Drugmaker AstraZeneca has seen its share price plummet more than 15% after announcing disappointing results.
The firm said first-quarter revenue fell 10% to $5.05bn (£3.84bn).
It also reported a major setback in trials of a new lung cancer drug therapy.
The company was by far the biggest loser on the benchmark FTSE 100 share index, which was down 5.99 points, or 0.08%, to 7,446.33 in early Thursday trading.
In the currency market, the pound edged higher against the dollar, up 0.12% at $1.3138. Against the euro, the pound was 0.29% higher at 1.1204 euros.