AstraZeneca said it has delivered a strong pipeline and financial performance in 2015, but also warned of tougher times ahead with a low to mid single-digit percentage drop in sales and earnings on the horizon.

The firm’s prediction for 2016 seems to have come as somewhat of a surprise to investors and analysts, which had been expecting that current sales and earnings levels would be maintained, sending stock down about 4% after the news.

The drug giant reported a 5% drop in total sales for the fourth quarter to $6.4 billion, though this masked organic growth of 2% when taking currency exchange effects out of the equation.

Core operating profit (which takes out any exceptional items) hit $1.6 billion, rising 28% over the year-ago period, or 31% higher at constant exchange rates (CER), while core earnings per share jumped 22% to $0.94 (up 26% at CER).

Looking ahead, while loss of exclusivity for cholesterol blockbuster Crestor (rosuvastatin) - which took home $1.3 billion for the quarter - will take a big bite out of sales and earnings, the group is anticipating six regulatory submissions and around ten major data readouts during the year.

“We’re confident that our strong execution on strategy, combined with the benefits of focused investments and new launches, keeps us on track to return to sustainable growth in line with our targets,” said AZ chief executive Pascal Soriot.