As of November 10, 2026, 5 holders' latest Schedule 13D or 13G filings report owning 5% or more of Sionna Therapeutics, Inc. The largest reported stake is RA Capital Management, L.P.'s, at 14.3%. 9 filings are on record since July 30, 2025 (Schedule 13D/A, September 21, 2026).
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Key facts
- · Reporting person: The Goldman Sachs Group, Inc. · Sole voting: 0 · Shared voting: 2,639,412 · Sole dispositive: 0 · Shared dispositive: 2,639,418 · SCHEDULE 13G, 2026-11-09
- · Reporting person: RA Capital Management, L.P. · Sole voting: 0 · Shared voting: 6,476,193 · Sole dispositive: 0 · Shared dispositive: 6,476,193 · SCHEDULE 13D/A, 2026-09-21
- · Holder: Viking Global Investors LP · Percent: 7.1% · SCHEDULE 13G/A
- · Holder: Qatar Investment Authority · Percent: 4.5% · SCHEDULE 13G/A
- · Holder: Orbimed Advisors LLC · Percent: 6.6% · SCHEDULE 13D/A
Sionna Therapeutics, Inc. has 9 Schedule 13D or 13G filings on record since 2025-07-30. 5 holders' latest filing reports 5% or more of common stock, $0.001 par value per share. Each figure below is the holder's own, as filed, with the filing linked.
Layoffs on record: 1 filing or notice, latest 2026-09-14 (layoff filings and notices).
Holders
| Holder | Percent | Shares | Latest | Event date |
|---|---|---|---|---|
| RA Capital Management, L.P. | 14.3% | 6,476,193 | SCHEDULE 13D/A, 2026-09-21 | 2026-09-17 |
| Viking Global Investors LP | 7.1% | 3,195,181 | SCHEDULE 13G/A, 2026-05-15 | 2026-03-31 |
| Orbimed Advisors LLC | 6.6% | 2,967,722 | SCHEDULE 13D/A, 2026-04-20 | 2026-04-15 |
| The Goldman Sachs Group, Inc. | 5.8% | 2,639,418 | SCHEDULE 13G, 2026-11-09 | 2026-09-30 |
| Atlas Venture Fund XI, L.P. | 5.4% | 2,382,495 | SCHEDULE 13D/A, 2025-10-20 | 2025-10-16 |
| Qatar Investment Authority | 4.5% | 2,020,258 | SCHEDULE 13G/A, 2026-05-12 | 2026-03-31 |
| Jpmorgan Chase & Co. | 4.4% | 1,980,626 | SCHEDULE 13G/A, 2025-10-31 | 2025-09-30 |
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More on Sionna Therapeutics, Inc. and the records around it.
Sionna Therapeutics, Inc. elsewhere on the record
- Layoff notices Sep 2026
- Who owns it
Companies that share a holder
- Atlas Venture Fund XI, L.P. also filed stake reports on 3 other companies: DYNE THERAPEUTICS, INC. (Aug 2026), Korro Bio, Inc. (Aug 2026), Day One Biopharmaceuticals, Inc. (May 2026)
- Qatar Investment Authority also filed stake reports on 11 other companies: Aspen Neuroscience, Inc. (Nov 2026), Global Business Travel Group, Inc. (Sep 2026), Nanobiotix SA (Jul 2026)
- VIKING GLOBAL INVESTORS LP also filed stake reports on 27 other companies: City Therapeutics, Inc. (Oct 2026), MID AMERICA APARTMENT COMMUNITIES INC. (Oct 2026), REGAL REXNORD CORP (Sep 2026)
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Voting and dispositive power, as filed
| Reporting person | Sole voting | Shared voting | Sole dispositive | Shared dispositive | Filing |
|---|---|---|---|---|---|
| RA Capital Management, L.P. | 0 | 6,476,193 | 0 | 6,476,193 | SCHEDULE 13D/A, 2026-09-21 |
| Peter Kolchinsky | 0 | 6,476,193 | 0 | 6,476,193 | SCHEDULE 13D/A, 2026-09-21 |
| Rajeev Shah | 0 | 6,476,193 | 0 | 6,476,193 | SCHEDULE 13D/A, 2026-09-21 |
| RA Capital Healthcare Fund, L.P. | 0 | 3,448,812 | 0 | 3,448,812 | SCHEDULE 13D/A, 2026-09-21 |
| RA Capital Nexus Fund III, L.P. | 0 | 2,198,082 | 0 | 2,198,082 | SCHEDULE 13D/A, 2026-09-21 |
| The Goldman Sachs Group, Inc. | 0 | 2,639,412 | 0 | 2,639,418 | SCHEDULE 13G, 2026-11-09 |
| Goldman Sachs & Co. LLC | 0 | 2,639,412 | 0 | 2,639,418 | SCHEDULE 13G, 2026-11-09 |
The latest filing identifies Sionna Therapeutics, Inc. by CUSIP 829401108 and gives its principal executive office as 21 Hickory Drive, Suite 500, Waltham (SCHEDULE 13G, 2026-11-09).
