Tax-related sale: Upstream Bio (UPB) CEO automatically sells 2,093 shares

Rhea-AI Filing Summary

Upstream Bio, Inc. Chief Executive Officer Everett Rand Sutherland reported an automatic sale of 2,093 shares of common stock at an average price of $9.29 per share. According to the company’s sell-to-cover policy, these shares were sold solely to satisfy tax withholding obligations from vesting restricted stock units.

After this tax-related transaction, Sutherland directly holds 72,907 shares of Upstream Bio common stock. Because the sale was automatic and not at his discretion, it reflects routine tax management rather than a discretionary change in investment stance.

Insights

Equity analyst

CEO’s sale is a small, automatic tax-related transaction, not a discretionary share disposal.

The CEO of Upstream Bio, Inc. sold 2,093 shares of common stock at $9.29 per share under a sell-to-cover policy tied to restricted stock unit vesting. The filing states the sale was automatic and not at his discretion.

Following the transaction, he still directly owns 72,907 shares, indicating a continuing substantial equity position. Because this is a routine tax-withholding event rather than an open-market portfolio decision, its informational value for assessing management’s view of the stock is limited.

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
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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^*

Sutherland Everett Rand

(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)

X	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Executive Officer

3. Date of Earliest Transaction (Month/Day/Year)
03/16/2026

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	03/16/2026		S(1)		2,093	D	$9.29	72,907	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

Explanation of Responses:

1. 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.

	/s/ Allison Ambrose, Attorney-in-Fact	03/17/2026
	** 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.

FAQ

What insider transaction did Upstream Bio (UPB) disclose in this Form 4?

Upstream Bio disclosed that CEO Everett Rand Sutherland sold 2,093 shares of common stock at $9.29 per share. The filing explains the sale was automatic under a sell-to-cover policy to satisfy tax withholding from vesting restricted stock units.

Was the Upstream Bio (UPB) CEO’s share sale a discretionary transaction?

No, the CEO’s sale was not discretionary. The footnote states the issuer’s sell-to-cover policy required selling 2,093 shares to cover tax withholding for vesting restricted stock units, and the sales were automatic rather than at the CEO’s discretion.

How many Upstream Bio (UPB) shares does the CEO hold after the reported sale?

After selling 2,093 shares, CEO Everett Rand Sutherland holds 72,907 shares of Upstream Bio common stock directly. This post-transaction holding, reported in the Form 4, shows he retains a significant equity stake in the company following the tax-related sale.

What price did the Upstream Bio (UPB) CEO receive for the sold shares?

The CEO’s automatic tax-related sale was executed at an average price of $9.29 per share for 2,093 shares. This price and share count are taken directly from the Form 4 transaction details for the reported open-market sale entry.

Why does Upstream Bio (UPB) use a sell-to-cover policy for its CEO’s RSUs?

The company’s sell-to-cover policy is used to satisfy tax withholding obligations when restricted stock units vest. Instead of the CEO paying cash for taxes, a portion of shares—2,093 in this case—is automatically sold, simplifying compliance with required tax payments.