On October 25, 2009, we posted an article on this blog that focused on liraglutide (Novo Nordisk’s Victoza) as a potential treatment for obesity. As we stated in the article, at that time liraglutide had recently been approved in Europe for treatment of type 2 diabetes. The drug was also awaiting FDA approval for that indication.
On January 26, 2010, after a 21-month review, the FDA approved liraglutide for treatment of type 2 diabetes. This followed the approval of the drug in Japan a week earlier.
The approval process for liraglutide in the United States had not been straightforward. In April 2009, the FDA’s Endocrinologic and Metabolic Drugs Advisory Committee voted 6-6 (with one abstention) on approval versus disapproval of liraglutide, because of the finding of thyroid C-cell tumors in studies of the drug in rodents. There is no evidence, however, that liraglutide has ever caused thyroid tumors (or other types of cancer) in humans.
As a result, the drug’s label carries a black box warning of the risk for thyroid cancer, and requires a risk-mitigation strategy. However, as we discussed in our article, liraglutide has an advantage over most antidiabetic drugs in that it induces weight loss. It also has a low risk of triggering hypoglycemia, which is a problem with several antidiabetic drugs.
As we also discussed in our article, liraglutide belongs to a class of agents known as incretin mimetics. The first incretin mimetic to reach the market was exenatide (Amylin/Lilly’s Byetta). Exenatide, which is approved for type 2 diabetes, also induces weight loss. Physicians therefore sometimes prescribe exenatide off-label for treatment of obesity. However, exenatide has a relatively short half-life, and must be self-injected twice a day. In contrast, liraglutide has a longer half-life than exenatide, and is self-injected only once a day. Amylin and Lilly are developing a longer-acting, once-weekly formulation of exenatide (known as Exenatide Once Weekly) for treatment of type 2 diabetes. The new formulation is being developed in collaboration with Alkermes, which developed the long-acting drug-delivery technology. Amylin, Lilly, and Alkermes are awaiting FDA approval of the NDA for Exenatide Once Weekly.
Exenatide’s label carries no warning with respect to thyroid cancer. However, it does carry a warning concerning the risk of drug-associated pancreatitis. Moreover, the FDA Advisory Committee raised concerns that the risk of thyroid C-cell tumors may be a class effect of incretin mimetics. The FDA has mandated that Amylin conduct postmarketing studies to deal with this concern; depending on the results of the studies, a warning of a risk for thyroid cancer may (or may not) appear on the labels of Byetta and Exenatide Once Weekly.
Despite these safety concerns, the stocks of not only Novo Nordisk, but also Amylin and Alkermes, rose on the news that the FDA had approved Victoza. Stock analysts predicted that the approval of Victoza implied that the FDA was likely to approve Exenatide Once Weekly later in 2010.
Our October 2009 blog post discussed exenatide and liraglutide in the context of the obesity drug market, and specifically drugs that treat both type 2 diabetes and obesity. Neither exenatide not liraglutide is approved for treatment of obesity in any jurisdiction, however. As we discussed in our original article, Novo Nordisk has been developing liraglutide for obesity, but Amylin is developing other, earlier-stage drugs for that indication despite the weight loss benefits seen with exenatide. Novo Nordisk had been waiting for FDA approval of liraglutide for treatment of type 2 diabetes before proceeding with further development of the drug for obesity. Now that the company has obtained that approval, we expect that development of liraglutide for obesity will be restarted.