Upstream Bio (NASDAQ: UPB) grants GC stock option and RSU awards

Rhea-AI Filing Summary

Upstream Bio, Inc. reported that its General Counsel, Allison Ambrose, received new equity awards. On January 2, 2026, she was granted 17,000 shares of Common Stock in the form of restricted stock units at a grant price of $0 under the company’s 2024 Stock Option and Incentive Plan.

The filing also shows a grant of a stock option for 51,000 shares of Common Stock with an exercise price of $27.07 per share, expiring on January 1, 2036. The 17,000 RSUs vest in sixteen equal quarterly installments following January 1, 2026, while the 51,000 options vest in forty-eight equal monthly installments after that date, in each case conditioned on her continued service with the company.

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^*

Ambrose Allison

(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)
	General Counsel

3. Date of Earliest Transaction (Month/Day/Year)
01/02/2026

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
Common Stock	01/02/2026		A(1)		17,000	A	$0	17,000	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)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Stock Option (Right to Buy)	$27.07	01/02/2026		A		51,000		(2)	01/01/2036	Common Stock	51,000	$0	51,000	D

Explanation of Responses:

1. Represents restricted stock units ("RSUs") granted pursuant to the Issuer's 2024 Stock Option and Incentive Plan. Each RSU represents the contingent right to receive one share of the Issuer's Common Stock upon vesting. The RSUs shall vest in sixteen equal quarterly installments following January 1, 2026, subject to the Reporting Person's continued service on each such vesting date.

2. The shares underlying this option shall vest in forty-eight equal monthly installments following January 1, 2026, subject to the Reporting Person's continued service on each such vesting date.

	/s/ Allison Ambrose	01/06/2026
	** 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).
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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.

FAQ

What does the latest Form 4 for UPB report?

The Form 4 reports that Upstream Bio, Inc. granted its General Counsel, Allison Ambrose, new equity compensation in the form of restricted stock units and stock options on January 2, 2026.

Who is the insider involved in this Upstream Bio (UPB) Form 4?

The reporting person is Allison Ambrose, who serves as General Counsel of Upstream Bio, Inc. She is identified as an officer and not as a director or 10% owner.

How many restricted stock units did the Upstream Bio General Counsel receive?

The General Counsel received 17,000 restricted stock units (RSUs) of Upstream Bio’s Common Stock at a grant price of $0 per share.

What stock options were granted in this Upstream Bio (UPB) insider filing?

The filing shows a grant of a Stock Option (Right to Buy) covering 51,000 shares of Common Stock with an exercise price of $27.07 per share and an expiration date of January 1, 2036.

What is the vesting schedule for the 17,000 Upstream Bio RSUs?

The 17,000 RSUs vest in sixteen equal quarterly installments following January 1, 2026, subject to Allison Ambrose’s continued service on each vesting date.

How do the 51,000 Upstream Bio stock options vest?

The 51,000 stock options vest in forty-eight equal monthly installments following January 1, 2026, conditioned on the General Counsel’s continued service on each vesting date.

Are these Upstream Bio equity awards held directly or indirectly?

Both the 17,000 RSUs and the 51,000 stock options are reported as directly owned by the reporting person, with no indirect ownership entity noted.