Pfizer moved to block Novo Nordisk’s unsolicited takeover attempt for obesity biotech Metsera after Novo lodged a higher bid, escalating a high‑stakes M&A battle in the obesity drug market. Pfizer filed suit in Delaware alleging Novo’s proposal is anticompetitive and not reasonably likely to close; Metsera’s board has judged Novo’s offer superior, triggering a narrow renegotiation window. The clash pits two major drugmakers against each other over Metsera’s next‑generation incretin and amylin portfolio and underscores heightened regulatory and antitrust scrutiny around consolidation in obesity therapeutics.