Sutro Biopharma, Inc. (STRO) Ownership
STRO ownership summary
as of October 17, 2026- Institutions
- 99.0% of shares outstanding
- Insiders
- 2.26% of shares outstanding
- Shares outstanding
- 16.6M
- Float
- 10.8M shares available to trade
- Short interest
- 11.18% 1.8M shares short
- Days to cover
- 5.93 short interest down 11.0% vs prior month
- Institutions 99.01%
- Insiders 2.26%
STRO top institutional holders
20 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | Perceptive Advisors LLC | 7.87% | 1.3M | $14.3M | +589,539 (+82.4%) | June 30, 2026 |
| 2 | Bvf Inc | 7.55% | 1.3M | $13.7M | — | June 30, 2026 |
| 3 | Affinity Asset Advisors, LLC | 7.07% | 1.2M | $12.8M | +102,968 (+9.6%) | June 30, 2026 |
| 4 | BlackRock Inc | 6.77% | 1.1M | $12.3M | +889,971 (+382.5%) | June 30, 2026 |
| 5 | Samsara BioCapital, LLC | 6.41% | 1.1M | $11.6M | — | June 30, 2026 |
| 6 | Kynam Capital Management, LP | 5.26% | 873K | $9.5M | — | June 30, 2026 |
| 7 | Orbimed Advisors LLC | 4.49% | 744K | $8.1M | −57,200 (−7.1%) | June 30, 2026 |
| 8 | Balyasny Asset Management LLC | 4.29% | 711K | $7.8M | +245,370 (+52.7%) | June 30, 2026 |
| 9 | Vanguard Capital Management, LLC | 4.19% | 694K | $7.6M | −26,223 (−3.6%) | June 30, 2026 |
| 10 | Eventide Asset Management, LLC | 3.53% | 585K | $6.4M | −130,045 (−18.2%) | June 30, 2026 |
| 11 | Velan Capital Investment Management LP | 3.09% | 512K | $5.6M | — | June 30, 2026 |
| 12 | Woodline Partners LP | 2.76% | 458K | $5.0M | +588 (+0.1%) | June 30, 2026 |
| 13 | ADAR1 Capital Management LLC | 2.44% | 404K | $4.4M | −120,427 (−23.0%) | June 30, 2026 |
| 14 | Geode Capital Management, LLC | 2.35% | 390K | $4.3M | +218,306 (+127.4%) | June 30, 2026 |
| 15 | Acadian Asset Management LLC | 2.25% | 374K | $4.1M | +38,026 (+11.3%) | June 30, 2026 |
| 16 | Millennium Management LLC | 2.21% | 366K | $4.0M | +155,594 (+74.0%) | June 30, 2026 |
| 17 | State Street Corp | 1.85% | 306K | $3.3M | +253,861 (+487.1%) | June 30, 2026 |
| 18 | Merck & Co Inc | 1.64% | 272K | $3.0M | — | June 30, 2026 |
| 19 | Longwood Capital Partners LLC | 1.63% | 270K | $3.0M | +826 (+0.3%) | June 30, 2026 |
| 20 | Ameriprise Financial Inc | 1.48% | 245K | $2.7M | +244,669 (0.0%) | June 30, 2026 |
Value at the latest close. Change = shares bought or sold in the latest quarterly filing (13F). In the top 20, 11 holders added 2.7M shares and 4 cut 334K.
