Alnylam Pharmaceuticals, Inc.
DE ˙ XTRA ˙ US02043Q1076
260,50 € ↑8,70 (3,46%)
2026-06-04
DEL PRIS
SecurityDE:DUL / Alnylam Pharmaceuticals, Inc.
InstitutionClearbridge Investments, LLC
Latest Disclosed Ownership1,356,036 shares
Latest Disclosed Value $ 448,671,479
Clearbridge Investments, LLC reports 127.14% increase in ownership of DUL / Alnylam Pharmaceuticals, Inc.

On May 13, 2026 - Clearbridge Investments, LLC filed a 13F-HR form disclosing ownership of 1,356,036 shares of Alnylam Pharmaceuticals, Inc. (DE:DUL) valued at $387,419,485 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 11, 2026 disclosing 597,013 shares of Alnylam Pharmaceuticals, Inc.. This represents a change in shares of 127.14% during the quarter. The current value of the position is $353,247,378 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)
2026-05-13 2026-03-31 13F Alnylam Pharmaceuticals COM 02043Q107 1,356,036 759,023 127.14 448,671 88.99 0.3515
2026-02-11 2025-12-31 13F Alnylam Pharmaceuticals COM 02043Q107 597,013 -25,422 -4.08 237,402 -16.36 0.1901
2025-11-13 2025-09-30 13F Alnylam Pharmaceuticals COM 02043Q107 622,435 65,336 11.73 283,830 56.24 0.2137
2025-08-12 2025-06-30 13F Alnylam Pharmaceuticals COM 02043Q107 557,099 549,322 7,063.42 181,664 8,550.67 0.1475
2025-05-13 2025-03-31 13F Alnylam Pharmaceuticals COM 02043Q107 7,777 7,777 2,100 0.0018
2023-11-13 2023-09-30 13F Alnylam Pharmaceuticals COM 02043Q107 0 -83,185 -100.00 0 -100.00
2023-08-11 2023-06-30 13F Alnylam Pharmaceuticals COM 02043Q107 83,185 6,911 9.06 15,800 3.41 0.0143
2023-05-12 2023-03-31 13F Alnylam Pharmaceuticals COM 02043Q107 76,274 19,614 34.62 15,279 13.47 0.0146
2023-02-10 2022-12-31 13F Alnylam Pharmaceuticals COM 02043Q107 56,660 56,660 13,465 0.0133
2020-11-12 2020-09-30 13F ALNYLAM PHARMACEUTICALS COM 02043Q107 0 -365 -100.00 0 -100.00
2020-08-14 2020-06-30 13F ALNYLAM PHARMACEUTICALS COM 02043Q107 365 0 0.00 54 35.00 0.0000
2020-05-22 2020-03-31 13F/A-1 ALNYLAM PHARMACEUTICALS COM 02043Q107 365 -12 -3.18 40 -9.09 0.0000
2020-05-15 2020-03-31 13F ALNYLAM PHARMACEUTICALS COM 02043Q107 365 -12 40 43.3611
2020-02-14 2019-12-31 13F ALNYLAM PHARMACEUTICALS COM 02043Q107 377 0 0.00 44 46.67 0.0000
2019-11-14 2019-09-30 13F ALNYLAM PHARMACEUTICALS COM 02043Q107 377 0 0.00 30 11.11 0.0000
2019-08-14 2019-06-30 13F ALNYLAM PHARMACEUTICALS COM 02043Q107 377 0 0.00 27 -22.86 0.0000
2019-05-15 2019-03-31 13F ALNYLAM PHARMACEUTICALS COM 02043Q107 377 0 0.00 35 29.63 0.0000
2019-02-14 2018-12-31 13F ALNYLAM PHARMACEUTICALS COM 02043Q107 377 0 0.00 27 -18.18 0.0000
2018-11-28 2018-09-30 13F/A-1 ALNYLAM PHARMACEUTICALS COM 02043Q107 377 0 0.00 33 -10.81 0.0000
2018-11-14 2018-09-30 13F ALNYLAM PHARMACEUTICALS COM 02043Q107 377 0 33
2018-08-14 2018-06-30 13F ALNYLAM PHARMACEUTICALS COM 02043Q107 377 -1,745 -82.23 37 -85.38 0.0000
2018-05-15 2018-03-31 13F ALNYLAM PHARMACEUTICALS COM 02043Q107 2,122 -394 -15.66 253 -20.94 0.0002
2018-02-14 2017-12-31 13F ALNYLAM PHARMACEUTICALS COM 02043Q107 2,516 -1,502 -37.38 320 -32.20 0.0003
2017-11-14 2017-09-30 13F ALNYLAM PHARMACEUTICALS COM 02043Q107 4,018 -219 -5.17 472 39.64 0.0005
2017-08-14 2017-06-30 13F ALNYLAM PHARMACEUTICALS COM 02043Q107 4,237 3,134 284.13 338 492.98 0.0003
2017-06-07 2017-03-31 13F/A-1 ALNYLAM PHARMACEUTICALS COM 02043Q107 1,103 0 0.00 57 39.02 0.0001
2017-05-15 2017-03-31 13F ALNYLAM PHARMACEUTICALS COM 02043Q107 1,103 57
2017-02-14 2016-12-31 13F ALNYLAM PHARMACEUTICALS COM 02043Q107 1,103 18 1.66 41 -44.59 0.0000
2016-11-14 2016-09-30 13F ALNYLAM PHARMACEUTICALS COM 02043Q107 1,085 491 82.66 74 124.24 0.0001
2016-08-15 2016-06-30 13F ALNYLAM PHARMACEUTICALS COM 02043Q107 594 594 33 0.0000
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.