disclosed in this Form 144?

The filing reports that William J. Peters sold 8,180 shares of Amphastar common stock on August 7, 2026 for total proceeds of $183,886.40 during the past three months.

Who is executing the AMPH share sale reported in this Form 144?

The shares are held and the notice is signed by UBS Financial Services Inc. as attorney-in-fact for William J. Peters. UBS is listed as the broker handling the common stock for this planned Rule 144 resale.

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

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Available on EDGAR 09/21/2026 - 06:37 PM Accepted by SEC EDGAR 09/21/2026 - 06:37 PM Learn about SEC filing dates

Form 144 Filer Information	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 144 NOTICE OF PROPOSED SALE OF SECURITIES PURSUANT TO RULE 144 UNDER THE SECURITIES ACT OF 1933
FORM 144

144: Filer Information

Filer CIK	0001263136
Filer CCC	XXXXXXXX
Is this a LIVE or TEST Filing?	LIVE TEST
Submission Contact Information
Name
Phone
E-Mail Address

144: Issuer Information

Name of Issuer	Amphastar Pharmaceuticals, Inc.
SEC File Number	001-36509
Address of Issuer	11570 SIXTH STREET RANCHO CUCAMONGA CALIFORNIA 91730
Phone	909-980-9484
Name of Person for Whose Account the Securities are To Be Sold	PETERS WILLIAM J
See the definition of "person" in paragraph (a) of Rule 144. Information is to be given not only as to the person for whose account the securities are to be sold but also as to all other persons included in that definition. In addition, information shall be given as to sales by all persons whose sales are required by paragraph (e) of Rule 144 to be aggregated with sales for the account of the person filing this notice.
Relationship to Issuer	Officer

144: Securities Information

Title of the Class of Securities To Be Sold	Name and Address of the Broker	Number of Shares or Other Units To Be Sold	Aggregate Market Value	Number of Shares or Other Units Outstanding	Approximate Date of Sale	Name the Securities Exchange
Common	UBS Financial Services, Inc. 1000 Harbor Blvd 3rd Floor Weehawken NJ 07086	4139	103475.00	42537944	09/21/2026	NASDAQ

Furnish the following information with respect to the acquisition of the securities to be sold and with respect to the payment of all or any part of the purchase price or other consideration therefor:

144: Securities To Be Sold

Title of the Class	Date you Acquired	Nature of Acquisition Transaction	Name of Person from Whom Acquired	Is this a Gift?	Date Donor Acquired	Amount of Securities Acquired	Date of Payment	Nature of Payment *
Common	03/17/2024	RSU Vesting	Issuer			4139	03/17/2024	NA

* If the securities were purchased and full payment therefor was not made in cash at the time of purchase, explain in the table or in a note thereto the nature of the consideration given. If the consideration consisted of any note or other obligation, or if payment was made in installments describe the arrangement and state when the note or other obligation was discharged in full or the last installment paid.

Furnish the following information as to all securities of the issuer sold during the past 3 months by the person for whose account the securities are to be sold.

144: Securities Sold During The Past 3 Months

Name and Address of Seller	Title of Securities Sold	Date of Sale	Amount of Securities Sold	Gross Proceeds
William J Peters 11570 Sixth Street Rancho Cucamonga CA 91730	Common	08/07/2026	8180	183886.40

144: Remarks and Signature

Remarks
Date of Notice	09/21/2026
Date of Plan Adoption or Giving of Instruction, If Relying on Rule 10b5-1	03/10/2026
ATTENTION:
The person for whose account the securities to which this notice relates are to be sold hereby represents by signing this notice that he does not know any material adverse information in regard to the current and prospective operations of the Issuer of the securities to be sold which has not been publicly disclosed. If such person has adopted a written trading plan or given trading instructions to satisfy Rule 10b5-1 under the Exchange Act, by signing the form and indicating the date that the plan was adopted or the instruction given, that person makes such representation as of the plan adoption or instruction date.
Signature	/s/ UBS Financial Services Inc, as attorney-in-fact for William J Peters
ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)