BlackRock (UPB) discloses 2.8M-share, 5.2% beneficial stake in BIO INC

Rhea-AI Filing Summary

BlackRock, Inc. reported a passive ownership stake in BIO INC common stock on Schedule 13G. BlackRock beneficially owns 2,814,714 shares, representing 5.2% of the outstanding common stock, with sole voting power over 2,764,429 shares and sole dispositive power over 2,814,714 shares.

The filing notes that various underlying clients or investors have rights to receive dividends or sale proceeds from these shares, but no single such person has an interest in more than five percent of BIO INC’s total outstanding common shares.

Key Figures

Shares beneficially owned: 2,814,714 shares Percent of class: 5.2% Sole Voting Power: 2,764,429 shares +3 more

6 metrics

Shares beneficially owned 2,814,714 shares BIO INC common stock reported by BlackRock on Schedule 13G

Percent of class 5.2% Percentage of BIO INC common stock beneficially owned by BlackRock

Sole Voting Power 2,764,429 shares BIO INC shares over which BlackRock has sole power to vote

Shared Voting Power 0 shares BIO INC shares over which BlackRock has shared voting power

Sole Dispositive Power 2,814,714 shares BIO INC shares over which BlackRock has sole power to dispose

Shared Dispositive Power 0 shares BIO INC shares over which BlackRock has shared power to dispose

Key Terms

beneficially owned, Sole Voting Power, Sole Dispositive Power, Schedule 13G, +1 more

5 terms

beneficially owned regulatory

"this reflects the securities beneficially owned, or deemed to be beneficially owned"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

Sole Voting Power regulatory

"5 | Sole Voting Power 2,764,429.00 6 | Shared Voting Power"

Sole voting power is the exclusive right to cast votes attached to a shareholder’s stock without needing approval from anyone else. Like holding the only remote control for a TV, it lets that holder decide corporate matters such as board members, mergers, and policy changes, making it important to investors because it concentrates control and can strongly influence a company’s strategy and the value of its shares.

Sole Dispositive Power regulatory

"7 | Sole Dispositive Power 2,814,714.00 8 | Shared Dispositive Power"

Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.

Schedule 13G regulatory

"In accordance with SEC Release No. 34-39538 this Schedule 13G reflects"

A Schedule 13G is a formal document that investors file with the government when they acquire a large ownership stake in a company, usually for investment purposes rather than control. It helps keep the public informed about who owns significant parts of a company's shares, which can influence how the company is managed and how investors make decisions. Filing this schedule is important for transparency and understanding the ownership landscape of publicly traded companies.

parent holding company regulatory

"Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company"

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 07/30/2026 - 11:20 AM Accepted by SEC EDGAR 07/30/2026 - 11:18 AM Learn about SEC filing dates

FAQ

What stake in BIO INC (UPB) does BlackRock report on this Schedule 13G?

BlackRock reports beneficial ownership of 2,814,714 BIO INC common shares, representing 5.2% of the class. This includes sole voting power over 2,764,429 shares and sole dispositive power over all 2,814,714 shares.

How much voting power in BIO INC (UPB) does BlackRock have?

BlackRock reports sole voting power over 2,764,429 BIO INC shares and no shared voting power. It also has sole dispositive power over 2,814,714 shares, with no shared dispositive power reported.

What percentage of BIO INC (UPB) common stock is owned by BlackRock?

BlackRock reports beneficial ownership of 5.2% of BIO INC’s common stock. This percentage is based on 2,814,714 shares that BlackRock and its reporting business units deem beneficially owned for Schedule 13G purposes.

Do any other investors hold more than 5% through BlackRock’s BIO INC (UPB) position?

The filing states that various persons have rights to dividends or sale proceeds from BIO INC shares, but no one person’s interest exceeds five percent of BIO INC’s total outstanding common shares.

Who signed the Schedule 13G filing for BIO INC (UPB) on behalf of BlackRock?

The Schedule 13G was signed by Spencer Fleming, identified as a Managing Director of BlackRock, Inc. The signature is supported by a Power of Attorney referenced as Exhibit 24.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

UPSTREAM BIO INC

(Name of Issuer)

Common Stock

(Title of Class of Securities)

91678A107

(CUSIP Number)

06/30/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 91678A107

1

Names of Reporting Persons

BlackRock, Inc.

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 2,764,429.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 2,814,714.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

2,814,714.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

5.2 %

12

Type of Reporting Person (See Instructions)

HC

SCHEDULE 13G

Item 1.
(a)	Name of issuer: UPSTREAM BIO INC
(b)	Address of issuer's principal executive offices: 890 Winter Street, Suite 200 Waltham MA 02451
Item 2.
(a)	Name of person filing: BlackRock, Inc. In accordance with SEC Release No. 34-39538 (January 12, 1998), this Schedule 13G reflects the securities beneficially owned, or deemed to be beneficially owned, by certain business units (collectively, the "Reporting Business Units") of BlackRock, Inc. and its subsidiaries and affiliates. It does not include securities, if any, beneficially owned by other business units whose beneficial ownership of securities are disaggregated from that of the Reporting Business Units in accordance with such release.
(b)	Address or principal business office or, if none, residence: BlackRock, Inc., 50 Hudson Yards New York, NY 10001
(c)	Citizenship: See Item 4 of Cover Page
(d)	Title of class of securities: Common Stock
(e)	CUSIP Number(s): 91678A107
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 2814714
(b)	Percent of class: 5.2 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 2764429
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 2814714
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. Various persons have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of the common stock of UPSTREAM BIO INC. No one person's interest in the common stock of UPSTREAM BIO INC is more than five percent of the total outstanding common shares.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	If a parent holding company has filed this schedule, pursuant to Rule 13d-1(b)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company has filed this schedule pursuant to Rule 13d-1(c) or Rule 13d-1(d), attach an exhibit stating the identification of the relevant subsidiary. See Exhibit 99
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

BlackRock, Inc.

Signature:	Spencer Fleming
Name/Title:	Managing Director
Date:	07/30/2026

Exhibit Information

Exhibit 24: Power of Attorney Exhibit 99: Item 7