As of November 6, 2026, 6 holders' latest Schedule 13D or 13G filings report owning 5% or more of Alector, Inc. The largest reported stake is Chen Yu's, at 9.2%. 16 filings are on record since August 14, 2025 (Schedule 13G, November 14, 2025).
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Key facts
- · Reporting person: RA Capital Management, L.P. · Sole voting: 0 · Shared voting: 7,500,000 · Sole dispositive: 0 · Shared dispositive: 7,500,000 · SCHEDULE 13G, 2026-10-26
- · Reporting person: Deep Track Capital, LP · Sole voting: 0 · Shared voting: 12,772,152 · Sole dispositive: 0 · Shared dispositive: 12,772,152 · SCHEDULE 13G, 2026-10-23
- · Reporting person: Biotechnology Value Fund L P · Sole voting: 0 · Shared voting: 4,900,143 · Sole dispositive: 0 · Shared dispositive: 4,900,143 · SCHEDULE 13G, 2026-09-18
- · Holder: Terrance G. McGuire · Percent: 4.7% · SCHEDULE 13G/A
- · Holder: BlackRock, Inc. · Percent: 5.2% · SCHEDULE 13G
Alector, Inc. has 16 Schedule 13D or 13G filings on record since 2025-08-14. 6 holders' latest filing reports 5% or more of common stock, $0.0001 par value per share. Each figure below is the holder's own, as filed, with the filing linked.
Layoffs on record: about 75 jobs, latest 2025-10-21 (layoff filings and notices).
Holders
| Holder | Percent | Shares | Latest | Event date |
|---|---|---|---|---|
| 9.2% | 10,000,000 | SCHEDULE 13G, 2025-11-14 | 2025-10-22 | |
| Deep Track Capital, LP | 8.61% | 12,772,152 | SCHEDULE 13G, 2026-10-23 | 2026-10-16 |
| Bvf Partners L P | 8.4% | 9,374,267 | SCHEDULE 13G, 2026-09-18 | 2026-09-11 |
| 7.4% | 8,213,925 | SCHEDULE 13G/A, 2026-02-06 | 2025-12-31 | |
| BlackRock, Inc. | 5.2% | 5,784,214 | SCHEDULE 13G, 2026-04-27 | 2026-03-31 |
| RA Capital Management, L.P. | 5.1% | 7,500,000 | SCHEDULE 13G, 2026-10-26 | 2026-10-19 |
| 4.7% | 5,173,499 | SCHEDULE 13G/A, 2026-05-14 | 2026-03-31 | |
| Fmr LLC | 3.6% | 3,599,820 | SCHEDULE 13G/A, 2025-11-07 | 2025-10-31 |
| RTW Investments, LP | 0% | 0 | SCHEDULE 13G/A, 2026-02-17 | 2025-12-31 |
| The Vanguard Group | 0% | 0 | SCHEDULE 13G/A, 2026-03-26 | 2026-03-13 |
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More on Alector, Inc. and the records around it.
Alector, Inc. elsewhere on the record
- Layoff notices Oct 2025
- Who owns it
Companies that share a holder
- TCG Crossover GP II, LLC also filed stake reports on 21 other companies: ALX Oncology Holdings Inc. (Aug 2026), First Tracks Biotherapeutics, Inc. (Aug 2026), Fulcrum Therapeutics, Inc. (Aug 2026)
- RTW Investments, LP also filed stake reports on 43 other companies: CG Oncology, Inc. (Aug 2026), iRhythm Holdings, Inc. (Aug 2026), Kailera Therapeutics, Inc. (Aug 2026)
- BIOTECHNOLOGY VALUE FUND L P also filed stake reports on 55 other companies: Frazier Life Sciences Acquisition Corp. II (Oct 2026), Olema Pharmaceuticals, Inc. (Oct 2026), Foghorn Therapeutics Inc. (Oct 2026)
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What the Full Report on Alector, 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
Sources
17 cited sources found
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Voting and dispositive power, as filed
| Reporting person | Sole voting | Shared voting | Sole dispositive | Shared dispositive | Filing |
|---|---|---|---|---|---|
| Deep Track Capital, LP | 0 | 12,772,152 | 0 | 12,772,152 | SCHEDULE 13G, 2026-10-23 |
| Deep Track Biotechnology Master Fund, Ltd. | 0 | 12,772,152 | 0 | 12,772,152 | SCHEDULE 13G, 2026-10-23 |
| David Kroin | 0 | 12,772,152 | 0 | 12,772,152 | SCHEDULE 13G, 2026-10-23 |
| Biotechnology Value Fund L P | 0 | 4,900,143 | 0 | 4,900,143 | SCHEDULE 13G, 2026-09-18 |
| Bvf I Gp LLC | 0 | 4,900,143 | 0 | 4,900,143 | SCHEDULE 13G, 2026-09-18 |
| Biotechnology Value Fund Ii LP | 0 | 3,671,016 | 0 | 3,671,016 | SCHEDULE 13G, 2026-09-18 |
