Bank of America Merrill Lynch has suffered the defection of a senior healthcare banker while the firm is advising US pharmaceutical company Pfizer on its $68.1bn (€50.4bn) acquisition, the largest global deal announced this year.

Credit Suisse has hired Thomas Davidson from BofA Merrill Lynch as co-head of Americas healthcare to work alongside Stuart Smith. Davidson had been head of US large-cap pharma at Bank of America Merrill Lynch, who declined to comment.