William Blair & Company
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William Blair & Company’s Ionis Pharmaceuticals IONS Stock Holding History

William Blair & Company’s Portfolio IONS Stock Details IONS Fund Activity
Bought
Maintained
Sold
Quarter Market Value Status Shares Change in
Stake 		Trade Value Portfolio Weight Portfolio Position
2026
Q1 		$2.54M Buy
33,857
+69
+0.2% +$5.45K 0.01% 666
2025
Q4 		$2.67M Sell
33,788
-583
-2% -$43.9K 0.01% 671
2025
Q3 		$2.25M Sell
34,371
-3,520
-9% -$172K 0.01% 705
2025
Q2 		$1.5M Sell
37,891
-490
-1% -$16K ﹤0.01% 785
2025
Q1 		$1.16M Sell
38,381
-1,501
-4% -$49.2K ﹤0.01% 844
2024
Q4 		$1.39M Sell
39,882
-6,769
-15% -$253K ﹤0.01% 807
2024
Q3 		$1.87M Buy
46,651
+21,389
+85% +$995K 0.01% 726
2024
Q2 		$1.2M Sell
25,262
-2,576
-9% -$106K ﹤0.01% 819
2024
Q1 		$1.21M Buy
27,838
+11,210
+67% +$534K ﹤0.01% 809
2023
Q4 		$841K Buy
16,628
+284
+2% +$13.6K ﹤0.01% 909
2023
Q3 		$741K Sell
16,344
-40
-0.2% -$1.65K ﹤0.01% 936
2023
Q2 		$672K Buy
16,384
+1,740
+12% +$66.9K ﹤0.01% 969
2023
Q1 		$523K Hold
14,644
– – ﹤0.01% 1032
2022
Q4 		$553K Sell
14,644
-200
-1% -$8.41K ﹤0.01% 1011
2022
Q3 		$657K Buy
14,844
+237
+2% +$9.99K ﹤0.01% 957
2022
Q2 		$541K Sell
14,607
-121
-0.8% -$4.56K ﹤0.01% 1037
2022
Q1 		$546K Buy
14,728
+264
+2% +$8.64K ﹤0.01% 1122
2021
Q4 		$440K Sell
14,464
-50
-0.3% -$1.57K ﹤0.01% 1266
2021
Q3 		$487K Buy
14,514
+4,226
+41% +$159K ﹤0.01% 1163
2021
Q2 		$410K Sell
10,288
-876
-8% -$34.3K ﹤0.01% 1223
2021
Q1 		$502K Sell
11,164
-4,000
-26% -$223K ﹤0.01% 1117
2020
Q4 		$857K Buy
15,164
+45
+0.3% +$2.24K ﹤0.01% 909
2020
Q3 		$717K Sell
15,119
-499
-3% -$27.7K ﹤0.01% 861
2020
Q2 		$921K Sell
15,618
-493
-3% -$27.4K ﹤0.01% 742
2020
Q1 		$762K Sell
16,111
-209
-1% -$11.6K ﹤0.01% 744
2019
Q4 		$986K Buy
16,320
+1,742
+12% +$104K 0.01% 783
2019
Q3 		$873K Buy
14,578
+402
+3% +$26.2K 0.01% 790
2019
Q2 		$911K Sell
14,176
-493
-3% -$34.9K 0.01% 784
2019
Q1 		$1.19M Buy
14,669
+179
+1% +$11.5K 0.01% 689
2018
Q4 		$783K Buy
14,490
+14
+0.1% +$714 0.01% 764
2018
Q3 		$747K Hold
14,476
– – ﹤0.01% 831
2018
Q2 		$603K Buy
14,476
+8,600
+146% +$381K ﹤0.01% 888
2018
Q1 		$259K Sell
5,876
-478
-8% -$24.3K ﹤0.01% 1126
2017
Q4 		$320K Buy
6,354
+900
+17% +$49.4K ﹤0.01% 1107
2017
Q3 		$277K Buy
5,454
+73
+1% +$3.82K ﹤0.01% 1139
2017
Q2 		$274K Hold
5,381
– – ﹤0.01% 1230
2017
Q1 		$258K Hold
5,381
– – ﹤0.01% 1141
2016
Q4 		$257K Buy
+5,381
New +$213K ﹤0.01% 1062
2016
Q2 		– Sell
-5,417
Closed -$219K – 1256
2016
Q1 		$219K Sell
5,417
-295
-5% -$12K ﹤0.01% 1041
2015
Q4 		$353K Buy
+5,712
New +$308K ﹤0.01% 906
2015
Q3 		– Sell
-5,975
Closed -$343K – 1480
2015
Q2 		$343K Sell
5,975
-118
-2% -$7.5K ﹤0.01% 1886
2015
Q1 		$388K Buy
6,093
+85
+1% +$5.77K ﹤0.01% 1807
2014
Q4 		$370K Buy
6,008
+196
+3% +$9.67K ﹤0.01% 1781
2014
Q3 		$225K Buy
+5,812
New +$206K ﹤0.01% 1931
2014
Q2 		– Sell
-5,612
Closed -$242K – 2097
2014
Q1 		$242K Hold
5,612
– – ﹤0.01% 1830
2013
Q4 		$223K Buy
5,612
+65
+1% +$2.32K ﹤0.01% 1840
2013
Q3 		$208K Buy
+5,547
New +$166K ﹤0.01% 1870

