Pfizer Inc. has filed a lawsuit against Metsera Inc. and Danish drugmaker Novo Nordisk A/S, aiming to block Novo's bid for the obesity treatment startup.
The legal move comes as a fast-developing battle over Metsera, which is developing potential oral and injectable treatments for obesity and diabetes.
According to Bloomberg, Pfizer told the Delaware Court of Chancery on Friday that Novo's offer cannot qualify as a "Superior Company Proposal" under the merger agreement, partly because it faces significant regulatory hurdles.
The pharmaceutical giant is asking the court to temporarily block Metsera from closing any deal with Novo, giving Pfizer time to present its case.
In a related announcement, Pfizer confirmed that US antitrust regulators have cleared its acquisition of Metsera.
The Federal Trade Commission's review, completed under the Hart-Scott-Rodino Antitrust Improvements Act, removes a waiting period that would have expired on November 7.
"This satisfies the regulatory review requirements under the previously announced proposed acquisition of Metsera," Pfizer said.
Novo Nordisk's late bid to hijack Pfizer's takeover of US obesity biotech Metsera marks an aggressive shift from the Danish drugmaker as it seeks to regain ground in the weight-loss drug market under a new CEO and board https://t.co/6Qz7tNsm9x pic.twitter.com/EvYvxeoaeC
— Reuters (@Reuters) October 30, 2025
Pfizer Sues to Block Novo's $9B Metsera Bid
Novo surprised the market with a bid for Metsera on Thursday, offering at least $6.5 billion, potentially rising to $9 billion if certain performance targets are met, ABC News reported. That maximum amount is roughly 11% higher than Pfizer's bid.
"Pfizer's claims against Novo Nordisk are meritless, and we will vigorously defend ourselves in any litigation," said Novo spokesperson Ambre James-Brown.
Metsera also issued a statement saying it "disagrees with the allegations in Pfizer's complaint and will address them in the Delaware Court of Chancery."
Pfizer has described Novo's bid as "reckless" and a potential misuse of a dominant market position to suppress competition.
The company emphasized it is ready to pursue legal options to enforce its deal with Metsera.
Industry experts say that stopping a merger through court intervention is difficult. Charles Elson, a retired University of Delaware professor, noted, "They rarely agree to stop something like this. It's got to be an egregious situation for them to issue a temporary restraining order."
The clock is ticking for Pfizer, which has until November 4 to respond with a counteroffer or walk away from the deal.
Shares reacted modestly after the announcements: Pfizer rose 0.2% in postmarket trading, Metsera fell 1.8%, and Novo's American shares were unchanged.
The case is officially titled Pfizer v. Metsera, No. 2025-1259, Delaware Chancery Court.
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