{"url_path":"/sec/upb/10-q/2026/item-6","section_key":"item-6","section_title":"Item 6 Exhibits.","topic":"sec","document":{"doc_type":"10-Q","doc_date":"2026-05-13","source_url":"https://www.sec.gov/Archives/edgar/data/2022626/0001193125-26-220584-index.html","accession_number":"0001193125-26-220584","cik":"0002022626","ticker":"UPB","issuer_name":"Upstream Bio, Inc.","edgar_url":"https://www.sec.gov/Archives/edgar/data/2022626/0001193125-26-220584-index.html","primary_entity_key":"0002022626","primary_entity_name":"Upstream Bio, Inc."},"word_count":480,"has_tables":true,"body_markdown":"Item 6. Exhibits.\n\n \n\nExhibit\n\nNumber\n\n \n\nDescription\n\n3.1\n\n \n\n[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).](https://www.sec.gov/Archives/edgar/data/2022626/000119312524237580/d897785dex31.htm)\n\n3.2\n\n \n\n[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).](https://www.sec.gov/Archives/edgar/data/2022626/000119312524237580/d897785dex32.htm)\n\n4.1\n\n \n\n[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).](https://www.sec.gov/Archives/edgar/data/2022626/000119312524221372/d843142dex41.htm)\n\n4.2+\n\n \n\n[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).](https://www.sec.gov/Archives/edgar/data/2022626/000119312524221372/d843142dex42.htm)\n\n10.1#\n\n \n\n[Amended and Restated Non-Employee Director Compensation Policy (incorporated by reference to Exhibit 10.7 to the Company's Annual Report on Form 10-K filed on March 26, 2026).](https://www.sec.gov/Archives/edgar/data/2022626/000119312526126188/upb-ex10_7.htm)\n\n31.1*\n\n \n\n[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.](upb-ex31_1.htm)\n\n31.2*\n\n \n\n[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.](upb-ex31_2.htm)\n\n32.1**\n\n \n\n[Certifications of Principal Executive Officer and Principal Financial Officer Pursuant to 18 U.S.C. Section 1350, as Adopted Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002.](upb-ex32_1.htm)\n\n101.INS*\n\n \n\nInline XBRL Instance Document – the instance document does not appear in the Interactive Data File because XBRL tags are embedded within the Inline XBRL document.\n\n101.SCH*\n\n \n\nInline XBRL Taxonomy Extension Schema With Embedded Linkbase Documents.\n\n104*\n\n \n\nCover Page Interactive Data File (embedded within the Inline XBRL document and included in Exhibit 101).\n\n \n\n* Filed herewith.\n\n** The certifications furnished in Exhibit 32.1 hereto are deemed to be furnished with this Quarterly Report on Form 10-Q 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.\n\n+ Certain exhibits and schedules to this agreement have been omitted pursuant to Item 601(a)(5) and (6) of Regulation S-K. The registrant will furnish copies of any of the exhibits and schedules to the Securities and Exchange Commission upon request.\n\n# Indicates a management contract or compensatory plan, contract or arrangement.\n\n81\n\nSIGNATURES\n\nPursuant 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 thereunto duly authorized.\n\n \n\n \n\n \n\nUPSTREAM BIO, INC.\n\n \n\n \n\n \n\n \n\nDate: May 13, 2026\n\n \n\nBy:\n\n/s/ E. Rand Sutherland\n\n \n\n \n\n \n\nE. Rand Sutherland\n\n \n\n \n\n \n\nChief Executive Officer\n\n(Principal Executive Officer)\n\n \n\n \n\n \n\nDate: May 13, 2026\n\n \n\nBy:\n\n/s/ Michael Paul Gray\n\n \n\n \n\n \n\nMichael Paul Gray\n\n \n\n \n\n \n\nChief Financial and Operating Officer\n\n(Principal Financial and Accounting Officer)\n\n \n\n82"}