Nelfinavir’s contamination with ethyl methanesulfonate (EMS) in the spring of 2007 was not of a level to involve any risk of cancer, evidence gathered by the drug’s manufacturer, Roche, shows.

Between March and May of 2007 batches of nelfinavir (Viracept) were accidentally contaminated with EMS during the drug’s manufacture. European drug regulatory authorities were informed once this problem became known, leading to a near-global recall of nelfinavir and the temporary suspension of nelfinavir’s licence.

Roche has undertaken studies to try and determine the risk to patients of exposure to EMS. Because EMS is a potentially cancer-causing substance it is not possible to conduct studies in humans to see what level of exposure involves a substantial cancer risk. Therefore the drug company looked at a number of studies involving animals.