Ionis Pharmaceuticals, Inc.
MX ˙ BMV ˙ US4622221004
SecurityMX:IONS / Ionis Pharmaceuticals, Inc.
InstitutionMarshall Wace, Llp
Latest Disclosed Ownership95,954 shares
Latest Disclosed Value $ 7,205,186
Marshall Wace, Llp reports 62.65% decrease in ownership of IONS / Ionis Pharmaceuticals, Inc.

On May 14, 2026 - Marshall Wace, Llp filed a 13F-HR form disclosing ownership of 95,954 shares of Ionis Pharmaceuticals, Inc. (MX:IONS) valued at $7,205,186 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 13, 2026 disclosing 256,933 shares of Ionis Pharmaceuticals, Inc.. This represents a change in shares of -62.65% 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)
2026-05-14 2026-03-31 13F IONIS PHARMACEUT COMMON STOCK 462222100 95,954 -160,979 -62.65 7,205 -64.55 0.0034
2026-02-13 2025-12-31 13F IONIS PHARMACEUT COMMON STOCK 462222100 256,933 -701,896 -73.20 20,326 -67.60 0.0185
2025-11-13 2025-09-30 13F IONIS PHARMACEUT COMMON STOCK 462222100 958,829 945,729 7,219.31 62,727 12,032.69 0.0636
2025-08-13 2025-06-30 13F IONIS PHARMACEUT COMMON STOCK 462222100 13,100 3,998 43.92 518 88.69 0.0006
2025-05-15 2025-03-31 13F IONIS PHARMACEUT COMMON STOCK 462222100 9,102 -803,204 -98.88 275 -99.04 0.0003
2025-02-13 2024-12-31 13F IONIS PHARMACEUT COMMON STOCK 462222100 812,306 -1,108,158 -57.70 28,398 -63.09 0.0341
2024-11-14 2024-09-30 13F IONIS PHARMACEUT COMMON STOCK 462222100 1,920,464 1,747,265 1,008.82 76,934 832.07 0.0937
2024-08-14 2024-06-30 13F IONIS PHARMACEUT COMMON STOCK 462222100 173,199 157,756 1,021.54 8,255 1,133.78 0.0110
2024-05-15 2024-03-31 13F IONIS PHARMACEUT COMMON STOCK 462222100 15,443 -118,106 -88.44 669 -90.10 0.0010
2024-02-14 2023-12-31 13F IONIS PHARMACEUT COMMON STOCK 462222100 133,549 65,422 96.03 6,756 118.64 0.0114
2023-11-14 2023-09-30 13F IONIS PHARMACEUT COMMON STOCK 462222100 68,127 -936 -1.36 3,090 9.07 0.0063
2023-08-14 2023-06-30 13F IONIS PHARMACEUT COMMON STOCK 462222100 69,063 -107,757 -60.94 2,834 -59.84 0.0055
2021-08-13 2021-06-30 13F IONIS PHARMACEUT COMMON STOCK 462222100 176,820 176,820 7,054 0.0344
2021-05-17 2021-03-31 13F IONIS PHARMACEUT COMMON STOCK 462222100 0 -111,269 -100.00 0 -100.00
2021-02-16 2020-12-31 13F IONIS PHARMACEUT COMMON STOCK 462222100 111,269 54,407 95.68 6,291 133.17 0.0341
2020-11-16 2020-09-30 13F IONIS PHARMACEUT COMMON STOCK 462222100 56,862 56,862 -48.90 2,698 -57.11 0.0173
2020-05-15 2020-03-31 13F IONIS PHARMACEUT COMMON STOCK 462222100 0 -1,016 -100.00 0 -100.00
2020-02-14 2019-12-31 13F IONIS PHARMACEUT COMMON STOCK 462222100 1,016 455 81.11 61 79.41 0.0004
2019-11-14 2019-09-30 13F IONIS PHARMACEUT COMMON STOCK 462222100 561 561 -44.78 34 -44.26 0.0003
2019-08-14 2019-06-30 13F IONIS PHARMACEUT COMMON STOCK 462222100 0 -45 -100.00 0 -100.00
2019-05-29 2019-03-31 13F/A-1 IONIS PHARMACEUT COMMON STOCK 462222100 45 45 4 0.0000
2019-05-14 2019-03-31 13F IONIS PHARMACEUT COMMON STOCK 462222100 45 45 4
2019-02-14 2018-12-31 13F IONIS PHARMACEUT COMMON STOCK 462222100 0 -8,939 -100.00 0 -100.00
2018-12-06 2018-09-30 13F/A-1 IONIS PHARMACEUT COMMON STOCK 462222100 8,939 8,939 461 0.0039
2018-11-14 2018-09-30 13F IONIS PHARMACEUT COMMON STOCK 462222100 8,939 8,939 461
2016-05-13 2016-03-31 13F IONIS PHARMACEUT COMMON STOCK 462222100 0 -128,328 -100.00 0 -100.00
2016-02-10 2015-12-31 13F IONIS PHARMACEUT COMMON STOCK 462222100 128,328 -2,842 -2.17 7,947 49.89 0.0746
2015-11-12 2015-09-30 13F ISIS PHARM COMMON STOCK 464330109 131,170 -18,115 -12.13 5,302 -38.28 0.0651
2015-08-14 2015-06-30 13F ISIS PHARM COMMON STOCK 464330109 149,285 149,285 8,591 0.1121
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.