{"schema_version":"secwatch.filing_event.v1","accession":"0001193125-26-126572","form_type":"8-K","ticker":"UPB","cik":"0002022626","company_name":"Upstream Bio, Inc.","filed_at":"2026-03-26T23:59:59+00:00","discovered_at":"2026-05-14T18:02:37.016330+00:00","generated_at":"2026-05-15T08:54:46.628212+00:00","sec_items":["1.01","9.01"],"event_type":"other_material","sentiment":"neutral","materiality_score":0.6,"calibrated_materiality_score":0.6,"confidence":"high","headline":"Upstream Bio enters into $150M at-the-market offering agreement with Leerink Partners","bullets":["Company may sell up to $150M of common stock through Leerink Partners as sales agent.","Agent will receive up to 3.0% commission on gross proceeds from sales.","Offering made under existing shelf registration statement; no obligation to sell any shares.","Sales may be made on Nasdaq or other markets as at-the-market offerings.","Company can suspend or terminate offering at any time."],"urls":{"canonical":"https://secwatch.observer/filing/0001193125-26-126572","json":"https://secwatch.observer/filing/0001193125-26-126572.json","markdown":"https://secwatch.observer/filing/0001193125-26-126572.md","text":"https://secwatch.observer/filing/0001193125-26-126572.txt","edgar_index":"https://www.sec.gov/Archives/edgar/data/2022626/000119312526126572/0001193125-26-126572-index.htm","edgar_primary_document":"https://www.sec.gov/Archives/edgar/data/2022626/000119312526126572/d110609d8k.htm"},"model":{"generated_by":"deepseek-v4-flash:cloud@v2","generated_at":"2026-05-15T08:54:46.628212+00:00"},"review":{"review_status":"machine_generated","human_reviewed":false,"corrected":false,"correction_note":null,"correction_timestamp":null,"superseded_by":null,"related_filings":[]},"source_grounded_claims":[{"claim_id":"9fdd8131aca96df1687847f864b025d691e4fd9d","claim":"Upstream Bio, Inc. entered into Sales Agreement with Leerink Partners LLC valued at up to $150,000,000 (effective 2026-03-26).","evidence_excerpt":"On March 26, 2026, Upstream Bio, Inc. (the “Company”) entered into a Sales Agreement (the “Sales Agreement”) with Leerink Partners LLC, as sales agent (the “Agent”), pursuant to which the Company from time to time may offer and sell shares (the “ATM Shares”) of its common stock","evidence_source":"SEC 8-K Item 1.01/1.02","evidence_url":"https://www.sec.gov/Archives/edgar/data/2022626/000119312526126572/0001193125-26-126572-index.htm","confidence":0.9,"family_label":"Material Agreements","details":[{"label":"Action","value":"entry"},{"label":"Agreement","value":"atm program"},{"label":"Counterparty","value":"Leerink Partners LLC"},{"label":"Value","value":"up to $150,000,000"},{"label":"Effective","value":"2026-03-26"}]}],"license":"Source filings: public domain (SEC EDGAR). Summaries (headline + bullets): CC-BY-4.0; attribute https://secwatch.observer"}