Who owns Sionna Therapeutics (SION)
Which tracked institutional funds hold SION, how they are positioned, and who is buying versus exiting — from SEC Form 13F-HR filings. See SION company fundamentals →
Ownership as of the 2026-Q2 13F filings (latest filed 2026-09-22). 13F is disclosed up to 45 days after quarter-end, so the most recent quarter fills in over the following weeks.
How the tape is positioned
The tracked-fund tape on SION is one-sided between 2026-Q1 and 2026-Q2: 67 added or opened and 18 trimmed or exited — on balance accumulating.
A prompt to read the filings, not a verdict. 13F is a quarter-end snapshot disclosed up to 45 days late; a fund adds or exits for mandate, benchmark, and timing reasons that have nothing to do with a view on the stock. This is a starting question, not a signal to trade.
Conviction spread
SION’s largest tracked holder by dollar value, RA CAPITAL MANAGEMENT, L.P., sizes it at 3.8% of its own reported 13F book, while the median holder sizes it at 0.0% of theirs — a 3.8pp conviction gap — its largest holder concentrates the name more heavily than the typical one.
Book-share is each fund’s reported value in SION divided by its whole reported 13F book, so it is comparable across funds of different sizes and is unaffected by stock splits. A higher share means a fund has committed more of its book to the name — a starting question about conviction, not a verdict or a signal to trade.
Institutional & insider positioning
Between 2026-Q1 and 2026-Q2, across 145 tracked filers holding SION, 92 increased or opened the position and 49 reduced or closed it; over the same quarter, open-market insider Form 4s were net sales.
This fuses two public signals for the same quarter — how tracked institutions changed their positions and whether insiders bought or sold in the open market. It describes what was filed; it is a starting question, not a verdict or a signal to trade.
New buyers & exits
Funds opening or closing a position in SION between the 2026-Q1 and 2026-Q2 13F filings, and the largest changes among funds holding it in both. New buyers and exits are counted on fund presence (split-invariant); adds and trims are measured on reported value.
New buyers 14
- Casdin Capital, LLC$18M
- Artisan Partners Limited Partnership$8M
- Sofinnova Investments, Inc.$6M
- First Turn Management, LLC$5M
- D. E. Shaw & Co., Inc.$4M
- MUTUAL OF AMERICA CAPITAL MANAGEMENT LLC$2M
Full exits 1
- POLEN CAPITAL MANAGEMENT LLC$1M
Largest adds
- ADAGE CAPITAL PARTNERS GP, L.L.C.$64M
- RA CAPITAL MANAGEMENT, L.P.$39M
- TPG GP A, LLC$25M
- Siren, L.L.C.$15M
- STATE STREET CORP$15M
- Driehaus Capital Management LLC$14M
Largest trims
- ORBIMED ADVISORS LLC$29M
- Aberdeen Group plc$10M
- PRICE T ROWE ASSOCIATES INC /MD/$9M
- DEERFIELD MANAGEMENT COMPANY, L.P.$9M
- JENNISON ASSOCIATES LLC$7M
- Sio Capital Management, LLC$6M
Institutional holders
One row per tracked fund, most shares held first (every row is from one quarter; reported value breaks ties). “% of value” is the fund’s share of this security’s tracked institutional value — not of shares outstanding.