STRO top mutual fund and ETF holders
20 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | Eventide Healthcare & Life Sciences I | 3.53% | 585K | $6.4M | −130,045 (−18.2%) | June 30, 2026 |
| 2 | Vanguard MStar Total Stk Mkt Idx Invest | 3.02% | 502K | $5.5M | — | August 31, 2026 |
| 3 | iShares Russell 2000 ETF | 2.29% | 380K | $4.2M | −4,352 (−1.1%) | September 30, 2026 |
| 4 | Fidelity Small Cap Index | 1.05% | 174K | $1.9M | +1,206 (+0.7%) | July 31, 2026 |
| 5 | Fidelity Enhanced Small Cap Core ETF | 0.94% | 157K | $1.7M | +327 (+0.2%) | September 30, 2026 |
| 6 | Nuveen Quant Small Cap Equity R6 | 0.76% | 126K | $1.4M | — | August 31, 2026 |
| 7 | iShares Russell 2000 Value ETF | 0.69% | 115K | $1.3M | +174 (+0.2%) | September 30, 2026 |
| 8 | Vanguard Russell 2000 ETF | 0.55% | 92K | $1.0M | +2,190 (+2.4%) | August 31, 2026 |
| 9 | Goldman Sachs Small Cap Eq Insghts Instl | 0.47% | 77K | $844,513 | +77,195 (0.0%) | July 31, 2026 |
| 10 | GS US Sm Cp CORE Eq Base Inc USD Snap | 0.41% | 68K | $743,187 | +55,278 (+436.8%) | July 31, 2026 |
| 11 | Goldman Sachs Small Cp Val Insghts Instl | 0.40% | 67K | $727,838 | +66,530 (0.0%) | July 31, 2026 |
| 12 | JPMorgan US Small Company L | 0.37% | 62K | $674,692 | +1,595 (+2.7%) | August 31, 2026 |
| 13 | Fidelity Extended Market Index | 0.36% | 59K | $644,661 | −16,192 (−21.6%) | August 31, 2026 |
| 14 | Vanguard Health Care ETF | 0.27% | 46K | $498,569 | −2,142 (−4.5%) | August 31, 2026 |
| 15 | iShares Micro-Cap ETF | 0.27% | 45K | $496,424 | −313 (−0.7%) | September 30, 2026 |
| 16 | Canada Life US Small-Mid Cap Growth F | 0.25% | 42K | $458,638 | +34,827 (+490.8%) | July 31, 2026 |
| 17 | Schwab Small Cap Index | 0.23% | 39K | $423,783 | — | August 31, 2026 |
| 18 | Mackenzie GQE US Small Cap F8 | 0.20% | 33K | $363,066 | +9,765 (+41.7%) | July 31, 2026 |
| 19 | iShares Russell 2000 Small-Cap Idx Instl | 0.18% | 30K | $326,187 | — | August 31, 2026 |
| 20 | iShares Core S&P Total US Stock Mkt ETF | 0.18% | 29K | $322,391 | +30 (+0.1%) | September 30, 2026 |
Funds report holdings monthly or quarterly; dates differ by fund.
STRO insider transactions
latest 5| Date | Name | Transaction | Price | Shares | Value |
|---|---|---|---|---|---|
| 2025-10-15 | Connie Matsui | Buy | $8.00 | 5,000 | $40,000 |
| 2025-10-15 | David Pauling | Buy | $8.00 | 1,250 | $10,000 |
| 2025-10-15 | Gregory K Chow | Buy | $8.10 | 1,975 | $15,998 |
| 2025-10-15 | Hans-Peter Gerber | Buy | $8.00 | 1,700 | $13,600 |
| 2025-10-15 | Jane Chung | Buy | $8.00 | 1,250 | $10,000 |
Reported trades by company officers, directors and other filers (including disclosures by members of Congress where EODHD lists them). "—" where the filing gives no share count.
STRO shares outstanding
Year-end shares outstanding, adjusted for splits.
Who owns STRO
Institutional investors own 99.0% of Sutro Biopharma's shares and insiders 2.26%. The largest holder is Perceptive Advisors LLC with 7.87% of the shares (1.3M), as of June 30, 2026. Among the top 20 institutions, 11 added shares and 4 reduced their stake in the latest filings. Short interest is 11.18% of the float, or 5.93 days of average trading volume. The share count rose 1,126.9% since 2017.
Related: STRO analyst forecast, STRO key metrics. See the STRO stock overview for the latest quote and news.
STRO ownership FAQ
Who owns the most Sutro Biopharma stock?
The largest shareholders of Sutro Biopharma are Perceptive Advisors LLC (7.87%), Bvf Inc (7.55%), Affinity Asset Advisors, LLC (7.07%), BlackRock Inc (6.77%), Samsara BioCapital, LLC (6.41%).
What percentage of Sutro Biopharma is owned by institutions?
Institutions hold 99.0% of Sutro Biopharma's shares outstanding; insiders hold 2.26%.
Which funds own Sutro Biopharma?
The largest fund holders of Sutro Biopharma are Eventide Healthcare & Life Sciences I (3.53%), Vanguard MStar Total Stk Mkt Idx Invest (3.02%), iShares Russell 2000 ETF (2.29%), Fidelity Small Cap Index (1.05%), Fidelity Enhanced Small Cap Core ETF (0.94%).
What is Sutro Biopharma's short interest?
1.8M shares of Sutro Biopharma were sold short, 11.18% of the float; at the average daily volume it would take 5.93 days to cover.
Are insiders buying or selling Sutro Biopharma?
Of the latest 5 reported insider transactions in Sutro Biopharma (since October 15, 2025), 5 were purchases and 0 were sales.
How many shares of Sutro Biopharma are outstanding?
Sutro Biopharma has 16.6M shares outstanding, of which 10.8M are in the public float.