On this page, we present all of the funds holding IRON from our database of 13F filers, detailed in the table below. The first column indicates the name of each of the funds holding IRON, with a link to that fund's top holdings. The next columns indicate the amount of IRON stock held by each of the funds holding IRON, followed by the IRON position size held by the fund, and lastly the date of the quarterly filing period the data represents. In total, we count 120 funds holding IRON within the last two filing periods in our coverage universe of 13F filers, with the largest position size having been reported by Atlas Venture Life Science Advisors LLC. For more details on the positions held by Atlas Venture Life Science Advisors LLC (or by any of the other funds holding IRON), click the fund name in the "Holder" column of the funds-holding-IRON table below.

Holder	Amount	Position Size ($ in 1000's)	As of
Atlas Venture Life Science Advisors LLC	2,555,172	$147,587	12/31/2023
IRON	2,555,172	$147,587	12/31/2023
Paradigm Biocapital Advisors LP	2,385,857	$137,807	12/31/2023
IRON	2,385,857	$137,807	12/31/2023
Orbimed Advisors LLC	1,702,237	$98,321	12/31/2023
IRON	1,702,237	$98,321	12/31/2023
Bain Capital Life Sciences Investors LLC	1,332,545	$76,968	12/31/2023
IRON	1,332,545	$76,968	12/31/2023
Perceptive Advisors LLC	1,023,045	$59,091	12/31/2023
IRON	1,023,045	$59,091	12/31/2023
BlackRock Inc.	868,440	$50,161	12/31/2023
IRON	868,440	$50,161	12/31/2023
Frazier Life Sciences Management L.P.	785,000	$45,342	12/31/2023
IRON	785,000	$45,342	12/31/2023
Vanguard Group Inc.	764,544	$44,160	12/31/2023
IRON	764,544	$44,160	12/31/2023
Adage Capital Partners GP L.L.C.	750,000	$43,320	12/31/2023
IRON	750,000	$43,320	12/31/2023
Price T Rowe Associates Inc. MD	590,831	$34,127	12/31/2023
IRON	590,831	$34,127	12/31/2023
State Street Corp	559,195	$32,299	12/31/2023
IRON	559,195	$32,299	12/31/2023
Polar Capital Holdings Plc	546,915	$31,590	12/31/2023
IRON	546,915	$31,590	12/31/2023
Deerfield Management Company L.P. Series C	464,292	$26,818	12/31/2023
IRON	464,292	$26,818	12/31/2023
Janus Henderson Group PLC	443,178	$25,600	12/31/2023
IRON	443,178	$25,600	12/31/2023
Rock Springs Capital Management LP	363,468	$20,994	12/31/2023
IRON	363,468	$20,994	12/31/2023
Alliancebernstein L.P.	363,085	$20,972	12/31/2023
IRON	363,085	$20,972	12/31/2023
5AM Venture Management LLC	294,221	$16,994	12/31/2023
IRON	294,221	$16,994	12/31/2023
Foresite Capital Management V LLC	243,513	$14,065	12/31/2023
IRON	243,513	$14,065	12/31/2023
Geode Capital Management LLC	229,419	$13,253	12/31/2023
IRON	229,419	$13,253	12/31/2023
Franklin Resources Inc.	221,424	$12,789	12/31/2023
IRON	221,424	$12,789	12/31/2023
FMR LLC	217,412	$12,558	12/31/2023
IRON	217,412	$12,558	12/31/2023
Citadel Advisors LLC		$11,668	12/31/2023
IRON	187,924	$10,854	12/31/2023
Call	16,100	$930	12/31/2023
Put	2,000	$116	12/31/2023
Pictet Asset Management Holding SA	195,091	$11,268	12/31/2023
IRON	195,091	$11,268	12/31/2023
Ikarian Capital LLC	194,982	$11,262	12/31/2023
IRON	194,982	$11,262	12/31/2023
Victory Capital Management Inc.	187,580	$10,835	12/31/2023
IRON	187,580	$10,835	12/31/2023
Wellington Management Group LLP	177,726	$10,265	12/31/2023
IRON	177,726	$10,265	12/31/2023
First Turn Management LLC	157,274	$9,084	12/31/2023
IRON	157,274	$9,084	12/31/2023
Blue Owl Capital Holdings LP	140,260	$8,101	12/31/2023
IRON	140,260	$8,101	12/31/2023
StemPoint Capital LP		$7,616	12/31/2023
IRON	125,429	$7,245	12/31/2023
Call	1,000	$371	12/31/2023
Cormorant Asset Management LP	125,000	$7,220	12/31/2023
