COPENHAGEN (Reuters) -Denmark's Novo Nordisk said on Monday it is confident that its proposed takeover of U.S. drugmaker Metsera ( MTSR ) does not raise any antitrust issues.

Novo Nordisk last week launched a rival bid for obesity biotech Metsera ( MTSR ), exceeding an offer from Pfizer ( PFE ) as the drugmakers jostled for advantage in the highly lucrative market for weight-loss medications.

Pfizer ( PFE ) in turn filed a lawsuit on Friday alleging breach of merger agreement obligations. 

Novo Nordisk said it adhered to all the Pfizer ( PFE ) merger agreement restrictions.

"This is an intensely competitive space, with at least a dozen other products being developed by major pharma companies. We are confident this transaction does not raise any antitrust issues," Novo said in an email statement.

Novo Nordisk, the company behind the blockbuster weight-loss drug Wegovy and related diabetes treatment Ozempic, bid up to $8.5 billion, with $6 billion upfront and later milestone payments, while Pfizer's ( PFE ) bid was worth up to $7.3 billion, including milestones.

The clash marks an escalating battle for dominance in the obesity drug market some analysts forecast will reach $150 billion annually within a few years. Novo is seeking to defend its position against rising competition from Eli Lilly ( LLY ), while Pfizer ( PFE ) aims to secure its entry into the weight-loss sector.

Metsera ( MTSR ) is working on experimental therapies that analysts say could generate $5 billion in sales.

Pfizer ( PFE ) said Novo's bid was an illegal attempt by a dominant player to suppress competition in the fast-growing obesity market. Both Metsera ( MTSR ) and Novo have dismissed Pfizer's ( PFE ) claims.