Pfizer filed suit in Delaware against Metsera and Novo Nordisk, alleging breach of a September merger agreement and seeking to block Metsera from terminating the Pfizer buyout while Novo pursues a rival offer. Pfizer says Novo’s bid and Metsera’s characterization of it as a “superior proposal” violate contractual and fiduciary duties. The suit accuses Novo of structuring an offer to avoid antitrust review and of wrongfully interfering with Pfizer’s agreed acquisition, asking the court for a temporary restraining order to preserve the original deal. Pfizer values Metsera’s assets as a strategic, immediate entry into obesity therapeutics after its $4.9 billion bid. Novo’s unsolicited proposal — structured to pay a large upfront sum for half the shares — has triggered a bidding war that highlights how strategic portfolios in obesity drugs are reshaping M&A. The dispute underlines regulatory and antitrust calculations that bidders and targets are weighing as they jockey for next‑generation metabolic and weight‑loss assets.