Ambrose Allison 4

What Happened

Ambrose Allison, General Counsel of Upstream Bio, sold 475 shares on March 16, 2026 at $9.29 per share, for proceeds of about $4,413. The filing lists the transaction as a sale (S), and the company footnote states the sale was an automatic "sell-to-cover" to satisfy tax withholding when restricted stock units vested — not an active discretionary sale.

Key Details

• Transaction date and price: 2026-03-16, 475 shares @ $9.29 each.
• Proceeds: Approximately $4,413.
• Shares owned after transaction: Not disclosed in the provided filing excerpt.
• Footnote: The issuer has a sell-to-cover policy; these shares were sold automatically to cover taxes on vested RSUs (not at the reporting person's discretion).
• Filing timeliness: Report filed 2026-03-17 for the 2026-03-16 transaction — appears timely based on the provided dates.

Context

Sell-to-cover transactions are routine tax-withholding actions tied to equity vesting and generally convey less information about an insider's market view than voluntary open-market purchases. This was a disposition (sale) solely to cover withholding on vested awards, per the filing footnote.