As of November 6, 2026, one holder's latest Schedule 13D or 13G filing report owning 5% or more of Generation Bio Co. The largest reported stake is SymBiosis Capital Partners, LLC's, at 6.3%. 12 filings are on record since July 17, 2025 (Schedule 13G/A, November 14, 2025).
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Key facts
- · Holder: Atlas Venture Fund X, L.P. · Percent: 0% · SCHEDULE 13G/A
- · Holder: T. Rowe Price Associates, Inc. · Percent: 3.1% · SCHEDULE 13G/A
- · Holder: Renaissance Technologies LLC · Percent: 4.27% · SCHEDULE 13G/A
- · Holder: Baselake Partners, LP · Percent: 0% · SCHEDULE 13G/A
- · Holder: Baselake Partners, LP · Percent: 5.2% · SCHEDULE 13G
Generation Bio Co. has 12 Schedule 13D or 13G filings on record since 2025-07-17. 1 holder's latest filing reports 5% or more of common stock, $0.0001 par value. Each figure below is the holder's own, as filed, with the filing linked.
Holders
| Holder | Percent | Shares | Latest | Event date |
|---|---|---|---|---|
| SymBiosis Capital Partners, LLC | 6.3% | 421,926 | SCHEDULE 13G/A, 2025-11-14 | 2025-09-30 |
| Renaissance Technologies LLC | 4.27% | 287,614 | SCHEDULE 13G/A, 2026-02-12 | 2025-12-31 |
| Fmr LLC | 3.5% | 2,345,624 | SCHEDULE 13G/A, 2025-08-06 | 2025-06-30 |
| T. Rowe Price Associates, Inc. | 3.1% | 209,641 | SCHEDULE 13G/A, 2026-02-17 | 2025-12-31 |
| BlackRock, Inc. | 1.7% | 1,152,047 | SCHEDULE 13G/A, 2025-07-17 | 2025-06-30 |
| Baselake Partners, LP | 0% | 0 | SCHEDULE 13G/A, 2026-02-11 | 2026-02-09 |
| Atlas Venture Fund X, L.P. | 0% | 0 | SCHEDULE 13G/A, 2026-05-14 | 2026-03-31 |
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More on Generation Bio Co. and the records around it.
Generation Bio Co. elsewhere on the record
- Acquisition Apr 2026
Companies that share a holder
- SymBiosis Capital Partners, LLC also filed stake reports on 1 other company: Rani Therapeutics Holdings, Inc. (May 2026)
- Atlas Venture Fund X, L.P. also filed stake reports on 5 other companies: Kymera Therapeutics, Inc. (Aug 2026), Obsidian Therapeutics, Inc. (Aug 2026), Q32 Bio Inc. (May 2026)
- Baselake Partners, LP also filed stake reports on 7 other companies: KIORA PHARMACEUTICALS, INC. (Sep 2026), Passage Bio, Inc. (Jun 2026), Athira Pharma, Inc. (Feb 2026)
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Timeline
| Filed | Holder | Percent | Filing |
|---|---|---|---|
| 2025-07-17 | BlackRock, Inc. | 1.7% | SCHEDULE 13G/A |
| 2025-08-06 | Fmr LLC | 3.5% | SCHEDULE 13G/A |
| 2025-08-14 | T. Rowe Price Associates, Inc. | 12.6% | SCHEDULE 13G/A |
| 2025-11-13 | Renaissance Technologies LLC | 5.11% | SCHEDULE 13G |
| 2025-11-14 | T. Rowe Price Associates, Inc. | 8.6% | SCHEDULE 13G/A |
| 2025-11-14 | SymBiosis Capital Partners, LLC | 6.3% | SCHEDULE 13G |
| 2025-11-14 | SymBiosis Capital Partners, LLC | 6.3% | SCHEDULE 13G/A |
| 2026-02-06 | Baselake Partners, LP | 5.2% | SCHEDULE 13G |
| 2026-02-11 | Baselake Partners, LP | 0% | SCHEDULE 13G/A |
| 2026-02-12 | Renaissance Technologies LLC | 4.27% | SCHEDULE 13G/A |
| 2026-02-17 | T. Rowe Price Associates, Inc. | 3.1% | SCHEDULE 13G/A |
| 2026-05-14 | Atlas Venture Fund X, L.P. | 0% | SCHEDULE 13G/A |
Questions about who owns Generation Bio Co.
Who owns Generation Bio Co.?
On this page, one holder's latest ownership filing reports 5% or more of Generation Bio Co.: SymBiosis Capital Partners, LLC (6.3%, Schedule 13G/A, filed 2025-11-14).
When did SymBiosis Capital Partners, LLC buy into Generation Bio Co.?
The filings give report dates, not purchase dates. The earliest filing from SymBiosis Capital Partners, LLC on this page is the Schedule 13G, filed 2025-11-14, reporting 6.3%; its latest, Schedule 13G/A filed 2025-11-14, reports 6.3%.
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%); 12 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 Generation Bio Co.
| Date | Record | Figure | Our page | Source |
|---|---|---|---|---|
| February 9, 2026 | Acquired by XOMA Royalty Corporation | — | Acquisition | 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.