Biogen Inc.
MX ˙ BMV ˙ US09062X1037
SecurityMX:BIIB / Biogen Inc.
InstitutionRenaissance Technologies Llc
ManagerJames Simons
Latest Disclosed Ownership203,396 shares
Latest Disclosed Value $ 37,288,589
Renaissance Technologies Llc reports 49.05% decrease in ownership of BIIB / Biogen Inc.

On May 14, 2026 - Renaissance Technologies Llc filed a 13F-HR form disclosing ownership of 203,396 shares of Biogen Inc. (MX:BIIB) valued at $37,288,589 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 12, 2026 disclosing 399,196 shares of Biogen Inc.. This represents a change in shares of -49.05% during the quarter.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

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Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date		 Effective
Date		Form Security Class ID Avg Price
Paid (Est)		 Reported
Shares		 ΔShares ΔShares
(%)		 Reported
Value
(x1000)		 ΔValue
(%)		 Alloc
(%)		 ΔAlloc ΔAlloc (%) Cost Basis
(x1000)		 Unrealized
Gain/Loss
(x1000)
2026-05-14 2026-03-31 13F BIOGEN COM 09062X103 203,396 -195,800 -49.05 37,289 -46.92 0.0583
2026-02-12 2025-12-31 13F BIOGEN COM 09062X103 399,196 -565,210 -58.61 70,255 -48.00 0.1090
2025-11-13 2025-09-30 13F BIOGEN COM 09062X103 964,406 -80,700 -7.72 135,094 2.92 0.1783
2025-08-13 2025-06-30 13F BIOGEN COM 09062X103 1,045,106 240,600 29.91 131,255 19.23 0.1746
2025-05-14 2025-03-31 13F BIOGEN COM 09062X103 804,506 -387,700 -32.52 110,089 -39.62 0.1666
2025-02-13 2024-12-31 13F BIOGEN COM 09062X103 1,192,206 239,500 25.14 182,312 -1.28 0.2699
2024-11-13 2024-09-30 13F BIOGEN COM 09062X103 952,706 334,600 54.13 184,673 28.88 0.2777
2024-08-09 2024-06-30 13F BIOGEN COM 09062X103 618,106 -266,598 -30.13 143,289 75,315.26 0.2430
2024-05-13 2024-03-31 13F BIOGEN COM 09062X103 884,704 126,098 16.62 191 -3.06 0.2998
2024-02-13 2023-12-31 13F BIOGEN COM 09062X103 758,606 -327,791 -30.17 196 -29.75 0.3038
2023-11-14 2023-09-30 13F BIOGEN COM 09062X103 1,086,397 -23,140 -2.09 279 -11.71 0.4760
2023-08-11 2023-06-30 13F BIOGEN COM 09062X103 1,109,537 -154,300 -12.21 316 -9.97 0.4555
2023-05-12 2023-03-31 13F BIOGEN COM 09062X103 1,263,837 263,561 26.35 351 27.17 0.4663
2023-02-13 2022-12-31 13F BIOGEN COM 09062X103 1,000,276 -154,231 -13.36 277 -99.91 0.3790
2022-11-14 2022-09-30 13F BIOGEN COM 09062X103 1,154,507 -391,500 -25.32 308,253 -2.23 0.4361
2022-08-12 2022-06-30 13F BIOGEN COM 09062X103 1,546,007 501,800 48.06 315,293 43.37 0.3733
2022-05-13 2022-03-31 13F BIOGEN COM 09062X103 1,044,207 -29,600 -2.76 219,910 -14.64 0.2581
2022-02-11 2021-12-31 13F BIOGEN COM 09062X103 1,073,807 92,100 9.38 257,628 -7.27 0.3205
2021-11-12 2021-09-30 13F BIOGEN COM 09062X103 981,707 -348,296 -26.19 277,813 -39.68 0.3588
2021-08-13 2021-06-30 13F BIOGEN COM 09062X103 1,330,003 -608,159 -31.38 460,540 -15.06 0.5749
2021-05-13 2021-03-31 13F BIOGEN COM 09062X103 1,938,162 -1,099,600 -36.20 542,201 -27.11 0.6745
