Merck & Co and Schering-Plough’s controversial cholesterol-lowerer Vytorin is back in the limelight after US regulators said that they are investigating whether the drug can increase patients' risk of developing cancer.

The US Food and Drug Administration said the agency announced it is investigating a report from the SEAS trial about a potential link between Vytorin (ezetimibe/simvastatin) and a potentially increased incidence of cancer. The agency anticipates receiving the final SEAS study report from Merck and S-P in about three months and will need another six “to fully evaluate the clinical trial data and other relevant information”.

However the FDA stressed that patients should not stop taking Vytorin, especially as two large ongoing cardiovascular trials of Vytorin – SHARP and IMPROVE-IT – show no increased risk of cancer with the combination of simvastatin plus ezetimibe.

Highly-anticipated data from the 1,873-patient SEAS study came out in July which confirmed that Vytorin failed to meet its primary goal of improving cardiovascular outcomes for patients with aortic stenosis compared to placebo. However eyes were raised on the data which demonstrated that 39 patients who took the drug died of cancer, compared with 23 in the placebo group.

S-P and Merck maintain that the cancer finding is likely to be an anomaly and due to chance, a view echoed by an independent analysis by the University of Oxford Clinical Trial Service Unit and Epidemiological Studies Unit. However, US lawmakers are not convinced.

The House Energy and Commerce Committee has asked the companies for extensive data on the clinical trial that indicated a possible cancer risk for Vytorin. Committee Chairman John Dingell and Bart Stupak, chairman of its Oversight and Investigations subcommittee, sent a letter to the chief executives of Merck and S-P, giving them two weeks to supply detailed information and Rep Stupak says that "Vytorin's effectiveness has been in doubt, and now its safety is questionable".

The latest Vytorin development comes just after the Journal of the American College of Cardiology published a new analysis of 15 statin studies including more than 90,000 patients that found statin users were no more likely to get cancer than people on placebo.