INDIVIOR PLC

(a)(i)Given changes in holdings of voting securities held by U.S. residents, Indivior has determined that as of June 30, 2025, it no longer qualifies as a “foreign private issuer” under applicable U.S. securities laws and, beginning January 1, 2026, will become subject to the rules and regulations of the SEC applicable to U.S. domestic issuers including, among other things, the rules governing solicitation of proxies and the furnishing and content of proxy statements.

(ii) Separately, following discussions, and based upon Indivior's desire to consolidate manufacturing locations, on July 31, 2025, Indivior UK Limited provided notice of termination for convenience of the Master Development and Supply Agreement, made as of January 1, 2022, as amended by the first amendment dated January 1, 2024, and the second amendment dated January 1, 2025 (collectively, the “Agreement”), between it and Curia Massachusetts, Inc. (“Curia”) to Curia. Such termination will take effect on January 31, 2026. Indivior does not expect to incur material termination penalties based upon its continued sourcing of product during the notice period which is expected to reach the contract minimums.

The notice of termination does not affect the Master Development and Supply Agreement effective the August 1, 2023 by and between Curia New Mexico, LLC and Indivior UK Limited.

(b)On May 8, 2025, Indivior’s shareholders approved amendments to the Indivior Articles effective upon the conclusion of the 2025 Annual General Meeting. Among other things, the amended Indivior Articles include additional and revised provisions regarding proposals by Indivior Shareholders to bring a resolution before a general meeting related to the nomination of candidates for election as directors.

Indivior Shareholders who wish to present a proposalin accordance with Exchange Act Rule 14a-8 for inclusion in Indivior’s proxy materials to be distributed in connection with Indivior’s 2026 Indivior AGM must submit their proposal in accordance with such rule’s requirements, including ensuring it is received by Indivior’s Company Secretary at the address set forth below no later than the close of business on November 27, 2025. Under such rule, if the date of the 2026 Indivior AGM is more than 30 days before or after May 8, 2026, then the deadline to timely receive such material will be a reasonable time before Indivior begins to print and send proxy materials relating to the 2026 Indivior AGM. Failure to deliver a proposal in accordance with this procedure may result in it not being deemed timely received.

The Indivior Articles require that Indivior Shareholders who intend to propose, outside of Exchange Act Rule 14a-8, any resolution, including nominating candidates for election as directors, at the 2026 Indivior AGM must provide notice of such proposals in writing to Indivior’s Company Secretary at the address set forth below no earlier than the close of business on January 8, 2026, and no later than the close of business on February 7, 2026. However, if the date of the 2026 Indivior AGM is more than 30 days before or more than 60 days after May 8, 2026, such shareholder’s notice must be delivered in writing not earlier than the close of business on the 120 th day prior to the date of the 2026 Indivior AGM and not later than the close of business on the later of: (A) the 90th day prior to the date of the 2026 Indivior AGM or (B) the 10 th day following the day on which public announcement of the date of the 2026 Indivior AGM is first made by Indivior. The notice must set forth the information required by the Indivior Articles, including, if the proposal involves a director nomination, prescribed information about the candidate and about the shareholder proposing the candidate. In addition to satisfying the requirements of the Indivior Articles, to comply with the SEC’s universal proxy rules, Indivior Shareholders who intend to solicit proxies in support of director nominees, other than Indivior’s nominees, must provide a notice that complies with the requirements of Exchange Act Rule 14a-19 no later than March 9, 2026, or if the date of the 2026 Indivior AGM is more than 30 days before or after May 8, 2026, then such notice must be provided by the later of 60 days prior to the date of the 2026 Indivior AGM or the 10 th day following the day on which public announcement of the date of the 2026 Indivior AGM is first made by Indivior.

Proposals should be sent to Indivior’s Company Secretary in writing to Indivior PLC, Attn: Company Secretary, 234 Bath Road, Slough, Berkshire, U.K., SL1 4EE. To be included in Indivior’s proxy materials, the proposal must comply with the requirements as to form and substance established by the SEC and the Indivior Articles and must be a proper subject for shareholder action under English law.

(c)As previously disclosed in a Current Report on Form 8-K filed June 24, 2025, effective June 20, 2025, each of Keith Humphreys, Daniel Ninivaggi, Barbara Ryan, Mark Stejbach, and David Wheadon, being the U.S. based non-executive directors of the Board of Directors (collectively, the “NEDs”), entered into a Purchase Plan with JP Morgan Securities LLC ("JPMS") pursuant to which JPMS will make quarterly purchases of the Company’s securities on behalf of each NED (the "Purchase Plan"). The NEDs intend for the Purchase Plan to qualify under SEC Rule 10b5-1. The Purchase Plan instructs JPMS to make purchases commencing on October 1, 2025 through and including July 6, 2026. The NEDs have instructed JPMS to make quarterly purchases of the Company's Ordinary Shares equal to approximately 70% (80% in the case of Dr. Wheadon) of their after-tax, base retainer fee for serviceas a director. The number of shares to be purchased cannot be determined at this time and will depend upon future market prices but is expected to consist of a minimum of $680,000 and a maximum of $715,000 worth of

Company shares (aggregate purchase price, before deduction of standard and customary commissions and fees).