Upstream Bio, Inc.

For the period ended Dec 31, 2025. Filed Mar 26, 2026.

About this filing

A company's yearly report to the SEC, with audited financial statements. It is the fullest account a company gives of its business, its finances and the risks it sees.

FY2025 · Filed Mar 26, 2026

UPB$3.38-5.6%Stored close · as of Nov 10, 2026

Extracted filing text, with the paragraph anchors used by the comparison.

See the whole filing, with its images and exhibits

Contents

Item 15. Exhibits and Financial Statement Schedules

(1)

Financial Statements.

For a list of the financial statements included herein, see Index to the Consolidated Financial Statements on page F-1 of this Annual Report on Form 10-K, incorporated into this Item by reference.

(2)

Financial Statement Schedules.

Certain schedules are omitted because they are not applicable, or are not required by smaller reporting companies.

(3)

Exhibits.

ExhibitNumber	Description
3.1	Third Amended and Restated Certificate of Incorporation of Upstream Bio, Inc. (incorporated by reference to Exhibit 3.1 to the Company's Current Report on Form 8-K filed on October 15, 2024).
3.2	Second Amended and Restated Bylaws of Upstream Bio, Inc. (incorporated by reference to Exhibit 3.2 to the Company’s Current Report on Form 8-K filed on October 15, 2024).
4.1	Specimen Common Stock Certificate (incorporated by reference to Exhibit 4.1 to the Company’s Registration Statement on Form S-1 filed on September 18, 2024).
4.2+	Amended and Restated Investors’ Rights Agreement, among the Company and certain of its stockholders, dated June 6, 2023 (incorporated by reference to Exhibit 4.2 to the Company’s Registration Statement on Form S-1 filed on September 18, 2024).
4.3	Description of Securities (incorporated by reference to Exhibit 4.3 to the Company’s Registration Statement on Form 10-K filed on March 12, 2025).
10.1#	2021 Stock Option and Grant Plan, as amended, and form of award agreements thereunder (incorporated by reference to Exhibit 10.1 to the Company’s Registration Statement on Form S-1 filed on September 18, 2024).
10.2#	Upstream Bio, Inc. 2024 Stock Option and Incentive Plan and form of award agreements thereunder (incorporated by reference to Exhibit 10.2 to Amendment No. 1 to the Company’s Registration Statement on Form S-1 filed on October 7, 2024).
10.3#	Upstream Bio, Inc. 2024 Employee Stock Purchase Plan (incorporated by reference to Exhibit 10.3 to Amendment No. 1 to the Company’s Registration Statement on Form S-1 filed on October 7, 2024).
10.4#	Form of Indemnification Agreement, by and between the Company and each of its directors and executive officers (incorporated by reference to Exhibit 10.4 to Amendment No. 1 to the Company’s Registration Statement on Form S-1 filed on October 7, 2024).
10.5#	Senior Executive Cash Incentive Bonus Plan (incorporated by reference to Exhibit 10.5 to Amendment No. 1 to the Company’s Registration Statement on Form S-1 filed on October 7, 2024).
10.6#	Executive Severance Plan (incorporated by reference to Exhibit 10.6 to Amendment No. 1 to the Company’s Registration Statement on Form S-1 filed on October 7, 2024).
10.7#*	Amended and Restated Non-Employee Director Compensation Policy.
10.8#	Form of Employment Agreement for Executive Officers (incorporated by reference to Exhibit 10.11 to the Company’s Registration Statement on Form S-1 filed on September 18, 2024).
10.9†+	Asset Purchase Agreement, by and between the Company and Astellas Pharma Inc., dated October 14, 2021 (incorporated by reference to Exhibit 10.12 to the Company’s Registration Statement on Form S-1 filed on September 18, 2024).
10.10†	Letter Agreement, by and among the Company, Astellas Pharma Inc. and Regeneron Pharmaceuticals Inc., dated October 19, 2021 (incorporated by reference to Exhibit 10.13 to the Company’s Registration Statement on Form S-1 filed on September 18, 2024).
10.11†+	Exclusive License Agreement, by and between the Company and Maruho Co., Ltd., dated October 14, 2021, as amended (incorporated by reference to Exhibit 10.14 to the Company’s Registration Statement on Form S-1 filed on September 18, 2024).
10.12†+	License Agreement, by and between the Company and Lonza Sales AG, dated October 21, 2021, as amended (incorporated by reference to Exhibit 10.15 to the Company’s Registration Statement on Form S-1 filed on September 18, 2024).

10.13+	Lease Agreement, by and between the Company and BXP Waltham Woods LLC, dated as of July 3, 2024 (incorporated by reference to Exhibit 10.18 to the Company’s Registration Statement on Form S-1 filed on September 18, 2024).
19.1*	Upstream Bio, Inc. Insider Trading Policy
21.1	Subsidiary of the registrant (incorporated by reference to Exhibit 21.1 to the Company’s Registration Statement on Form S-1 filed on September 18, 2024).
23.1*	Consent of PricewaterhouseCoopers LLP, independent registered public accounting firm.
24.1*	Power of attorney (included on signature page).
31.1*	Certification of Principal Executive Officer Pursuant to Rules 13a-14(a) and 15d-14(a) under the Securities Exchange Act of 1934, as Adopted Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.
31.2*	Certification of Principal Financial Officer Pursuant to Rules 13a-14(a) and 15d-14(a) under the Securities Exchange Act of 1934, as Adopted Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.
32.1**	Certification of Principal Executive Officer Pursuant to 18 U.S.C. Section 1350, as Adopted Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002.
97.1	Upstream Bio, Inc. Compensation Recovery Policy (incorporated by reference to Exhibit 97.1 to the Company’s Annual Report on Form 10-K filed on March 12, 2025).
101.INS	Inline XBRL Instance Document – the instance document does not appear in the Interactive Data File because XBRL tags are embedded within the Inline XBRL document.
101.SCH	Inline XBRL Taxonomy Extension Schema With Embedded Linkbase Documents.
104	Cover Page Interactive Data File (embedded within the Inline XBRL document).

Filed herewith.

** The certifications furnished in Exhibit 32.1 hereto are deemed to be furnished with this Annual Report on Form 10-K and will not be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended, except to the extent that the registrant specifically incorporates it by reference.

ContentsView on SEC.gov

The text of this filing, as the company filed it with the SEC, without its images or exhibits. This is not investment advice.