The future prospects for Pfizer’s cholesterol-lowering drug Lipitor (atorvastatin), currently the top-selling drug in the world, could be dramatically affected by a UK court ruling later today.

The court is due to deliver its verdict on the case, which centres around a patent challenge brought by Indian generic drugmaker Ranbaxy Laboratories. The Indian company is claiming that Pfizer’s patents on the statin are invalid and, if the court backs its case, the product could face early competition to the nearly $11 billion dollar-a-year drug. Lipitor is not due to lose patent protection until at least 2010.

While the UK is a relatively small market for the drug, the fear is that a negative outcome for Pfizer could influence ongoing patent litigation between the two companies in the USA, the drug’s biggest market with annual revenues of $6.6 billion last year.

Meanwhile, a study has found that average levels of low-density lipoprotein-cholesterol – a form of cholesterol linked to the development of heart disease – has dropped 10% on average amongst Americans over the last four years. However, US testing company, Quest Diagnostics, which carried out the study, suggested that the decline was linked to an increasing use of statins, rather than any lifestyle changes affecting the US population.