As of November 7, 2026, 3 holders' latest Schedule 13D or 13G filings report owning 5% or more of Upstream Bio Inc. The largest reported stake is Norges Bank's, at 7.73%. 9 filings are on record since August 6, 2025 (Schedule 13G/A, August 12, 2026).
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Key facts
- · Reporting person: Fmr LLC · Sole voting: 3,790,763 · Shared voting: 0 · Sole dispositive: 3,793,955 · Shared dispositive: 0 · SCHEDULE 13G/A, 2026-11-06
- · Reporting person: Decheng Capital Global Life Sciences Fund IV, L.P. · Sole voting: 0 · Shared voting: 2,724,868 · Sole dispositive: 0 · Shared dispositive: 2,724,868 · SCHEDULE 13G/A, 2026-10-29
- · Reporting person: Norges Bank · Sole voting: 3,768,619 · Shared voting: 0 · Sole dispositive: 3,768,619 · Shared dispositive: 437,967 · SCHEDULE 13G/A, 2026-08-12
- · Reporting person: BlackRock, Inc. · Sole voting: 2,764,429 · Shared voting: 0 · Sole dispositive: 2,814,714 · Shared dispositive: 0 · SCHEDULE 13G, 2026-07-30
- · Holder: Decheng Capital Global Life Sciences Fund IV, L.P. · Percent: 5% · SCHEDULE 13G/A
Upstream Bio Inc has 9 Schedule 13D or 13G filings on record since 2025-08-06. 3 holders' latest filing reports 5% or more of common stock. Each figure below is the holder's own, as filed, with the filing linked.
Holders
| Holder | Percent | Shares | Latest | Event date |
|---|---|---|---|---|
| Norges Bank | 7.73% | 4,206,586 | SCHEDULE 13G/A, 2026-08-12 | 2026-06-30 |
| Fmr LLC | 6.9% | 3,793,955 | SCHEDULE 13G/A, 2026-11-06 | 2026-10-30 |
| BlackRock, Inc. | 5.2% | 2,814,714 | SCHEDULE 13G, 2026-07-30 | 2026-06-30 |
| Decheng Capital Global Life Sciences Fund IV, L.P. | 4.9% | 2,724,868 | SCHEDULE 13G/A, 2026-10-29 | 2026-09-30 |
| HBM Healthcare Investments (Cayman) Ltd. | 4.1% | 2,195,111 | SCHEDULE 13G/A, 2025-11-14 | 2025-09-30 |
| TCG Crossover GP I, LLC | 3.9% | 2,117,103 | SCHEDULE 13G/A, 2025-11-14 | 2025-09-30 |
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Keep reading
More on Upstream Bio Inc and the records around it.
Upstream Bio Inc elsewhere on the record
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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What the Full Report on Upstream Bio Inc covers
The Short Answer
Which Company This Is
What They Do, And How The Money Works
Who Runs It, And How To Reach Them
The Money: Funding, Valuation, Runway
Who Pays Them, And Who They Are Up Against
Warning Bells
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Voting and dispositive power, as filed
| Reporting person | Sole voting | Shared voting | Sole dispositive | Shared dispositive | Filing |
|---|---|---|---|---|---|
| Norges Bank | 3,768,619 | 0 | 3,768,619 | 437,967 | SCHEDULE 13G/A, 2026-08-12 |
| Fmr LLC | 3,790,763 | 0 | 3,793,955 | 0 | SCHEDULE 13G/A, 2026-11-06 |
| Abigail P. Johnson | 0 | 0 | 3,793,955 | 0 | SCHEDULE 13G/A, 2026-11-06 |
| BlackRock, Inc. | 2,764,429 | 0 | 2,814,714 | 0 | SCHEDULE 13G, 2026-07-30 |
| Decheng Capital Global Life Sciences Fund IV, L.P. | 0 | 2,724,868 | 0 | 2,724,868 | SCHEDULE 13G/A, 2026-10-29 |
| Decheng Capital Management IV (Cayman), LLC | 0 | 2,724,868 | 0 | 2,724,868 | SCHEDULE 13G/A, 2026-10-29 |
| Xiangmin Cui | 0 | 2,724,868 | 0 | 2,724,868 | SCHEDULE 13G/A, 2026-10-29 |
| TCG Crossover GP I, LLC | 0 | 2,117,103 | 0 | 2,117,103 | SCHEDULE 13G/A, 2025-11-14 |
| TCG Crossover Fund I, L.P. | 0 | 2,117,103 | 0 | 2,117,103 | SCHEDULE 13G/A, 2025-11-14 |
| Chen Yu | 0 | 2,117,103 | 0 | 2,117,103 | SCHEDULE 13G/A, 2025-11-14 |
The latest filing identifies Upstream Bio Inc by CUSIP 91678A107 and gives its principal executive office as 890 WINTER STREET, SUITE 200, WALTHAM, MA 02451 (SCHEDULE 13G/A, 2026-11-06).
What the percentages are based on
As of September 30, 2026, each Reporting Person beneficially owned 4.98% of the Issuer's common stock. Such percentage is based upon 54,771,041 shares of the Issuer's common stock outstanding as of August 4, 2026, as reported in the Issuer's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission (the "SEC") on August 11, 2026.Decheng Capital Global Life Sciences Fund IV, L.P., SCHEDULE 13G/A, 2026-10-29
Timeline
| Filed | Holder | Percent | Filing |
|---|---|---|---|
| 2025-08-06 | Fmr LLC | 14.8% | SCHEDULE 13G/A |
| 2025-10-24 | Norges Bank | 5.3% | SCHEDULE 13G |
| 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/A |
| 2026-05-15 | Decheng Capital Global Life Sciences Fund IV, L.P. | 5% | SCHEDULE 13G/A |
| 2026-07-30 | BlackRock, Inc. | 5.2% | SCHEDULE 13G |
| 2026-08-12 | Norges Bank | 7.73% | SCHEDULE 13G/A |
| 2026-10-29 | Decheng Capital Global Life Sciences Fund IV, L.P. | 4.9% | SCHEDULE 13G/A |
| 2026-11-06 | Fmr LLC | 6.9% | SCHEDULE 13G/A |
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.
Also on the record for Upstream Bio Inc
| Date | Record | Figure | Our page | Source |
|---|---|---|---|---|
| October 11, 2024 | IPO filing, Form 424B4 | $17 a share | IPO filings | Source |
| October 7, 2024 | IPO filing, Form S-1/A | $15 to $17 a share | IPO filings | Source |
| September 18, 2024 | IPO filing, Form S-1 | — | IPO filings | Source |
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Where this comes from
Anyone who comes to own more than 5% of a class of a listed company's voting shares has to tell the SEC. A holder who may seek to change or influence the company files Schedule 13D, and has to say in Item 4, "Purpose of Transaction", what it intends to do. A holder with no such intent, such as many index and passive funds, may file the shorter Schedule 13G. Both are amended when the stake changes, including when it falls below 5%.
Every row here is one of those filings, linked to the filing itself. Percentages and share counts are exactly as the holder filed them, for the holder the filing names; an amendment showing a lower figure is shown as filed. Item 4 text is quoted word for word. Where a 13D's Item 4 contains a sentence stating a definite intent to influence the company, that sentence is marked and quoted; the page does not describe the holder or its motives beyond the words it filed. Nothing here is investment advice.