UPB Upstream Bio Inc

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
	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* Deykin Aaron (Last) (First) (Middle) UPSTREAM BIO, INC. 890 WINTER STREET, SUITE 200 (Street) WALTHAM MA 02451 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol Upstream Bio, Inc. [ UPB ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director 10% Owner X Officer (give title below) Other (specify below) Chief Medical Officer
	3. Date of Earliest Transaction (Month/Day/Year) 02/06/2025
	4. If Amendment, Date of Original Filed (Month/Day/Year)	6. Individual or Joint/Group Filing (Check Applicable Line) X Form filed by One Reporting Person Form filed by More than One Reporting Person

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)
			Code	V	Amount	(A) or (D)	Price

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)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Stock Option (Right to Buy)	$8.53	02/06/2025		A		165,000		(1)	02/05/2035	Common Stock	165,000	$0	165,000	D

Explanation of Responses:

1. The shares underlying this option shall vest in forty-eight equal monthly installments following February 6, 2025, subject to the Reporting Person's continued service on each such vesting date.

Remarks:

Exhibit 24.2 - Substitute Power of Attorney

	/s/ Allison Ambrose, Attorney-in-Fact	02/07/2025
	** 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.

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SUBSTITUTE POWER OF ATTORNEY

 

Under the terms of powers of attorney (each, a “Power of Attorney”) previously filed with the U.S. Securities and Exchange Commission, the undersigned was appointed an attorney-in-fact for the below listed individuals, as of October 10, 2024, to, among other things, execute for and on behalf of the following individuals any Forms 3, 4 or 5, Schedule 13D or 13G, or any amendment(s) thereto, in accordance with Section 16(a) of the Securities Exchange Act of 1934, as amended, and the rules thereunder:

 

Daniella Beckman

Erez Chimovits

Aaron Deykin

H. Edward Fleming, Jr.

Adam Houghton

Liam Ratcliffe

Ronald C. Renaud, Jr.

Marcella Kuhlman Ruddy

E. Rand Sutherland

 

In accordance with the authority granted under each Power of Attorney, including the full power of substitution, the undersigned hereby appoints Allison Ambrose as substitute attorney-in-fact, on behalf of the individuals listed above, with the power to exercise and execute all of the powers granted or conferred in the original Power of Attorney. For the avoidance of doubt, the foregoing appointment shall not serve as a revocation of the powers granted to the undersigned himself in each Power of Attorney.

 

This substitute Power of Attorney shall remain in full force and effect with respect to each Power of Attorney until such underlying Power of Attorney is revoked or terminated, unless earlier revoked by the undersigned in a signed writing.

 

Date: 12/19/24

By: /s/ Michael Gray

Name: Michael Gray

Title: Attorney-in-Fact

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SUBSTITUTE POWER OF ATTORNEY

 

Under the terms of powers of attorney (each, a “Power of Attorney”) previously filed with the U.S. Securities and Exchange Commission, the undersigned was appointed an attorney-in-fact for the below listed individuals, as of October 10, 2024, to, among other things, execute for and on behalf of the following individuals any Forms 3, 4 or 5, Schedule 13D or 13G, or any amendment(s) thereto, in accordance with Section 16(a) of the Securities Exchange Act of 1934, as amended, and the rules thereunder:

 

Daniella Beckman

Erez Chimovits

Aaron Deykin

H. Edward Fleming, Jr.

Adam Houghton

Liam Ratcliffe

Ronald C. Renaud, Jr.

Marcella Kuhlman Ruddy

E. Rand Sutherland

 

In accordance with the authority granted under each Power of Attorney, including the full power of substitution, the undersigned hereby appoints Allison Ambrose as substitute attorney-in-fact, on behalf of the individuals listed above, with the power to exercise and execute all of the powers granted or conferred in the original Power of Attorney. For the avoidance of doubt, the foregoing appointment shall not serve as a revocation of the powers granted to the undersigned himself in each Power of Attorney.

 

This substitute Power of Attorney shall remain in full force and effect with respect to each Power of Attorney until such underlying Power of Attorney is revoked or terminated, unless earlier revoked by the undersigned in a signed writing.

 

Date: 12/19/24

By: /s/ Michael Gray

Name: Michael Gray

Title: Attorney-in-Fact

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