Stocks
BIIB
CITADEL ADVISORS LLC

CITADEL ADVISORS LLC

CIK

0001423053

City

Chicago

State / Country

Stock

BIIB — BIOGEN INC.

Holdings in BIIB

Position Over Time

Report Date	Value (USD)	Shares	Change	Type	Discretion	Filed
2025-12-31	$71,627,930	407,000	+906.8%	Shares	Defined	2026-02-17
2025-12-31	$7,114,219	40,424	-75.0%	Shares	Defined	2026-02-17
2025-12-31	$28,510,380	162,000	-32.8%	Shares	Defined	2026-02-17
2025-09-30	$33,787,296	241,200	+52.7%	Shares	Defined	2025-11-14
2025-09-30	$22,132,640	158,000	-57.6%	Shares	Defined	2025-11-14
2025-09-30	$52,211,738	372,728	+41.3%	Shares	Defined	2025-11-14
2025-06-30	$33,130,642	263,800	-44.2%	Shares	Defined	2025-08-14
2025-06-30	$59,416,629	473,100	-22.3%	Shares	Defined	2025-08-14
2025-06-30	$76,432,818	608,590	-39.0%	Shares	Defined	2025-08-14
2025-03-31	$136,621,056	998,400	+384.4%	Shares	Defined	2025-05-15
2025-03-31	$28,202,724	206,100	-62.0%	Shares	Defined	2025-05-15
2025-03-31	$74,134,985	541,764	+252.6%	Shares	Defined	2025-05-15
2024-12-31	$23,497,687	153,660	-35.6%	Shares	Defined	2025-02-14
2024-12-31	$36,502,004	238,700	+38.5%	Shares	Defined	2025-02-14
2024-12-31	$26,363,408	172,400	+14.1%	Shares	Defined	2025-02-14
2024-09-30	$29,289,224	151,100	-59.4%	Shares	Defined	2024-11-14
2024-09-30	$72,179,424	372,366	+245.4%	Shares	Defined	2024-11-14
2024-09-30	$20,895,952	107,800	-31.9%	Shares	Defined	2024-11-14
2024-06-30	$36,720,288	158,400	+36.1%	Shares	Defined	2024-08-14
2024-06-30	$26,983,848	116,400	-22.0%	Shares	Defined	2024-08-14
2024-03-31	$32,193,127	149,298	+13.5%	Shares	Defined	2024-05-15
2024-03-31	$28,355,345	131,500	+6.0%	Shares	Defined	2024-05-15
2024-03-31	$26,738,120	124,000	-48.9%	Shares	Defined	2024-05-15
2023-12-31	$62,777,602	242,600	+4511.3%	Shares	Defined	2024-02-14
2023-12-31	$1,361,388	5,261	-97.1%	Shares	Defined	2024-02-14
2023-12-31	$47,484,295	183,500	+134.8%	Shares	Defined	2024-02-14
2023-09-30	$20,081,733	78,136	-73.6%	Shares	Defined	2023-11-14
2023-09-30	$76,152,063	296,300	+19.9%	Shares	Defined	2023-11-14
2023-09-30	$63,532,872	247,200	-33.5%	Shares	Defined	2023-11-14
2023-06-30	$105,907,230	371,800	-1.0%	Shares	Defined	2023-08-14
2023-06-30	$106,989,660	375,600	-29.8%	Shares	Defined	2023-08-14
2023-03-31	$148,718,247	534,900	+2.0%	Shares	Defined	2023-05-15
2023-03-31	$145,826,735	524,500	+114.0%	Shares	Defined	2023-05-15
2023-03-31	$68,140,703	245,084	-75.3%	Shares	Defined	2023-05-15
2022-12-31	$274,510,796	991,300	+13.2%	Shares	Defined	2023-02-14
2022-12-31	$242,471,152	875,600	+253.3%	Shares	Defined	2023-02-14
2022-12-31	$68,624,098	247,812	-0.6%	Shares	Defined	2023-02-14
2022-09-30	$66,583,926	249,378	-81.2%	Shares	Defined	2022-11-14
2022-09-30	$353,694,900	1,324,700	-5.3%	Shares	Defined	2022-11-14
2022-09-30	$373,346,100	1,398,300	+152.1%	Shares	Defined	2022-11-14
2022-06-30	$113,125,518	554,700	-5.1%	Shares	Defined	2022-08-15
2022-06-30	$119,162,142	584,300	+180.3%	Shares	Defined	2022-08-15
2022-06-30	$42,509,865	208,443	-56.1%	Shares	Defined	2022-08-15
2022-03-31	$100,056,060	475,100	+506.0%	Shares	Defined	2022-05-16
2022-03-31	$16,509,986	78,395	-87.5%	Shares	Defined	2022-05-16
2022-03-31	$132,067,260	627,100	+602.7%	Shares	Defined	2022-05-16
2021-12-31	$21,410,700	89,241	-85.3%	Shares	Defined	2022-02-14
2021-12-31	$145,175,592	605,100	+4.4%	Shares	Defined	2022-02-14
2021-12-31	$139,105,616	579,800	-33.9%	Shares	Defined	2022-02-14
2021-06-30	$303,505,655	876,500	—	Shares	Defined	2021-08-16