| Fund | Shares | Reported value | % of value | Quarter |
|---|---|---|---|---|
| RA CAPITAL MANAGEMENT, L.P. | 9,905,045 | $436M | 20.7% | 2026-Q2 |
| TPG GP A, LLC | 6,494,962 | $286M | 13.6% | 2026-Q2 |
| VIKING GLOBAL INVESTORS LP | 3,195,181 | $141M | 6.7% | 2026-Q2 |
| Atlas Venture Life Science Advisors, LLC | 2,995,602 | $132M | 6.3% | 2026-Q2 |
| ORBIMED ADVISORS LLC trimmed | 2,555,877 | $112M | 5.3% | 2026-Q2 |
| ENAVATE SCIENCES GP, LLC | 2,478,030 | $109M | 5.2% | 2026-Q2 |
| ADAGE CAPITAL PARTNERS GP, L.L.C. added | 1,600,000 | $70M | 3.3% | 2026-Q2 |
| JPMORGAN CHASE & CO added | 1,490,508 | $64M | 3.0% | 2026-Q2 |
| BlackRock, Inc. added | 1,474,769 | $65M | 3.1% | 2026-Q2 |
| JENNISON ASSOCIATES LLC trimmed | 1,172,133 | $52M | 2.4% | 2026-Q2 |
| CITADEL ADVISORS LLC added | 1,147,636 | $50M | 2.4% | 2026-Q2 |
| VANGUARD CAPITAL MANAGEMENT LLC added | 1,132,001 | $50M | 2.4% | 2026-Q2 |
| STATE STREET CORP added | 1,021,534 | $45M | 2.1% | 2026-Q2 |
| PERCEPTIVE ADVISORS LLC added | 905,000 | $40M | 1.9% | 2026-Q2 |
| DEERFIELD MANAGEMENT COMPANY, L.P. trimmed | 680,916 | $30M | 1.4% | 2026-Q2 |
| Siren, L.L.C. added | 610,515 | $27M | 1.3% | 2026-Q2 |
| PRICE T ROWE ASSOCIATES INC /MD/ trimmed | 478,016 | $21M | 1.0% | 2026-Q2 |
| EVENTIDE ASSET MANAGEMENT, LLC trimmed | 474,981 | $21M | 1.0% | 2026-Q2 |
| GEODE CAPITAL MANAGEMENT, LLC added | 457,145 | $20M | 1.0% | 2026-Q2 |
| Casdin Capital, LLC new | 400,000 | $18M | 0.8% | 2026-Q2 |
| BAKER BROS. ADVISORS LP | 400,000 | $18M | 0.8% | 2026-Q2 |
| GOLDMAN SACHS GROUP INC added | 388,810 | $17M | 0.8% | 2026-Q2 |
| Driehaus Capital Management LLC added | 385,447 | $17M | 0.8% | 2026-Q2 |
| FRANKLIN RESOURCES INC added | 290,113 | $13M | 0.6% | 2026-Q2 |
| Aberdeen Group plc trimmed | 284,138 | $12M | 0.6% | 2026-Q2 |
| FMR LLC added | 278,292 | $12M | 0.6% | 2026-Q2 |
| MILLENNIUM MANAGEMENT LLC added | 276,733 | $12M | 0.6% | 2026-Q2 |
| Candriam S.C.A. trimmed | 233,208 | $10M | 0.5% | 2026-Q2 |
| VANGUARD PORTFOLIO MANAGEMENT LLC added | 222,949 | $10M | 0.5% | 2026-Q2 |
| Kalehua Capital Management LLC | 197,072 | $9M | 0.4% | 2026-Q2 |
| Longaeva Partners L.P. added | 196,352 | $9M | 0.4% | 2026-Q2 |
| Artisan Partners Limited Partnership new | 189,498 | $8M | 0.4% | 2026-Q2 |
| Ensign Peak Advisors, Inc trimmed | 184,532 | $8M | 0.4% | 2026-Q2 |
| Soleus Capital Management, L.P. trimmed | 177,687 | $8M | 0.4% | 2026-Q2 |
| NORTHERN TRUST CORP added | 154,476 | $7M | 0.3% | 2026-Q2 |
| MORGAN STANLEY added | 151,047 | $7M | 0.3% | 2026-Q2 |
| Sofinnova Investments, Inc. new | 144,432 | $6M | 0.3% | 2026-Q2 |
| Qube Research & Technologies Ltd added | 140,309 | $6M | 0.3% | 2026-Q2 |
| Alyeska Investment Group, L.P. | 136,222 | $6M | 0.3% | 2026-Q2 |
