Vanguard Portfolio Management Reports 5.03% Stake in Alnylam Pharmaceuticals

Overview of Filing

On October 30, 2026, Vanguard Portfolio Management LLC filed a Schedule 13G with the SEC disclosing a passive 5.03% beneficial ownership stake in Alnylam Pharmaceuticals Inc ($ALNY) as of September 30, 2026.

Key Ownership Details

• Issuer: Alnylam Pharmaceuticals Inc (CIK: 0001178670)
• Reporting Entity: Vanguard Portfolio Management LLC (CIK: 0002100121)
• Class of Security: Common Stock (CUSIP: 02043Q107)
• Aggregate Beneficial Ownership: 6,732,082 shares
• Ownership Percentage: 5.03% of the outstanding common stock
• Voting Authority:
  • Sole Voting Power: 34,162 shares
  • Shared Voting Power: 0 shares
• Dispositive Authority:
  • Sole Dispositive Power: 6,732,082 shares
  • Shared Dispositive Power: 0 shares

Market Impact & Analysis

• Filing Rule: Filed pursuant to Rule 13d-1(b) as an investment adviser, certifying the shares are held in the ordinary course of business without an intent to change or influence control of the issuer.
• Significance: Low. Institutional passive 13G filings from index and mutual fund managers like Vanguard reflect regular portfolio rebalancing, ETF creations, or passive indexing rather than activist pressure or fundamental corporate intervention.