Pfizer has followed through on its threats, filing a lawsuit against both Metsera and Novo Nordisk during a M&A bidding war for the obesity-focused biotech.

This follows Novo Nordisk’s last-minute interception of Pfizer’s September 2025 acquisition deal for the New York-based biotech, which could see Pfizer pay up to $7.3bn for the rights to Metsera.

Through its counter-offer, Novo Nordisk trumped this value, offering Metsera up to $9bn, which the biotech considered a “superior company proposal”.

The lawsuit, filed in the Delaware Court of Chancery, alleges that Novo Nordisk and Metsera breached the contractual merger agreement, claiming “breach of contract, breach of fiduciary duty, and tortious interference”.

Pfizer made additional claims against Novo Nordisk in its lawsuit announcement, alleging that the Danish pharma’s acquisition offer of Metsera is an “illegal attempt by a company with a dominant market position to suppress competition” in the obesity field, as Novo Nordisk currently holds a dominant market position in this segment.

Pfizer refuted Metsera’s claims that Novo Nordisk’s proposal was superior, noting that it “cannot qualify as superior” relative to its deal with Metsera under the merger agreement. In Pfizer’s eyes, this is because Novo Nordisk’s transaction is unlikely to be completed due to the regulatory risk associated with it.

In a statement released on 31 October, Metsera noted that it “disagrees with the allegations in Pfizer’s complaint”, adding that the company will address them in court.

Metsera’s future up in the air

Despite its souring sentiments toward the obesity biotech, Pfizer plans to soldier on with the acquisition, which could be ready to complete following a Metsera stockholder meeting on 13 November.

In an attempt to block any further discourse on this matter, Pfizer has also filed a motion with the Court of Chancery to request a temporary restraining order on Metsera to block the biotech from terminating the merger agreement, which Pfizer noted would give it “time to be heard on this important matter”.

Despite Novo Nordisk’s attempt to intercept Pfizer’s deal with Metsera, it appears that the latter may prevail, as the US Federal Trade Commission granted early termination of the waiting period to the New York pharma’s pending acquisition.

Obesity market spikes big pharma interest

This back-and-forth comes at a time when Pfizer is keen to make its name in the metabolic health sector, which GlobalData forecasts will be worth $206.5bn in 2031 – up from $12.3bn in 2021.

GlobalData is the parent company of Pharmaceutical Technology.

Currently, glucagon-like peptide-1 receptor agonists (GLP-1RAs) are consistently delivering high sales performance, with Eli Lilly’s star type 2 diabetes and obesity assets, Mounjaro and Zepbound (tirzepatide), bringing in $6.5bn and $3.6bn in Q3 alone – surpassing analyst expectations and raising the company’s projected revenue ceiling for this financial year.

Novo Nordisk and Eli Lilly have been the two key players in this segment, fighting for market share with their best-selling injectable GLP-1RAs, Wegovy (semaglutide) and Zepbound.

However, Pfizer has been looking to jump on the obesity bandwagon, having developed its own assets to compete with both Lilly and Novo Nordisk’s marketed therapies.

Despite its efforts to develop an oral GLP-1RA, Pfizer had to terminate the development programme for its obesity pill, danuglipron, after the medication caused a drug-induced liver injury in a Phase IIa trial.

If Pfizer’s acquisition of Metsera is completed, the big pharma will claim Metsera’s range of obesity assets, including monthly GLP-1RA, MET-097i, which recently posted weight loss of 14.1% in a Phase IIb trial.

Alongside its next-generation injectable portfolio, Metsera could offer Pfizer another chance at commercialising an oral obesity drug, as the company’s MET-224o pill is currently in Phase I trials.