Sionna Therapeutics, Inc.
Sionna Therapeutics, Inc. (SION) Stock Ownership
Institutional vs insider vs public ownership from 13F and float data — top holders, activity, and insider trades below.
SEC 13F · FMP · SION · as of Sep 30, 2025
Ownership Breakdown
78
Institutional Holders
▲ 13 vs Q2
$1.26B
Total Inst. Value
▲ $506.11M vs Q2
45.15M
Shares Outstanding
freeFloat 58.35%
42.84M
13F Shares Held
▼ 607,830 vs Q2
Institutional ownership = 13F shares ÷ total outstanding. Insider % = 100 − free float. Public % = free float − institution %. Data: FMP /symbol-positions-summary + /shares-float + SEC EDGAR.
Top Institutional Holders
SION largest shareholders · institutional ownership
Q3 2025 · SEC 13F
Showing top 10 holders
| Holder | Shares | % Owned | Weight | Value | Reported | Change |
|---|---|---|---|---|---|---|
RA CAPITAL MANAGEMENT, L.P. pharmaceutical preparations | 10.45M | 23.68% | 23.68% | $307.20B | Nov 14, 2025 | — held |
TPG GP A, LLC pharmaceutical preparations | 6.74M | 15.29% | 15.29% | $198.37B | Nov 14, 2025 | — held |
ORBIMED ADVISORS LLC pharmaceutical preparations | 3.70M | 8.40% | 8.40% | $108.96B | Nov 14, 2025 | — held |
ATLAS VENTURE LIFE SCIENCE ADVISORS, LLC pharmaceutical preparations | 3.62M | 8.20% | 8.20% | $106.33B | Nov 13, 2025 | ▼ 78.5K |
VIKING GLOBAL INVESTORS LP pharmaceutical preparations | 3.20M | 7.24% | 7.24% | $93.97B | Nov 14, 2025 | — held |
ENAVATE SCIENCES GP, LLC pharmaceutical preparations | 2.48M | 5.62% | 5.62% | $72.88B | Nov 14, 2025 | — held |
JPMORGAN CHASE & CO pharmaceutical preparations | 1.98M | 4.49% | 4.49% | $58.19B | Nov 26, 2025 | ▼ 242.6K |
PERCEPTIVE ADVISORS LLC pharmaceutical preparations | 1.18M | 2.67% | 2.67% | $34.68B | Nov 14, 2025 | ▼ 36.9K |
VANGUARD GROUP INC pharmaceutical preparations | 1.14M | 2.59% | 2.59% | $33.62B | Nov 7, 2025 | ▲ 512.8K |
JENNISON ASSOCIATES LLC pharmaceutical preparations | 997.4K | 2.26% | 2.26% | $29.33B | Oct 30, 2025 | ▲ 244.6K |
Data from SEC Form 13F filings. Ownership bar normalised to largest holder. Change flags: isNew / isSoldOut / changeInSharesNumber (FMP extract-analytics/holder).
Institutional Activity
Q3 2025 vs prior quarter
Q3 2025
15
Increased
+1.47M shares3
New Positions
first time holders16
Decreased
−1.94M shares0
Sold Out
fully exitedNet shares change (top 50)
478.9K
+1.47M / −1.94M
Net new holders
+2
3 new / 0 exited
Based on top 50 institutional holders by position size. Fields: isNew, isSoldOut, changeInSharesNumber (FMP extract-analytics/holder, limit=50).
Insider Buying vs Selling
SION insider trading · insider activity
Source: SEC Form 4
Insiders have been primarily selling shares recently. Selling may be driven by pre-scheduled Rule 10b5-1 plans rather than negative sentiment.
0
Buy transactions
18
Sell transactions
0.00
Buy/Sell ratio
$2M
Total disposed
Recent Insider Transactions
Showing 10 most recent · Common Stock only
| Name · Role | Date | Type | Shares | Price | Value | After Trans. | Filing |
|---|---|---|---|---|---|---|---|
Thompson Peter A. director | May 27, 2026 | Sale | 101 | $44.49 | $4.5K | 2.67M | Form 4 ↗ |
ORBIMED ADVISORS LLC director | May 27, 2026 | Sale | 101 | $44.49 | $4.5K | 2.67M | Form 4 ↗ |
Thompson Peter A. director | May 7, 2026 | Sale | 48,546 | $44.61 | $2.17M | 2.92M | Form 4 ↗ |
Thompson Peter A. director | May 8, 2026 | Sale | 59,767 | $44.58 | $2.66M | 2.86M | Form 4 ↗ |
Thompson Peter A. director | May 11, 2026 | Sale | 184,639 | $46.22 | $8.53M | 2.67M | Form 4 ↗ |
ORBIMED ADVISORS LLC director | May 7, 2026 | Sale | 48,546 | $44.61 | $2.17M | 2.92M | Form 4 ↗ |
ORBIMED ADVISORS LLC director | May 8, 2026 | Sale | 59,767 | $44.58 | $2.66M | 2.86M | Form 4 ↗ |
ORBIMED ADVISORS LLC director | May 11, 2026 | Sale | 184,639 | $46.22 | $8.53M | 2.67M | Form 4 ↗ |
Thompson Peter A. director | Apr 17, 2026 | Sale | 52,397 | $44.68 | $2.34M | 2.97M | Form 4 ↗ |
Thompson Peter A. director | Apr 18, 2026 | Sale | 2,948 | $44.52 | $131.2K | 2.96M | Form 4 ↗ |
Source: /insider-trading/search (FMP stable). Buy/Sell direction: acquisitionOrDisposition A=Buy, D=Sell. RSU vesting (M-Exempt) excluded from sentiment bar. All data from SEC EDGAR public filings.
About institutional & insider ownership
Sionna Therapeutics, Inc. (SION) is primarily owned by institutional investors, who hold approximately 94.9% of total shares outstanding. Company insiders own approximately 41.65%, while retail and public investors account for the remaining 0.00%.
The largest institutional shareholder of Sionna Therapeutics, Inc. is RA CAPITAL MANAGEMENT, L.P., holding approximately 10.45 million shares — equal to 23.68% of outstanding shares — as of September 30, 2025.
A total of 78 institutional investors currently hold SION stock, with a combined institutional value of approximately $1.26 billion as of the most recent 13F filing period.
Frequently asked questions
SION ownershipSionna Therapeutics, Inc. (SION) is primarily owned by institutional investors, who hold approximately 94.9% of shares. The largest shareholder is RA CAPITAL MANAGEMENT, L.P. with a 23.68% stake. Company insiders hold 41.65%. Data sourced from SEC Form 13F as of September 30, 2025.