Key Takeaways Merck stock jumps almost 14% as investor optimism grew after Pfizer's drug pricing deal.The deal boosts sector sentiment by reducing drug costs and driving investment in the U.S. pharma sector.Investor optimism lifted Merck and other big drugmakers like AstraZeneca, Eli Lilly and others.Shares of Merck (MRK) have rallied almost 14% so far this week as investors’ optimism grew concerning the broader pharmaceutical sector in the United States after Pfizer (PFE) announced a landmark deal with the ...