Purpose of Transaction (Item 4)
Orbimed Advisors LLC
The Reporting Persons from time to time intend to review their investment in the Issuer on the basis of various factors, including the Issuer's business, financial condition, results of operations and prospects, general economic and industry conditions, the securities markets in general and those for the Issuer's Shares in particular, as well as other developments and other investment opportunities. Based upon such review, the Reporting Persons will take such actions in the future as the Reporting Persons may deem appropriate in light of the circumstances existing from time to time. If the Reporting Persons believe that further investment in the Issuer is attractive, whether because of the market price of Shares or otherwise, they may acquire Shares or other securities of the Issuer either in the open market or in privately negotiated transactions. Similarly, depending on market and other factors, the Reporting Persons may determine to dispose of some or all of the Shares currently owned by the Reporting Persons or otherwise acquired by the Reporting Persons either in the open market or in privately negotiated transactions. Except as set forth in this Schedule 13D, the Reporting Persons have not formulated any plans or proposals which relate to or would result in: (a) the acquisition by any person of additional securities of the Issuer or the disposition of securities of the Issuer, (b) an extraordinary corporate transaction, such as a merger, reorganization or liquidation, …The first part of Item 4 of the SCHEDULE 13D/A filed 2026-04-20; the filing has the rest
Timeline
| Filed | Holder | Percent | Filing |
|---|---|---|---|
| 2025-07-30 | Jpmorgan Chase & Co. | 5% | SCHEDULE 13G |
| 2025-10-20 | Atlas Venture Fund XI, L.P. | 5.4% | SCHEDULE 13D/A |
| 2025-10-31 | Jpmorgan Chase & Co. | 4.4% | SCHEDULE 13G/A |
| 2025-11-07 | RA Capital Management, L.P. | 22.6% | SCHEDULE 13D/A |
| 2026-04-20 | Orbimed Advisors LLC | 6.6% | SCHEDULE 13D/A |
| 2026-05-12 | Qatar Investment Authority | 4.5% | SCHEDULE 13G/A |
| 2026-05-15 | Viking Global Investors LP | 7.1% | SCHEDULE 13G/A |
| 2026-09-21 | RA Capital Management, L.P. | 14.3% | SCHEDULE 13D/A |
| 2026-11-09 | The Goldman Sachs Group, Inc. | 5.8% | SCHEDULE 13G |
Questions about who owns Sionna Therapeutics, Inc.
Who owns Sionna Therapeutics, Inc.?
On this page, 5 holders' latest ownership filings report 5% or more of Sionna Therapeutics, Inc.: RA Capital Management, L.P. (14.3%, Schedule 13D/A, filed 2026-09-21), Viking Global Investors LP (7.1%, Schedule 13G/A, filed 2026-05-15), Orbimed Advisors LLC (6.6%, Schedule 13D/A, filed 2026-04-20), The Goldman Sachs Group, Inc. (5.8%, Schedule 13G, filed 2026-11-09) and Atlas Venture Fund XI, L.P. (5.4%, Schedule 13D/A, filed 2025-10-20).
Who are the largest shareholders of Sionna Therapeutics, Inc.?
By the share each holder's latest filing reports, the largest holders of Sionna Therapeutics, Inc. on this page are RA Capital Management, L.P. (14.3%), Viking Global Investors LP (7.1%) and Orbimed Advisors LLC (6.6%).
When did RA Capital Management, L.P. buy into Sionna Therapeutics, Inc.?
The filings give report dates, not purchase dates. The earliest filing from RA Capital Management, L.P. on this page is the Schedule 13D/A, filed 2025-11-07, reporting 22.6%; its latest, Schedule 13D/A filed 2026-09-21, reports 14.3%. That earliest filing is itself an amendment, which updates an earlier report.
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 Sionna Therapeutics, Inc.
| Date | Record | Figure | Our page | Source |
|---|---|---|---|---|
| February 7, 2025 | IPO filing, Form 424B4 | $18 a share | IPO filings | Source |
| February 3, 2025 | IPO filing, Form S-1/A | — | IPO filings | Source |
| January 17, 2025 | 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.