Dimensional Fund Advisors stake in Amphastar Pharmaceuticals (AMPH) hits 5.2%

Rhea-AI Filing Summary

Dimensional Fund Advisors LP, a Delaware limited partnership and registered investment adviser, reports beneficial ownership of 2,305,107 shares of Amphastar Pharmaceuticals common stock, representing 5.2% of the class as of June 30, 2026.

Dimensional has sole voting power over 2,251,660 shares and sole dispositive power over 2,305,107 shares, with no shared voting or dispositive power. The shares are held by client funds for which Dimensional or its subsidiaries provide advisory or management services, and Dimensional disclaims beneficial ownership beyond Section 13(d) reporting. No individual fund’s interest exceeds 5% of the class.

Key Figures

Beneficial ownership: 2,305,107 shares Percent of class: 5.2 % Sole voting power: 2,251,660 shares +2 more

5 metrics

Beneficial ownership 2,305,107 shares Common stock of Amphastar Pharmaceuticals reported as beneficially owned by Dimensional

Percent of class 5.2 % Portion of Amphastar common stock represented by Dimensional’s reported holdings

Sole voting power 2,251,660 shares Shares for which Dimensional can vote or direct the vote

Sole dispositive power 2,305,107 shares Shares for which Dimensional can dispose or direct disposition

Ownership threshold More than 5 % Holdings reported as ownership of more than 5 percent on behalf of others

Key Terms

beneficial owner, sole voting power, dispositive power, disclaims beneficial ownership, +2 more

6 terms

beneficial owner financial

"may be deemed to be the beneficial owner of the shares of the Issuer"

A beneficial owner is the person who ultimately owns or controls a financial asset or property, even if their name isn't directly on official documents. Think of it like someone who secretly holds the keys to a safe deposit box—others may appear to have access, but the true owner is the one who benefits from what's inside. Identifying beneficial owners helps ensure transparency and prevent illegal activities like money laundering or fraud.

sole voting power financial

"Sole Voting Power 2,251,660.00"

Sole voting power is the exclusive right to cast votes attached to a shareholder’s stock without needing approval from anyone else. Like holding the only remote control for a TV, it lets that holder decide corporate matters such as board members, mergers, and policy changes, making it important to investors because it concentrates control and can strongly influence a company’s strategy and the value of its shares.

dispositive power financial

"Sole Dispositive Power 2,305,107.00"

Dispositive power is the authority to decide the final outcome of an asset, legal claim, contract, or corporate action — in effect the power to dispose of or resolve something. For investors it matters because whoever holds that authority can determine who gets paid, who controls an asset or vote, and how risks and returns are allocated; think of it like holding the key that lets you lock in the winner or loser in a deal.

disclaims beneficial ownership financial

"Dimensional disclaims beneficial ownership of such securities"

Investment Company Act of 1940 regulatory

"investment companies registered under the Investment Company Act of 1940"

A U.S. federal law that sets the rulebook for pooled investment vehicles such as mutual funds, exchange-traded funds and similar money managers, requiring them to register with regulators, disclose holdings and fees, limit conflicts of interest, and follow governance standards. It matters to investors because these protections and transparency rules act like a referee and scoreboard, helping people compare funds, trust that managers follow fair practices, and spot hidden costs or risks.

Section 13(d) of the Securities Exchange Act of 1934 regulatory

"for any other purposes than Section 13(d) of the Securities Exchange Act of 1934"

Section 13(d) of the Securities Exchange Act of 1934 is a U.S. rule that requires anyone who buys more than 5% of a public company’s shares to publicly disclose who they are, how many shares they own, and their intentions toward the company. For investors, this is like a neighborhood alert when someone acquires a large stake in a building: it reveals potential changes in control or strategy that could affect the stock’s price, governance, or future direction.

See more from StockTitan in Google Search and AI answers. Adds StockTitan as a preferred source · opens Google

Add on Google Not now

Available on EDGAR 07/14/2026 - 01:28 PM Accepted by SEC EDGAR 07/14/2026 - 01:27 PM Learn about SEC filing dates

FAQ

What percentage of Amphastar Pharmaceuticals (AMPH) does Dimensional Fund Advisors report owning?

