Biogen Inc.
US ˙ NasdaqGS ˙ US09062X1037

SecurityBIIB / Biogen Inc.
InstitutionCwm, Llc
Latest Disclosed Ownership55,175 shares
Latest Disclosed Value $ 10,115,215
Cwm, Llc reports 12.86% increase in ownership of BIIB / Biogen Inc.

On May 14, 2026 - Cwm, Llc filed a 13F-HR form disclosing ownership of 55,175 shares of Biogen Inc. (US:BIIB) valued at $10,115,233 USD as of March 31, 2026. The entity filed a previous 13F-HR on January 26, 2026 disclosing 48,890 shares of Biogen Inc.. This represents a change in shares of 12.86% during the quarter. The current value of the position is $10,812,093 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)
2026-05-14 2026-03-31 13F BIOGEN COM 09062X103 55,175 6,285 12.86 10,115 126,337.50 0.0263
2026-01-26 2025-12-31 13F BIOGEN COM 09062X103 48,890 1,435 3.02 9 33.33 0.0233
2025-10-15 2025-09-30 13F BIOGEN COM 09062X103 47,455 12,673 36.44 7 50.00 0.0200
2025-07-25 2025-06-30 13F BIOGEN COM 09062X103 34,782 6,639 23.59 4 33.33 0.0154
2025-05-01 2025-03-31 13F BIOGEN COM 09062X103 28,143 12,418 78.97 4 50.00 0.0154
2025-02-04 2024-12-31 13F BIOGEN COM 09062X103 15,725 12,440 378.69 2 0.0100
2024-10-08 2024-09-30 13F BIOGEN COM 09062X103 3,285 -480 -12.75 1 0.0027
2024-07-10 2024-06-30 13F BIOGEN COM 09062X103 3,765 62 1.67 1 0.0041
2024-04-05 2024-03-31 13F BIOGEN COM 09062X103 3,703 245 7.09 1 0.0039
2024-02-01 2023-12-31 13F BIOGEN COM 09062X103 3,458 -200 -5.47 1 0.0048
2023-10-11 2023-09-30 13F BIOGEN COM 09062X103 3,658 -456 -11.08 1 -100.00 0.0058
2023-08-03 2023-06-30 13F BIOGEN COM 09062X103 4,114 1,312 46.82 1 0.0072
2023-05-01 2023-03-31 13F BIOGEN COM 09062X103 2,802 1,074 62.15 1 0.0053
2023-02-01 2022-12-31 13F BIOGEN COM 09062X103 1,728 233 15.59 0 -100.00 0.0035
2022-10-27 2022-09-30 13F BIOGEN COM 09062X103 1,495 248 19.89 399 57.09 0.0032
2022-07-28 2022-06-30 13F BIOGEN COM 09062X103 1,247 113 9.96 254 6.28 0.0020
2022-04-21 2022-03-31 13F BIOGEN COM 09062X103 1,134 150 15.24 239 1.27 0.0017
2022-01-31 2021-12-31 13F BIOGEN COM 09062X103 984 164 20.00 236 -16.90 0.0017
2021-09-15 2021-06-30 13F/A-1 BIOGEN COM 09062X103 820 0 0.00 284 0.00 0.0023
2021-07-29 2021-06-30 13F BIOGEN COM 09062X103 820 0 284 0.0023
2021-09-15 2021-03-31 13F/A-1 BIOGEN COM 09062X103 820 0 0.00 284 0.00 0.0023
2021-04-27 2021-03-31 13F BIOGEN COM 09062X103 706 -114 198 0.0017
2021-09-15 2020-12-31 13F/A-1 BIOGEN COM 09062X103 820 0 0.00 284 0.00 0.0023
2021-01-27 2020-12-31 13F BIOGEN COM 09062X103 442 -378 108 0.0010
2021-09-15 2020-09-30 13F/A-1 BIOGEN COM 09062X103 820 0 0.00 284 0.00 0.0023
2020-10-19 2020-09-30 13F BIOGEN COM 09062X103 712 -108 202 0.0022
2021-09-15 2020-06-30 13F/A-1 BIOGEN COM 09062X103 820 0 0.00 284 0.00 0.0023
2020-07-22 2020-06-30 13F BIOGEN COM 09062X103 679 -141 182 0.0022
2021-09-15 2020-03-31 13F/A-1 BIOGEN COM 09062X103 820 0 0.00 284 0.00 0.0023
2020-04-28 2020-03-31 13F BIOGEN COM 09062X103 680 -140 215 0.0032
2021-09-14 2019-12-31 13F/A-1 BIOGEN COM 09062X103 820 0 0.00 284 0.00 0.0023
2020-01-27 2019-12-31 13F BIOGEN COM 09062X103 650 -170 193 0.0025
2021-09-14 2019-09-30 13F/A-1 BIOGEN COM 09062X103 820 0 0.00 284 0.00 0.0023
2019-10-22 2019-09-30 13F BIOGEN COM 09062X103 557 -263 130 0.0019
2021-09-14 2019-06-30 13F/A-1 BIOGEN COM 09062X103 820 0 0.00 284 0.00 0.0023
2019-07-31 2019-06-30 13F BIOGEN COM 09062X103 823 3 192 0.0032
2021-09-02 2019-03-31 13F/A-1 BIOGEN COM 09062X103 820 544 197.10 284 242.17 0.0023
2019-04-22 2019-03-31 13F BIOGEN COM 09062X103 420 144 99 0.0020
2019-01-25 2018-12-31 13F BIOGEN COM 09062X103 276 146 112.31 83 80.43 0.0021
2018-10-29 2018-09-30 13F BIOGEN COM 09062X103 130 19 17.12 46 43.75 0.0012
2018-07-31 2018-06-30 13F BIOGEN COM 09062X103 111 -3 -2.63 32 3.23 0.0011
2018-04-26 2018-03-31 13F BIOGEN COM 09062X103 114 44 62.86 31 40.91 0.0012
2018-01-16 2017-12-31 13F BIOGEN COM 09062X103 70 0 0.00 22 0.00 0.0010
2017-10-16 2017-09-30 13F BIOGEN COM 09062X103 70 1 1.45 22 15.79 0.0010
2017-07-17 2017-06-30 13F BIOGEN COM 09062X103 69 13 23.21 19 26.67 0.0010
2017-04-17 2017-03-31 13F BIOGEN COM 09062X103 56 -40 -41.67 15 -44.44 0.0008
2017-01-19 2016-12-31 13F BIOGEN COM 09062X103 96 48 100.00 27 80.00 0.0017
2016-10-17 2016-09-30 13F BIOGEN COM 09062X103 48 48 0.00 15 0.0010
2016-04-18 2016-03-31 13F BIOGEN COM 09062X103 0 -15 -100.00 0 -100.00
2016-02-01 2015-12-31 13F BIOGEN COM 09062X103 15 -20 -57.14 5 -50.00 0.0005
2014-02-14 2013-12-31 13F BIOGEN IDEC COM 09062X103 35 4 12.90 10 42.86 0.0016
2013-11-14 2013-09-30 13F BIOGEN IDEC COM 09062X103 31 31 7 0.0018
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.