Analysts' forecasts were yesterday being slashed to between zero and $200m after the cardiovascular and renal drugs advisory committee on Thursday voted four-to-two against recommending use of the treatment. The decision is a setback for SmithKline, led by chief executive Jan Leschly, because rarely does the FDA overrule a committee recommendation.
Shares in the group slid 49.5p to 662p, after dipping $31/2 overnight in New York.
One London analyst said: "The market is looking at this as a significant blow. Coreg was their highest-profile product and there were some very high expectations, particularly from US analysts, who were expecting to see sales of $1bn-plus before the end of the century. That's going to have to be scaled back to say the least. There's no doubt this is a blow to sentiment."
Although Coreg is already approved in the US for high blood pressure, its main application is as a treatment for congestive heart failure, which is a principal cause of around 40,000 deaths in the US every year and a contributory factor in a further 225,000. The success of clinical trials caused their abandonment in February so that patients receiving the placebo could be given the new drug, which is being jointly developed with Boehringer Mannheim of Germany. The FDA committee said the trials' six-month length was insufficient to establish the efficacy of Coreg.