Pfizer sued Metsera and Novo Nordisk in Delaware’s Court of Chancery seeking to block Metsera from accepting Novo’s counteroffer and to enforce a previously agreed buyout. Pfizer had bid roughly $4.9 billion; Novo’s structurally unusual proposal attached a large up‑front cash payment for half the shares to mitigate regulatory delay risk. Metsera’s board and prospective bidders are in a legal and strategic tug-of-war over an obesity pipeline that has drawn intense buyer interest.