Other funds holding IONS

Fidelity Investments
Fidelity Investments Boston, Massachusetts $1.9T AUM 41.92% 1-Year Est. Return
Capital World Investors
Capital World Investors Los Angeles, California $733B AUM 35.63% 1-Year Est. Return
BlackRock
BlackRock New York $6.73T AUM 46.02% 1-Year Est. Return
VPM
Vanguard Portfolio Management Malvern, Pennsylvania $1.91T AUM
VCM
Vanguard Capital Management Malvern, Pennsylvania $4.04T AUM
Wellington Management Group
Wellington Management Group Boston, Massachusetts $535B AUM 26.23% 1-Year Est. Return
T. Rowe Price Investment Management
T. Rowe Price Investment Management Baltimore, Maryland $145B AUM 22.78% 1-Year Est. Return
Two Sigma Investments
Two Sigma Investments New York $124B AUM 33.93% 1-Year Est. Return
Geode Capital Management
Geode Capital Management Boston, Massachusetts $1.61T AUM 30.72% 1-Year Est. Return
State Street
State Street Boston, Massachusetts $3.37T AUM 44.26% 1-Year Est. Return

William Blair & Company's IONS Position: Q1 2026 in Review

William Blair & Company increased its Ionis Pharmaceuticals (IONS) stake by 0.2% in Q1 2026, buying an estimated $5.45K and bringing the position to 33,857 shares worth $2.54M. The position accounts for 0.01% of the portfolio, ranked #666.

William Blair & Company first reported a position in IONS in Q3 2013 and has held it in 47 quarters since. The position peaked at $2.67M in Q4 2025. 494 funds tracked by Wall St. Rank hold IONS as of Q1 2026.

  • William Blair & Company held 33,857 shares of Ionis Pharmaceuticals worth $2.54M as of Q1 2026.
  • William Blair & Company bought 69 Ionis Pharmaceuticals shares in Q1 2026, an estimated $5.45K.
  • Ionis Pharmaceuticals made up 0.01% of William Blair & Company's portfolio in Q1 2026, its #666 holding.
  • William Blair & Company first reported a position in Ionis Pharmaceuticals in Q3 2013 and has held it in 47 quarters since.
  • William Blair & Company's Ionis Pharmaceuticals position peaked at $2.67M in Q4 2025.
  • 494 funds tracked by Wall St. Rank held Ionis Pharmaceuticals as of Q1 2026.

Based on William Blair & Company's 13F filing for Q1 2026, filed 8 May 2026.