Ionis Pharmaceuticals, Inc.
US ˙ NasdaqGS ˙ US4622221004

SecurityIONS / Ionis Pharmaceuticals, Inc.
InstitutionSei Investments Co
Latest Disclosed Ownership115,917 shares
Latest Disclosed Value $ 9,170,229
Sei Investments Co reports 2.61% decrease in ownership of IONS / Ionis Pharmaceuticals, Inc.

On February 13, 2026 - Sei Investments Co filed a 13F-HR form disclosing ownership of 115,917 shares of Ionis Pharmaceuticals, Inc. (US:IONS) valued at $9,170,194 USD as of December 31, 2025. The entity filed a previous 13F-HR on November 13, 2025 disclosing 119,028 shares of Ionis Pharmaceuticals, Inc.. This represents a change in shares of -2.61% during the quarter. The current value of the position is $8,633,498 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)
2026-02-13 2025-12-31 13F IONIS PHARMACEUTICALS COM 462222100 115,917 -3,111 -2.61 9,170 17.78 0.0091
2025-11-13 2025-09-30 13F IONIS PHARMACEUTICALS COM 462222100 119,028 20,680 21.03 7,787 100.41 0.0084
2025-08-14 2025-06-30 13F IONIS PHARMACEUTICALS COM 462222100 98,348 26,790 37.44 3,886 80.03 0.0045
2025-05-14 2025-03-31 13F/A-1 IONIS PHARMACEUTICALS COM 462222100 71,558 1,467 2.09 2,159 -11.92 0.0028
2025-05-13 2025-03-31 13F IONIS PHARMACEUTICALS COM 462222100 70,119 28 2,450 0.0027
2025-02-11 2024-12-31 13F IONIS PHARMACEUTICALS COM 462222100 70,091 -119,746 -63.08 2,450 -67.78 0.0031
2024-11-12 2024-09-30 13F IONIS PHARMACEUTICALS COM 462222100 189,837 57,526 43.48 7,605 20.60 0.0099
2024-08-13 2024-06-30 13F IONIS PHARMACEUTICALS COM 462222100 132,311 52,424 65.62 6,306 82.07 0.0089
2024-05-07 2024-03-31 13F IONIS PHARMACEUTICALS COM 462222100 79,887 9,714 13.84 3,463 -2.45 0.0051
2024-02-14 2023-12-31 13F IONIS PHARMACEUTICALS COM 462222100 70,173 5,462 8.44 3,550 20.95 0.0057
2023-11-14 2023-09-30 13F IONIS PHARMACEUTICALS COM 462222100 64,711 49,401 322.67 2,935 367.36 0.0053
2023-08-11 2023-06-30 13F IONIS PHARMACEUTICALS COM 462222100 15,310 -30,614 -66.66 628 -61.73 0.0011
2023-05-12 2023-03-31 13F IONIS PHARMACEUTICALS COM 462222100 45,924 -17 -0.04 1,641 -5.42 0.0030
2023-02-10 2022-12-31 13F IONIS PHARMACEUTICALS COM 462222100 45,941 26,812 140.16 1,735 105.33 0.0039
2022-11-14 2022-09-30 13F IONIS PHARMACEUTICALS COM 462222100 19,129 8,503 80.02 845 115.56 0.0019
2022-08-15 2022-06-30 13F IONIS PHARMACEUTICALS COM 462222100 10,626 -392 -3.56 392 -3.69 0.0008
2022-05-13 2022-03-31 13F IONIS PHARMACEUTICALS COM 462222100 11,018 -176 -1.57 407 20.06 0.0008
2022-02-14 2021-12-31 13F IONIS PHARMACEUTICALS COM 462222100 11,194 -2,763 -19.80 339 -15.46 0.0006
2021-11-12 2021-09-30 13F IONIS PHARMACEUTICALS COM 462222100 13,957 -95 -0.68 401 -18.50 0.0008
2021-08-06 2021-06-30 13F IONIS PHARMACEUTICALS COM 462222100 14,052 -13,410 -48.83 492 -64.27 0.0011
2021-05-12 2021-03-31 13F IONIS PHARMACEUTICALS COM 462222100 27,462 811 3.04 1,377 -5.88 0.0035
2021-02-08 2020-12-31 13F IONIS PHARMACEUTICALS COM 462222100 26,651 -58,480 -68.69 1,463 -63.54 0.0038
