Shares in Amylin Pharmaceuticals have taken a bashing in after-hours trading after the firm and partner Eli Lilly reported four new deaths among patients with pancreatitis who took their type II diabetes drug Byetta, in addition to the two cases reported last week by US regulators.

The companies held a conference call to “provide context” and transparency about the safety profile of the injectable drug Byetta (exenatide). Their response comes a week after the US Food and Drug Administration said it has received six reports of haemorrhagic or necrotising pancreatitis of patients receiving the drug, two of whom died.

Amylin and Lilly noted that the additional four deaths did not involve patients with the necrotising form of diabetes, which affects 15%-20% of patients with inflammation of the pancreas. The FDA already knew about these cases when it made the announcement last week but is presently concentrating on the severest form of pancreatitis, Lilly’s medical director James Malone said.

Furthermore, it is not yet clear whether the patients in the four new cases were taking Byetta at the time of deaths and they were not directly attributable to pancreatitis, said Orville Kolterman, Amylin’s senior vice president of R&D. In one case, the patient appeared to die from a relapse of leukaemia two months after the pancreatitis issue surfaced.

The main message that Amylin and Lilly were looking to get over again is that patients with type II diabetes have a greater risk of pancreatitis than healthy people and while the companies cannot rule out a connection between Byetta and pancreas problems, there have been reports of similar problems with other drugs. They are also hoping to ease concerns about the long-acting version of Byetta - formulated for use once a week, instead of twice a day – which Amylin and Lilly still hope to get to the market by mid-2009. There are no plans for additional studies, they said, as there have been no cases of pancreatitis in the 600 patients using Byetta LAR in trials.

Analysts have not reacted negatively to the announcement of the four new deaths, as many believe that the original reaction to the pancreatitis problem was a little excessive. However Amylin’s stock fell by as much as 13% in extended trading.