A Form 4 filed on August 20, 2026, reports that Haiping Dun, a director of ACM Research, Inc. (NASDAQ:ACMR), exercised stock options and sold Class A Common Stock on August 18, 2026, pursuant to a pre-established Rule 10b5-1 trading plan.

Key Highlights

  • Option exercise: Haiping Dun exercised a stock option for 5,000 shares of Class A Common Stock at an exercise price of $5.6 per share on August 18, 2026.
  • Shares sold: A total of 5,000 shares were sold across three separate tranches on August 18, 2026, at weighted average prices of $80.29, $81.31, and $82.17.
  • Direct ownership following transactions: Following all reported transactions, Dun holds 0 shares of Class A Common Stock directly.
  • Indirect ownership: Dun retains indirect beneficial ownership of 100,000 shares through the Dun Family GST Trust and 755,090 shares through the Haiping Dun & Chi-Pin H Dun Revocable Trust.
  • Remaining options: Dun continues to hold 45,000 vested and exercisable stock options with an exercise price of $5.6, expiring April 22, 2029.
  • 10b5-1 plan: The sales were made pursuant to a Rule 10b5-1 trading plan adopted on August 13, 2025.

Dun Haiping's August 2026 Transactions in ACM Research Class A Shares

According to the Form 4 filing, Haiping Dun, who is identified as a director of ACM Research, Inc., exercised a stock option on August 18, 2026, acquiring 5,000 shares of Class A Common Stock at a price of $5.6 per share. The option was reported as fully vested and exercisable, with an expiration date of April 22, 2029. Following the exercise, Dun held 5,000 shares directly before subsequent sale transactions were executed on the same date.

The filing reports three sale transactions, all executed on August 18, 2026, under a Rule 10b5-1 trading plan that Dun adopted on August 13, 2025. The first tranche involved 1,200 shares sold at a weighted average price of $80.29, with individual transaction prices ranging from $79.89 to $80.77. The second tranche covered 3,400 shares at a weighted average of $81.31, with prices ranging from $80.95 to $81.91. The third tranche covered 400 shares at a weighted average of $82.17, with prices ranging from $81.97 to $82.33. After these three sales, Dun's direct beneficial ownership in Class A Common Stock was reported as 0 shares.

The filing also discloses that Dun retains indirect beneficial ownership of 100,000 shares through the Dun Family GST Trust and 755,090 shares through the Haiping Dun & Chi-Pin H Dun Revocable Trust. The remaining stock options position stands at 45,000 shares, reported as directly held. The Form 4 was signed by Mark McKechnie as Attorney-in-Fact for Haiping Dun and filed on August 20, 2026.

What Was Disclosed

The filing disclosed a stock option exercise of 5,000 shares at $5.6 and the subsequent sale of all 5,000 resulting shares at weighted average prices between $80.29 and $82.17, reducing Dun's direct share ownership to zero while indirect holdings through two trusts remain unchanged.