{"url_path":"/sec/upb/10-q/2026/item-2","section_key":"item-2","section_title":"Item 2 Unregistered Sales of Equity Securities and Use of Proceeds.","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":99,"has_tables":true,"body_markdown":"Item 2. Unregistered Sales of Equity Securities and Use of Proceeds.\n\n(a) Recent sales of unregistered equity securities\n\nNone.\n\n(b) Use of proceeds\n\nOn October 10, 2024, our Registration Statement on Form S-1 (No. 333-282197) for our initial public offering (“IPO”) was declared effective by the Securities and Exchange Commission (the “SEC”).\n\nThere has been no material change in the planned use of proceeds from our IPO as described in our final prospectus filed with the SEC pursuant to Rule 424(b)(4) under the Securities Act on October 11, 2024 (File No. 333-282197).\n\n(c) Issuer purchases of equity securities\n\nNone."}