IRON	125,000	$7,220	12/31/2023
Acuta Capital Partners LLC	115,500	$6,671	12/31/2023
IRON	115,500	$6,671	12/31/2023
Invesco Ltd.	114,068	$6,589	12/31/2023
IRON	114,068	$6,589	12/31/2023
Morgan Stanley	112,387	$6,491	12/31/2023
IRON	112,387	$6,491	12/31/2023
Northern Trust Corp	95,259	$5,502	12/31/2023
IRON	95,259	$5,502	12/31/2023
Parkman Healthcare Partners LLC	92,871	$5,364	12/31/2023
IRON	92,871	$5,364	12/31/2023
Charles Schwab Investment Management Inc.	89,725	$5,183	12/31/2023
IRON	89,725	$5,183	12/31/2023
Candriam Luxembourg S.C.A.	80,000	$4,621	12/31/2023
IRON	80,000	$4,621	12/31/2023
Saturn V Capital Management LLC	64,784	$3,742	12/31/2023
IRON	64,784	$3,742	12/31/2023
Goldman Sachs Group Inc.	62,175	$3,591	12/31/2023
IRON	62,175	$3,591	12/31/2023
Hudson Bay Capital Management LP	62,000	$3,581	12/31/2023
IRON	62,000	$3,581	12/31/2023
Schroder Investment Management Group	58,260	$3,365	12/31/2023
IRON	58,260	$3,365	12/31/2023
Susquehanna International Group LLP		$3,292	12/31/2023
Call	50,100	$2,894	12/31/2023
IRON	6,882	$398	12/31/2023
JPMorgan Chase & Co.		$3,236	12/31/2023
Call	40,000	$2,310	12/31/2023
IRON	16,029	$926	12/31/2023
EAM Investors LLC	52,895	$3,055	12/31/2023
IRON	52,895	$3,055	12/31/2023
Qube Research & Technologies Ltd	50,711	$2,929	12/31/2023
IRON	50,711	$2,929	12/31/2023
MPM Oncology Impact Management LP	50,000	$2,888	12/31/2023
IRON	50,000	$2,888	12/31/2023
Renaissance Technologies LLC	48,280	$2,789	12/31/2023
IRON	48,280	$2,789	12/31/2023
Boothbay Fund Management LLC	43,150	$2,492	12/31/2023
IRON	43,150	$2,492	12/31/2023
Jennison Associates LLC	43,031	$2,485	12/31/2023
IRON	43,031	$2,485	12/31/2023
Nicholas Investment Partners LP	40,494	$2,339	12/31/2023
IRON	40,494	$2,339	12/31/2023
Ensign Peak Advisors Inc	40,000	$2,310	12/31/2023
IRON	40,000	$2,310	12/31/2023
Rafferty Asset Management LLC	39,863	$2,302	12/31/2023
IRON	39,863	$2,302	12/31/2023
Nuveen Asset Management LLC	33,932	$1,960	12/31/2023
IRON	33,932	$1,960	12/31/2023
Bank of America Corp DE	31,960	$1,846	12/31/2023
IRON	31,960	$1,846	12/31/2023
Bank of New York Mellon Corp	26,956	$1,678	03/31/2024
IRON	26,956	$1,678	03/31/2024
Barclays PLC	28,464	$1,643	12/31/2023
IRON	28,464	$1,643	12/31/2023
Jane Street Group LLC		$1,464	12/31/2023
IRON	20,845	$1,204	12/31/2023
Call	4,500	$260	12/31/2023
Connor Clark & Lunn Investment Management Ltd.	25,057	$1,447	12/31/2023
IRON	25,057	$1,447	12/31/2023
Two Sigma Investments LP	23,094	$1,334	12/31/2023
IRON	23,094	$1,334	12/31/2023
Schonfeld Strategic Advisors LLC	22,346	$1,291	12/31/2023
IRON	22,346	$1,291	12/31/2023
Millennium Management LLC	20,697	$1,195	12/31/2023
IRON	20,697	$1,195	12/31/2023
TD Asset Management Inc.	20,214	$1,168	12/31/2023
IRON	20,214	$1,168	12/31/2023
The Manufacturers Life Insurance Company	18,889	$1,091	12/31/2023
IRON	18,889	$1,091	12/31/2023
HRT Financial LP	16,870	$974	12/31/2023
IRON	16,870	$974	12/31/2023
Citigroup Inc.	16,681	$963	12/31/2023
IRON	16,681	$963	12/31/2023
Alps Advisors Inc.	16,150	$933	12/31/2023
IRON	16,150	$933	12/31/2023
Swiss National Bank	15,800	$913	12/31/2023
IRON	15,800	$913	12/31/2023
Virtu Financial LLC	13,802	$797	12/31/2023
IRON	13,802	$797	12/31/2023
UBS Group AG	13,622	$787	12/31/2023
IRON	13,622	$787	12/31/2023
Rhumbline Advisers	12,646	$730	12/31/2023
IRON	12,646	$730	12/31/2023
Engineers Gate Manager LP	11,427	$660	12/31/2023
IRON	11,427	$660	12/31/2023
Martingale Asset Management L P	11,300	$653	12/31/2023
IRON	11,300	$653	12/31/2023
The PNC Financial Services Group Inc.	10,000	$578	12/31/2023
IRON	10,000	$578	12/31/2023
