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In a dramatic escalation of a high-stakes biopharma showdown, Pfizer Inc. has filed suit in Delaware Chancery Court to stop Metsera from backing out of their multibillion-dollar merger, accusing Novo Nordisk of orchestrating an “old-fashioned bribe” to derail the deal and crush future competition in the booming weight-loss drug market.

Pfizer’s lawsuit, filed Friday—the same day it received early antitrust clearance for the acquisition—alleges Metsera breached its merger agreement, that its directors violated fiduciary duties, and that Novo Nordisk engaged in tortious and anticompetitive interference.

Pfizer: Novo Nordisk’s $9B Offer Is a “Catch and Kill” Scheme

According to the complaint, Pfizer struck a deal in September to acquire Metsera for up to $7.3 billion, including $4.9 billion in cash and contingent payments worth an additional $22.50 per share. Just as the merger appeared set to close, Novo Nordisk—maker of Ozempic and Wegovy—swooped in with a $9 billion buyout proposal that Pfizer says was meant to sabotage the merger.

Pfizer’s filing paints the rival’s offer as a “plot to catch and kill Metsera before Pfizer can nurture its products into healthy competition.”

The pharma powerhouse asserts Novo Nordisk’s move is “virtually unprecedented and unlawful,” and that it cannot legally qualify as a “superior company proposal.”

“It’s an illegal transaction that cannot be completed on its terms,” Pfizer claimed, adding that Novo’s offer is “nothing more than a bribe” aimed at suppressing a rival’s innovation pipeline.

Regulatory Greenlight and Imminent Merger Deadline

Pfizer said the merger was on track to close imminently, noting it received early clearance from the Federal Trade Commission—ahead of its scheduled Nov. 7 antitrust deadline.
A shareholder vote is set for Nov. 13, with the deal expected to close within three business days afterward.

But on Oct. 25, Novo Nordisk unveiled its counteroffer to acquire interests in Metsera. The next day, Metsera’s board declared the $9 billion bid a “superior company proposal” and gave Pfizer four business days to respond.

Pfizer fired back in court, insisting Novo Nordisk’s proposal “does not, and cannot” qualify as such, citing regulatory risks, Delaware law violations, and an alleged breach of contract.

Pfizer Alleges Corruption and Collusion

The lawsuit claims Metsera’s board members switched allegiance only after securing broad indemnification from Novo Nordisk for their conduct—essentially protecting themselves before abandoning Pfizer.

Pfizer argues the proposal was crafted to evade review under the Hart-Scott-Rodino Antitrust Act and that it “requires a dividend that will be illegal under Delaware law.”

“This is a brazen attempt to induce Metsera’s board and controlling shareholders to breach their obligations,” the complaint states.

Pfizer’s Strategic Stakes in the Weight-Loss War

Pfizer’s pursuit of Metsera is rooted in the biotech’s promising GLP-1 diabetes and obesity treatment pipeline—a direct threat to Novo Nordisk’s market dominance with Ozempic and Wegovy.

“Acquiring Metsera marks a unique and irreplaceable opportunity for Pfizer,” the company said, emphasizing that any delay would harm its competitive position in the fast-growing weight management drug space.

Responses and Legal Teams

Pfizer said in a statement that it is “taking this action to enforce and preserve its rights”, adding that the conduct of Metsera’s board and Novo Nordisk “clearly violates contractual and legal obligations.”

Metsera countered Friday, saying it “disagrees with the allegations in Pfizer’s complaint and will address them in court.” Novo Nordisk did not immediately comment.

Pfizer is represented by Jonathan M. Moses, Ryan A. McLeod, Carrie M. Reilly, and Adam L. Goodman of Wachtell Lipton Rosen & Katz, alongside Kevin R. Shannon, Berton W. Ashman Jr., Mathew A. Golden, and Callan R. Jackson of Potter Anderson & Corroon LLP.

Counsel information for Metsera and Novo Nordisk was not immediately available.

A Corporate Battle with Industry-Wide Consequences

The Pfizer v. Metsera case may redefine how Big Pharma handles hostile counteroffers and antitrust scrutiny in the emerging obesity drug gold rush.

For now, Pfizer’s lawsuit—“Pfizer Sues Metsera”—signals that the company is unwilling to yield ground in what could become one of the decade’s fiercest pharmaceutical battles.