Material Event (Form 8-K)

Item 8.01 Other Events.

As previously disclosed, on August 3, 2026, Lantheus Holdings, Inc., a Delaware corporation ("Lantheus" or the "Company"), entered into an Agreement and Plan of Merger (the "Merger Agreement") by and among the Company, Curium US Holdings LLC, a Delaware limited liability company ("Parent"), and Coco Merger Sub Inc., a Delaware corporation and a wholly owned subsidiary of Parent ("Merger Sub"), pursuant to which, subject to the terms and conditions set forth therein, including the expiration or termination of the applicable waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended (the "HSR Act"), Merger Sub will merge with and into the Company (the "Merger"), with the Company surviving the Merger as a wholly owned subsidiary of Parent.

On October 21, 2026, the Company and Parent each received a request for additional information and documentary materials (each, a "Second Request") from the Federal Trade Commission ("FTC") in connection with the FTC's review of the Merger. The effect of a Second Request is to extend the waiting period imposed by the HSR Act, until 30 days after the Company and Parent each have substantially complied with the Second Request issued to it, unless that period is terminated sooner by the FTC. The parties expect to promptly respond to the Second Requests and to continue to work cooperatively with the FTC in its review of the Merger. Completion of the Merger remains subject to the expiration or termination of the waiting period under the HSR Act and the satisfaction or waiver of the other closing conditions specified in the Merger Agreement. The Company and Parent continue to expect to consummate the Merger in the first half of 2027.