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Ironwood Pharmaceuticals IRWD

US equityMarket cap rank #3604Drug Manufacturers - Specialty & Generic

$3.75 +$0.12 (+3.31%)

Pre-market · Oct 8, 9:00 am ET · After hours $3.54 -5.59%

Open$3.58

Prev close$3.63

Day range$3.54 – $3.87

Volume2.05M

Market cap$619.65M

P/E (TTM)4.7

Dividend yield–

Ownership & positioning

Who holds it, who is betting against it, and where the big money is moving

Institutional ownership99.0%-1.17 pts vs. prior quarter

Institutions holding260+0 vs. prior quarter

Insider trades (recent)29 buys / 21 sellsNet buying

Short interest11.33% of floatDays to cover 13.1 · as of 15 Sep 2026

Short-sale volume share18.1%5-day average of daily volume

Short-sale volume as % of daily volume

Large-order net flow, last 20 sessions

Net of large-order buying minus selling, in USD. Over this window: −$1.09M (8 inflow days, 12 outflow days).

Net flow by order size, last 20 sessions

Super/Big orders approximate institutional-size trades; Mid/Small approximate retail-size trades. Net buy minus sell value in each bucket, summed over the window.

The five largest holders on file together own 35.3% of shares outstanding.

Largest holders

BlackRock10.77%
Armistice Capital LLC8.43%
Sarissa Capital Management LP5.56%
State Street Global Advisors5.33%
Bank of America Corporation5.26%
Renaissance Technologies Corp.4.84%
Vanguard Capital Management, LLC4.63%
AQR Capital Management3.81%

By investor type

Mutual Fund58.67%
Hedge Fund29.20%
Public Company8.71%
Individual/Insider3.24%
Private Company0.83%
Government Pension Fund0.74%
Bank/Investment Bank0.31%
Family Office/Trust0.23%

Reported short interest has risen from 9.86% to 11.33% of float over the last 6 biweekly reports (30 Jun 2026 to 15 Sep 2026).

Recent institutional activity

Holder	Type	Period	Share change	New stake
Nuveen Asset Management LLC	Insurance Company	2026/Q3	+313,518	0.2%
BlackRock	Mutual Fund	2026/Q3	+4,425,627	10.8%
Mackenzie Financial Corporation	Mutual Fund	2026/Q3	+1,807,459	1.4%
State Street Global Advisors	Mutual Fund	2026/Q3	+1,352,657	5.3%
Wells Fargo & Company	Public Company	2026/Q3	+1,147,348	0.7%
Morgan Stanley	Public Company	2026/Q3	+1,039,251	0.9%
Goldman Sachs Asset Management, L.P.	Mutual Fund	2026/Q3	+619,531	0.8%
Hudson River Trading LLC	Private Company	2026/Q3	+577,337	0.3%
Vanguard Capital Management, LLC	Mutual Fund	2026/Q3	+562,759	4.6%
Dimensional Fund Advisors	Mutual Fund	2026/Q3	+440,836	1.5%
Jacobs Levy Equity Management Inc	Mutual Fund	2026/Q3	+433,487	2.5%
Citadel Advisors LLC	Hedge Fund	2026/Q3	+384,127	0.3%
Voya Investment Management LLC	Mutual Fund	2026/Q3	+338,631	0.3%
O'Shaughnessy Asset Management, LLC	Mutual Fund	2026/Q3	+310,668	0.3%
CWA Asset Management Group, LLC	Mutual Fund	2026/Q3	+290,366	0.2%

Institutional buy/sell activity by reporting period, largest moves first.

Insider transactions

Date	Insider	Title	Transaction	Shares	Price	Held after
23 Sep 2026	Michael Shetzline	Chief Medical Officer, Senior VP and Head of Research & Drug Development	Intent to Sell (Form 144)	-83,306	$4.53	–
14 Sep 2026	Alexander Denner	Independent Director	Other Acquisition	+3,694	–	327,549
19 Jul 2026	Jeffrey Silber	Chief Medical Officer, Head of Research & Drug Development	Other Acquisition	+137,036	–	137,036
6 Jul 2026	Ronald Silver	Corporate Controller & Principal Accounting Officer	Automatic Disposition	-127,890	$4.52	2,235
15 Jun 2026	Jay Shepard	Director	Other Acquisition	+63,481	–	235,036
15 Jun 2026	Mark Currie	Director	Other Acquisition	+63,481	–	676,900
15 Jun 2026	Catherine Moukheibir	Independent Director	Other Acquisition	+63,481	–	181,425
15 Jun 2026	Julie McHugh	Executive Chairperson	Other Acquisition	+63,481	–	250,749
15 Jun 2026	Julie McHugh	Executive Chairperson	Automatic Disposition	-21,571	$3.73	250,749
15 Jun 2026	Marla Kessler	Independent Director	Other Acquisition	+63,481	–	229,364
15 Jun 2026	Jon Duane	Independent Director	Other Acquisition	+63,481	–	253,820
15 Jun 2026	Alexander Denner	Independent Director	Other Acquisition	+67,546	–	323,855
18 May 2026	Ronald Silver	Corporate Controller & Principal Accounting Officer	Other Acquisition	+25,000	–	311,445
16 Mar 2026	Sarissa Capital Management LP		Open Market Disposition	-6,730,800	$3.31	9,188,635
12 Mar 2026	Alexander Denner	Independent Director	Other Acquisition	+4,451	–	256,309
9 Mar 2026	Thomas McCourt	Chief Executive Officer	Other Acquisition	+409,836	–	1,038,128
9 Mar 2026	Michael Shetzline	Chief Medical Officer, Senior VP and Head of Research & Drug Development	Other Acquisition	+136,612	–	281,293
9 Mar 2026	Ronald Silver	Corporate Controller & Principal Accounting Officer	Other Acquisition	+163,934	–	286,445
9 Mar 2026	John Minardo	Chief Legal Officer	Other Acquisition	+136,612	–	271,868
9 Mar 2026	Gregory Martini	Vice President of Strategic Finance & Investor Relations	Other Acquisition	+136,612	–	219,945

From Form 4/Form 144 filings. Negative share counts are disposals (sales, gifts, or shares withheld for taxes); positive are acquisitions.

Short interest, by report

Report date	Shares short	% of float	Days to cover
15 Sep 2026	18,728,986	11.3%	13.1
31 Aug 2026	17,654,677	10.7%	11.9
14 Aug 2026	18,066,382	10.9%	6.4
31 Jul 2026	16,542,403	10.0%	10.0
15 Jul 2026	17,191,892	10.4%	6.3
30 Jun 2026	16,230,028	9.9%	5.7

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