Dimensional Fund Advisors reports beneficial ownership of 5.2% of Amphastar Pharmaceuticals common stock, equal to 2,305,107 shares as of June 30, 2026. These shares are held in client funds it advises, and Dimensional disclaims beneficial ownership outside its Section 13(d) reporting obligations.

How many Amphastar (AMPH) shares can Dimensional Fund Advisors vote and dispose of?

Dimensional reports sole voting power over 2,251,660 shares and sole dispositive power over 2,305,107 shares of Amphastar common stock. It has no shared voting or shared dispositive power; all reported securities are held in client funds for which it provides advisory or management services.

Who are the actual economic owners of the Amphastar (AMPH) shares tied to Dimensional Fund Advisors?

The client funds advised or managed by Dimensional Fund Advisors or its subsidiaries are the economic owners of the Amphastar shares. Dimensional may be deemed a beneficial owner for Section 13(d) purposes but disclaims beneficial ownership of all such securities beyond that reporting context.

Does any single Dimensional-advised fund hold more than 5% of Amphastar (AMPH)?

Dimensional states that, to its knowledge, the interest of no single client fund exceeds 5% of Amphastar’s common stock. The overall 5.2% position reflects aggregate holdings across multiple funds and accounts that Dimensional advises or manages.

What is Dimensional Fund Advisors’ legal status and role regarding Amphastar (AMPH) shares?

Dimensional Fund Advisors LP is a Delaware limited partnership and a registered investment adviser. It furnishes investment advice and management to various funds and accounts that hold Amphastar shares, giving it voting and investment power, but it disclaims beneficial ownership of those securities.

What rights do Dimensional’s client funds have over Amphastar (AMPH) securities?

The client funds have the right to receive dividends and sale proceeds from the Amphastar securities held in their accounts. Dimensional indicates these funds direct the economic benefits, while Dimensional exercises voting and investment power as adviser or manager.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Amphastar Pharmaceuticals Inc

(Name of Issuer)

Common Stock

(Title of Class of Securities)

03209R103

(CUSIP Number)

06/30/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 03209R103

1

Names of Reporting Persons

Dimensional Fund Advisors LP

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 2,251,660.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 2,305,107.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

2,305,107.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

5.2 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Amphastar Pharmaceuticals Inc
(b)	Address of issuer's principal executive offices: 11570 6th Street, Rancho Cucamonga, CA 91730
Item 2.
(a)	Name of person filing: Dimensional Fund Advisors LP
(b)	Address or principal business office or, if none, residence: 6300 Bee Cave Road, Building One, Austin, TX 78746
(c)	Citizenship: Delaware Limited Partnership
(d)	Title of class of securities: Common Stock
(e)	CUSIP Number(s): 03209R103
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 2,305,107 ** see Note 1 ** ** Note 1 ** Dimensional Fund Advisors LP, an investment adviser registered under Section 203 of the Investment Advisors Act of 1940, furnishes investment advice to four investment companies registered under the Investment Company Act of 1940, and serves as investment manager or sub-adviser to certain other commingled funds, group trusts and separate accounts (such investment companies, trusts and accounts, collectively referred to as the "Funds"). In certain cases, subsidiaries of Dimensional Fund Advisors LP may act as an adviser or sub-adviser to certain Funds. In its role as investment advisor, sub-adviser and/or manager, Dimensional Fund Advisors LP or its subsidiaries (collectively, "Dimensional") may possess voting and/or investment power over the securities of the Issuer that are owned by the Funds, and may be deemed to be the beneficial owner of the shares of the Issuer held by the Funds. However, all securities reported in this schedule are owned by the Funds. Dimensional disclaims beneficial ownership of such securities. In addition, the filing of this Schedule 13G shall not be construed as an admission that the reporting person or any of its affiliates is the beneficial owner of any securities covered by this Schedule 13G for any other purposes than Section 13(d) of the Securities Exchange Act of 1934.
(b)	Percent of class: 5.2 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 2,251,660** see Note 1 **
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 2,305,107** see Note 1 **
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. The Funds described in Note 1 above have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of the securities held in their respective accounts. To the knowledge of Dimensional, the interest of any one such Fund does not exceed 5% of the class of securities. Dimensional Fund Advisors LP disclaims beneficial ownership of all such securities.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Dimensional Fund Advisors LP

Signature:	Selwyn Notelovitz
Name/Title:	Global Chief Compliance Officer
Date:	07/14/2026