Commitments and Contingencies	9 Months Ended
Sep. 30, 2026
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	15. 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 business, financial condition, results of operations and cash flows. 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. On January 26, 2024, the Company was sued in the United States District Court for the District of Delaware (the “District Court”) by Advanced Accelerator Applications USA, Inc. and Advanced Accelerator Applications SA (collectively known as “ADACAP” in the court proceedings), each a Novartis entity, for patent infringement in response to the filing of the Company’s Abbreviated New Drug Application (“ANDA”) and Paragraph IV certification in connection with PNT2003, consistent with the process established by the Hatch-Waxman Act. In December 2025, the court conducted its trial. On June 17, 2026, the District Court issued an opinion in Lantheus’s favor; specifically, the District Court determined that all the patents asserted by ADACAP are invalid. On June 23, 2026, ADACAP appealed the District Court’s decision to the Court of Appeals for the Federal Circuit (“CAFC”) and moved for an emergency injunction to stay Lantheus’s launch of PNT2003 pending appeal. On July 2, 2026, the CAFC denied ADACAP’s motion to stay Lantheus from launching PNT2003 during the appeal process. As of the date of this Form 10-Q, the Company has received final FDA approval for PNT2003, now referred to as BRAVNETSA (lutetium Lu 177 dotatate), and is participating in the appeal briefing process on an expedited basis which will culminate in an oral hearing before the CAFC currently scheduled for December 14, 2026. The timing of the final decision of the CAFC on ADACAP’s appeal is not known. 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 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. A related action, styled Indiana Pub. Ret. Sys. v. Lantheus Holdings, Inc., et al., was filed in the same court on November 5, 2025. Those actions are now consolidated into a single putative securities class action (captioned In re Lantheus Holdings, Inc. Secs. Litig.), the theory of which is that the defendants made materially false or misleading statements (or omitted material facts) in violation of the Exchange Act. The lead plaintiff filed an amended complaint on March 13, 2026. The Company and its executives filed a motion to dismiss the amended complaint on May 11, 2026, and under the operative scheduling order, that motion was fully briefed by August 10, 2026. Additionally, on December 17, 2025, another alleged stockholder of the Company filed a shareholder derivative action in the same court, styled Lelchuk v. Heino et al., nominally on behalf of the Company and naming as defendants the current directors of the Board and the same officers named in the consolidated securities class action described above (a similar derivative complaint styled Jones v. Markison et al., was previously filed on October 31, 2025 but was voluntarily withdrawn without prejudice). The derivative complaint largely repeats the allegations asserted in the consolidated securities class action, and asserts claims for alleged breaches of fiduciary duties, aiding and abetting breach of fiduciary duty, unjust enrichment, waste of corporate assets, and violations of the Exchange Act. The plaintiff seeks damages and other relief on behalf of the Company. The derivative action is stayed pending one or more of the following events: (i) a public announcement of any settlement of the putative securities class action; (ii) a ruling on the defendants’ motion to dismiss; or (iii) a dismissal with prejudice of the putative securities class action and exhaustion of all related appeals. Because the outcome of litigation is uncertain, the Company cannot predict how or when these matters will ultimately be resolved. Following the filing on September 8, 2026 of the Company’s definitive proxy statement (the “Definitive Proxy Statement”) relating to the Merger (as defined below), three complaints were filed by purported stockholders against the Company and certain members of the Board in connection with the Merger. Two such complaints were filed in the Supreme Court of the State of New York, County of New York: Hamilton v. Lantheus Holdings, Inc., et al., Index No. 655291/2026, filed on September 16, 2026, and McDaniels v. Lantheus Holdings, Inc., et al., Index No. 655281/2026, filed on September 16, 2026, and one was filed in the Superior Court of the Commonwealth of Massachusetts, Middlesex County: Garfield v. Lantheus Holdings, Inc., et al., Civil Docket No. 2681CV02581, filed on September 25, 2026 (collectively, the “Merger Complaints”). The Merger Complaints generally alleged, among other things, that the Definitive Proxy Statement omitted or misrepresented certain material information and asserted claims under state common law. In addition to the Merger Complaints, the Company has received sixteen demand letters from purported stockholders of the Company, two of which attached a draft complaint, making similar allegations to the Merger Complaints (the “Demand Letters”). On October 2, 2026, solely to avoid the costs, burden, nuisance and uncertainties inherent in litigation and without admitting any liability or wrongdoing, the Company filed supplemental disclosures to the Definitive Proxy Statement. On October 14, 2026, the Company’s stockholders adopted the Merger Agreement (as defined below) and approved related proposals at a special meeting of stockholders. The Company believes the Merger Complaints and the Demand Letters are without merit. Additional demand letters or lawsuits may be received or filed in connection with the Merger. Because the outcome of litigation is uncertain, the Company cannot predict how or when these matters will ultimately be resolved. As of September 30, 2026, the Company was not a party to any other material ongoing legal proceedings and has determined that the aforementioned matters are not expected to have a material adverse effect on its business or consolidated financial results. 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 specified 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. Repurchase of License In June 2026, the Company entered into a repurchase agreement (the “Repurchase Agreement”) with its distributor in China pursuant to which the Company repurchased from the distributor the license to DEFINITY in China along with the related materials, approvals and clinical trial research that had been accumulated since the original Distribution and Supply Agreement between the same parties (the “Supply Agreement”), which was executed in April 2012. The Company’s repurchase right was in accordance with the Supply Agreement. The total consideration to be paid as part of the Repurchase Agreement is $30.0 million. The Company paid $15.0 million of this consideration during the three months ended September 30, 2026. The remaining $15.0 million is expected to be paid in two tranches by the end of 2026 upon satisfaction of certain conditions, is recorded as an obligation in accrued expenses and other current liabilities on the Company’s condensed consolidated balance sheet as of September 30, 2026 and was fully expensed to sales and marketing expenses on the Company’s condensed consolidated statements of operations during the second quarter of 2026.

