X0306 4 2021-02-17 0 0001492426 Horizon Therapeutics Public Ltd Co HZNP 0001699488 Karnani Vikram C/O HORIZON THERAPEUTICS PLC, CONNAUGHT HOUSE, 1ST FL, 1 BURLINGTON RD DUBLIN L2 4 IRELAND 0 1 0 0 EVP & President, International Ordinary Shares 2021-02-17 4 A 0 1965 0.00 A 113394 D Ordinary Shares 2021-02-17 4 F 0 871 87.17 D 112523 D Performance Restricted Stock Units (PSUs) 2021-02-17 4 A 0 3931 0.00 A Ordinary Shares 3931 3931 D Performance Restricted Stock Units (PSUs) 2021-02-17 4 A 0 14512 0.00 A Ordinary Shares 14512 14512 D On January 3, 2020, the reporting person was granted performance-based restricted stock units (PSUs) of the Issuer, which vest upon the satisfaction of certain performance criteria. On February 17, 2021, such performance criteria were met, and the PSUs vested as to the number of shares reported in Table I above. The remaining ordinary shares subject to the PSUs vest in equal annual installments on January 5, 2022 and January 5, 2023. Each PSU represents a contingent right to receive one ordinary share of the Issuer. On January 3, 2020, the reporting person was granted performance-based restricted stock units (PSUs) of the Issuer, which vest upon the satisfaction of certain performance criteria. On February 17, 2021, such performance criteria were met. Two-thirds of the ordinary shares subject to the PSUs vest on January 5, 2022 and the remaining one-third of the ordinary shares vest on January 5, 2023. /s/ Miles W. McHugh, Attorney-in-Fact 2021-02-19