SEC Form 4
| FORM 4 | UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP
Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940 | | OMB APPROVAL | | OMB Number: | 3235-0287 | | Estimated average burden | | hours per response: | 0.5 |
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| Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue.
See
Instruction 1(b). |
| Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10. |
1. Name and Address of Reporting Person*
| UPSTREAM BIO, INC. | | 890 WINTER STREET, SUITE 200 |
(Street)| WALTHAM |
MASSACHUSETTS
| 02451 |
(Country) | 2. Issuer Name and Ticker or Trading Symbol
Upstream Bio, Inc.
[ UPB ]
| 5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)| X | Director | | 10% Owner | | X | Officer (give title below) | | Other (specify below) | | Chief Executive Officer | | |
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2a. Foreign Trading Symbol
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3. Date of Earliest Transaction
(Month/Day/Year)
06/16/2026 | 6. Individual or Joint/Group Filing (Check Applicable Line)
| X | Form filed by One Reporting Person | | Form filed by More than One Reporting Person |
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4. If Amendment, Date of Original Filed
(Month/Day/Year)
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| Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned |
|---|
| 1. Title of Security (Instr.
3)
| 2. Transaction Date
(Month/Day/Year) | 2A. Deemed Execution Date, if any
(Month/Day/Year) | 3. Transaction Code (Instr.
8)
| 4. Securities Acquired (A) or Disposed Of (D) (Instr.
3, 4 and 5)
| 5.
Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr.
3 and 4)
| 6. Ownership Form: Direct (D) or Indirect (I) (Instr.
4)
| 7. Nature of Indirect Beneficial Ownership (Instr.
4)
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|---|
| Code | V | Amount | (A) or (D) | Price |
|---|
| Common Stock | 06/16/2026 | | S | | 2,095 | D | $6.1 | 70,812 | D | |
Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities) |
|---|
| 1. Title of Derivative Security (Instr.
3)
| 2. Conversion or Exercise Price of Derivative Security
| 3. Transaction Date
(Month/Day/Year) | 3A. Deemed Execution Date, if any
(Month/Day/Year) | 4. Transaction Code (Instr.
8)
| 5.
Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr.
3, 4 and 5)
| 6. Date Exercisable and Expiration Date
(Month/Day/Year) | 7. Title and Amount of Securities Underlying Derivative Security (Instr.
3 and 4)
| 8. Price of Derivative Security (Instr.
5)
| 9.
Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr.
4)
| 10. Ownership Form: Direct (D) or Indirect (I) (Instr.
4)
| 11. Nature of Indirect Beneficial Ownership (Instr.
4)
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|---|
| Code | V | (A) | (D) | Date Exercisable | Expiration Date | Title | Amount or Number of Shares |
|---|
| Explanation of Responses: |
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| /s/ Allison Ambrose, Attorney-in-Fact | 06/17/2026 |
| ** Signature of Reporting Person | Date |
| Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly. |
| * If the form is filed by more than one reporting person,
see
Instruction
4
(b)(v). |
| ** Intentional misstatements or omissions of facts constitute Federal Criminal Violations
See
18 U.S.C. 1001 and 15 U.S.C. 78ff(a). |
| Note: File three copies of this Form, one of which must be manually signed. If space is insufficient,
see
Instruction 6 for procedure. |
| Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number. |
| * Form 4: SEC 1474 (03-26) |
