Westfield Capital Management
ALNY icon

Westfield Capital Management’s Alnylam Pharmaceuticals ALNY Stock Holding History

Westfield Capital Management’s Portfolio ALNY Stock Details ALNY Fund Activity
Bought
Maintained
Sold
Quarter Market Value Status Shares Change in
Stake 		Trade Value Portfolio Weight Portfolio Position
2026
Q2 		$76M Buy
252,383
+6,844
+3% +$2.06M 0.25% 112
2026
Q1 		$81.2M Buy
245,539
+152,095
+163% +$51.8M 0.34% 95
2025
Q4 		$37.2M Buy
93,444
+5,536
+6% +$2.45M 0.15% 165
2025
Q3 		$40.1M Sell
87,908
-98,997
-53% -$40.3M 0.17% 165
2025
Q2 		$60.9M Sell
186,905
-5,267
-3% -$1.46M 0.26% 120
2025
Q1 		$51.9M Sell
192,172
-23,954
-11% -$6.16M 0.25% 124
2024
Q4 		$50.9M Buy
+216,126
New +$56.8M 0.22% 136
2020
Q2 		– Sell
-138,664
Closed -$15.1M – 231
2020
Q1 		$15.1M Sell
138,664
-110,345
-44% -$12.7M 0.13% 160
2019
Q4 		$28.7M Sell
249,009
-31,288
-11% -$3.12M 0.2% 137
2019
Q3 		$22.5M Sell
280,297
-155,736
-36% -$12.3M 0.18% 147
2019
Q2 		$31.6M Buy
436,033
+116,110
+36% +$8.91M 0.24% 136
2019
Q1 		$29.9M Buy
319,923
+49,480
+18% +$4.14M 0.23% 140
2018
Q4 		$19.7M Buy
270,443
+99,588
+58% +$7.66M 0.17% 162
2018
Q3 		$15M Sell
170,855
-57,285
-25% -$5.76M 0.11% 189
2018
Q2 		$22.5M Buy
+228,140
New +$22.6M 0.17% 177
2016
Q4 		– Sell
-271,302
Closed -$18.4M – 259
2016
Q3 		$18.4M Sell
271,302
-5,465
-2% -$386K 0.15% 176
2016
Q2 		$15.4M Buy
+276,767
New +$17.4M 0.13% 185

Other funds holding ALNY

Fidelity Investments
Fidelity Investments Boston, Massachusetts $2.3T AUM 54.33% 1-Year Est. Return
Capital World Investors
Capital World Investors Los Angeles, California $846B AUM 46.74% 1-Year Est. Return
BlackRock
BlackRock New York $6.73T AUM 46.02% 1-Year Est. Return
Capital Research Global Investors
Capital Research Global Investors Los Angeles, California $717B AUM 35.42% 1-Year Est. Return
Vanguard Portfolio Management
Vanguard Portfolio Management Malvern, Pennsylvania $2.22T AUM
Vanguard Capital Management
Vanguard Capital Management Malvern, Pennsylvania $4.68T AUM
T. Rowe Price Investment Management
T. Rowe Price Investment Management Baltimore, Maryland $153B AUM 38.14% 1-Year Est. Return
Invesco
Invesco Atlanta, Georgia $1.26T AUM 61.52% 1-Year Est. Return
State Street
State Street Boston, Massachusetts $3.37T AUM 44.26% 1-Year Est. Return
Geode Capital Management
Geode Capital Management Boston, Massachusetts $1.88T AUM 44.46% 1-Year Est. Return

Westfield Capital Management's ALNY Position: Q2 2026 in Review

Westfield Capital Management increased its Alnylam Pharmaceuticals (ALNY) stake by 2.8% in Q2 2026, buying an estimated $2.06M and bringing the position to 252,383 shares worth $76M. The position accounts for 0.25% of the portfolio, ranked #112.

Westfield Capital Management first reported a position in ALNY in Q2 2016 and has held it in 17 quarters since. The position peaked at $81.2M in Q1 2026. 788 funds tracked by Wall St. Rank hold ALNY as of Q2 2026.

  • Westfield Capital Management held 252,383 shares of Alnylam Pharmaceuticals worth $76M as of Q2 2026.
  • Westfield Capital Management bought 6,844 Alnylam Pharmaceuticals shares in Q2 2026, an estimated $2.06M.
  • Alnylam Pharmaceuticals made up 0.25% of Westfield Capital Management's portfolio in Q2 2026, its #112 holding.
  • Westfield Capital Management first reported a position in Alnylam Pharmaceuticals in Q2 2016 and has held it in 17 quarters since.
  • Westfield Capital Management's Alnylam Pharmaceuticals position peaked at $81.2M in Q1 2026.
  • 788 funds tracked by Wall St. Rank held Alnylam Pharmaceuticals as of Q2 2026.

Based on Westfield Capital Management's 13F filing for Q2 2026, filed 12 Aug 2026.