| Bvf Ii Gp LLC | 0 | 3,671,016 | 0 | 3,671,016 | SCHEDULE 13G, 2026-09-18 |
| Biotechnology Value Trading Fund OS LP | 0 | 619,317 | 0 | 619,317 | SCHEDULE 13G, 2026-09-18 |
| BVF Partners OS Ltd. | 0 | 619,317 | 0 | 619,317 | SCHEDULE 13G, 2026-09-18 |
| Bvf Gp Holdings LLC | 0 | 8,571,159 | 0 | 8,571,159 | SCHEDULE 13G, 2026-09-18 |
| Bvf Partners L P | 0 | 9,374,267 | 0 | 9,374,267 | SCHEDULE 13G, 2026-09-18 |
| Bvf Inc | 0 | 9,374,267 | 0 | 9,374,267 | SCHEDULE 13G, 2026-09-18 |
| Lampert Mark N | 0 | 9,374,267 | 0 | 9,374,267 | SCHEDULE 13G, 2026-09-18 |
| RA Capital Management, L.P. | 0 | 7,500,000 | 0 | 7,500,000 | SCHEDULE 13G, 2026-10-26 |
| Peter Kolchinsky | 0 | 7,500,000 | 0 | 7,500,000 | SCHEDULE 13G, 2026-10-26 |
| Rajeev Shah | 0 | 7,500,000 | 0 | 7,500,000 | SCHEDULE 13G, 2026-10-26 |
| RA Capital Healthcare Fund, L.P. | 0 | 7,500,000 | 0 | 7,500,000 | SCHEDULE 13G, 2026-10-26 |
The latest filing identifies Alector, Inc. by CUSIP 014442107 and gives its principal executive office as 131 Oyster Point Blvd. Suite 600, South San Francisco, CA 94080 (SCHEDULE 13G, 2026-10-26).
What the percentages are based on
The following percentages are based on 111,656,919 Shares outstanding as of July 31, 2026, which is the total number of Shares outstanding as reported in the Issuer's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on August 6, 2026.Bvf Partners L P, SCHEDULE 13G, 2026-09-18
Row 11 of each Reporting Person's cover page to this Schedule 13G sets forth the percentage of shares of common stock of the Issuer beneficially owned by such Reporting Person and is incorporated by reference.RA Capital Management, L.P., SCHEDULE 13G, 2026-10-26
Timeline
| Filed | Holder | Percent | Filing |
|---|---|---|---|
| 2025-08-14 | RA Capital Management, L.P. | 0% | SCHEDULE 13G/A |
| 2025-10-17 | BlackRock, Inc. | 5.1% | SCHEDULE 13G/A |
| 2025-11-07 | Fmr LLC | 3.6% | SCHEDULE 13G/A |
| 2025-11-13 | Terrance G. McGuire | 6.5% | SCHEDULE 13G/A |
| 2025-11-14 | Chen Yu | 9.2% | SCHEDULE 13G |
| 2025-11-14 | RTW Investments, LP | 6.9% | SCHEDULE 13G |
| 2026-01-21 | BlackRock, Inc. | 4.7% | SCHEDULE 13G/A |
| 2026-01-30 | The Vanguard Group | 6.32% | SCHEDULE 13G/A |
| 2026-02-06 | Arnon Rosenthal | 7.4% | SCHEDULE 13G/A |
| 2026-02-17 | RTW Investments, LP | 0% | SCHEDULE 13G/A |
| 2026-03-26 | The Vanguard Group | 0% | SCHEDULE 13G/A |
| 2026-04-27 | BlackRock, Inc. | 5.2% | SCHEDULE 13G |
| 2026-05-14 | Terrance G. McGuire | 4.7% | SCHEDULE 13G/A |
| 2026-09-18 | Bvf Partners L P | 8.4% | SCHEDULE 13G |
| 2026-10-23 | Deep Track Capital, LP | 8.61% | SCHEDULE 13G |
| 2026-10-26 | RA Capital Management, L.P. | 5.1% | SCHEDULE 13G |
Questions about who owns Alector, Inc.
Who owns Alector, Inc.?
On this page, 6 holders' latest ownership filings report 5% or more of Alector, Inc.: Chen Yu (9.2%, Schedule 13G, filed 2025-11-14), Deep Track Capital, LP (8.61%, Schedule 13G, filed 2026-10-23), Bvf Partners L P (8.4%, Schedule 13G, filed 2026-09-18), Arnon Rosenthal (7.4%, Schedule 13G/A, filed 2026-02-06) and BlackRock, Inc. (5.2%, Schedule 13G, filed 2026-04-27); 1 more is listed above.
Who are the largest shareholders of Alector, Inc.?
By the share each holder's latest filing reports, the largest holders of Alector, Inc. on this page are Chen Yu (9.2%), Deep Track Capital, LP (8.61%) and Bvf Partners L P (8.4%).
When did Chen Yu buy into Alector, Inc.?
The filings give report dates, not purchase dates. The earliest filing from Chen Yu on this page is the Schedule 13G, filed 2025-11-14, reporting 9.2%.
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%); 16 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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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.