ACM Research director exercises options, sells shares

ACM Research, Inc. director Haiping Dun exercised stock options for 5,000 shares of Class A Common Stock at $5.60 per share, then sold 5,000 shares in open-market transactions around $43–$44 per share.

Rhea-AI Filing Summary

ACM Research, Inc. director Haiping Dun exercised stock options for 5,000 shares of Class A Common Stock at $5.60 per share, then sold 5,000 shares in open-market transactions around $43–$44 per share. These sales were made under a pre-arranged Rule 10b5-1 trading plan adopted on August 13, 2025. Following the trades, Dun reported no direct Class A Common Stock holdings, while continuing to hold 55,000 stock options and indirect ownership of 100,000 and 755,090 Class A shares through family trusts.

Insider Trade Summary 10b5-1

Exercise and Sale: 5,000 shares ($189K approx. pre-tax spread)

Exercise and Sale 6 txns

Insider Dun Haiping

Role Director

Sold 5,000 shs ($217K)

Approx. gross sale proceeds $217K

Approx. exercise cost $28K

Approx. pre-tax spread $189K

Type	Security	Shares	Price	Value
Exercise	Stock Option	5,000	$0.00	$0.00
Exercise	Class A Common Stock	5,000	$5.60	$28K
Sale	Class A Common Stock	4,100	$43.37	$178K
Sale	Class A Common Stock	900	$43.94	$40K
holding	Class A Common Stock	--	--	--
holding	Class A Common Stock	--	--	--

Holdings After Transaction: Stock Option — 55,000 contracts (Direct); Class A Common Stock — 0 shares (Direct); Class A Common Stock — 100,000 shares (Indirect, Dun Family GST Trust); Class A Common Stock — 755,090 shares (Indirect, Haiping Dun & Chi-Pin H Dun Revocable Trust)

Footnotes (4)

1. F1. The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on August 13, 2025.
2. F2. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $42.88 to $43.87, 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 within the ranges set forth in footnote (2) and (3) to this Form 4.
3. F3. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $43.90 to $44.00, inclusive.
4. F4. The option is fully vested and exercisable.

FAQ

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

What did ACMR director Haiping Dun do in this Form 4 filing?

ACM Research director Haiping Dun exercised options for 5,000 Class A shares at $5.60 and sold 5,000 shares in open-market trades around $43–$44. The activity reflects an exercise-and-sell sequence rather than a new open-market purchase.

Were Haiping Dun’s ACMR share sales pre-planned under a Rule 10b5-1 plan?

Yes. The filing states the sales were made under a Rule 10b5-1 trading plan adopted on August 13, 2025. Such plans pre-schedule trades, indicating the timing of these sales was set in advance rather than chosen opportunistically.

At what prices did Haiping Dun sell ACMR Class A Common Stock?

The Form 4 reports weighted average prices of $43.37 and $43.94 per share. Footnotes explain the actual trades occurred in multiple transactions within ranges of $42.88–$43.87 and $43.90–$44.00 per share, respectively.

How many ACMR shares did Haiping Dun sell in this transaction?

The filing shows sales of 4,100 and 900 Class A Common Stock shares, totaling 5,000 shares. These disposals followed the exercise of options for 5,000 shares, effectively converting an option position into cash through same-day open-market sales.

What are Haiping Dun’s ACMR holdings after these transactions?

After the reported trades, Dun lists no directly held Class A shares but continues to hold 55,000 stock options. Indirectly, trusts associated with Dun report ownership of 100,000 and 755,090 Class A Common Stock shares, indicating substantial ongoing exposure to ACM Research.

Were the options exercised by Haiping Dun fully vested?

Yes. A footnote clarifies that the stock option is fully vested and exercisable. Dun exercised 5,000 underlying shares at an exercise price of $5.60 per share, with the remaining option position after the transaction shown as 55,000 stock options.

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Accepted by SEC EDGAR 03/11/2026 - 04:30 PM Learn about SEC filing dates

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).

X

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^*

Dun Haiping

(Last) (First) (Middle)

C/O ACM RESEARCH, INC.

42307 OSGOOD ROAD, SUITE I

(Street)

FREMONT CA 94539

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
ACM Research, Inc. [ ACMR ]

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)
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
Class A Common Stock	03/09/2026		M		5,000	A	$5.6	5,000	D
Class A Common Stock	03/09/2026		S(1)		4,100	D	$43.37(2)	900	D
Class A Common Stock	03/09/2026		S(1)		900	D	$43.94(3)	0	D
Class A Common Stock								100,000	I	Dun Family GST Trust
Class A Common Stock								755,090	I	Haiping Dun & Chi-Pin H Dun Revocable Trust

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	$5.6	03/09/2026		M			5,000	(4)	04/22/2029	Class A Common Stock	5,000	$0	55,000	D

Explanation of Responses:

1. The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on August 13, 2025.

2. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $42.88 to $43.87, 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 within the ranges set forth in footnote (2) and (3) to this Form 4.

3. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $43.90 to $44.00, inclusive.

4. The option is fully vested and exercisable.

	/s/ Mark McKechnie, Attorney-in-Fact for Haiping Dun	03/11/2026
	** 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.
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