Pfizer is preparing to sweeten its offer again for Metsera, the weight-loss drug startup at the center of a bidding war that also involves Novo Nordisk.

New York-based Pfizer is making plans to deliver a fresh bid Wednesday, according to people familiar with the matter, ahead of a deadline it has to respond to Novo Nordisk's latest proposal.

Under the terms of its existing merger agreement with Metsera, Pfizer's next likely step is to match Novo Nordisk's offer, one of the people said.

Metsera shares closed Wednesday at $71.38 and rose over 6% in overnight trading after The Wall Street Journal reported on Pfizer's plans. Novo Nordisk's offer valued the company at $86.20 a share, while Pfizer's most recent offer valued it at $70 a share, Metsera said.

Three-year-old Metsera is developing drugs that promise to help people lose significant weight, one of the fastest-growing and lucrative markets in pharmaceuticals. It has a market value of around $7.5 billion after its shares have risen roughly 170% so far this year.

Pfizer reached a deal in September to buy Metsera for up to $7.3 billion. Then last month, Novo Nordisk made an unsolicited proposal to pay up to $9 billion.

Both parties boosted their offers earlier this week: Novo Nordisk increased its offer to about $10 billion, while Pfizer upped its proposal to up to $8.1 billion. Metsera then deemed Novo Nordisk's offer superior, leaving Pfizer to counter by the end of Wednesday or risk losing its deal.

Pfizer sued to block Metsera from terminating their agreement, saying a Novo Nordisk deal is unlikely to be completed due to antitrust issues, which Novo Nordisk said isn't true.

On Wednesday afternoon, a Delaware judge rejected a request by Pfizer to get a temporary restraining order to stop Novo's proposal. Pfizer said in a written statement after the ruling that it intends to continue pursuing its lawsuit as well as separate antitrust litigation.

Meanwhile, the Federal Trade Commission on Tuesday warned Novo Nordisk that its offer for Metsera appeared to be structured in a way that would sidestep or delay the necessary antitrust review.

Novo Nordisk's deal is structured to happen in two stages. In the first, Novo Nordisk would acquire nonvoting securities in Metsera. Later, after receiving all regulatory clearance, it would buy the remaining shares and Metsera shareholders would receive an additional payment depending on certain milestones.

The FTC urged Metsera and Novo Nordisk to consider whether the deal should be submitted for antitrust review immediately instead.

Novo Nordisk sells two drugs--Ozempic and Wegovy--that are among the leading sellers in the category. Anti-obesity drugs are on track for $72 billion in worldwide sales this year, according to TD Cowen, which projects the market could reach $139 billion in 2030.

Pfizer is among the companies seeking to enter the market. It had been developing its own pills, but their testing results were disappointing.