DOSSIER · 13F Holders · Q1 2026Healthcare · Pharmaceutical Preparations
ALNY

ALNYLAM PHARMACEUTICALS INC

816 institutions still hold ALNYLAM PHARMACEUTICALS INC as of Q1 2026. Tracked across SEC 13F-HR filings, with insider and 13D/G activity surfaced alongside.

CUSIP 02043Q107·Pharmaceutical Preparations·816 13F holders·last filed Mar 31, 2026
Market cap
13F value held
$31.3B
visible holders
Holders
816
filers reporting
Concentration
15.40%
FMR LLC #1
top holder share
AI Holders Summary · Q1 2026

Alnylam Pharmaceuticals' stock (ALNY, CUSIP 02043Q107) entered Q1 2026 with 754 institutional holders controlling $39.3B of positions across the 13F universe, making it one of the densest institutional-ownership names in healthcare. The quarter's signal is not accumulation — it is active rotation at the manager tier: FMR LLC cut by $1.5B (–9.4% of its position), Capital World Investors slashed by $2.9B (–17.8%), Invesco shed $434M, Baillie Gifford trimmed $209M, and Dodge & Cox decreased $143M. On the other side, Capital Research Global Investors added $438M (+64.8% increase), Two Sigma built a new $659M position (+$414M), Clearbridge entered with a $449M new stake (+$211M), JPMorgan added $122M, and Bank of America added $75M. Three Vanguard entities (Portfolio Management, Capital Management, Fiduciary Trust) are all shown as new positions totaling ~$2.9B. This is a textbook institutional rebalancing story — the smart-money consensus on ALNY's RNAi platform is not withdrawing, but the active-manager composition of the holder base is shifting.

The Q1 rotation pattern matters: FMR (–$1.5B) and Capital World (–$2.9B) making the two largest reductions among active managers signals they are rotating out of biotech overweight into something else — perhaps cash or sector rotation. Meanwhile Two Sigma and Capital Research Global are building fresh stakes at $659M and $938M respectively, suggesting systematic/quantamental managers see value where fundamental-growth managers saw crowded positioning.

The three Vanguard entities marked NEW is notable — Vanguard Portfolio Management and Capital Management are passive/smarts-beta vehicles that typically build positions gradually. Their simultaneous appearance as NEW holders in a single quarter is unusual and worth watching.

Top holders

Sorted by position value. Source: SEC EDGAR 13F-HR filings.

#HolderValueShares% port.Quarter
01
FMR LLC
CIK 0000315066
$4.8B14.6M0.25%Q1 2026
02
Capital World Investors
CIK 0001422849
$3.6B10.8M0.49%Q1 2026
03
BlackRock, Inc.
CIK 0002012383
$3.5B10.4M0.06%Q1 2026
04
Capital Research Global Investors
CIK 0001422848
$3.1B9.5M0.49%Q1 2026
05
Vanguard Portfolio Management
CIK 0002100121· Index
$2.1B6.5M0.11%Q1 2026
06
JPMORGAN CHASE & CO
CIK 0000019617
$2.0B6.3M0.13%Q1 2026
07
VANGUARD CAPITAL MANAGEMENT LLC
CIK 0002100119· Index
$2.0B5.9M0.05%Q1 2026
08
T. Rowe Price Investment Management, Inc.
CIK 0001897612
$1.7B5.2M1.18%Q1 2026
09
Invesco Ltd.
CIK 0000914208
$1.3B4.1M0.13%Q1 2026
10
STATE STREET CORP
CIK 0000093751
$1.1B3.3M0.04%Q1 2026
11
GEODE CAPITAL MANAGEMENT, LLC
CIK 0001214717· Index
$885M2.7M0.06%Q1 2026
12
BAILLIE GIFFORD & CO
CIK 0001088875
$825M2.5M0.84%Q1 2026
13
TWO SIGMA INVESTMENTS, LP
CIK 0001179392
$659M2.0M0.53%Q1 2026
14
WELLINGTON MANAGEMENT GROUP LLP
CIK 0000902219
$641M1.9M0.12%Q1 2026
15
DODGE & COX
CIK 0000200217
$638M1.9M0.35%Q1 2026
16
AMERICAN CENTURY COMPANIES INC
CIK 0000748054
$596M1.8M0.31%Q1 2026
17
PRICE T ROWE ASSOCIATES INC /MD/
CIK 0000080255
$474M1.4M0.05%Q1 2026
18
TWO SIGMA ADVISERS, LP
CIK 0001478735
$450M1.1M0.88%Q4 2025
19
Clearbridge Investments, LLC
CIK 0001348883
$449M1.4M0.39%Q1 2026
20
Orbis Allan Gray Ltd
CIK 0001663865
$442M1.3M1.86%Q1 2026
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Insiders at ALNYLAM PHARMACEUTICALS INC
Cravatt BenjaminSchulman Amy WSigal Charles ElliottAusiello Dennis ABrandicourt OlivierMclaughlin MelissaGreenstreet YvonneFitzgerald Kevin Joseph