William D. McCombe, Chief Financial Officer of Cytek Biosciences, Inc. (NASDAQ:CTKB), filed a Form 4 on August 20, 2026, reporting the vesting of three separate restricted stock unit awards and the withholding of shares to cover tax obligations, all transacted on August 18, 2026.

Key Highlights

  • Three RSU tranches vested: McCombe acquired 6,320, 13,051, and 16,049 shares of common stock through RSU conversions (transaction code M) on August 18, 2026.
  • Tax withholding disposals: 2,111, 4,392, and 5,401 shares were withheld and surrendered to the issuer to satisfy tax obligations, each at a price of $4.67 per share.
  • Resulting direct ownership: Following all transactions, McCombe directly held 134,693 shares of common stock.
  • Remaining RSU balances: After the vesting events, McCombe held 44,249, 134,862, and 230,042 derivative RSUs outstanding across the three awards.
  • All transactions direct: All reported holdings and transactions are listed as directly owned by the reporting person.

Cytek Biosciences CFO RSU Vesting and Tax Withholding Details

According to the filing, McCombe's three RSU awards each represent a contingent right to receive one share of Cytek Biosciences common stock per unit. On August 18, 2026, portions of all three awards vested simultaneously. The first award contributed 6,320 shares, the second contributed 13,051 shares, and the third contributed 16,049 shares, for a combined total of 35,420 shares acquired through the M-coded transactions.

The filing reports that 2,111, 4,392, and 5,401 shares, respectively, were "withheld by and surrendered to the Issuer on August 18, 2026 to satisfy tax withholding obligations that arose in connection with the vesting of the RSU Award." All withholding transactions were recorded at $4.67 per share. The total shares withheld across the three tranches amounted to 11,904 shares.

Each of the three RSU awards carries a distinct vesting schedule spread over four years. The first award began vesting with 12/48 of total shares on May 18, 2025, followed by quarterly increments. The second award started with 2/48 vesting on May 18, 2025, with quarterly portions thereafter. The third award, the most recently granted based on its schedule, began with 2/48 vesting on May 18, 2026, with subsequent quarterly installments running through at least March 10, 2027, as described in the filing's footnotes.

What Was Disclosed

The filing reports three RSU vesting events and corresponding tax-withholding share disposals by Cytek Biosciences CFO William D. McCombe on August 18, 2026, leaving him with 134,693 shares of common stock held directly and a combined 409,153 RSUs remaining.