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
2022 Q4	–	Sell	-31,000	Closed	-$8.28M	–	959
2022 Q3	$8.28M	Buy	+31,000	New	+$6.58M	0.39%	47
2022 Q1	–	Sell	-11,000	Closed	-$2.64M	–	1171
2021 Q4	$2.64M	Buy	11,000 +8,700	+378%	+$2.24M	0.09%	196
2021 Q3	$651K	Sell	2,300 -9,200	-80%	-$3.02M	0.03%	554
2021 Q2	$3.98M	Buy	+11,500	New	+$3.48M	0.16%	120
2021 Q1	–	Sell	-25,800	Closed	-$6.32M	–	935
2020 Q4	$6.32M	Buy	25,800 +1,800	+8%	+$464K	0.24%	71
2020 Q3	$6.81M	Sell	24,000 -10,000	-29%	-$2.79M	0.32%	63
2020 Q2	$9.1M	Buy	34,000 +10,000	+42%	+$3.01M	0.52%	41
2020 Q1	$7.59M	Buy	24,000 +21,500	+860%	+$6.52M	0.6%	38
2019 Q4	$742K	Buy	+2,500	New	+$694K	0.04%	294

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.