X0306 4 2020-01-21 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, Chief Commercial Officer Ordinary Shares 2020-01-21 4 A 0 5353 0.00 A 83499 D Ordinary Shares 2020-01-21 4 F 0 2372 38.25 D 81127 D Performance Restricted Stock Units (PSUs) 2020-01-21 4 A 0 10708 0.00 A Ordinary Shares 10708 10708 D On January 4, 2019, the reporting person was granted performance-based restricted stock units (PSUs) of the Issuer, which vest upon the satisfaction of certain performance criteria. On January 21, 2020, 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 21, 2021 and January 21, 2022. Each PSU represents a contingent right to receive one ordinary share of the Issuer. /s/ Miles W. McHugh, Attorney-in-Fact 2020-01-23