Erez Chimovits - 09 Jun 2026 Form 4 Insider Report for Upstream Bio, Inc. (UPB)

Reporting relationship: Director
Issuer ticker: UPB
Reported as of: 09 Jun 2026
Net transaction value: $0
SEC form: 4
Accepted by SEC: 11 Jun 2026, 20:00:03 UTC
Prior SEC filing: 12 Jun 2025
Next SEC filing: 05 Aug 2026
Source filing: View source filing
Reporting owner signature: /s/ Allison Ambrose, Attorney-in-Fact

Key filing fact

Erez Chimovits filed Form 4 for Upstream Bio, Inc. (UPB) on 11 Jun 2026.

Key facts

This page summarizes Erez Chimovits's Form 4 filing for Upstream Bio, Inc. (UPB).
1 reported transaction and 1 derivative row are listed below.
Accepted by SEC: 11 Jun 2026, 20:00.

Change

Previous filing in this sequence was filed on 12 Jun 2025.
Current net transaction value: $0.

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 0001706399 Primary reporting owner

Chimovits Erez

Relationship: Director
Address: UPSTREAM BIO, INC., 890 WINTER STREET, SUITE 200, WALTHAM
Signature: /s/ Allison Ambrose, Attorney-in-Fact
Signature date: 11 Jun 2026

Reported derivative securities

Options, warrants, convertible securities, or similar derivative positions disclosed in the filing.

UPB transaction Derivative

Stock Option (Right to Buy)

Award

Transaction value
Shares: +17,096
Change %
Price: $0.000000^*
Shares after: 17,096
Date: 09 Jun 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 17,096
Exercise price: $6.69
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 shares underlying this option shall vest in full upon the earlier of (i) June 9, 2027 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.

Footnote F2

Pursuant to an agreement with OrbiMed Advisors LLC, OrbiMed Capital GP VIII LLC, OrbiMed Israel GP II, L.P., and OrbiMed Advisors Israel II Limited, the Reporting Person is obligated to transfer any securities issued under any such stock options or other awards, or the economic benefit thereof, to OrbiMed Advisors LLC, OrbiMed Capital GP VIII LLC, OrbiMed Israel GP II, L.P., and OrbiMed Advisors Israel II Limited, which will in turn ensure that such securities or economic benefits are provided to OrbiMed Private Investments VIII, LP and OrbiMed Israel Partners II, L.P.