Pfizer filed suit in Delaware to enforce its September acquisition agreement with obesity biotech Metsera and to block Novo Nordisk’s competing proposal. Pfizer alleges Metsera’s board and Novo breached contractual duties by treating Novo’s unconventional, up‑front‑heavy bid as a “superior proposal” despite regulatory risks. The company is seeking a temporary restraining order to prevent Metsera terminating the Pfizer deal while courts weigh the merits. The dispute centers on a $4.9 billion Pfizer offer and a structurally unusual Novo proposal valuing Metsera at roughly $6 billion, raising questions about antitrust exposure and deal certainty in the high‑stakes obesity M&A market.