Upstream Bio, Inc. — Director's Dealing 2025

Jun 12, 2025

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: Upstream Bio, Inc. (UPB)
CIK: 0002022626
Period of Report: 2025-06-10

Reporting Person: Fleming Harold Edward (N/A)

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2025-06-10	Stock Option (Right to Buy)	$11.59	A	17096	Acquired	2035-06-09	Common Stock (17096)	Direct

Footnotes

F1: The shares underlying this option shall vest upon the earlier of (i) June 10, 2026 and (ii) the date of the next Annual Meeting of Stockholders of the Issuer, subject to the Reporting Person's continued service on such vesting date.

F2: Mr. Fleming has agreed to receive and hold for the benefit of Enavate Sciences, LP, any securities granted to him for his service as a director on the Issuer's board of directors. As such, Mr. Fleming disclaims beneficial ownership of, and all right, title and interest in, the option and the shares issuable upon exercise thereof.