Aaron Deykin - 16 Jun 2026 Form 4 Insider Report for Upstream Bio, Inc. (UPB)

Reporting relationship: Chief Medical Officer
Issuer ticker: UPB
Reported as of: 16 Jun 2026
Net transaction value: -$5,460
SEC form: 4
Accepted by SEC: 17 Jun 2026, 16:05:04 UTC
Prior SEC filing: 17 Mar 2026
Source filing: View source filing
Reporting owner signature: /s/ Allison Ambrose, Attorney-in-Fact

Key filing fact

Aaron Deykin filed Form 4 for Upstream Bio, Inc. (UPB) on 17 Jun 2026.

Key facts

This page summarizes Aaron Deykin's Form 4 filing for Upstream Bio, Inc. (UPB).
1 reported transaction and 0 derivative rows are listed below.
Accepted by SEC: 17 Jun 2026, 16:05.

Change

Previous filing in this sequence was filed on 17 Mar 2026.
Current net transaction value: -$5,460.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Filed on Form 4

Ownership activity is grounded in SEC Form 4 disclosures.

View source filing

Reporting Owners (1)

CIK 0002031693 Primary reporting owner

Deykin Aaron

Relationship: Chief Medical Officer
Address: UPSTREAM BIO, INC., 890 WINTER STREET, SUITE 200, WALTHAM
Signature: /s/ Allison Ambrose, Attorney-in-Fact
Signature date: 17 Jun 2026

Reported non-derivative transactions

Shares, units, or other non-derivative securities reported in this filing.

UPB transaction

Common Stock

Sale

Transaction value: $5,460
Shares: -895
Change %: -2.6%
Price: $6.10
Shares after: 33,197
Date: 16 Jun 2026
Ownership: Direct
Footnotes: F1, F2

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Explanation of responses 2 footnotes

Footnote 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.

Footnote F2

Includes 1,405 shares of Common Stock previously acquired under the Issuer's 2024 Employee Stock Purchase Plan.