Biogen Inc.
MX ˙ BMV ˙ US09062X1037
SecurityMX:BIIB / Biogen Inc.
InstitutionNatixis Advisors, L.p.
Latest Disclosed Ownership41,272 shares
Latest Disclosed Value $ 7,566
Natixis Advisors, L.p. reports 23.81% increase in ownership of BIIB / Biogen Inc.

On May 13, 2026 - Natixis Advisors, L.p. filed a 13F-HR form disclosing ownership of 41,272 shares of Biogen Inc. (MX:BIIB) valued at $7,566 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 10, 2026 disclosing 33,336 shares of Biogen Inc.. This represents a change in shares of 23.81% 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)
2026-05-13 2026-03-31 13F BIOGEN COM 09062X103 41,272 7,936 23.81 8 40.00 0.0105
2026-02-10 2025-12-31 13F BIOGEN COM 09062X103 33,336 -6,180 -15.64 6 0.00 0.0083
2025-11-13 2025-09-30 13F BIOGEN COM 09062X103 39,516 1,317 3.45 6 25.00 0.0081
2025-08-13 2025-06-30 13F BIOGEN COM 09062X103 38,199 11,292 41.97 5 33.33 0.0076
2025-05-08 2025-03-31 13F BIOGEN COM 09062X103 26,907 9,946 58.64 4 50.00 0.0068
2025-02-10 2024-12-31 13F BIOGEN COM 09062X103 16,961 -7,796 -31.49 3 -50.00 0.0048
2024-11-06 2024-09-30 13F BIOGEN COM 09062X103 24,757 -10,054 -28.88 5 -50.00 0.0094
2024-08-01 2024-06-30 13F BIOGEN COM 09062X103 34,811 9,714 38.71 8 60.00 0.0175
2024-04-25 2024-03-31 13F BIOGEN COM 09062X103 25,097 931 3.85 5 -16.67 0.0124
2024-02-06 2023-12-31 13F BIOGEN COM 09062X103 24,166 565 2.39 6 0.00 0.0165
2023-11-13 2023-09-30 13F BIOGEN COM 09062X103 23,601 -4,720 -16.67 6 -25.00 0.0186
2023-08-15 2023-06-30 13F BIOGEN COM 09062X103 28,321 1,791 6.75 8 14.29 0.0249
2023-05-11 2023-03-31 13F BIOGEN COM 09062X103 26,530 4,429 20.04 7 16.67 0.0254
2023-01-27 2022-12-31 13F BIOGEN COM 09062X103 22,101 874 4.12 6 -99.89 0.0231
2022-11-14 2022-09-30 13F BIOGEN INC COM COM 09062X103 21,227 3,376 18.91 5,668 55.67 0.0240
2022-08-12 2022-06-30 13F BIOGEN COM 09062X103 17,851 1,973 12.43 3,641 8.88 0.0160
2022-05-12 2022-03-31 13F BIOGEN COM 09062X103 15,878 -521 -3.18 3,344 -15.02 0.0128
2022-02-08 2021-12-31 13F BIOGEN COM 09062X103 16,399 -5,526 -25.20 3,935 -36.57 0.0150
2021-11-15 2021-09-30 13F BIOGEN COM 09062X103 21,925 1,920 9.60 6,204 -10.44 0.0255
2021-08-12 2021-06-30 13F BIOGEN COM 09062X103 20,005 681 3.52 6,927 28.16 0.0323
2021-05-05 2021-03-31 13F BIOGEN COM 09062X103 19,324 68 0.35 5,405 14.63 0.0282
2021-02-12 2020-12-31 13F BIOGEN COM 09062X103 19,256 -67,917 -77.91 4,715 -80.93 0.0272
2020-11-12 2020-09-30 13F BIOGEN COM 09062X103 87,173 1,757 2.06 24,729 8.21 0.1556
2020-08-11 2020-06-30 13F BIOGEN COM 09062X103 85,416 -15,202 -15.11 22,853 -28.21 0.1517
2020-04-27 2020-03-31 13F BIOGEN COM 09062X103 100,618 11,432 12.82 31,833 20.29 0.2594