2021-02-10 2020-12-31 13F BIOGEN COM 09062X103 3,037,762 -779,199 -20.41 743,826 -31.31 0.8077
2020-11-13 2020-09-30 13F BIOGEN COM 09062X103 3,816,961 -88,961 -2.28 1,082,795 3.61 1.0812
2020-08-13 2020-06-30 13F BIOGEN COM 09062X103 3,905,922 -567,990 -12.70 1,045,029 -26.17 0.9021
2020-05-14 2020-03-31 13F BIOGEN COM 09062X103 4,473,912 -95,994 -2.10 1,415,456 4.38 1.3747
2020-02-13 2019-12-31 13F BIOGEN COM 09062X103 4,569,906 348,700 8.26 1,356,028 37.98 1.0421
2019-11-13 2019-09-30 13F BIOGEN COM 09062X103 4,221,206 1,738,129 70.00 982,781 69.24 0.8318
2019-08-12 2019-06-30 13F BIOGEN COM 09062X103 2,483,077 851,263 52.17 580,717 50.55 0.5113
2019-05-14 2019-03-31 13F BIOGEN COM 09062X103 1,631,814 617,100 60.82 385,728 26.32 0.3507
2019-02-12 2018-12-31 13F BIOGEN COM 09062X103 1,014,714 168,639 19.93 305,348 2.15 0.3343
2018-11-13 2018-09-30 13F BIOGEN COM 09062X103 846,075 524,575 163.16 298,927 220.35 0.3073
2018-08-13 2018-06-30 13F/A-1 BIOGEN COM 09062X103 321,500 -306,161 -48.78 93,312 -45.71 0.1017
2018-08-13 2018-06-30 13F BIOGEN COM 09062X103 627,661 171,866
2018-05-14 2018-03-31 13F BIOGEN COM 09062X103 627,661 627,661 95.23 171,866 84.18 0.1880
2018-02-13 2017-12-31 13F BIOGEN COM 09062X103 0 -120,161 -100.00 0 -100.00
2017-11-13 2017-09-30 13F BIOGEN COM 09062X103 120,161 -642,700 -84.25 37,625 -81.82 0.0443
2017-08-11 2017-06-30 13F BIOGEN COM 09062X103 762,861 -86,100 -10.14 207,010 -10.82 0.2642
2017-05-12 2017-03-31 13F BIOGEN COM 09062X103 848,961 141,466 20.00 232,123 15.70 0.3243
2017-02-13 2016-12-31 13F BIOGEN COM 09062X103 707,495 469,234 196.94 200,631 169.00 0.3174
2016-11-14 2016-09-30 13F BIOGEN COM 09062X103 238,261 197,861 489.75 74,583 663.39 0.1318
2016-08-12 2016-06-30 13F BIOGEN COM 09062X103 40,400 -87,261 -68.35 9,770 -70.60 0.0186
2016-05-13 2016-03-31 13F BIOGEN COM 09062X103 127,661 127,661 215.99 33,233 240.15 0.0632
2016-02-11 2015-12-31 13F BIOGEN IDEC COM 09062X103 0 -34,961 -100.00 0 -100.00
2015-11-12 2015-09-30 13F BIOGEN COM 09062X103 34,961 -70,300 -66.79 10,202 -76.01 0.0243
2015-08-14 2015-06-30 13F BIOGEN COM 09062X103 105,261 74,961 247.40 42,519 232.34 0.0969
2015-05-13 2015-03-31 13F BIOGEN COM 09062X103 30,300 -34,861 -53.50 12,794 -42.16 0.0272
2015-02-13 2014-12-31 13F BIOGEN IDEC COM 09062X103 65,161 -27,500 -29.68 22,119 -27.84 0.0534
2014-11-12 2014-09-30 13F BIOGEN IDEC COM 09062X103 92,661 -36,600 -28.31 30,653 -24.79 0.0839
2014-08-13 2014-06-30 13F BIOGEN IDEC COM 09062X103 129,261 -413,077 -76.17 40,757 -73.12 0.0950
2014-02-14 2013-12-31 13F BIOGEN IDEC COM 09062X103 542,338 -327,362 -37.64 151,623 -27.59 0.3631
2013-11-13 2013-09-30 13F BIOGEN IDEC COM 09062X103 869,700 -523,800 -37.59 209,389 -30.18 0.5079
2013-08-12 2013-06-30 13F BIOGEN IDEC COM 09062X103 1,393,500 1,393,500 299,881 0.7863
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.