Lantheus Lawsuit: Pylarify Securities Fraud, Lutathera Patent Fight

Lantheus Holdings, the Massachusetts radiopharmaceutical company known for its prostate cancer imaging agent Pylarify, is currently defending a securities fraud class action in federal court in New York, recently defeated a patent infringement suit brought by Novartis affiliates over a generic version of Lutathera, and settled a New York False Claims Act tax case back in 2014. The Lantheus lawsuit drawing the most investor attention is the securities case, filed in September 2025 after two disclosures wiped out more than half the company’s stock value.

The Securities Fraud Class Action Over Pylarify

The case is Margolis v. Lantheus Holdings, Inc., et al., filed September 9, 2025, in the U.S. District Court for the Southern District of New York (No. 1:25-cv-07491) and assigned to Judge Jennifer H. Rearden.¹² It names the company along with the CEO, CFO, President, and Chief Commercial Officer, bringing claims under Section 10(b) of the Securities Exchange Act and Rule 10b-5, plus Section 20(a) control-person claims against the individual defendants.³

What Investors Say Lantheus Hid

The complaint focuses on Pylarify, a PET imaging agent Lantheus has described as the top-ordered PSMA PET imaging agent in the United States, with more than 400,000 scans across 48 states.⁴ On February 26, 2025, Lantheus projected 2025 revenue of $1.545 billion to $1.61 billion and told investors Pylarify would grow in the “low to mid-single digits on a net basis,” would hold a premium price, and would keep its market lead.⁵

Investors allege those statements were misleading. According to the complaint, Lantheus had already raised Pylarify’s price in early 2025 despite price erosion the prior year, and the increase invited competitors to undercut it.⁶ A competing F-18 PSMA agent was discounting aggressively and pulling volume from Pylarify at smaller, non-contracted imaging centers, but Lantheus’s internal forecasting was not catching that in real time. Management, the plaintiffs say, also concealed that it was renegotiating strategic partnerships and walking away from accounts unwilling to pay a premium.⁵ Generic competition and reimbursement warnings did appear in SEC filings, but the complaint argues those disclosures failed to reveal that Pylarify’s pricing model was already under real strain.³

The Two Stock Drops at the Center of the Case

The lawsuit points to two disclosure days. On May 7, 2025, Lantheus reported first-quarter results, acknowledged “temporal competitive disruption” for Pylarify, and cut adjusted EPS guidance from $7.00–$7.20 to $6.60–$6.70. The stock fell from $104.84 to $80.49, roughly 23%.⁷

On August 6, 2025, the company said Pylarify sales had dropped 8.3% year over year, lowered the product’s revenue forecast to $940 million–$965 million, cut total revenue guidance to $1.475 billion–$1.51 billion, and reduced adjusted EPS guidance again to $5.50–$5.70. Shares fell from $72.83 to $51.87 in a single day, about 29%.⁵¹

Where the Case Stands

The lead plaintiff deadline passed on November 10, 2025.⁶ An amended complaint has since pushed the class period back to July 10, 2024, sweeping in earlier statements about Pylarify’s competitive position and pricing. Lantheus moved to dismiss on May 11, 2026, and briefing on that motion is underway. No class has been certified and no substantive ruling has been issued.²

Shareholder Investigation of Officers and Directors

Alongside the class action, the law firm Kahn Swick & Foti, LLC announced an investigation into Lantheus’s officers and directors for possible breaches of fiduciary duty and state or federal law. The firm has said its probe was prompted by the securities case and centers on whether the company adequately accounted for pricing and reimbursement risks tied to a CMS rule shifting Pylarify hospital reimbursement from an Average Sales Price model to Mean Unit Cost rates.⁸ No derivative lawsuit or additional legal action beyond the investigation has been publicly announced.

The Novartis Patent Fight Over Generic Lutathera

The other major Lantheus lawsuit involved Lutathera, a treatment for somatostatin receptor-positive gastroenteropancreatic neuroendocrine tumors. In January 2024, Lantheus announced the FDA had accepted its abbreviated new drug application for PNT2003, a generic version of Lutathera, and claimed first-applicant status under Hatch-Waxman, which would give it 180 days of generic marketing exclusivity in the United States. Lantheus had picked up worldwide commercialization rights from POINT Biopharma Global, Inc. in December 2022.⁹

Novartis affiliates Advanced Accelerator Applications USA, Inc. and Advanced Accelerator Applications SA responded on January 25, 2024, suing Lantheus for patent infringement in the U.S. District Court for the District of Delaware (No. 1:24-cv-00095), before Judge Maryellen Noreika.¹⁰ The case was consolidated with a related action involving Curium US LLC, and six patents were asserted.¹¹

After a Markman hearing in July 2025 and a claim-construction order in August 2025, the case went to a bench trial. On June 18, 2026, Judge Noreika held that all of the asserted patent claims were invalid, clearing Lantheus.¹²¹³¹⁴

The 2014 New York False Claims Act Settlement

Lantheus’s earlier legal history includes a March 2014 settlement in which Lantheus Medical Imaging and its former parent Bristol-Myers Squibb agreed to pay $6.2 million to resolve a New York False Claims Act case. The state alleged the companies failed to pay New York State business franchise taxes, New York City corporation taxes, and Metropolitan Transportation Authority surcharges from 2002 through 2006, while selling medical imaging products to hospitals and clinics in the state.¹⁵

Investigators found the companies had knowingly underpaid more than $2.2 million in taxes; damages and penalties brought the total to $6.2 million. The case grew out of a May 2012 whistleblower complaint by a tax services provider, who received about $1.14 million. The City of New York recovered roughly $693,000 in owed taxes as part of the resolution.¹⁵

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