Alnylam Pharmaceuticals, Inc.
Alnylam Pharmaceuticals, Inc. (ALNY) Stock Ownership
Institutional vs insider vs public ownership from 13F and float data — top holders, activity, and insider trades below.
SEC 13F · FMP · ALNY · as of Mar 31, 2025
Ownership Breakdown
684
Institutional Holders
▲ 48 vs Q4
$34.84B
Total Inst. Value
▲ $4.79B vs Q4
133.51M
Shares Outstanding
freeFloat 99.57%
130.97M
13F Shares Held
▲ 1.35M vs Q4
Institutional ownership = 13F shares ÷ total outstanding. Insider % = 100 − free float. Public % = free float − institution %. Data: FMP /symbol-positions-summary + /shares-float + SEC EDGAR.
Top Institutional Holders
ALNY largest shareholders · institutional ownership
Q1 2025 · SEC 13F
Showing top 10 holders
| Holder | Shares | % Owned | Weight | Value | Reported | Change |
|---|---|---|---|---|---|---|
CAPITAL WORLD INVESTORS pharmaceutical preparations | 16.75M | 12.92% | 12.92% | $4.52T | May 12, 2025 | ▲ 149.1K |
FMR LLC pharmaceutical preparations | 15.31M | 11.81% | 11.81% | $4.13T | May 12, 2025 | ▲ 1.82M |
VANGUARD GROUP INC pharmaceutical preparations | 13.06M | 10.07% | 10.07% | $3.53T | May 9, 2025 | ▲ 323.2K |
BLACKROCK, INC. pharmaceutical preparations | 9.56M | 7.37% | 7.37% | $2.58T | May 2, 2025 | ▼ 325.9K |
CAPITAL RESEARCH GLOBAL INVESTORS pharmaceutical preparations | 7.15M | 5.52% | 5.52% | $1.93T | May 12, 2025 | ▲ 186.2K |
REGENERON PHARMACEUTICALS, INC. pharmaceutical preparations | 4.44M | 3.43% | 3.43% | $1.20T | May 2, 2025 | — held |
T. ROWE PRICE INVESTMENT MANAGEMENT, INC. pharmaceutical preparations | 4.42M | 3.41% | 3.41% | $1.19T | May 14, 2025 | ▲ 33.7K |
BAILLIE GIFFORD & CO pharmaceutical preparations | 3.66M | 2.82% | 2.82% | $987.63B | May 7, 2025 | ▼ 382.7K |
PRICE T ROWE ASSOCIATES INC /MD/ pharmaceutical preparations | 3.51M | 2.70% | 2.70% | $946.47B | May 14, 2025 | ▲ 185.8K |
STATE STREET CORP pharmaceutical preparations | 3.37M | 2.60% | 2.60% | $909.04B | May 15, 2025 | ▼ 56.3K |
Data from SEC Form 13F filings. Ownership bar normalised to largest holder. Change flags: isNew / isSoldOut / changeInSharesNumber (FMP extract-analytics/holder).
Institutional Activity
Q1 2025 vs prior quarter
Q1 2025
27
Increased
+4.78M shares2
New Positions
first time holders20
Decreased
−3.45M shares0
Sold Out
fully exitedNet shares change (top 50)
+1.34M
+4.78M / −3.45M
Net new holders
+9
2 new / 0 exited
Based on top 50 institutional holders by position size. Fields: isNew, isSoldOut, changeInSharesNumber (FMP extract-analytics/holder, limit=50).
Insider Buying vs Selling
ALNY insider trading · insider activity
Source: SEC Form 4
Insiders have been primarily selling shares recently. Selling may be driven by pre-scheduled Rule 10b5-1 plans rather than negative sentiment.
19
Buy transactions
15
Sell transactions
1.27
Buy/Sell ratio
$0M
Total disposed
Recent Insider Transactions
Showing 10 most recent · Common Stock only
| Name · Role | Date | Type | Shares | Price | Value | After Trans. | Filing |
|---|---|---|---|---|---|---|---|
PYOTT DAVID E I director | Jun 1, 2026 | Sale | 921 | $297.71 | $274.2K | 4.5K | Form 4 ↗ |
PYOTT DAVID E I director | Jun 1, 2026 | Sale | 1,175 | $298.91 | $351.2K | 3.3K | Form 4 ↗ |
PYOTT DAVID E I director | Jun 1, 2026 | Sale | 1,222 | $299.87 | $366.4K | 2.1K | Form 4 ↗ |
PYOTT DAVID E I director | Jun 1, 2026 | Sale | 495 | $300.72 | $148.9K | 1.6K | Form 4 ↗ |
PYOTT DAVID E I director | Jun 1, 2026 | Sale | 17 | $302.65 | $5.1K | 1.6K | Form 4 ↗ |
Cravatt Benjamin director | Jun 1, 2026 | Award | 4,393 | $295.63 | $1.30M | 4.4K | Form 4 ↗ |
Sigal Charles Elliott director | May 20, 2026 | Award | 671 | — | — | 1.4K | Form 4 ↗ |
Sigal Charles Elliott director | May 20, 2026 | Award | 1,441 | $298.48 | $430.1K | 1.4K | Form 4 ↗ |
SCHULMAN AMY W director | May 20, 2026 | Award | 838 | — | — | 24.0K | Form 4 ↗ |
SCHULMAN AMY W director | May 20, 2026 | Award | 1,802 | $298.48 | $537.9K | 1.8K | Form 4 ↗ |
Source: /insider-trading/search (FMP stable). Buy/Sell direction: acquisitionOrDisposition A=Buy, D=Sell. RSU vesting (M-Exempt) excluded from sentiment bar. All data from SEC EDGAR public filings.
About institutional & insider ownership
Alnylam Pharmaceuticals, Inc. (ALNY) is primarily owned by institutional investors, who hold approximately 98.1% of total shares outstanding. Company insiders own approximately 0.43%, while retail and public investors account for the remaining 1.47%.
The largest institutional shareholder of Alnylam Pharmaceuticals, Inc. is CAPITAL WORLD INVESTORS, holding approximately 16.75 million shares — equal to 12.92% of outstanding shares — as of March 31, 2025.
A total of 684 institutional investors currently hold ALNY stock, with a combined institutional value of approximately $34.84 billion as of the most recent 13F filing period.
Frequently asked questions
ALNY ownershipAlnylam Pharmaceuticals, Inc. (ALNY) is primarily owned by institutional investors, who hold approximately 98.1% of shares. The largest shareholder is CAPITAL WORLD INVESTORS with a 12.92% stake. Company insiders hold 0.43%. Data sourced from SEC Form 13F as of March 31, 2025.