A Pfizer logo is displayed at a research facility in the La Jolla neighborhood of San Diego, California, U.S., September 30, 2025. REUTERS/Mike Blake

(Corrects spelling of Metsera in first sub-header)

By Kamal Choudhury, Sabrina Valle and Tom Hals

(Reuters) -Pfizer on Friday filed a lawsuit against Metsera and Novo Nordisk, saying Metsera breached its merger agreement obligations in declaring the Danish drugmaker's $8.5 billion bid for the U.S. obesity drug developer to be a superior offer.

Pfizer asked the Delaware court to issue a temporary restraining order to block Metsera from terminating the agreement. Metsera has given Pfizer until Tuesday to raise its offer. Pfizer wants Metsera's scheduled shareholder vote to take place on November 13.

The legal action comes as Pfizer received early antitrust clearance for its proposed $7.3 billion acquisition of Metsera from the U.S. Federal Trade Commission. It granted early termination of the waiting period under the Hart-Scott-Rodino Act, more than a week ahead of the November 7 deadline.

"Pfizer's claims against Novo Nordisk are meritless, and we will vigorously defend ourselves in any litigation," a Novo spokesperson said.

Metsera said in a statement that it disagreed with Pfizer’s allegations and would address them in court.

PFIZER AND NOVO TALKS WITH METSERA BEGAN IN 2024

The lawsuit details a tussle for Metsera that began with discussions between the company and potential acquirers in early 2024, with both Pfizer and Novo Nordisk expressing interest.

Novo Nordisk, the maker of Wegovy and Ozempic, is trying to regain ground in the obesity drug race after losing market share to Eli Lilly. Metsera is working on experimental therapies that analysts say could generate $5 billion in sales.

Pfizer, which does not currently sell a weight-loss drug, is betting on Metsera to help it enter the $150 billion obesity market and offset falling COVID-related revenue and looming patent expirations.

Pfizer claimed Novo's bid was an illegal attempt by a dominant player to suppress competition in the fast-growing obesity drug market.

Novo made its first formal offer on January 23, 2025, valuing Metsera at $2 billion, which the board rejected due to regulatory risks and low valuation, the lawsuit said.

Pfizer entered the process with a $30 per share non-binding proposal on June 2, followed by a series of improved bids. Metsera's board rejected the proposal but was determined to continue negotiations with Pfizer.

Novo made additional bids that were rejected by Metsera's board and, by September, both parties had submitted revised proposals. Pfizer says Novo's last bid, made on September 20, involved a complex structure with non-voting shares and a dividend, which Metsera's board deemed too risky.

ANTITRUST CONCERNS AND FOREIGN OWNERSHIP

Even before Novo Nordisk formally renewed its bid for Metsera on Oct 25, Pfizer alleged that both Novo and Metsera were quietly preparing for the transaction.

According to the complaint, Novo Nordisk representatives had begun reaching out to government officials to discuss regulatory issues, suggesting pre-coordination.

Meanwhile, Metsera's lead law firm requested a conflict waiver from Pfizer just days before Novo's proposal was submitted - despite having negotiated opposite Pfizer for months without raising any conflict concerns.

Pfizer argues this timing indicates that discussions were underway before the bid was made public, potentially in violation of the merger agreement's non-solicitation provisions.

Pfizer's lawsuit emphasized its role as a leading U.S. corporation, and Novo Nordisk as a foreign competitor.

A Wednesday letter to Metsera from Pfizer's lawyers that was disclosed in the lawsuit repeatedly described Pfizer as "an American company" and said a Novo Nordisk deal "may draw scrutiny from CFIUS," a reference to the Committee on Foreign Investment in the United States.

The government body reviews foreign investment in the United States, which can give the U.S. president ultimate authority over a transaction.

Pfizer is asking the court for a declaration that Novo's proposal is not a superior offer under the merger agreement, as well as damages and injunctive relief.

(Reporting by Kamal Choudhury, Christy Santhosh and Siddhi Mahatole in Bengaluru; additional reporting by Mike Erman, Sabrina Valle and Jon Stempel in New York, Tom Hals in Wilmington, Del. and Vallari Srivastava in Bengaluru; Editing by Shilpi Majumdar, Anil D'Silva and Caroline Humer)