X0306 4 2022-03-02 0 0001492426 Horizon Therapeutics Public Ltd Co HZNP 0001512985 DesJardin Michael A. C/O HORIZON THERAPEUTICS PLC, 70 SAINT STEPHEN?S GREEN DUBLIN L2 D02 E2X4 IRELAND 0 1 0 0 EVP, Technical Operations Ordinary Shares 2022-03-02 4 S 0 21482 97.05 D 116078 D Ordinary Shares 2022-03-02 4 S 0 13518 97.42 D 102560 D The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $96.24 to $97.24 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. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $97.26 to $97.50 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. /s/ Miles W. McHugh, Attorney-in-Fact 2022-03-04