Eisai’s plans to submit its investigational severe sepsis drug eritoran for approval by mid-2010 have suffered a setback because an independent data monitoring committee said the Japanese firm needs to enrol another 500 patients in a late-stage study.

The Tokyo-based company had been hoping that data from a 1,500-patient Phase III trial would provide the basis of a filing to regulators in the USA, Europe and Japan. However as part of an interim analysis of the safety and efficacy data, “the DMC recommended continued enrollment to the planned goal of 2,000 patients”, Eisai says, noting that the committee “did not express safety concerns that would warrant stopping the trial at this time”.

This means that a more likely submission date will be mid-2011. The company has high hopes for eritoran, which is believed to block activation of toll-like receptor 4 which, when activated “may play an important role in the course of severe sepsis”, Eisai added.

Worldwide, sepsis affects 18 million people every year and represents a huge opportunity but the severe blood infection is notoriously difficult to treat. The only drug that has been approved for sepsis, despite decades of research and dozens of clinical candidates, is Eli Lilly's Xigris (drotrecogin alfa), and that is recommended only for patients with the most severe forms of the disease and comes with a warning of an increased risk of serious bleeding events.

The longer-than-expected trial for eritoran comes at a time when Eisai is preparing for the loss of the US patent on its Alzheimer's disease drug Aricept (donepezil) in November. The treatment, which is co-marketed with Pfizer, is far and away Eisai’s biggest earner.