Biogen Inc.
MX ˙ BMV ˙ US09062X1037
SecurityMX:BIIB / Biogen Inc.
InstitutionFred Alger Management, Llc
Latest Disclosed Ownership733,194 shares
Latest Disclosed Value $ 134,416,456
Fred Alger Management, Llc reports 8.21% decrease in ownership of BIIB / Biogen Inc.

On May 15, 2026 - Fred Alger Management, Llc filed a 13F-HR form disclosing ownership of 733,194 shares of Biogen Inc. (MX:BIIB) valued at $134,416,456 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 17, 2026 disclosing 798,774 shares of Biogen Inc.. This represents a change in shares of -8.21% 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)
2026-05-15 2026-03-31 13F Biogen Equity 09062X103 733,194 -65,580 -8.21 134,416 -4.38 0.3756
2026-02-17 2025-12-31 13F Biogen Equity 09062X103 798,774 796,735 39,074.79 140,576 49,224.91 0.5514
2025-11-14 2025-09-30 13F Biogen Equity 09062X103 2,039 2,039 286 0.0011
2025-08-14 2025-06-30 13F Biogen Equity 09062X103 0 -12,159 -100.00 0 -100.00
2025-05-16 2025-03-31 13F Biogen Equity 09062X103 12,159 12,159 1,664 0.0095
2024-05-15 2024-03-31 13F BIOGEN Common 09062X103 0 -13,235 -100.00 0 -100.00
2024-02-14 2023-12-31 13F BIOGEN Common 09062X103 13,235 13,235 3,425 0.0185
2023-11-14 2023-09-30 13F BIOGEN Common 09062X103 0 -125,980 -100.00 0 -100.00
2023-11-14 2023-09-30 13F BIOGEN Common 09062X103 0 0
2023-08-14 2023-06-30 13F BIOGEN Common 09062X103 125,980 -143,458 -53.24 35,885 -52.10 0.1833
2023-05-16 2023-03-31 13F/A-1 BIOGEN Common 09062X103 269,438 -62,627 -18.86 74,912 -18.54 0.4006
2023-05-15 2023-03-31 13F BIOGEN Common 09062X103 269,438 -62,627 74,912 0.3715
2023-02-14 2022-12-31 13F BIOGEN Common 09062X103 332,065 188,033 130.55 91,955 139.11 0.4984
2022-11-15 2022-09-30 13F BIOGEN Common 09062X103 144,032 144,032 38,457 0.1949
2021-11-15 2021-09-30 13F BIOGEN Common 09062X103 0 -85,613 -100.00 0 -100.00
2021-08-16 2021-06-30 13F BIOGEN Common 09062X103 85,613 67,888 383.01 29,645 497.80 0.0700
2021-05-17 2021-03-31 13F BIOGEN Common 09062X103 17,725 13,766 347.71 4,959 411.76 0.0130
2021-02-16 2020-12-31 13F BIOGEN Common 09062X103 3,959 3,942 23,188.24 969 19,280.00 0.0025
2020-11-13 2020-09-30 13F BIOGEN Common 09062X103 17 -3,850 -99.56 5 -99.52 0.0000
2020-08-14 2020-06-30 13F BIOGEN Common 09062X103 3,867 -159,223 -97.63 1,035 -97.99 0.0034
2020-05-19 2020-03-31 13F/A-1 BIOGEN Common 09062X103 163,090 24,245 17.46 51,598 25.24 0.2267
2020-05-15 2020-03-31 13F BIOGEN Common 09062X103 163,090 24,245 51,598 227,018.5714
2020-02-14 2019-12-31 13F BIOGEN Common 09062X103 138,845 138,845 41,199 0.1516
2019-11-14 2019-09-30 13F BIOGEN Common 09062X103 0 -42 -100.00 0 -100.00
2019-08-14 2019-06-30 13F BIOGEN Common 09062X103 42 -1,979 -97.92 10 -97.91 0.0000
2019-05-14 2019-03-31 13F BIOGEN Common 09062X103 2,021 -215,110 -99.07 478 -99.27 0.0019
2019-02-14 2018-12-31 13F BIOGEN Common 09062X103 217,131 -80,405 -27.02 65,339 -37.84 0.3008
2018-11-14 2018-09-30 13F BIOGEN Common 09062X103 297,536 284,735 2,224.32 105,122 2,729.66 0.3947
2018-07-19 2018-06-30 13F BIOGEN Common 09062X103 12,801 -1,620 -11.23 3,715 -5.93 0.0156
2018-05-10 2018-03-31 13F BIOGEN Common 09062X103 14,421 1,092 8.19 3,949 -6.99 0.0184
2018-02-14 2017-12-31 13F BIOGEN Common 09062X103 13,329 5,537 71.06 4,246 74.02 0.0192
2017-11-14 2017-09-30 13F BIOGEN Common 09062X103 7,792 1,250 19.11 2,440 37.46 0.0114
2017-08-14 2017-06-30 13F BIOGEN Common 09062X103 6,542 -6,861 -51.19 1,775 -51.57 0.0085
2017-05-15 2017-03-31 13F BIOGEN Common 09062X103 13,403 -522,626 -97.50 3,665 -97.59 0.0182
2017-02-14 2016-12-31 13F BIOGEN Common 09062X103 536,029 86,307 19.19 152,007 7.98 0.8271
2016-11-14 2016-09-30 13F BIOGEN Common 09062X103 449,722 -138,659 -23.57 140,776 -1.06 0.7226
2016-08-15 2016-06-30 13F BIOGEN Common 09062X103 588,381 -119,522 -16.88 142,283 -22.79 0.7513
2016-05-16 2016-03-31 13F BIOGEN Common 09062X103 707,903 121,551 20.73 184,282 2.59 0.9334
2016-02-16 2015-12-31 13F BIOGEN Common 09062X103 586,352 117,434 25.04 179,629 31.27 0.8736
2015-11-16 2015-09-30 13F BIOGEN Common 09062X103 468,918 -403,077 -46.22 136,835 -61.15 0.7467
2015-08-14 2015-06-30 13F BIOGEN Common 09062X103 871,995 19,093 2.24 352,234 -2.19 1.5850
2015-05-15 2015-03-31 13F BIOGEN Common 09062X103 852,902 252,392 42.03 360,129 76.67 1.6219
2015-02-17 2014-12-31 13F BIOGEN IDEC Common 09062X103 600,510 170,810 39.75 203,843 43.40 0.9812
2014-11-14 2014-09-30 13F BIOGEN IDEC Common 09062X103 429,700 -43,899 -9.27 142,149 -4.81 0.6913
2014-08-14 2014-06-30 13F BIOGEN IDEC Common 09062X103 473,599 -34,220 -6.74 149,331 -3.86 0.7353
2014-05-15 2014-03-31 13F BIOGEN IDEC Common 09062X103 507,819 -71,811 -12.39 155,327 -4.15 0.7699
2014-02-14 2013-12-31 13F BIOGEN IDEC Common 09062X103 579,630 253,735 77.86 162,048 106.53 0.8259
2013-11-14 2013-09-30 13F BIOGEN IDEC Common 09062X103 325,895 64,841 24.84 78,463 39.67 0.4363
2013-08-14 2013-06-30 13F BIOGEN IDEC Common 09062X103 261,054 261,054 56,178 0.3338
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.