Biogen Inc.
US ˙ NasdaqGS ˙ US09062X1037

SecurityBIIB / Biogen Inc.
InstitutionDimensional Fund Advisors Lp
Latest Disclosed Ownership1,079,119 shares
Latest Disclosed Value $ 197,881,455
Dimensional Fund Advisors Lp reports 12.33% increase in ownership of BIIB / Biogen Inc.

On May 7, 2026 - Dimensional Fund Advisors Lp filed a 13F-HR form disclosing ownership of 1,079,119 shares of Biogen Inc. (US:BIIB) valued at $197,834,886 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 12, 2026 disclosing 960,645 shares of Biogen Inc.. This represents a change in shares of 12.33% during the quarter. The current value of the position is $210,795,105 USD.

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)
2026-05-07 2026-03-31 13F BIOGEN COM 09062X103 1,079,119 118,474 12.33 197,881 17.04 0.0411
2026-02-12 2025-12-31 13F BIOGEN COM 09062X103 960,645 87,551 10.03 169,066 38.25 0.0355
2025-11-12 2025-09-30 13F BIOGEN COM 09062X103 873,094 -55,402 -5.97 122,293 4.87 0.0262
2025-08-12 2025-06-30 13F BIOGEN COM 09062X103 928,496 -58,223 -5.90 116,618 -13.64 0.0270
2025-05-13 2025-03-31 13F BIOGEN COM 09062X103 986,719 -35,305 -3.45 135,040 -13.58 0.0336
2025-02-13 2024-12-31 13F BIOGEN COM 09062X103 1,022,024 -92,316 -8.28 156,251 -27.66 0.0375
2024-11-07 2024-09-30 13F BIOGEN COM 09062X103 1,114,340 4,228 0.38 216,010 -16.05 0.0524
2024-08-09 2024-06-30 13F BIOGEN COM 09062X103 1,110,112 -210,874 -15.96 257,308 -9.67 0.0672
2024-05-10 2024-03-31 13F BIOGEN COM 09062X103 1,320,986 -103,673 -7.28 284,844 -22.74 0.0771
2024-02-07 2023-12-31 13F BIOGEN COM 09062X103 1,424,659 43,444 3.15 368,685 3.85 0.1077
2023-11-09 2023-09-30 13F BIOGEN COM 09062X103 1,381,215 35,473 2.64 355,004 -7.38 0.1164
2023-08-09 2023-06-30 13F BIOGEN COM 09062X103 1,345,742 -70,779 -5.00 383,306 -2.67 0.1222
2023-05-12 2023-03-31 13F BIOGEN COM 09062X103 1,416,521 73,289 5.46 393,801 106,045.82 0.1327
2023-02-09 2022-12-31 13F BIOGEN COM 09062X103 1,343,232 -19,821 -1.45 372 -99.90 0.1099
2022-11-10 2022-09-30 13F BIOGEN COM 09062X103 1,363,053 112,599 9.00 363,909 42.70 0.1397
2022-08-12 2022-06-30 13F BIOGEN COM 09062X103 1,250,454 15,431 1.25 255,011 -1.96 0.0915
2022-05-13 2022-03-31 13F BIOGEN COM 09062X103 1,235,023 42,773 3.59 260,103 -9.07 0.0801
2022-02-09 2021-12-31 13F BIOGEN COM 09062X103 1,192,250 62,060 5.49 286,043 -10.58 0.0865
2021-11-12 2021-09-30 13F BIOGEN COM 09062X103 1,130,190 -57,498 -4.84 319,872 -22.22 0.1030
2021-08-12 2021-06-30 13F BIOGEN COM 09062X103 1,187,688 75,020 6.74 411,253 32.15 0.1302
2021-05-14 2021-03-31 13F BIOGEN COM 09062X103 1,112,668 -3,883 -0.35 311,210 13.84 0.1029
2021-03-08 2020-12-31 13F/A-2 BIOGEN COM 09062X103 1,116,551 38,870 3.61 273,380 -10.57 0.0987
2021-02-11 2020-12-31 13F BIOGEN COM 09062X103 1,116,551 38,870 273,380 98,730.3251
