Commitments and Contingencies	9 Months Ended
Sep. 30, 2025
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	16. Commitments and Contingencies Legal Proceedings From time to time, the Company is a party to various legal proceedings arising in the ordinary course of business. In addition, the Company has in the past been, and may in the future be, subject to investigations by governmental and regulatory authorities, which expose it to greater risks associated with litigation, regulatory or other proceedings, as a result of which the Company could be required to pay significant fines or penalties. The costs and outcome of litigation, regulatory or other proceedings cannot be predicted with certainty, and some lawsuits, claims, actions or proceedings may be disposed of unfavorably to the Company and could have a material adverse effect on the Company’s results of operations or financial condition. In addition, intellectual property disputes often have a risk of injunctive relief which, if imposed against the Company, could materially and adversely affect its financial condition or results of operations. If a matter is both probable to result in material liability and the amount of loss can be reasonably estimated, the Company estimates and discloses the possible material loss or range of loss. If such loss is not probable or cannot be reasonably estimated, a liability is not recorded in its condensed consolidated financial statements. As of September 30, 2025, the Company did not have any material ongoing litigation to which the Company was a party. On January 26, 2024, the Company was sued in the United States District Court for the District of Delaware by Advanced Accelerator Applications USA, Inc. and Advanced Accelerator Applications SA, each a Novartis entity, for patent infringement in response to the filing of the Company’s Abbreviated New Drug Application and Paragraph IV certification in connection with PNT2003, consistent with the process established by the Hatch-Waxman Act. Because the outcome of litigation is uncertain, the Company cannot predict how or when this matter will ultimately be resolved. On February 23, 2024, the Company filed a patent infringement lawsuit against a healthcare-related imaging software developer, and that developer filed a motion to dismiss the case based on grounds of invalidity for certain patents and failure to state a claim for infringement for other patents. The court dismissed the developer’s motion to dismiss as to invalidity, and granted the motion as to certain allegations of infringement. Because the outcome of litigation is uncertain, the Company cannot predict how or when this matter will ultimately be resolved. On September 9, 2025, an alleged stockholder of the Company initiated a putative securities class action against the Company in the United States District Court for the Southern District of New York, styled Margolis v. Lantheus Holdings, Inc., et al. The operative complaint also asserts claims against certain of the Company’s named executives. The plaintiff alleges that the defendants made materially false or misleading statements (or omitted material facts) in violation of the Exchange Act. Under the operative scheduling order in the case, members of the putative class of stockholders have an opportunity to move the court for appointment as lead plaintiff, after which there is an opportunity for the lead plaintiff to file an amended complaint. Because the outcome of litigation is uncertain, the Company cannot predict how or when this matter will ultimately be resolved. On October 31, 2025, another alleged stockholder of the Company filed a shareholder derivative action in the same court, styled Jones v. Markison et al., nominally on behalf of the Company and naming as defendants the current directors of the Company’s Board and the same officers named in the securities class action described in the preceding paragraph. The derivative complaint largely repeats the allegations asserted in the securities class action, and asserts claims for alleged breaches of fiduciary duties, gross mismanagement, corporate waste, unjust enrichment, and violation of Section 14(a) of the Exchange Act. The plaintiff seeks damages and other relief on behalf of the Company. Because the outcome of litigation is uncertain, the Company cannot predict how or when this matter will ultimately be resolved. Technology License and Other Commitments The Company has licensed from third parties the rights to use certain technologies in its R&D processes as well as in other products it may develop, commercialize, or sell. In accordance with the related license or sublicense agreements, the Company is contractually required to make certain future payments to these third parties contingent upon i) the achievement of regulatory, development and/or commercialization milestones and ii) future sales of specified products in the form of royalty payments. Milestone payments are generally recognized in the period in which the achievement of the underlying milestone becomes probable, which is generally the period in which it is actually achieved. Royalty payments are generally recognized in the period in which the associated revenue is recognized.