| GordonMD Global Investments LP | 136,000 | $6M | 0.3% | 2026-Q2 |
| CHARLES SCHWAB INVESTMENT MANAGEMENT INC added | 129,753 | $6M | 0.3% | 2026-Q2 |
| Sio Capital Management, LLC trimmed | 127,808 | $6M | 0.3% | 2026-Q2 |
| Ishara Investments LP added | 123,000 | $1M | 0.1% | 2026-Q2 |
| VANGUARD FIDUCIARY TRUST CO added | 121,442 | $5M | 0.3% | 2026-Q2 |
| Artia Global Partners LP | 119,741 | $5M | 0.3% | 2026-Q2 |
| UBS Group AG trimmed | 116,206 | $5M | 0.2% | 2026-Q2 |
| First Turn Management, LLC new | 110,493 | $5M | 0.2% | 2026-Q2 |
| CITIGROUP INC added | 110,163 | $5M | 0.2% | 2026-Q2 |
| D. E. Shaw & Co., Inc. added | 101,644 | $4M | 0.2% | 2026-Q2 |
| Rock Springs Capital Management LP | 99,429 | $4M | 0.2% | 2026-Q2 |
| Walleye Capital LLC added | 97,347 | $4M | 0.2% | 2026-Q2 |
| Rhenman & Partners Asset Management AB added | 97,100 | $4M | 0.2% | 2026-Q2 |
| BANK OF AMERICA CORP /DE/ added | 88,908 | $4M | 0.2% | 2026-Q2 |
| AMERIPRISE FINANCIAL INC added | 82,232 | $4M | 0.2% | 2026-Q2 |
| Integral Health Asset Management, LLC added | 75,000 | $3M | 0.2% | 2026-Q2 |
| SUPERSTRING CAPITAL MANAGEMENT LP trimmed | 63,156 | $3M | 0.1% | 2026-Q2 |
| STEMPOINT CAPITAL LP added | 59,426 | $3M | 0.1% | 2026-Q2 |
| DEUTSCHE BANK AG\ added | 53,353 | $2M | 0.1% | 2026-Q2 |
| SEVEN GRAND MANAGERS, LLC | 50,000 | $2M | 0.1% | 2026-Q2 |
| Point72 Asset Management, L.P. trimmed | 49,328 | $2M | 0.1% | 2026-Q2 |
| TD Asset Management Inc trimmed | 47,396 | $2M | 0.1% | 2026-Q2 |
| ALPS ADVISORS INC added | 45,525 | $2M | 0.1% | 2026-Q2 |
| SILVERARC CAPITAL MANAGEMENT, LLC added | 42,478 | $2M | 0.1% | 2026-Q2 |
| Russell Investments Group, Ltd. trimmed | 42,258 | $2M | 0.1% | 2026-Q2 |
| Bank of New York Mellon Corp added | 41,586 | $2M | 0.1% | 2026-Q2 |
| Nuveen, LLC added | 41,259 | $2M | 0.1% | 2026-Q2 |
| XTX Topco Ltd added | 38,096 | $2M | 0.1% | 2026-Q2 |
| WELLINGTON MANAGEMENT GROUP LLP trimmed | 37,365 | $2M | 0.1% | 2026-Q2 |
| MUTUAL OF AMERICA CAPITAL MANAGEMENT LLC new | 35,968 | $2M | 0.1% | 2026-Q2 |
| MANUFACTURERS LIFE INSURANCE COMPANY, THE trimmed | 35,420 | $2M | 0.1% | 2026-Q2 |
| BNP PARIBAS FINANCIAL MARKETS trimmed | 31,803 | $1M | 0.1% | 2026-Q2 |
| Swiss National Bank new | 27,000 | $1M | 0.1% | 2026-Q2 |
| Quadrature Capital Ltd new | 26,023 | $1M | 0.1% | 2026-Q2 |
| ALLIANCEBERNSTEIN L.P. added | 25,450 | $1M | 0.0% | 2026-Q2 |
| Trexquant Investment LP new | 23,810 | $1M | 0.0% | 2026-Q2 |
| NEW YORK STATE COMMON RETIREMENT FUND added | 23,586 | $1M | 0.0% | 2026-Q2 |
| TUDOR INVESTMENT CORP ET AL new | 22,575 | $993K | 0.0% | 2026-Q2 |
| RHUMBLINE ADVISERS added | 22,309 | $981K | 0.0% | 2026-Q2 |
| Maven Securities LTD trimmed | 20,000 | $880K | 0.0% | 2026-Q2 |
| LOS ANGELES CAPITAL MANAGEMENT LLC added | 18,645 | $820K | 0.0% | 2026-Q2 |
