Hornby Zachary 4

What Happened Zachary Hornby, President & CEO and a director of Boundless Bio, was granted 600,000 derivative securities (reported as an award/acquisition) on 2026-01-23 at a reported price of $0.00 per share (total reported acquisition value $0). The grant is a stock option/award subject to vesting and is not an open-market purchase or sale.

Key Details

• Transaction date and price: 2026-01-23; 600,000 shares/options at $0.00 per share (derivative award).
• Shares owned after transaction: Not disclosed in this Form 4 filing.
• Vesting: Vesting commencement date is January 1, 2026; the award vests in 48 substantially equal monthly installments (1/48th vests on Feb 1, 2026, and monthly thereafter).
• Filing timeliness: Reported on Form 4 filed 2026-01-26 (appears to be filed timely, not marked late).
• Footnote: The filing specifies these are stock options that vest monthly over four years (see note above).

Context This was a company compensation grant (an award of derivative securities) rather than a personal open-market purchase or sale. The reported acquisition value is $0 on the Form 4; any future value to the insider depends on vesting and the company’s stock price at exercise or sale. Grants like this are common for executives as part of compensation and do not, by themselves, indicate a buy/sell signal.