SCHEDULE 13G

ALKERMES PLC

Ordinary Shares, $0.01 per share · CUSIP: G01767105

Event date: 2025-12-31

Reporting persons may disclose overlapping interests. Their amounts are shown individually and are not added into a filing total.

Filing-level shares

Unavailable

Percent of class

Unavailable

• Baker Bros. Advisors LP

  Shares: 10,012,267.00 · Class: 6.1%

• Baker Bros. Advisors (GP) LLC

  Shares: 10,012,267.00 · Class: 6.1%

• Julian C. Baker

  Shares: 10,012,267.00 · Class: 6.1%

• Felix J. Baker

  Shares: 10,012,267.00 · Class: 6.1%

Amounts are as disclosed in this filing. Schedule type alone does not establish investment intent.