Pfizer revealed it has filed multiple lawsuits against Metsera, its directors, and Novo Nordisk, with one suit filed for breach of contract, and another for violation of antitrust claims.^1,2

Following the announcement of these suits, Metsera issued the following statement: "Pfizer is trying to litigate its way to buying Metsera for a lower price than Novo Nordisk. Metsera's Board of Directors will continue to stand firm on behalf of shareholders and patients. Pfizer's litigation arguments are nonsense, and Metsera will address them in court."

Pfizer’s initial lawsuit against Metsera, its board of directors, and Novo Nordisk

On Friday, October 31, 2025, Pfizer announced its first lawsuit against Metsera Inc., its board of directors, and Novo Nordisk, claiming breach of contract, breach of fiduciary duty, and tortious interference in contract.1 Pfizer says that it believes that Novo Nordisk’s unsolicited proposal offer to acquire Metsera cannot qualify as a “Superior Company Proposal” under the terms of the Pfizer and Metsera merger agreement.¹

Pfizer released a statement in a news release, saying, “Relative to the Pfizer deal, the Novo Nordisk transaction is not reasonably likely to be completed on the terms proposed in light of the significant regulatory risk of the proposal.”

Pfizer continued to say, “The proposed Novo Nordisk transaction is an illegal attempt by a company with a dominant market position to suppress competition and uses an unprecedented structure designed to deliberately evade antitrust review.” Pfizer’s lawsuit continues to note that Metsera’s board had previously determined Novo Nordisk’s prior proposal included unacceptable regulatory risks and was structured similar to its most recent proposal.¹

Pfizer continued, saying it “is taking this action to enforce and preserve its rights under the merger agreement. Metsera’s and its Directors’ actions, as well as those of Novo Nordisk, are in clear violation of their respective contractual and legal obligations. We are confident in the merits of our case and look forward to presenting it to the Court.”

Pfizer files second lawsuit for federal antitrust claims

On Monday, November 3, 2025, Pfizer filed its second suit against Metsera, its controlling stockholders, and Novo Nordisk, alleging that Novo Nordisk’s proposal to acquire Metsera violates Section 7 of the Clayton Act due to the anticompetitive effects it would have in the GLP-1 drug markets. Pfizer says that this constitutes an anticompetitive conspiracy between Novo Nordisk and Metsera in restraint of trade in violation of Section 1 of the Sherman Act, and constitutes an attempted monopolization and conspiracy to monopolize under Section 2 of the Sherman Act.² Pfizer’s lawsuit also alleges Metsera’s controlling stockholders to have conspired with Metsera and Novo Nordisk in furtherance of these anticompetitive activities.² Metsera’s controlling stock holders are as follows.

• Validae Health, L.P.
• ARCH Venture Fund XIII, L.P.
• Population Health Partners GP, LLC
• ARCH Venture Fund XII, L.P.,

According to a press release from Pfizer, the company intends on seeking all “appropriate” remedies to the situation, which includes relief ensuring Novo Nordisk’s proposed acquisition is not permitted to continue.

Sources

1. Pfizer Files Lawsuit Against Metsera and its Directors and Novo Nordisk for Breach of Merger Agreement Pfizer October 31, 2025 https://www.businesswire.com/news/home/20251031742790/en/Pfizer-Files-Lawsuit-Against-Metsera-and-its-Directors-and-Novo-Nordisk-for-Breach-of-Merger-Agreement
2. Pfizer Files Federal Antitrust Claims in Second Lawsuit Against Metsera, its Controlling Stockholders and Novo Nordisk Pfizer November 3, 2025 https://www.pfizer.com/news/press-release/press-release-detail/pfizer-files-federal-antitrust-claims-second-lawsuit
3. Metsera Issues Statement in Response to Litigation Metsera November 3, 2025 https://www.prnewswire.com/news-releases/metsera-issues-statement-in-response-to-litigation-302602743.html