According to Amylin Pharmaceuticals, Inc., the new long-acting version of their diabetes drug Byetta does not have the same link to thyroid cancer recently associated with Novo Nordisk’s Liraglutide, a similar diabetes drug in the same class of medications that the FDA is also considering for approval.
Concerns about potential Byetta thyroid cancer side effects emerged last week after an FDA advisory panel revealed that there is a link between Liraglutide and thyroid cancer in animals. Since Byetta (exenatide) belongs to the same class of diabetes drugs, known as GLP-1 agonists, it was suggested that the thyroid tumor risk may be a class effect.
The FDA panel arrived at a split vote on the question of whether to recommend that permission to market Liraglutide be approved for Novo Nordisk. Analysts have speculated that this may delay approval for the new once-daily version of exenatide (which will be marketed as Byetta LAR) or that the FDA may place substantial restrictions on the use of both drugs.
This week Amylin has jumped to the defense of their drug, which is critical to the future of the relatively small pharmaceutical company. Although the drugs are in the same class, Amylin points out that exenatide and liraglutide are different molecules.
Amylin says that their data from a two-year study of the potential cancer side effects of Byetta LAR in rodents did not find the same tyroid tumor risk demonstrated with Liraglutide. While Liraglutide was found to cause tumors in both female and male rats at multiple doses, Byetta LAR was only found to produce an abnormal number of thyroid cancers in female rats that were given high doses of the drug.
Of the approximately 1 million diabetes patients who have used the current version of Byetta, which is injected multiple times a day, Amylin indicates that only 9 reports of spontaneous thyroid cancer have been reported. However, none of these cases were fatal or similar to the tumors associated with Liraglutide.
The FDA’s review of Byetta LAR has already been delayed several times due to requests for additional safety data and concerns that Byetta side effects may increase the risk of pancreatitis.
In October 2007, the FDA released a statement indicating that about 30 cases of acute pancreatitis with Byetta use had been reported. This alert was updated in August 2008, to notify doctors that at least six additional cases had been reported involving severe forms of pancreatitis, known a hemorrhagic and necrotizing pancreatitis. At that time, the FDA indicated that two of the six severe cases had resulted in death.
Although Amylin and Eli Lilly & Co, who co-market Byetta, denied that there is any causal connection between Byetta and pancreatitis, the FDA has reportedly been considering a stronger warning about the potential side effect, which may include a “black box” Byetta warning, which is the strongest warning that can be placed on a prescription medication.
Amylin and Eli Lilly currently face a number of Byetta pancreatitis lawsuits filed on behalf of users of the current version of the drug, which allege that the drug makers failed to adequately test and monitor the side effects of their drug and failed to issue sufficient warnings about the potential pancreatitis risk.