NEW YORK/LONDON: Pfizer has clinched a US$10 billion deal to acquire obesity drug developer Metsera, ending a heated bidding war with Danish rival Novo Nordisk, which dropped out of the race after U.S. antitrust concerns derailed its offer.

Metsera said that it accepted Pfizer's revised bid, citing "unacceptably high legal and regulatory risks" tied to Novo's proposal. The U.S. Federal Trade Commission had contacted both companies earlier in the week, warning that Novo's deal could violate antitrust laws. Novo confirmed it would not raise its offer and officially withdrew from the competition on Saturday.

"Following a competitive process and after careful consideration, Novo Nordisk will not increase its offer to acquire Metsera," the company said in a statement, adding that it remains focused on advancing its own obesity treatment pipeline.

Pfizer's victory secures it a long-sought foothold in the booming weight-loss drug market, which analysts estimate could reach $150 billion globally by the next decade. Though Metsera's experimental drugs are still in early stages, the deal gives Pfizer a strategic entry point into a field dominated by Novo and U.S. rival Eli Lilly.

Pfizer will pay $86.25 per share, including $65.60 in cash and a contingent value right worth up to $20.65 per share tied to future milestones. The total deal value represents a 3.7 percent premium to Metsera's close on November 7. Pfizer said it expects the merger to close shortly after Metsera's November 13 shareholder meeting.

The bidding war, described by one investor as a "Game of Thrones-level" corporate showdown, sent Metsera's shares up nearly 60 percent in a week, lifting its market value to $8.75 billion. Novo Nordisk shares slipped as much as 3 percent on Friday before recovering.

Pfizer first struck a deal with Metsera in September for about $7.3 billion, but Novo's surprise counteroffer reignited competition between the two pharmaceutical giants. Despite Novo's aggressive bid, Metsera's board ultimately sided with Pfizer, citing the smoother regulatory path and lower legal risks.

"This was always a bolt-on acquisition for Novo," said a person familiar with the Danish company's strategy. "Its last bid represented the maximum value it placed on Metsera."

Bernstein analyst Courtney Breen said Pfizer's $10 billion price tag reflected "optimistic assumptions" about Metsera's revenue potential, suggesting the company would need to reach $11 billion in annual sales by 2040 to justify the valuation.

Former Pfizer R&D chief John LaMattina compared the battle to the company's 2000 takeover of Warner-Lambert, saying, "While this is a smaller deal, Pfizer must believe Metsera's pipeline is key for its future."

Metsera's lead candidates include MET-097i, a GLP-1 injectable, and MET-233i, which mimics the pancreatic hormone amylin. Analysts at Leerink Partners project the two could reach $5 billion in combined peak sales if successful.

For Novo, the loss is a setback in its push to maintain dominance in obesity care after losing market share to Eli Lilly. Still, Novo said it will "continue to assess opportunities for acquisitions" aligned with its strategy.