2020-11-12 2020-09-30 13F BIOGEN COM 09062X103 1,077,681 10,176 0.95 305,678 7.08 0.1296
2020-08-13 2020-06-30 13F BIOGEN COM 09062X103 1,067,505 108,516 11.32 285,476 -5.90 0.1255
2020-05-14 2020-03-31 13F BIOGEN COM 09062X103 958,989 123,667 14.80 303,373 22.40 0.1580
2020-02-14 2019-12-31 13F BIOGEN COM 09062X103 835,322 147,300 21.41 247,851 54.77 0.0903
2019-11-12 2019-09-30 13F BIOGEN COM 09062X103 688,022 10,697 1.58 160,139 1.03 0.0622
2019-08-13 2019-06-30 13F BIOGEN COM 09062X103 677,325 35,206 5.48 158,512 4.44 0.0615
2019-08-12 2019-03-31 13F/A-2 BIOGEN COM 09062X103 642,119 -357 -0.06 151,772 -21.49 0.0604
2019-05-10 2019-03-31 13F BIOGEN COM 09062X103 642,119 -357 151,772
2019-02-26 2018-12-31 13F/A-1 BIOGEN COM 09062X103 642,476 12,226 1.94 193,311 -13.19 0.0876
2019-02-13 2018-12-31 13F BIOGEN COM 09062X103 642,476 12,226 193,311
2018-11-13 2018-09-30 13F BIOGEN COM 09062X103 630,250 -1,043 -0.17 222,680 21.53 0.0848
2018-08-10 2018-06-30 13F BIOGEN COM 09062X103 631,293 16,288 2.65 183,224 8.80 0.0730
2018-05-11 2018-03-31 13F BIOGEN COM 09062X103 615,005 49,309 8.72 168,401 -6.56 0.0702
2018-02-12 2017-12-31 13F BIOGEN COM 09062X103 565,696 38,365 7.28 180,224 9.16 0.0747
2017-11-13 2017-09-30 13F BIOGEN COM 09062X103 527,331 8,704 1.68 165,106 17.31 0.0722
2017-08-11 2017-06-30 13F BIOGEN COM 09062X103 518,627 -1,219 -0.23 140,739 -0.97 0.0650
2017-05-12 2017-03-31 13F BIOGEN COM 09062X103 519,846 -11,856 -2.23 142,117 -5.76 0.0679
2017-02-09 2016-12-31 13F BIOGEN COM 09062X103 531,702 9,175 1.76 150,796 -7.79 0.0753
2016-11-10 2016-09-30 13F BIOGEN COM 09062X103 522,527 7,959 1.55 163,540 31.44 0.0884
2016-08-09 2016-06-30 13F BIOGEN COM 09062X103 514,568 37,922 7.96 124,425 0.30 0.0716
2016-05-13 2016-03-31 13F BIOGEN COM 09062X103 476,646 57,998 13.85 124,056 -3.28 0.0743
2016-02-10 2015-12-31 13F BIOGEN COM 09062X103 418,648 19,889 4.99 128,259 10.26 0.0799
2015-11-13 2015-09-30 13F BIOGEN COM 09062X103 398,759 26,456 7.11 116,328 -22.64 0.0764
2015-08-14 2015-06-30 13F BIOGEN COM 09062X103 372,303 31,654 9.29 150,374 4.54 0.0921
2015-05-14 2015-03-31 13F BIOGEN COM 09062X103 340,649 10,033 3.03 143,849 28.16 0.0908
2015-02-06 2014-12-31 13F BIOGEN IDEC COM 09062X103 330,616 29,200 9.69 112,239 12.56 0.0737
2014-11-13 2014-09-30 13F BIOGEN IDEC COM 09062X103 301,416 23,137 8.31 99,714 13.63 0.0707
2014-08-08 2014-06-30 13F BIOGEN IDEC COM 09062X103 278,279 9,065 3.37 87,750 6.55 0.0610
2014-05-14 2014-03-31 13F BIOGEN IDEC COM 09062X103 269,214 20,325 8.17 82,357 18.28 0.0615
2014-02-12 2013-12-31 13F BIOGEN IDEC COM 09062X103 248,889 1,749 0.71 69,626 17.00 0.0543
2013-11-13 2013-09-30 13F BIOGEN IDEC COM 09062X103 247,140 7,175 2.99 59,507 15.27 0.0515
2013-08-15 2013-06-30 13F BIOGEN IDEC COM 09062X103 239,965 239,965 51,626 0.0486
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.