UPB files 8-K, furnishes press release for quarter ended Sept 30, 2025

Rhea-AI Filing Summary

Upstream Bio, Inc. furnished an update on operations by announcing its results and business highlights for the quarter ended September 30, 2025. The company submitted a Form 8-K noting that a detailed press release was provided as Exhibit 99.1.

The information under Item 2.02, including Exhibit 99.1, is being furnished and is not deemed filed under the Exchange Act. Upstream Bio’s common stock trades on the Nasdaq Global Select Market under the symbol UPB.

8-K Event Classification

2 items: 2.02, 9.01

2 items

Item 2.02 Results of Operations and Financial Condition Financial

Disclosure of earnings results, typically an earnings press release or preliminary financials.

Item 9.01 Financial Statements and Exhibits Exhibits

Financial statements, pro forma financial information, and exhibit attachments filed with this report.

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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of report (date of earliest event reported): November 05, 2025

UPSTREAM BIO, INC.

(Exact name of registrant as specified in its charter)

Delaware			001-42366	38-4187694
(State or other jurisdiction of incorporation)			(Commission file number)	(IRS employer identification no.)
890 Winter Street Suite 200
Waltham, Massachusetts				02451
(Address of principal executive offices)				(Zip code)

Registrant’s telephone number, including area code: (781) 208-2466

Not Applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class		Trading Symbol(s)		Name of each exchange on which registered
Common Stock, $0.001 par value per share		UPB		The Nasdaq Global Select Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 2.02 Results of Operations and Financial Condition.

On November 5, 2025, Upstream Bio, Inc. (the “Company”) announced its financial results and business highlights for the quarter ended September 30, 2025. A copy of the press release is being furnished as Exhibit 99.1 to this Current Report on Form 8-K.

The information included under Item 2.02 of this Current Report on Form 8-K, including Exhibit 99.1, is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, and shall not be incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits

99.1		Press Release issued by Upstream Bio, Inc. on November 5, 2025, furnished herewith.
104		Cover Page Interactive Data File (embedded within the Inline XBRL document)

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

			Upstream Bio, Inc.
Date:	November 5, 2025	By:	/s/ E. Rand Sutherland
			E. Rand Sutherland, M.D. Chief Executive Officer

FAQ

What did Upstream Bio (UPB) disclose in this 8-K?

The company announced its financial results and business highlights for the quarter ended September 30, 2025, furnished as Exhibit 99.1.

Which period does the UPB update cover?

It covers the quarter ended September 30, 2025.

How is Exhibit 99.1 treated legally?

The information in Item 2.02, including Exhibit 99.1, is furnished and not deemed filed under the Exchange Act.

What exhibit accompanies the disclosure?

Exhibit 99.1, the press release issued on November 5, 2025.

Where is Upstream Bio’s stock listed and under what symbol?

It is listed on the Nasdaq Global Select Market under the symbol UPB.

Who signed the report for Upstream Bio?

E. Rand Sutherland, M.D., Chief Executive Officer, signed the report.