GRAY MICHAEL 4

What Happened
Michael Gray, Upstream Bio’s (UPB) Chief Financial Officer and Chief Operating Officer, reported a sale of 852 shares on 2026-03-16. The shares were sold at $9.29 per share for total proceeds of approximately $7,915. The filing lists the transaction as a sale (code S).

Key Details

• Transaction date and price: 2026-03-16, 852 shares at $9.29 each (total ≈ $7,915)
• Transaction type: Reported as "Open market or private sale" (Sale, code S)
• Footnote: The sale was an automatic "sell-to-cover" to satisfy tax withholding on vested restricted stock units (RSUs); not at the insider’s discretion.
• Filing timeliness: Reported on Form 4 filed 2026-03-17 (next business day), which is timely under Form 4 rules.
• Shares owned after transaction: Not specified in the provided filing excerpt.

Context
Sell-to-cover transactions are routine administrative sales to cover tax withholding when RSUs vest; they generally reflect tax obligations rather than a discretionary decision to divest significant holdings. This is distinct from open-market purchases, which some investors view as a stronger signal of insider confidence.