In a 6-6 vote by the FDA Scientific Advisory Committe, it was determined that Liraglutide (a diabetes drug made by Novo Nordisk (NVO)) posed a significant risk in causing thyroid tumors in humans. While the panel was worried about animal studies showing that liraglutide caused medullary thryroid cancer in both mice and rats, Novo Nordisk denied any evidence of the drug causing such a cancer in humans.
Moroever, some members of the panel were worried that any thyroid risk might apply to the whole class of drugs: GLP -1 class. However, there is currently no clinical evidence that thyroid cancer is a GLP-1 class effect. Amylin Pharmaceuticals (AMLN), which is conducting clinical trials on the safety and efficacy of another diabetes agent, Byetta (GLP -1 drug), found no thyroid C-cell carcinoma association. Amylin executives stated that they haven't seen any risks of cancerous tumors with Byetta, and only minimal evidence with the long-acting version, exenatide LAR, which will be submitted for FDA approval in coming months.
No cases of thyroid cancer have been documented in patients enrolled in clinical trials of Byetta, according to Amylin Pharmaceuticals. Amylin conducted a two-year cancer study of long-acting Byetta in rats and mice and found a statistically significant increase in tumors only in female rates treated with doses of long-acting Byetta four-fold higher than what would be given to humans. By comparison, Novo Nordisk's liraglutide was found to cause tumors in male and female rats, sometimes at human-equivalent doses.
Last week, Amylin released positive results from DURATION-2 that demonstrated superiority of Byetta once weekly as compared to two commonly prescribed diabetes medications, Januvia(TM) (sitagliptin) and Actos® (pioglitazone). Also, a meta-analysis of primary cardiovascular events across controlled clinical studies of three months or greater, from the BYETTA® (exenatide) injection database, showed no increased risk of cardiovascular events associated with the use of exenatide.
Since Byetta and liraglutide are distinct molecules, how is it scientifically sound to assume that what is seen with one molecule will automatically be seen with the other? Clearly, the FDA's concern regarding the threat of thyroid cancer in Amylin's Byetta is ridiculous! As a matter of fact, FDA officials publicly pointed out, last week, that they did not see any risk of thyroid cancer with Byetta after re-examining data on the four-year-old drug. Additionally, animal testing of Byetta did not uncover the same level of a thyroid tumor risk as Novo Nordisk's Liraglutide.
Though both liraglutide and Byetta belong to the sames class of drugs called GLP-1s, the latter may deliver a cleaner preclinical safety profile than liraglutide. However, there is one shortcoming in Byetta's clinical trial. Scientists wonder if less than 500 patients from Byetta's LAR's DURATION-1-3 trials are sufficient to address the FDA's concern over a potential 'class effect' for thyroid cancer that could increase with longer-acting agents, and if additional trials would be required. I think not.
According to President and Chief Executive Officer Daniel M. Bradbury and his management team, exenatide once weekly is on track for a planned launch in 2010. The steps that the company has taken to enhance the commercial opportunities of the product are already beginning to yield results. With data supporting efficacy, safety and manufacturing now in hand, Amylin anticipates filing a new drug application (NDA) for exenatide once weekly by the end of this quarter.
Disclosure: Long AMLN.