X0306 4 2019-09-11 0 0001492426 Horizon Therapeutics Public Ltd Co HZNP 0001716059 Konstantinovsky Irina C/O HORIZON THERAPEUTICS PLC CONNAUGHT HOUSE, 1ST FL, 1 BURLINGTON RD DUBLIN L2 4 IRELAND 0 1 0 0 EVP, Chief Human Resources Off Ordinary Shares 2019-09-11 4 A 0 16014 0.00 A 44819 D Ordinary Shares 2019-09-11 4 F 0 7095 26.71 D 37724 D Ordinary Shares 2019-09-12 4 S 0 17838 26.70 D 19886 D Restricted Stock Units 2019-09-11 4 M 0 16014 0.00 D Ordinary Shares 16014 32028 D The sales reported in this Form 4 were effected pursuant to a Rule10b5-1 trading plan adopted by the reporting person on August 14, 2019. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $26.52 to $26.90 per share, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. Each restricted stock unit represents a contingent right to receive one ordinary share of the Issuer. The restricted stock units vest in four annual installments of 16,014 shares, on each anniversary of the grant date (September 11, 2017). /s/ Miles W. McHugh, Attorney-in-Fact 2019-09-13