Alkermes plc.

Trading Plans

During the three months ended December 31, 2025, the following contracts, instructions or written plans for the purchase or sale of the Company’s securities that are or were intended to satisfy the affirmative defense conditions of Rule 10b5-1(c) under the Exchange Act (each, a “Rule 10b5-1 plan”) were adopted by officers (as defined in Rule 16a-1(f) under the Exchange Act) and directors of the Company: (i) on November 7, 2025, Samuel Parisi, our Vice President, Finance and Interim Principal Accounting Officer, adopted a Rule 10b5-1 plan providing for the sale of up to 10,055 ordinary shares of the Company that may be obtained from the vesting of restricted stock unit awards; this plan is scheduled to expire on December 31, 2026; (ii) on November 19, 2025, David Gaffin, our Executive Vice President, Chief Legal Officer, Chief Compliance Officer and Secretary, adopted a Rule 10b5-1 plan providing for the sale of up to 77,518 ordinary shares of the Company that may be obtained from the exercise of vested stock options and the sale of up to 20,341 ordinary shares of the Company; this plan is scheduled to expire on February 17, 2027; (iii) on November 19, 2025, Blair Jackson, our Executive Vice President, Chief Operating Officer, adopted a Rule 10b5-1 plan providing for the sale of up to 45,899 ordinary shares of the Company that may be obtained from the exercise of vested and expiring stock options; this plan is scheduled to expire on February 27, 2026; (iv) on November 19, 2025, Christian Todd Nichols, our Senior Vice President, Chief Commercial Officer, adopted a Rule 10b5-1 plan providing for the sale of up to 6,000 ordinary shares of the Company; this plan is scheduled to expire on December 31, 2026; and (v) on November 19, 2025, Richard Pops, our Chairman and Chief Executive Officer, adopted a Rule 10b5-1 plan providing for the sale of up to 305,999 ordinary shares of the Company that may be obtained from the exercise of vested and expiring stock options; this plan is scheduled to expire on February 27, 2026. During the three months ended December 31, 2025, noother directors or officers of the Company adopted or terminated a Rule 10b5-1 plan or a trading plan not intended to satisfy the affirmative defense conditions of Rule 10b5-1(c) under the Exchange Act.