Lantheus Holdings, Inc. filed a Form 8-K on September 21, 2026, disclosing that Parent Curium US Holdings LLC withdrew and resubmitted its pre-merger HSR notification on September 17 and September 21, 2026, respectively, commencing a new 30-day antitrust waiting period in connection with the pending merger.

Key Highlights

  • Merger Agreement dated August 3, 2026: Lantheus Holdings entered into an Agreement and Plan of Merger with Curium US Holdings LLC (Parent) and Coco Merger Sub Inc., under which Merger Sub will merge with and into Lantheus, making the company a wholly owned subsidiary of Parent.
  • HSR withdrawal on September 17, 2026: Parent voluntarily withdrew its pre-merger Notification and Report Form to provide the FTC additional time to review the Merger.
  • Refiling on September 21, 2026: Parent resubmitted its pre-merger Notification and Report Form, commencing a new 30-day waiting period under the HSR Act.
  • New waiting period expires October 21, 2026: The statutory period will expire at 11:59 p.m., Eastern Time, unless terminated earlier or extended by an FTC request for additional information.
  • Merger closing expected first half of 2027: According to the filing, the company and Parent "continue to expect to consummate the Merger in the first half of 2027," subject to regulatory approvals, stockholder adoption of the Merger Agreement, and other customary closing conditions.
  • Definitive proxy statement filed September 8, 2026: The company filed its definitive proxy statement with the SEC in connection with the proposed acquisition.

Lantheus and Curium Reset HSR Clock as FTC Review Continues

Lantheus Holdings, Inc. (NASDAQ:LNTH), a Delaware corporation headquartered in Bedford, Massachusetts, disclosed in an 8-K filing that Parent Curium US Holdings LLC voluntarily withdrew its pre-merger Notification and Report Form filed under the Hart-Scott-Rodino Antitrust Improvements Act of 1976 on September 17, 2026. The withdrawal was made "in order to provide the Federal Trade Commission (the 'FTC') with additional time to review the Merger," according to the filing. Parent resubmitted the notification form on September 21, 2026, starting a new 30-day waiting period that is set to expire on October 21, 2026, at 11:59 p.m., Eastern Time.

The filing characterized the procedure as routine, stating that "withdrawing and refiling pre-merger notifications is a routine procedure in order to provide additional time for antitrust review of certain transactions." The company reported that it and Parent "continue to work constructively with the FTC staff in the FTC's review of the Merger." The statutory waiting period may be extended if the FTC issues a request for additional information and documentary material.

Under the terms of the Merger Agreement signed on August 3, 2026, Coco Merger Sub Inc., a wholly owned subsidiary of Parent, is to merge with and into Lantheus, with Lantheus surviving as a wholly owned subsidiary of Parent. Closing remains subject to expiration or termination of the applicable HSR waiting period, adoption of the Merger Agreement by the company's stockholders, receipt of required regulatory approvals, and satisfaction or waiver of other customary closing conditions. The filing notes that forward-looking statements, including the expected first-half 2027 closing timeline, are subject to the company's cautionary language and various risks and uncertainties described therein.

What Was Disclosed

Lantheus Holdings reported that Curium US Holdings LLC withdrew and resubmitted its HSR pre-merger notification, commencing a new 30-day FTC waiting period expiring October 21, 2026, while the parties continue to expect to close the merger in the first half of 2027.