According to a report in The New York Times' web edition, Eli Lilly and Co is said to have concealed health risks that it was aware of for over decade on the adverse effect of its blockbuster anti-psychotic drug Zyprexa, used in the treatment of schizophrenia and bipolar disorder.
Eli Lilly has denied the allegation, saying, that the documents were released "illegally" and that they did not accurately portray Lilly's marketing behaviour.
"The Times failed to mention that these leaked documents are a tiny fraction of the more than 11 million pages of documents provided by Lilly as part of the litigation process," the company said in a statement. "They do not accurately portray Lilly's conduct."
Lilly has been embroiled in long-standing litigation with Zyprexa users who claim the drug can trigger obesity and diabetes.
With sales of $4.2 billion last year, Zyprexa, which is taken by an estimated two million patients, is Lilly's best-selling product that accounts for around a third of the company's sales.
Incidentally, Lilly's second most lucrative product line is its range of diabetes treatment drugs that include Actos, Humulin, and Humalog. Lilly's sales from anti-diabetics are around $2.51 billion.
The report is said to be based on the drug maker's internal marketing documents and e-mail messages among top managers, provided to it a lawyer representing mentally ill patients.
According to The New York Times, lawyer James Gottstein, provided the Lilly documents that show its executives knowingly concealed information from doctors linking the drug to unmanageable weight gain and tendency towards diabetes. Gottstein had subpoenaed the documents from a party involved in litigation.
The report says that Lilly's own published data, covering the period 1995 to 2004, has shown that 30 per cent of patients taking Zyprexa gained between 22 pounds and 100 pounds. The report accuses Lilly of being concerned that the drug's sales would be hurt.
Critics, including the American Diabetes Association, have argued that Zyprexa, introduced in 1996, is more likely to cause diabetes than other widely used schizophrenia drugs.
In 2004 the FDA had asked Lilly to add a warning on the drug's label describing the increased risk of hyperglycemia (abnormally high blood sugar, usually associated with diabetes) and diabetes in patients taking Zyprexa. Earlier, in 2002, British and Japanese regulatory agencies had warned that Zyprexa may be linked to diabetes.