Commitments and Contingencies

9 Months Ended

Sep. 30, 2026

Commitments and Contingencies Disclosure [Abstract]

15. 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 business, financial condition, results of operations and cash flows. 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.

On January 26, 2024, the Company was sued in the United States District Court for the District of Delaware (the “District Court”) by Advanced Accelerator Applications USA, Inc. and Advanced Accelerator Applications SA (collectively known as “ADACAP” in the court proceedings), each a Novartis entity, for patent infringement in response to the filing of the Company’s Abbreviated New Drug Application (“ANDA”) and Paragraph IV certification in connection with PNT2003, consistent with the process established by the Hatch-Waxman Act. In December 2025, the court conducted its trial. On June 17, 2026, the District Court issued an opinion in Lantheus’s favor; specifically, the District Court determined that all the patents asserted by ADACAP are invalid. On June 23, 2026, ADACAP appealed the District Court’s decision to the Court of Appeals for the Federal Circuit (“CAFC”) and moved for an emergency injunction to stay Lantheus’s launch of PNT2003 pending appeal. On July 2, 2026, the CAFC denied ADACAP’s motion to stay Lantheus from launching PNT2003 during the appeal process. As of the date of this Form 10-Q, the Company has received final FDA approval for PNT2003, now referred to as BRAVNETSA (lutetium Lu 177 dotatate), and is participating in the appeal briefing process on an expedited basis which will culminate in an oral hearing before the CAFC currently scheduled for December 14, 2026. The timing of the final decision of the CAFC on ADACAP’s appeal is not known. 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 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. A related action, styled Indiana Pub. Ret. Sys. v. Lantheus Holdings, Inc., et al., was filed in the same court on November 5, 2025. Those actions are now consolidated into a single putative securities class action (captioned In re Lantheus Holdings, Inc. Secs. Litig.), the theory of which is that the defendants made materially false or misleading statements (or omitted

