David Tsao, Chief Technology Officer and Director of BillionToOne, Inc. (NASDAQ:BLLN), filed a Form 4 on September 11, 2026, disclosing the exercise of stock options and the sale of Class A Common Stock on September 9, 2026, pursuant to a Rule 10b5-1 trading plan.

Key Highlights

  • Option exercises: Tsao exercised two tranches of 10,000 stock options each, acquiring a total of 20,000 shares of Class A Common Stock at an exercise price of $2.8 per share.
  • Share sales: Tsao sold 10,000 shares at $97.54 per share and 10,000 shares at $100.00 per share, disposing of 20,000 shares in total.
  • Remaining ownership: Following all reported transactions, Tsao directly holds 1,000 shares of Class A Common Stock.
  • Remaining options: Tsao holds 560,000 vested and exercisable stock options with an exercise price of $2.8 and an expiration date of June 7, 2031.
  • 10b5-1 plan: According to the filing, all transactions were effected pursuant to a Rule 10b5-1 trading plan adopted by Tsao on June 5, 2026.
  • Options fully vested: The filing states the options exercised are "fully vested and exercisable."

BillionToOne CTO Option Exercise and Sale Activity on September 9, 2026

According to the Form 4 filed with the SEC, David Tsao, who serves as both Chief Technology Officer and Director of BillionToOne, Inc., carried out four transactions in Class A Common Stock on September 9, 2026. The filing indicates the transactions were made under a Rule 10b5-1 trading plan that Tsao adopted on June 5, 2026, with the form signed by Thomas P. Lynch as Attorney-in-Fact on September 11, 2026.

The filing reports two option exercise transactions, each coded "M," in which Tsao acquired 10,000 shares at a price of $2.8 per share, bringing his direct Class A Common Stock holdings to 21,000 shares at the midpoint of those transactions. The underlying stock options carry an expiration date of June 7, 2031, and the filing states they are fully vested and exercisable. Following both exercises, the filing shows 560,000 stock options remaining beneficially owned directly by Tsao.

The filing also discloses two separate sale transactions, each coded "S." Tsao disposed of 10,000 shares at $97.54 per share, reducing his direct holdings to 11,000 shares, and subsequently sold an additional 10,000 shares at $100.00 per share, leaving a reported direct beneficial ownership of 1,000 shares of Class A Common Stock following all four transactions.

What Was Disclosed

The filing disclosed two stock option exercises and two open-market sales of Class A Common Stock by BillionToOne's CTO and Director, David Tsao, on September 9, 2026, all conducted under a pre-established Rule 10b5-1 trading plan.