| Susquehanna Portfolio Strategies, LLC new | 18,034 | $793K | 0.0% | 2026-Q2 |
| Rafferty Asset Management, LLC trimmed | 18,004 | $792K | 0.0% | 2026-Q2 |
| Shay Capital LLC new | 18,000 | $792K | 0.0% | 2026-Q2 |
| WELLS FARGO & COMPANY/MN added | 16,821 | $740K | 0.0% | 2026-Q2 |
| Engineers Gate Manager LP new | 15,603 | $686K | 0.0% | 2026-Q2 |
| CALIFORNIA STATE TEACHERS RETIREMENT SYSTEM added | 14,852 | $653K | 0.0% | 2026-Q2 |
| KENNEDY CAPITAL MANAGEMENT LLC added | 12,621 | $555K | 0.0% | 2026-Q2 |
| MARSHALL WACE, LLP trimmed | 12,599 | $554K | 0.0% | 2026-Q2 |
| Invesco Ltd. added | 12,418 | $546K | 0.0% | 2026-Q2 |
| MetLife Investment Management, LLC added | 10,972 | $483K | 0.0% | 2026-Q2 |
| UBS AM, a distinct business unit of UBS ASSET MANAGEMENT AMERICAS LLC added | 10,622 | $467K | 0.0% | 2026-Q2 |
| MIRAE ASSET GLOBAL ETFS HOLDINGS Ltd. added | 10,582 | $463K | 0.0% | 2026-Q2 |
| Jump Financial, LLC new | 10,473 | $461K | 0.0% | 2026-Q2 |
| VANGUARD ASSET MANAGEMENT, Ltd new | 9,535 | $419K | 0.0% | 2026-Q2 |
| PROFUND ADVISORS LLC trimmed | 9,140 | $402K | 0.0% | 2026-Q2 |
| Virtus Investment Advisers, LLC added | 9,109 | $401K | 0.0% | 2026-Q2 |
| Legal & General Group Plc added | 9,044 | $398K | 0.0% | 2026-Q2 |
| Vanguard Global Advisers, LLC trimmed | 7,852 | $345K | 0.0% | 2026-Q2 |
| China Universal Asset Management Co., Ltd. trimmed | 7,186 | $316K | 0.0% | 2026-Q2 |
| Quarry LP added | 6,750 | $297K | 0.0% | 2026-Q2 |
Ownership over time
Tracked institutional holder count and total shares held by filing quarter (independent scales). The curated-era tail and any mid-ingest latest quarter are handled honestly — a partial quarter is not drawn as a collapse.
Reading this table
Funds hold the same stock for different reasons — an index fund “holds” almost everything, an active manager sizes a name to a mandate and a benchmark, and each fund entered at its own price and time. Because 13F is filed up to 45 days after quarter-end, every row is a backward-looking snapshot; a manager may have traded since. Share-class siblings (a company’s A and C shares) are rolled up to one line so a dual-class name is never double-counted. Compare like-for-like. A large holder is not an endorsement, and a fund exiting is not a warning — this is a starting question, not a verdict.
About 13F filings
A Form 13F is a quarterly disclosure that institutional investment managers with over $100 million in US-listed equities must file with the SEC. In plain English: it is a snapshot of the long stock positions a fund held at the end of a quarter. It covers long US-listed equities only — not short positions, options, cash, or private holdings — and the funds shown are the large sample we track, not the complete 13F universe.