GlaxoSmithKline Plc insisted its diabetes pill Avandia was safe as U.S. advisers began a two-day meeting to consider if the medicine is too dangerous to stay on the market.
The scientific experts assembled by the U.S. Food and Drug Administration are sorting through sharply conflicting data on whether Avandia causes heart attacks.
Follow the science where it leads and the rest will fall into place, urged FDA Commissioner Margaret Hamburg in opening the meeting held in a packed hotel ballroom, acknowledging that the advisers had a difficult job.
The recommendations of the panel, with 33 voting members, are expected to weigh heavily on the FDA in making its final decision in the coming months.
British-based Glaxo, which could face a new wave of lawsuits if the drug comes off the market, said diabetes was a serious disease that needed multiple treatment options to control blood sugar and prevent devastating complications including amputations and blindness.
When used appropriately, (Avandia) has a positive benefit/risk profile and should remain a treatment for type 2 diabetes, said Dr. Murray Stewart, a Glaxo vice president for drug research and development.
The pill was once Glaxo's second-biggest drug but its sales have plunged since safety fears erupted three years ago. Revenues totaled 771 million pounds ($1.16 billion) in 2009, equivalent to 2.7 percent of Glaxo's group sales.
Added pressure is coming from the European Medicines Agency, which has launched a new review into Avandia's risks and benefits.
For the FDA, the case is seen as a test of how the agency will handle major controversies under Democratic President Barack Obama. Officials are facing heavy pressure from consumer groups and some lawmakers who say the FDA fumbled decisions in past administrations and failed to protect the public.
Shares of Glaxo were up almost one percent in both London and New York trading, amid a broad rally in stocks.
More information on Avandia could come from lawsuits against Glaxo and congressional investigations, but panel proceedings have been confined so far to the over 700 pages of briefing documents released last week.
The top Democrat and Republican on the Senate Finance Committee wrote FDA's Hamburg on Monday saying internal e-mails showed Glaxo back in 2000 downplayed data showing heart risks for Avandia and did not submit it in a timely way to the FDA.
The New York Times, which first reported the material in its Tuesday edition, quoted Glaxo spokeswoman Mary Anne Rhyne as saying the company had not provided the study because it did not contribute any significant new information.
Views on Avandia are mixed inside the FDA.
Some staff see the Glaxo drug as more dangerous to the heart than Takeda Pharmaceutical Co's rival diabetes pill, Actos, with no unique benefits. Others remain unconvinced Avandia raises heart-attack risk. The current warning on the drug, added in 2007, says the data is inconclusive.
Glaxo's defense of Avandia is based in part on a study called Record that found no higher rates of heart-related hospitalizations or deaths.
A parade of FDA staff and outside experts will continue to make presentations on Tuesday and on Wednesday morning.
On Wednesday afternoon, the panel of cardiologists, endocrinologist and other experts will be asked to choose one of five options, ranging from keeping the drug on the market without a heart-attack warning to recommending a withdrawal. Restricting use or beefing up warnings are other choices.
Glaxo has asked the FDA to remove the existing heart warning because it says the data does not support it.
Some doctors want to keep Avandia as an option for lowering blood sugar when other medicines do not help.
The Avandia decision rests on which of many studies the panelists view as stronger. All have strengths and weaknesses.
Glaxo says six randomized clinical trials, considered the gold standard of medical evidence, showed Avandia did not raise the overall risk of heart attack, stroke or death.
But the company's Record trial has come under sharp attack from an FDA heart expert who concluded it was inadequately designed to rule out cardiovascular risk.
Dr. Thomas Marciniak, a medical team leader in the FDA division that reviews heart drugs, added in briefing materials released last week that biases in the study suggest that the true risk (of heart attack) could be higher.
Other FDA staff said the study backed Avandia as safe.
An ongoing study comparing Avandia and Actos could provide a more definitive answer but critics argue it is wrong to wait years for those results. They say findings against Avandia are strong enough now to warrant the drug's removal. (Reporting by Lisa Richwine; Editing by Tim Dobbyn)