Ironwood Pharmaceuticals, Inc. (IRWD) Ownership
IRWD ownership summary
as of October 18, 2026- Institutions
- 99.1% of shares outstanding
- Insiders
- 3.24% of shares outstanding
- Shares outstanding
- 165.2M
- Float
- 136.8M shares available to trade
- Short interest
- 10.29% 15.6M shares short
- Days to cover
- 7.79 short interest down 16.9% vs prior month
- Institutions 99.08%
- Insiders 3.24%
IRWD top institutional holders
20 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | BlackRock Inc | 10.77% | 17.8M | $62.3M | +4.4M (+33.1%) | June 30, 2026 |
| 2 | Armistice Capital, LLC | 8.43% | 13.9M | $48.8M | −1.1M (−7.3%) | June 30, 2026 |
| 3 | Sarissa Capital Management LP | 5.56% | 9.2M | $32.2M | — | June 30, 2026 |
| 4 | State Street Corp | 5.33% | 8.8M | $30.8M | +1.4M (+18.1%) | June 30, 2026 |
| 5 | Bank of America Corp | 5.26% | 8.7M | $30.4M | +896 (+0.0%) | June 30, 2026 |
| 6 | Renaissance Technologies Corp | 4.84% | 8.0M | $28.0M | −67,847 (−0.8%) | June 30, 2026 |
| 7 | Vanguard Capital Management, LLC | 4.00% | 6.6M | $23.1M | +511,054 (+8.4%) | June 30, 2026 |
| 8 | AQR Capital Management LLC | 3.91% | 6.5M | $22.6M | −1.1M (−14.2%) | June 30, 2026 |
| 9 | Acadian Asset Management LLC | 3.54% | 5.9M | $20.5M | −723,941 (−11.0%) | June 30, 2026 |
| 10 | Vanguard Portfolio Management, LLC | 3.34% | 5.5M | $19.3M | −1.2M (−17.5%) | June 30, 2026 |
| 11 | Geode Capital Management, LLC | 2.92% | 4.8M | $16.9M | +288,135 (+6.3%) | June 30, 2026 |
| 12 | Two Sigma Investments LLC | 2.76% | 4.6M | $15.9M | −1.3M (−22.1%) | June 30, 2026 |
| 13 | Marshall Wace Asset Management Ltd | 2.60% | 4.3M | $15.0M | −234,971 (−5.2%) | June 30, 2026 |
| 14 | Jacobs Levy Equity Management, Inc. | 2.46% | 4.1M | $14.2M | +433,487 (+11.9%) | June 30, 2026 |
| 15 | The Goldman Sachs Group Inc | 2.01% | 3.3M | $11.6M | +623,174 (+23.2%) | June 30, 2026 |
| 16 | Charles Schwab Investment Management Inc | 2.00% | 3.3M | $11.6M | −1.4M (−30.3%) | June 30, 2026 |
| 17 | Federated Hermes Inc | 1.96% | 3.2M | $11.3M | −117,568 (−3.5%) | June 30, 2026 |
| 18 | Arrowstreet Capital Limited Partnership | 1.83% | 3.0M | $10.6M | −380,153 (−11.2%) | June 30, 2026 |
| 19 | Dimensional Fund Advisors, Inc. | 1.53% | 2.5M | $8.8M | +440,836 (+21.2%) | June 30, 2026 |
| 20 | Mackenzie Investments | 1.43% | 2.4M | $8.3M | +1.8M (+322.7%) | June 30, 2026 |
Value at the latest close. Change = shares bought or sold in the latest quarterly filing (13F). In the top 20, 9 holders added 9.9M shares and 10 cut 7.6M.
