AstraZeneca (AZN) shares extended declines Thursday in London after the company said sales of its blockbuster Crestor drug fell sharply in the face of generic competition.

Britain's second-biggest drugsmaker reported earnings per share of $0.80, up 32% from the same period last year and ahead of analysts' forecasts of $0.74 per share. But sales of Crestor, its key cholesterol blockbuster drug, fell 44% from the same quarter last year to $688 million, the company said, while sales of Symbicort dropped 17% to $697 million. 

Core EPS, the company said, was up 28% to $1.32. Profit before tax, however, fell 27% to 676 million and missed analysts' expectations of $731 million. Total group revenues slipped 4% to $5.7 billion, largely in-line with forecasts.

AstraZeneca shares fell 4.13% in London by 12:30 GMT, against a broader FTSE 100 gain, to trade at 4,394 pence each. The stock has fallen 15% over the past three months, outpacing an 8.4% decline for the FTSE 350 Healthcare Index.

"The performance in the third quarter was in line with our expectations, reflecting the transitional impact from the first full quarter of generic competition to Crestor in the US," CEO Pascal Soriot said. "We sharpened significantly our focus on our three therapy areas, by prioritising our portfolio through externalisation and divestments. This focus, underpinned by our productivity initiatives, supported the rapid reduction in SG&A costs."

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