FORM 8.3   IRISH TAKEOVER PANEL DISCLOSURE UNDER RULE 8.3 OF THE IRISH TAKEOVER PANEL ACT, 1997, TAKEOVER RULES, 2013 DEALINGS BY PERSONS WITH INTERESTS IN RELEVANT SECURITIES REPRESENTING 1% OR MORE   1. KEY INFORMATION   Name of person dealing (Note 1)State Street Global Advisors & AffiliatesCompany dealt inHorizon Therapeutics plcClass of relevant security to which the dealings being disclosed relate (Note 2)$0.0001 ordinary sharesDate of dealing12th Dec 2022       2. INTERESTS AND SHORT POSITIONS   (a) Interests and short positions (following dealing) in the class of relevant security dealt in (Note 3)    LongShort Number(%)Number(%)(1) Relevant securities5,938,6852.61982%  (2) Derivatives (other than options)5080.000224%  (3) Options and agreements to purchase/sellN/AN/A  Total5,939,1932.62005%       (b) Interests and short positions in relevant securities of the company, other than the class dealt in (Note 3)   Class of relevant security:LongShort Number(%)Number(%)(1) Relevant securitiesN/A   (2) Derivatives (other than options)N/A   (3) Options and agreements to purchase/sellN/A   TotalN/A        3. DEALINGS (Note 4)   (a) Purchases and sales   Purchase/saleNumber of relevant securitiesPrice per unit (Note 5)Purchase3,600111.98Purchase2,000112.36 Purchase 200 97.29 Sale13,338112.36     (b) Derivatives transactions (other than options transactions)   Product name, e.g. CFDNature of transaction (Note 6)Number of relevant securities (Note 7)Price per unit (Note 5)N/A               (c) Options transactions in respect of existing relevant securities   (i) Writing, selling, purchasing or varying   Product name, e.g. call optionWriting, selling, purchasing varying etc.Number of securities to which the option relates (Note 7)Exercise priceType, e.g. American, European etc.Expiry dateOption money paid/received per unit (Note 5)N/A           (ii) Exercising   Product name, e.g. call optionNumber of securitiesExercise price per unit (Note 5)N/A       (d) Other dealings (including transactions in respect of new securities) (Note 4)   Nature of transaction (Note 8)DetailsPrice per unit (if applicable) (Note 5)N/A       4. OTHER INFORMATION   Agreements, arrangements or understandings relating to options or derivatives   Full details of any agreement, arrangement or understanding between the person disclosing and any other person relating to the voting rights of any relevant securities under any option referred to on this form or relating to the voting rights or future acquisition or disposal of any relevant securities to which any derivative referred to on this form is referenced. If none, this should be stated.N/A     Is a Supplemental Form 8 attached? (Note 9)NO Date of disclosure13th Dec 2022 Contact nameLionel ColacoTelephone number                                020 33956098If a connected EFM, name of offeree/offeror with which connectedN/AIf a connected EFM, state nature of connection (Note 10)N/A