Anglo-Swedish pharmaceutical company AstraZeneca has reported a 56 percent drop in net income in the third quarter as it suffered from the loss of exclusivity on a big-selling drug.

For the three months ending Sept. 30, AstraZeneca said Thursday that net profit fell to $1.5 billion compared to $3.5 billion a year earlier. Revenue was down 15 percent to $6.7 billion.

The company said generic competition for Seroquel IR, used to treat depression, accounted for most of the drop in revenue. Revenue was also hit by the sale of dental unit Astra Tech and cancer services unit Aptium.

Excluding Seroquel IR, the company says revenue for the rest of its drug portfolio rose by 6 percent in the quarter.