2020-02-10 2019-12-31 13F BIOGEN COM 09062X103 89,186 -1,199 -1.33 26,464 25.76 0.1867
2019-11-12 2019-09-30 13F BIOGEN COM 09062X103 90,385 6,129 7.27 21,043 6.79 0.1670
2019-08-12 2019-06-30 13F BIOGEN COM 09062X103 84,256 24,999 42.19 19,705 40.68 0.1609
2019-05-15 2019-03-31 13F/A-1 BIOGEN COM 09062X103 59,257 -13,524 -18.58 14,007 -36.04 0.1226
2019-05-15 2019-03-31 13F BIOGEN COM 09062X103 59,257 -13,524 14,007
2019-02-13 2018-12-31 13F/A-1 BIOGEN COM 09062X103 72,781 -8,853 -10.84 21,901 -24.06 0.2162
2019-02-13 2018-12-31 13F BIOGEN COM 09062X103 72,781 -8,853 21,901
2018-11-13 2018-09-30 13F BIOGEN COM 09062X103 81,634 609 0.75 28,841 22.64 0.2539
2018-08-14 2018-06-30 13F/A-1 BIOGEN COM 09062X103 81,025 1,213 1.52 23,516 7.60 0.2246
2018-08-14 2018-06-30 13F BIOGEN COM 09062X103 81,025 23,516
2018-05-10 2018-03-31 13F BIOGEN COM 09062X103 79,812 10,561 15.25 21,855 -0.93 0.2157
2018-02-14 2017-12-31 13F BIOGEN COM 09062X103 69,251 4,519 6.98 22,061 8.85 0.2247
2017-11-14 2017-09-30 13F BIOGEN COM 09062X103 64,732 4,155 6.86 20,268 23.30 0.2141
2017-07-27 2017-06-30 13F BIOGEN COM 09062X103 60,577 1,765 3.00 16,438 2.23 0.1779
2017-05-12 2017-03-31 13F BIOGEN COM 09062X103 58,812 4,078 7.45 16,080 3.59 0.1782
2017-02-07 2016-12-31 13F BIOGEN COM 09062X103 54,734 8,386 18.09 15,522 6.99 0.1866
2016-11-04 2016-09-30 13F BIOGEN COM 09062X103 46,348 -1,805 -3.75 14,508 24.60 0.1879
2016-08-01 2016-06-30 13F BIOGEN COM 09062X103 48,153 3,302 7.36 11,644 -0.27 0.1610
2016-05-06 2016-03-31 13F BIOGEN COM 09062X103 44,851 7,420 19.82 11,676 1.82 0.1747
2016-02-12 2015-12-31 13F BIOGEN COM 09062X103 37,431 -12,213 -24.60 11,467 -20.85 0.1880
2015-11-12 2015-09-30 13F BIOGEN COM 09062X103 49,644 1,558 3.24 14,487 -25.42 0.2513
2015-08-14 2015-06-30 13F BIOGEN INC COM COM 09062X103 48,086 4,339 9.92 19,424 5.15 0.3298
2015-05-15 2015-03-31 13F BIOGEN COM 09062X103 43,747 1,356 3.20 18,472 28.37 0.3242
2015-02-05 2014-12-31 13F BIOGEN IDEC COM 09062X103 42,391 4,752 12.63 14,390 15.57 0.2693
2014-11-03 2014-09-30 13F BIOGEN IDEC COM 09062X103 37,639 13,428 55.46 12,451 63.10 0.2498
2014-08-13 2014-06-30 13F BIOGEN IDEC COM 09062X103 24,211 450 1.89 7,634 5.04 0.1094
2014-05-13 2014-03-31 13F BIOGEN IDEC COM 09062X103 23,761 1,753 7.97 7,268 18.12 0.1119
2014-02-12 2013-12-31 13F BIOGEN IDEC COM 09062X103 22,008 1,012 4.82 6,153 21.72 0.1007
2013-10-30 2013-09-30 13F BIOGEN IDEC COM 09062X103 20,996 562 2.75 5,055 14.94 0.0931
2013-07-19 2013-06-30 13F BIOGEN IDEC COM 09062X103 20,434 20,434 4,398 0.0876
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.