Upstream Bio, Inc. — Director's Dealing 2026

Mar 17, 2026

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: Upstream Bio, Inc. (UPB)
CIK: 0002022626
Period of Report: 2026-03-16

Reporting Person: GRAY MICHAEL (N/A)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2026-03-16	Common Stock	S	852	$9.29	Disposed	29648	Direct

Footnotes

F1: The Issuer has adopted a "sell-to-cover" policy to satisfy the tax withholding obligations of the Reporting Person. The sales reported on this Form 4 represent the number of shares required to be sold by the Reporting Person to cover tax withholding obligations in connection with the vesting of restricted stock units. Such sales were automatic and not at the discretion of the Reporting Person.