This week’s roundup of deals worth $1 billion or more includes Am Law firms working on a $15.2 billion pharmaceutical transaction between Pfizer and Hospira; a $10.54 billion telecom deal between Frontier and Verizon; a $7.3 billion asset sale by building material manufacturers Holcim and Lafarge; and a $6.3 billion merger between Staples and Office Depot.

Leading the way by transaction value was Skadden, Arps, Slate, Meagher & Flom and Davis Polk & Wardwell, each of which advised on $25.7 billion worth of deals. Davis Polk also had the most deals by volume, counseling on four transactions.