As of November 7, 2026, Upstream Bio, Inc. is a publicly traded company (Nasdaq: UPB); its largest reported holder is Norges Bank, with 7.73% on Schedule 13G/A of August 12, 2026, then Fidelity (FMR) (6.9%). The largest insider holding is AI Upstream LLC, a 10% owner, with 5,494,410 shares (10.0% of shares outstanding), per Form 4 of October 17, 2024 (Schedule 13G/A, August 12, 2026).
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Is Upstream Bio, Inc. a real, registered company?
- Upstream Bio, Inc. files with the SEC under CIK 2022626 (its SEC filings).
- Its shares are listed under the ticker UPB on Nasdaq (SEC company record).
- Incorporated in Delaware; business address in Waltham, Massachusetts, as its SEC filings state.
- Court and bankruptcy records: see Before you sign or pay below.
Before you sign or pay
- Court and bankruptcy: No federal court case or bankruptcy filing found under UPSTREAM BIO INC in our court records and SEC 8-K records (as of 2026-11-07).
- Ownership: 5%+ holders are reported on Schedule 13D or 13G; the latest names Fidelity (FMR) (filed 2026-11-06).
Who are Upstream Bio, Inc.'s owners and officers?
Upstream Bio, Inc.: incorporated in Delaware; business address in Waltham, Massachusetts; industry Pharmaceutical Preparations (Schedule 13G/A, 2026-11-06).
| Report | Holder | Share |
|---|---|---|
| Schedule 13G/A, 2026-11-06 | Fmr LLC | 6.9% |
| Schedule 13G/A, 2026-10-29 | Decheng Capital Global Life Sciences Fund Iv, L.P. | 4.9% |
| Schedule 13G/A, 2026-08-12 | Norges Bank | 7.73% |
| Schedule 13G, 2026-07-30 | Blackrock, Inc. | 5.2% |
| Schedule 13G/A, 2026-05-15 | Decheng Capital Global Life Sciences Fund Iv, L.P. | 5% |
| Schedule 13G/A, 2025-11-14 | Hbm Healthcare Investments (Cayman) LTD. | 4.1% |
| Schedule 13G/A, 2025-11-14 | Tcg Crossover Gp I, LLC | 3.9% |
| Schedule 13G, 2025-10-24 | Norges Bank | 5.3% |
| Schedule 13G/A, 2025-08-06 | Fmr LLC | 14.8% |
Questions about who owns Upstream Bio, Inc.
Who owns Upstream Bio, Inc.?
On this page, 3 holders' latest ownership filings report 5% or more of Upstream Bio, Inc.: Norges Bank (7.73%, Schedule 13G/A, filed 2026-08-12), Fmr LLC (6.9%, Schedule 13G/A, filed 2026-11-06) and Blackrock, Inc. (5.2%, Schedule 13G, filed 2026-07-30).
Who are the largest shareholders of Upstream Bio, Inc.?
By the share each holder's latest filing reports, the largest holders of Upstream Bio, Inc. on this page are Norges Bank (7.73%), Fmr LLC (6.9%) and Blackrock, Inc. (5.2%).
When did Norges Bank buy into Upstream Bio, Inc.?
The filings give report dates, not purchase dates. The earliest filing from Norges Bank on this page is the Schedule 13G, filed 2025-10-24, reporting 5.3%; its latest, Schedule 13G/A filed 2026-08-12, reports 7.73%.
Is this an audit or a full list?
Neither. The ownership list on this page covers only Schedule 13D and 13G filings, which holders make once they own 5% or more of a class of shares (an amendment can report a stake that has since fallen below 5%); 9 such filings are shown here. It is not an audit and not a full cap table: holders who never reached 5% are not listed, and a stake can change after its latest filing.
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Which insiders own Upstream Bio, Inc. shares?
Directors, officers and holders of 10% or more report their shares on Forms 3, 4 and 5. Each line is the latest such report, largest holding first.
- AI Upstream LLC, a 10% owner: 5,494,410 shares (10.0% of shares outstanding), on a joint filing (Form 4, 2024-10-17).
- Access Industries Management, LLC, a 10% owner: 5,494,410 shares (10.0% of shares outstanding), on a joint filing (Form 4, 2024-10-17).
- , a 10% owner: 5,494,410 shares (10.0% of shares outstanding), on a joint filing (Form 4, 2024-10-17).
- Access Industries Holdings LLC, a 10% owner: 5,494,410 shares (10.0% of shares outstanding), on a joint filing (Form 4, 2024-10-17).
- AI Biotechnology LLC, a 10% owner: 5,494,410 shares (10.0% of shares outstanding), on a joint filing (Form 4, 2024-10-17).
Shares outstanding: 54,771,041 as of 2026-08-04, from the company's latest SEC cover page.
How much has Upstream Bio, Inc. raised?
Latest IPO step: Upstream Bio, Inc. filed its final IPO prospectus (424B4, 2024-10-11).
IPO filings: 424B4, 2024-10-11, S-1/A, 2024-10-07, S-1, 2024-09-18.
Keep reading
More on Upstream Bio, Inc. and the records around it.
Upstream Bio, Inc. elsewhere on the record
- 5%+ stake filings Nov 2026
Companies that share a holder
- TCG Crossover GP I, LLC also filed stake reports on 6 other companies: Abivax SA (Aug 2026), Entrada Therapeutics, Inc. (Aug 2026), Vistagen Therapeutics, Inc. (Aug 2026)
- HBM Healthcare Investments (Cayman) Ltd. also filed stake reports on 7 other companies: Chemomab Therapeutics Ltd. (Sep 2026), ALX ONCOLOGY HOLDINGS INC (May 2026), IO Biotech, Inc. (Apr 2026)
- Norges Bank also filed stake reports on 36 other companies: Atour Lifestyle Holdings Ltd (Aug 2026), BXP, Inc. (Aug 2026), Cabaletta Bio, Inc. (Aug 2026)
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