Pfizer, the largest US drugmaker, reported quarterly revenue that missed estimates as sales of its key drugs fell short of expectations.
Sales of breast cancer drug Ibrance, which is expected to face competition from rival Novartis's Kisqali, rose more than 58% to $679m, but missed the consensus estimate of $682m.
Analysts said that sales of the company's arthritis drug Xeljanz were particularly weak, adding that cancer drug Xtandi and Prevnar vaccine also came in lower than expectations.
Pfizer said three fewer selling days in the quarter, compared with the same time last year, reduced sales by about $300m, surprising some Wall Street analysts.
The company also lost marketing exclusivity for its depression drug Pristiq in the US during the quarter.
Overall, sales of Pfizer's array of patent-protected drugs jumped about 12% in the quarter to $7.42 billion, while sales of its generics and biosimilars fell 10% to $5.36 billion.
Revenue fell 1.7% to $12.78 billion, missing the average estimate of $13.09 billion.
Pfizer, which closed its $14 billion acquisition of Medivation in September, said net profit rose to $3.12 billion, or 51 cents per share, in the first quarter, from $3.04 billion, or 49 cents per share, a year earlier.
Total expenses fell 6% to $7.49 billion in the quarter.
Excluding items, the company earned 69 cents per share, beating the average analyst estimate of 67 cents, according to Thomson Reuters.
Pfizer reaffirmed its 2017 adjusted earnings forecast of $2.50-$2.60 per share on revenue of $52 billion-$54 billion.