Commitments and Contingencies

9 Months Ended

Sep. 30, 2025

Commitments and Contingencies Disclosure [Abstract]

16. Commitments and Contingencies

Legal Proceedings

From time to time, the Company is a party to various legal proceedings arising in the ordinary course of business. In addition, the Company has in the past been, and may in the future be, subject to investigations by governmental and regulatory authorities, which expose it to greater risks associated with litigation, regulatory or other proceedings, as a result of which the Company could be required to pay significant fines or penalties. The costs and outcome of litigation, regulatory or other proceedings cannot be predicted with certainty, and some lawsuits, claims, actions or proceedings may be disposed of unfavorably to the Company and could have a material adverse effect on the Company’s results of operations or financial condition. In addition, intellectual property disputes often have a risk of injunctive relief which, if imposed against the Company, could materially and adversely affect its financial condition or results of operations. If a matter is both probable to result in material liability and the amount of loss can be reasonably estimated, the Company estimates and discloses the possible material loss or range of loss. If such loss is not probable or cannot be reasonably estimated, a liability is not recorded in its condensed consolidated financial statements.

As of September 30, 2025, the Company did not have any material ongoing litigation to which the Company was a party.

On January 26, 2024, the Company was sued in the United States District Court for the District of Delaware by Advanced Accelerator Applications USA, Inc. and Advanced Accelerator Applications SA, each a Novartis entity, for patent infringement in response to the filing of the Company’s Abbreviated New Drug Application and Paragraph IV certification in connection with PNT2003, consistent with the process established by the Hatch-Waxman Act. Because the outcome of litigation is uncertain, the Company cannot predict how or when this matter will ultimately be resolved.

On February 23, 2024, the Company filed a patent infringement lawsuit against a healthcare-related imaging software developer, and that developer filed a motion to dismiss the case based on grounds of invalidity for certain patents and failure to state a claim for infringement for other patents. The court dismissed the developer’s motion to dismiss as to invalidity, and granted the motion as to certain allegations of infringement. Because the outcome of litigation is uncertain, the Company cannot predict how or when this matter will ultimately be resolved.

On September 9, 2025, an alleged stockholder of the Company initiated a putative securities class action against the Company in the United States District Court for the Southern District of New York, styled Margolis v. Lantheus Holdings, Inc., et al. The operative complaint also asserts claims against certain of the Company’s named executives. The plaintiff alleges that the defendants made materially false or misleading statements (or omitted material facts) in violation of the Exchange Act. Under the operative scheduling order in the case, members of the putative class of stockholders have an opportunity to move the court for appointment as lead plaintiff, after which there is an opportunity for the lead plaintiff to file an amended complaint. Because the outcome of litigation is uncertain, the Company cannot predict how or when this matter will ultimately be resolved.

On October 31, 2025, another alleged stockholder of the Company filed a shareholder derivative action in the same court, styled Jones v. Markison et al., nominally on behalf of the Company and naming as defendants the current directors of the Company’s Board and the same officers named in the securities class action described in the preceding paragraph. The derivative complaint largely repeats the allegations asserted in the securities class action, and asserts claims for alleged breaches of fiduciary duties, gross mismanagement, corporate waste, unjust

enrichment, and violation of Section 14(a) of the Exchange Act. The plaintiff seeks damages and other relief on behalf of the Company. Because the outcome of litigation is uncertain, the Company cannot predict how or when this matter will ultimately be resolved.

Technology License and Other Commitments

The Company has licensed from third parties the rights to use certain technologies in its R&D processes as well as in other products it may develop, commercialize, or sell. In accordance with the related license or sublicense agreements, the Company is contractually required to make certain future payments to these third parties contingent upon i) the achievement of regulatory, development and/or commercialization milestones and ii) future sales of specified products in the form of royalty payments. Milestone payments are generally recognized in the period in which the achievement of the underlying milestone becomes probable, which is generally the period in which it is actually achieved. Royalty payments are generally recognized in the period in which the associated revenue is recognized.