IRWD top mutual fund and ETF holders
20 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | Vanguard MStar Total Stk Mkt Idx Invest | 2.89% | 4.8M | $16.7M | — | August 31, 2026 |
| 2 | iShares Russell 2000 ETF | 2.57% | 4.3M | $14.9M | −49,024 (−1.1%) | September 30, 2026 |
| 3 | State Street® SPDR® S&P® Biotech ETF | 2.02% | 3.3M | $11.7M | −63,900 (−1.9%) | September 30, 2026 |
| 4 | Fidelity Small Cap Index | 1.08% | 1.8M | $6.3M | +15,969 (+0.9%) | July 31, 2026 |
| 5 | Vanguard Strategic Equity Inv | 1.06% | 1.8M | $6.1M | −350,742 (−16.7%) | June 30, 2026 |
| 6 | iShares Russell 2000 Growth ETF | 0.88% | 1.5M | $5.1M | −1,848 (−0.1%) | September 30, 2026 |
| 7 | Vanguard Explorer Inv | 0.85% | 1.4M | $4.9M | −228,342 (−14.0%) | June 30, 2026 |
| 8 | Pacer US Small Cap Cash Cows 100 ETF | 0.81% | 1.3M | $4.7M | +3,009 (+0.2%) | September 30, 2026 |
| 9 | Federated Hermes MDT Small Cap Core IS | 0.78% | 1.3M | $4.5M | — | June 30, 2026 |
| 10 | iShares Biotechnology ETF | 0.76% | 1.3M | $4.4M | −9,536 (−0.8%) | September 30, 2026 |
| 11 | Fidelity Enhanced Small Cap Core ETF | 0.65% | 1.1M | $3.8M | +2,268 (+0.2%) | September 30, 2026 |
| 12 | BlackRock Advantage Small Cap Core Instl | 0.65% | 1.1M | $3.8M | — | August 31, 2026 |
| 13 | Xtrackers S&P 500 Swap ETF 1C | 0.60% | 988K | $3.5M | −7,290 (−0.7%) | December 31, 2025 |
| 14 | Canada Life US Small-Mid Cap Growth F | 0.59% | 978K | $3.4M | −110,381 (−10.1%) | July 31, 2026 |
| 15 | Vanguard Russell 2000 ETF | 0.57% | 940K | $3.3M | +21,040 (+2.3%) | August 31, 2026 |
| 16 | Schwab Fundamental U.S. Small CompanyETF | 0.54% | 892K | $3.1M | +1,267 (+0.1%) | September 30, 2026 |
| 17 | Bridge Builder Small/Mid Cap Value | 0.53% | 882K | $3.1M | +876,893 (+16,582.7%) | September 30, 2026 |
| 18 | Schwab US Small-Cap ETF™ | 0.49% | 811K | $2.8M | +540 (+0.1%) | September 30, 2026 |
| 19 | Federated Hermes MDT Small Cap Growth IS | 0.44% | 732K | $2.6M | +3,912 (+0.5%) | June 30, 2026 |
| 20 | Fidelity Extended Market Index | 0.42% | 698K | $2.4M | +70,443 (+11.2%) | August 31, 2026 |
Funds report holdings monthly or quarterly; dates differ by fund.
IRWD insider transactions
latest 1| Date | Name | Transaction | Price | Shares | Value |
|---|---|---|---|---|---|
| 2026-03-17 | Alexander J Denner | Sell | $3.05 | 6,730,800 | $20.5M |
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.
IRWD shares outstanding
Year-end shares outstanding, adjusted for splits.
Who owns IRWD
Institutional investors own 99.1% of Ironwood Pharmaceuticals's shares and insiders 3.24%. The largest holder is BlackRock Inc with 10.77% of the shares (17.8M), as of June 30, 2026. Among the top 20 institutions, 9 added shares and 10 reduced their stake in the latest filings. Short interest is 10.29% of the float, or 7.79 days of average trading volume. The share count rose 27.1% since 2014.
Related: IRWD analyst forecast, IRWD key metrics. See the IRWD stock overview for the latest quote and news.
IRWD ownership FAQ
Who owns the most Ironwood Pharmaceuticals stock?
The largest shareholders of Ironwood Pharmaceuticals are BlackRock Inc (10.77%), Armistice Capital, LLC (8.43%), Sarissa Capital Management LP (5.56%), State Street Corp (5.33%), Bank of America Corp (5.26%).
What percentage of Ironwood Pharmaceuticals is owned by institutions?
Institutions hold 99.1% of Ironwood Pharmaceuticals's shares outstanding; insiders hold 3.24%.
Which funds own Ironwood Pharmaceuticals?
The largest fund holders of Ironwood Pharmaceuticals are Vanguard MStar Total Stk Mkt Idx Invest (2.89%), iShares Russell 2000 ETF (2.57%), State Street® SPDR® S&P® Biotech ETF (2.02%), Fidelity Small Cap Index (1.08%), Vanguard Strategic Equity Inv (1.06%).
What is Ironwood Pharmaceuticals's short interest?
15.6M shares of Ironwood Pharmaceuticals were sold short, 10.29% of the float; at the average daily volume it would take 7.79 days to cover.
Are insiders buying or selling Ironwood Pharmaceuticals?
Of the latest 1 reported insider transactions in Ironwood Pharmaceuticals (since March 17, 2026), 0 were purchases and 1 were sales.
How many shares of Ironwood Pharmaceuticals are outstanding?
Ironwood Pharmaceuticals has 165.2M shares outstanding, of which 136.8M are in the public float.