Pfizer saw its share price dip yesterday after it released updated preliminary results of its torcetrapib/atorvastatin clinical trials showing that while the combination drug lowered LDL cholesterol and raised HDL cholesterol compared to atorvastatin alone, it also seemed to increase blood pressure.

The update was provided in connection with the release of an American Heart Association abstract of a Phase III study in patients with heterozygous familial hypercholesterolemia.

The shares responded poorly to the news because torcetrapib has been billed as such an important new drug for Pfizer, with some analysts predicting that it could even top atorvastatin’s $12 billion in annual sales. Atorvastatin, sold by Pfizer as Lipitor, is the biggest-selling drug in the world, but will lose patent protection in 2010.

Pfizer's chief medical officer Dr Joseph Feczko said the results of the trial 'generally show torcetrapib/atorvastatin significantly increasing HDL or ‘good ‘cholesterol by 55% to 60%, as well as lowering LDL or 'bad' cholesterol by 10% to 15% more than atorvastatin alone.

But torcetrapib was also associated with a 3-4 millimetre increase in systolic blood pressure, roughly 1mmHg more than had been seen in earlier studies, and analysts are concerned that regulators might ask for evidence that the increase does not worsen outcomes in patients, delaying the drug’s approval.

Pfizer stressed that the Phase III trial programme for torcetrapib is incomplete and the early results cover less than 25% of all the patients in the studies, so drawing any conclusions on the safety or efficacy of the drug would be premature.