material facts) in violation of the Exchange Act. The lead plaintiff filed an amended complaint on March 13, 2026. The Company and its executives filed a motion to dismiss the amended complaint on May 11, 2026, and under the operative scheduling order, that motion was fully briefed by August 10, 2026. Additionally, on December 17, 2025, another alleged stockholder of the Company filed a shareholder derivative action in the same court, styled Lelchuk v. Heino et al., nominally on behalf of the Company and naming as defendants the current directors of the Board and the same officers named in the consolidated securities class action described above (a similar derivative complaint styled Jones v. Markison et al., was previously filed on October 31, 2025 but was voluntarily withdrawn without prejudice). The derivative complaint largely repeats the allegations asserted in the consolidated securities class action, and asserts claims for alleged breaches of fiduciary duties, aiding and abetting breach of fiduciary duty, unjust enrichment, waste of corporate assets, and violations of the Exchange Act. The plaintiff seeks damages and other relief on behalf of the Company. The derivative action is stayed pending one or more of the following events: (i) a public announcement of any settlement of the putative securities class action; (ii) a ruling on the defendants’ motion to dismiss; or (iii) a dismissal with prejudice of the putative securities class action and exhaustion of all related appeals. Because the outcome of litigation is uncertain, the Company cannot predict how or when these matters will ultimately be resolved.

Following the filing on September 8, 2026 of the Company’s definitive proxy statement (the “Definitive Proxy Statement”) relating to the Merger (as defined below), three complaints were filed by purported stockholders against the Company and certain members of the Board in connection with the Merger. Two such complaints were filed in the Supreme Court of the State of New York, County of New York: Hamilton v. Lantheus Holdings, Inc., et al., Index No. 655291/2026, filed on September 16, 2026, and McDaniels v. Lantheus Holdings, Inc., et al., Index No. 655281/2026, filed on September 16, 2026, and one was filed in the Superior Court of the Commonwealth of Massachusetts, Middlesex County: Garfield v. Lantheus Holdings, Inc., et al., Civil Docket No. 2681CV02581, filed on September 25, 2026 (collectively, the “Merger Complaints”). The Merger Complaints generally alleged, among other things, that the Definitive Proxy Statement omitted or misrepresented certain material information and asserted claims under state common law.

In addition to the Merger Complaints, the Company has received sixteen demand letters from purported stockholders of the Company, two of which attached a draft complaint, making similar allegations to the Merger Complaints (the “Demand Letters”).

On October 2, 2026, solely to avoid the costs, burden, nuisance and uncertainties inherent in litigation and without admitting any liability or wrongdoing, the Company filed supplemental disclosures to the Definitive Proxy Statement. On October 14, 2026, the Company’s stockholders adopted the Merger Agreement (as defined below) and approved related proposals at a special meeting of stockholders. The Company believes the Merger Complaints and the Demand Letters are without merit. Additional demand letters or lawsuits may be received or filed in connection with the Merger. Because the outcome of litigation is uncertain, the Company cannot predict how or when these matters will ultimately be resolved.

As of September 30, 2026, the Company was not a party to any other material ongoing legal proceedings and has determined that the aforementioned matters are not expected to have a material adverse effect on its business or consolidated financial results.

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 specified 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.

Repurchase of License

In June 2026, the Company entered into a repurchase agreement (the “Repurchase Agreement”) with its distributor in China pursuant to which the Company repurchased from the distributor the license to DEFINITY in China along with the related materials, approvals and clinical trial research that had been accumulated since the original Distribution and Supply Agreement between the same parties (the “Supply Agreement”), which was executed in April 2012. The Company’s repurchase right was in accordance with the Supply Agreement. The total consideration to be paid as part of the Repurchase Agreement is $30.0 million. The Company paid $15.0 million of this consideration during the three months ended September 30, 2026. The remaining $15.0 million is expected to be paid in two tranches by the end of 2026 upon satisfaction of certain conditions, is recorded as an obligation in accrued expenses and other current liabilities on the Company’s condensed consolidated balance sheet as of September 30, 2026 and was fully expensed to sales and marketing expenses on the Company’s condensed consolidated statements of operations during the second quarter of 2026.