Checkpoint Capital L.P.	10,000	$578	12/31/2023
IRON	10,000	$578	12/31/2023
Y Intercept Hong Kong Ltd	9,844	$569	12/31/2023
IRON	9,844	$569	12/31/2023
New York State Common Retirement Fund	9,686	$559	12/31/2023
IRON	9,686	$559	12/31/2023
UBS Oconnor LLC	9,338	$539	12/31/2023
IRON	9,338	$539	12/31/2023
SG Americas Securities LLC	9,135	$528	12/31/2023
IRON	9,135	$528	12/31/2023
Legal & General Group Plc	8,782	$507	12/31/2023
IRON	8,782	$507	12/31/2023
California State Teachers Retirement System	8,600	$497	12/31/2023
IRON	8,600	$497	12/31/2023
Legato Capital Management LLC	7,872	$490	03/31/2024
IRON	7,872	$490	03/31/2024
Stifel Financial Corp	8,160	$471	12/31/2023
IRON	8,160	$471	12/31/2023
Squarepoint Ops LLC	8,107	$468	12/31/2023
IRON	8,107	$468	12/31/2023
Credit Suisse AG	7,927	$458	12/31/2023
IRON	7,927	$458	12/31/2023
Raymond James & Associates	6,400	$398	03/31/2024
IRON	6,400	$398	03/31/2024
State of Wisconsin Investment Board	6,762	$391	12/31/2023
IRON	6,762	$391	12/31/2023
Profund Advisors LLC	6,506	$376	12/31/2023
IRON	6,506	$376	12/31/2023
Pale Fire Capital SE	6,120	$353	12/31/2023
IRON	6,120	$353	12/31/2023
China Universal Asset Management Co. Ltd.	4,641	$289	03/31/2024
IRON	4,641	$289	03/31/2024
Simplicity Wealth LLC	4,566	$284	03/31/2024
IRON	4,566	$284	03/31/2024
MetLife Investment Management LLC	4,792	$277	12/31/2023
IRON	4,792	$277	12/31/2023
Deutsche Bank AG	4,522	$261	12/31/2023
IRON	4,522	$261	12/31/2023
American International Group Inc.	4,444	$257	12/31/2023
IRON	4,444	$257	12/31/2023
Jump Financial LLC	4,306	$249	12/31/2023
IRON	4,306	$249	12/31/2023
Fiduciary Trust Co.	4,051	$234	12/31/2023
IRON	4,051	$234	12/31/2023
Sawtooth Solutions LLC	3,716	$215	12/31/2023
IRON	3,716	$215	12/31/2023
Bleakley Financial Group LLC	3,716	$215	12/31/2023
IRON	3,716	$215	12/31/2023
Voya Investment Management LLC	3,578	$207	12/31/2023
IRON	3,578	$207	12/31/2023
Royal Bank of Canada	2,651	$153	12/31/2023
IRON	2,651	$153	12/31/2023
Wells Fargo & Company MN	2,571	$149	12/31/2023
IRON	2,571	$149	12/31/2023
Tower Research Capital LLC TRC	2,339	$135	12/31/2023
IRON	2,339	$135	12/31/2023
Virtus ETF Advisers LLC	1,589	$92	12/31/2023
IRON	1,589	$92	12/31/2023
US Bancorp DE	1,176	$68	12/31/2023
IRON	1,176	$68	12/31/2023
AJOVista LLC	1,091	$63	12/31/2023
IRON	1,091	$63	12/31/2023
Strs Ohio	1,000	$57	12/31/2023
IRON	1,000	$57	12/31/2023
Ameritas Investment Partners Inc.	885	$51	12/31/2023
IRON	885	$51	12/31/2023
Steward Partners Investment Advisory LLC	600	$35	12/31/2023
IRON	600	$35	12/31/2023
Metropolitan Life Insurance Co NY	529	$31	12/31/2023
IRON	529	$31	12/31/2023
Fortitude Family Office LLC	356	$22	03/31/2024
IRON	356	$22	03/31/2024
Amalgamated Bank	321	$20	03/31/2024
IRON	321	$20	03/31/2024
Group One Trading L.P.		$17	12/31/2023
Call	1,300	$75	12/31/2023
Put	1,000	$58	12/31/2023
Amundi	252	$15	12/31/2023
IRON	252	$15	12/31/2023
Daiwa Securities Group Inc.	99	$6	12/31/2023
IRON	99	$6	12/31/2023
Lindbrook Capital LLC	67	$4	03/31/2024
IRON	67	$4	03/31/2024
GAMMA Investing LLC	10	$1	03/31/2024
IRON	10	$1	03/31/2024
CWM LLC	1	$0	03/31/2024
IRON	1	$0	03/31/2024
Proequities Inc.		$0	12/31/2023
Put	0	$0	12/31/2023
Call	0	$0	12/31/2023
IRON	0	$0	12/31/2023
Covestor Ltd	2	$0	12/31/2023
IRON	2	$0	12/31/2023
Cutler Group LP		$-2	03/31/2024
Put	300	$2	03/31/2024
Call	200	$0	03/31/2024
Caption Management LLC		$-1,351	12/31/2023
Put	162,300	$9,374	12/31/2023
Call	95,900	$5,539	12/31/2023
IRON	43,000	$2,484	12/31/2023
Simplex Trading LLC	5,700	$-2,410	03/31/2024
Put	44,400	$2,764	03/31/2024
Call	5,700	$354	03/31/2024