CSS LLC’s Biogen BIIB Stock Holding History

CSS LLC’s Portfolio BIIB Stock Details BIIB Fund Activity

Bought

Maintained

Sold

Quarter	Market Value	Status	Shares	Change in Stake	Trade Value	Portfolio Weight	Portfolio Position
2023 Q1	–	Sell	-16,900	Closed	-$4.68M	–	741
2022 Q4	$4.68M	Sell	16,900 -6,700	-28%	-$1.89M	0.26%	83
2022 Q3	$6.3M	Buy	+23,600	New	+$5.01M	0.3%	74
2022 Q2	–	Sell	-10,500	Closed	-$2.21M	–	1111
2022 Q1	$2.21M	Sell	10,500 -36,900	-78%	-$8.02M	0.08%	249
2021 Q4	$11.4M	Buy	47,400 +34,100	+256%	+$8.77M	0.4%	50
2021 Q3	$3.76M	Sell	13,300 -11,700	-47%	-$3.83M	0.16%	120
2021 Q2	$8.66M	Sell	25,000 -79,500	-76%	-$24.1M	0.36%	56
2021 Q1	$29.2M	Sell	104,500 -100,500	-49%	-$27.1M	1.2%	13
2020 Q4	$50.2M	Buy	205,000 +157,300	+330%	+$40.6M	1.92%	7
2020 Q3	$13.5M	Buy	47,700 +46,900	+5,863%	+$13.1M	0.64%	23
2020 Q2	$215K	Sell	800 -2,000	-71%	-$601K	0.01%	484
2020 Q1	$886K	Sell	2,800 -2,200	-44%	-$668K	0.07%	222
2019 Q4	$1.48M	Buy	+5,000	New	+$1.39M	0.08%	197

Other funds holding BIIB

BlackRock New York $5.72T AUM 30.48% 1-Year Est. Return

Primecap Management Pasadena, California $127B AUM 44.11% 1-Year Est. Return

Fidelity Investments Boston, Massachusetts $1.9T AUM 41.92% 1-Year Est. Return

VCM

Vanguard Capital Management Malvern, Pennsylvania $4.04T AUM

State Street Boston, Massachusetts $2.9T AUM 29.55% 1-Year Est. Return

VPM

Vanguard Portfolio Management Malvern, Pennsylvania $1.91T AUM

Geode Capital Management Boston, Massachusetts $1.61T AUM 30.72% 1-Year Est. Return

Wellington Management Group Boston, Massachusetts $535B AUM 26.23% 1-Year Est. Return

Morgan Stanley New York $1.66T AUM 25.57% 1-Year Est. Return

JP Morgan Chase New York $1.56T AUM 27.86% 1-Year Est. Return

CSS LLC's BIIB Position: Q1 2026 in Review

CSS LLC reduced its Biogen (BIIB) stake by 55% in Q1 2026, selling an estimated $619K and leaving 2,720 shares worth $499K. The position accounts for 0.02% of the portfolio, ranked #525.

CSS LLC first reported a position in BIIB in Q1 2020 and has held it in 12 quarters since. The position peaked at $5.14M in Q2 2020. 1,002 funds tracked by Wall St. Rank hold BIIB as of Q1 2026.

CSS LLC held 2,720 shares of Biogen worth $499K as of Q1 2026.
CSS LLC sold 3,360 Biogen shares in Q1 2026, an estimated $619K.
Biogen made up 0.02% of CSS LLC's portfolio in Q1 2026, its #525 holding.
CSS LLC first reported a position in Biogen in Q1 2020 and has held it in 12 quarters since.
CSS LLC's Biogen position peaked at $5.14M in Q2 2020.
1,002 funds tracked by Wall St. Rank held Biogen as of Q1 2026.

Based on CSS LLC's 13F filing for Q1 2026, filed 15 May 2026.