2020-12-04 2020-09-30 13F/A-1 IONIS PHARMACEUTICALS COM 462222100 85,131 -8,920 -9.48 4,013 -27.42 0.0116
2020-11-06 2020-09-30 13F IONIS PHARMACEUTICALS COM 462222100 85,402 -8,649 4,026 9,693.7129
2020-08-17 2020-06-30 13F/A-1 IONIS PHARMACEUTICALS COM 462222100 94,051 3,568 3.94 5,529 29.24 0.0172
2020-08-11 2020-06-30 13F IONIS PHARMACEUTICALS COM 462222100 101,471 10,988 6,109 16,570.9877
2020-05-14 2020-03-31 13F IONIS PHARMACEUTICALS COM 462222100 90,483 -8,214 -8.32 4,278 -28.25 0.0157
2020-02-06 2019-12-31 13F IONIS PHARMACEUTICALS COM 462222100 98,697 26,555 36.81 5,962 37.95 0.0178
2019-11-12 2019-09-30 13F IONIS PHARMACEUTICALS COM 462222100 72,142 3,101 4.49 4,322 -2.59 0.0111
2019-08-14 2019-06-30 13F IONIS PHARMACEUTICALS COM 462222100 69,041 1,792 2.66 4,437 -18.72 0.0145
2019-05-15 2019-03-31 13F IONIS PHARMACEUTICALS COM 462222100 67,249 12,772 23.44 5,459 94.27 0.0183
2019-02-13 2018-12-31 13F IONIS PHARMACEUTICALS COM 462222100 54,477 0 0.00 2,810 0.00 0.0100
2018-11-08 2018-09-30 13F IONIS PHARMACEUTICALS COM 462222100 54,477 -44,728 -45.09 2,810 -32.03 0.0102
2018-08-03 2018-06-30 13F IONIS PHARMACEUTICALS COM 462222100 99,205 23,572 31.17 4,134 24.00 0.0141
2018-05-11 2018-03-31 13F IONIS PHARMACEUTICALS COM 462222100 75,633 19,238 34.11 3,334 17.56 0.0128
2018-02-08 2017-12-31 13F IONIS PHARMACEUTICALS COM 462222100 56,395 546 0.98 2,836 0.14 0.0098
2017-11-06 2017-09-30 13F IONIS PHARMACEUTICALS COM 462222100 55,849 4,492 8.75 2,832 8.38 0.0101
2017-07-31 2017-06-30 13F IONIS PHARMACEUTICALS COM 462222100 51,357 11,120 27.64 2,613 61.50 0.0104
2017-05-05 2017-03-31 13F IONIS PHARMACEUTICALS COM 462222100 40,237 4,030 11.13 1,618 -6.58 0.0071
2017-02-02 2016-12-31 13F IONIS PHARMACEUTICALS COM 462222100 36,207 -91,878 -71.73 1,732 -63.09 0.0084
2016-11-04 2016-09-30 13F IONIS PHARMACEUTICALS COM 462222100 128,085 -6,345 -4.72 4,693 49.89 0.0238
2016-08-11 2016-06-30 13F IONIS PHARMACEUTICALS COM 462222100 134,430 92,676 221.96 3,131 85.16 0.0188
2016-05-10 2016-03-31 13F/A-1 IONIS PHARMACEUTICALS COM 462222100 41,754 39,514 1,764.02 1,691 1,116.55 0.0105
2016-02-03 2015-12-31 13F IONIS PHARMACEUTICALS COM 462222100 2,240 -719 -24.30 139 16.81 0.0008
2015-11-02 2015-09-30 13F/A-1 ISIS PHARMACEUTICALS COM 464330109 2,959 -5,839 -66.37 119 -76.53 0.0011
2015-10-30 2015-09-30 13F ISIS PHARMACEUTICALS COM 464330109 2,959 120
2015-08-07 2015-06-30 13F/A-1 ISIS PHARMACEUTICALS COM 464330109 8,798 672 8.27 507 -2.31 0.0046
2015-08-04 2015-06-30 13F ISIS PHARMACEUTICALS COM 464330109 8,798 672 507 0.0046
2015-05-14 2015-03-31 13F/A-1 ISIS PHARMACEUTICALS COM 464330109 8,126 -1,801 -18.14 519 -15.33 0.0045
2015-05-01 2015-03-31 13F ISHARES TR 2020 CP TM ETF 464330109 8,126 519
2015-02-10 2014-12-31 13F ISIS PHARMACEUTICALS COM 464330109 9,927 9,927 613 0.0054
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.