Shares of Merck & Co. Inc. /zigman2/quotes/209956077/composite MRK +0.03% dropped 3.4% in premarket trading Thursday, after the drug giant reported first-quarter profit and revenue that missed expectations, as the COVID-19 pandemic and loss of market exclusivity weighed on pharmaceutical sales. Net income slipped to $3.18 billion, or $1.25 a share, from $3.22 billion, or $1.26 a share, in the year-ago period. Excluding nonrecurring items, adjusted earnings per share fell to $1.40 from $1.51, missing the FactSet consensus of a rise to $1.61. Revenue inched up to $12.08 billion from $12.06 billion, but was below the FactSet consensus of $12.61 billion, as pharmaceutical sales ticked up 0.2% to $10.68 billion. Among Merck's biggest drugs, Keytruda sales rose 19% to $3.90 billion but missed the FactSet consensus of $3.97 billion and Januvia/Janumet sales rose 1% to $1.30 billion but missed expectations of $1.34 billion. Animal health sales rose 17% to $1.4 billion. For 2021, Merck expects adjusted EPS of $6.48 to $6.68 and revenue of $51.8 billion to $53.8 billion, surrounding expectations of EPS for $6.49 and for revenue of $52.0 billion. The stock has dropped 5.8% year to date through Wednesday, while the Dow Jones Industrial Average /zigman2/quotes/210598065/realtime DJIA -1.86% has gained 10.5%.