Jonathan M. Rothberg holds 7.20% of Quantum-Si’s Class A common stock and 100.00% of its Class B common stock in an activist position. An estate-planning sales plan could permit the disposition of up to 8,947,746 Class A shares between January 15, 2027 and January 15, 2028.

Key Highlights

  • Jonathan M. Rothberg’s Class A position totals 14,376,415 shares, including stock Options exercisable within 60 days.
  • The Class B holdings are split between 4C Holdings I, LLC at 90.00% and 4C Holdings V, LLC at 10.00%.
  • A Rule 10b5-1 plan covers up to 8,947,746 Class A shares and runs through January 15, 2028.

Quantum-Si Inc (NASDAQ: QSI) is held by Jonathan M. Rothberg, Ph.D. At 7.20% of its Class A common stock and 100.00% of its Class B common stock. The position is reported as activist under Schedule 13D. Rothberg’s holdings total 14,376,415 Class A shares (14.4 million) and 19,937,500 Class B shares (19.9 million).

Rothberg’s Quantum-Si Position

The Class A position also includes 1,917,067 shares held by 23rd Century Capital LLC and 273,422 shares held by Rothberg’s spouse, Bonnie E. Gould Rothberg, M.D. The 7.20% Class A ownership calculation uses 198,946,412 Class A shares outstanding as of August 11, 2026. Rothberg’s Class B ownership consists of 17,943,750 shares held by 4C Holdings I, LLC and 1,993,750 shares held by 4C Holdings V, LLC. The Class B percentage is based on 19,937,500 shares outstanding as of August 11, 2026. 23rd Century Capital LLC separately reports 1,917,067 Class A shares, representing 0.96% of that class. 4C Holdings I, LLC reports 17,943,750 Class B shares, or 90.00% of the class, while 4C Holdings V, LLC reports 1,993,750 Class B shares, or 10.00%.

Estate Plan Sets Share Sales

The plan is intended to permit an orderly disposition of part of the seller’s common-stock holding. The sales plan applies to up to 8,947,746 Class A shares. Its effective date is August 26, 2026, and the stated sales period begins on January 15, 2027, after the applicable cooling-off period. Jefferies LLC acts as broker under the plan. Any commission may not exceed $.01 per share. The plan ends on January 15, 2028, or earlier if 8,947,746 shares are sold or another termination event under the plan occurs.

Minimum Prices Govern Potential Sales

Sales under the plan are subject to minimum price parameters. The plan also states that there is no assurance that any of the Class A shares will be sold. The plan states that the seller owns the securities free and clear, subject to limitations imposed by Rule 144 or arrangements with the broker. The seller also agreed not to alter or deviate from the plan while it remains active and acknowledged that the seller will not control how, when or whether sales are executed under its terms. The stated sales window runs from January 15, 2027 through January 15, 2028, subject to the plan’s conditions.

Peers Moving on This News