After two rejections, the US Food and Drug Administration has finally given the green light to Amylin Pharmaceuticals' once-weekly diabetes drug Bydureon.

Bydureon is an extended-release formulation of Amylin's Byetta (exenatide) which uses long-acting technology developed by Alkermes, and although approved in Europe in June 2011, the regulatory path across the Atlantic for the drug has been less direct. In October 2010, the FDA said it could not approve the companies' first marketing application for Bydureon, a glucagon-like peptide-1 receptor agonist, without more data on its how it affects the heart.

That was the second time the agency turned down Bydureon - it also declined to give a green light to the drug in March 2010 at its first bid for approval. Now, the FDA is seemingly happy with data presented in support of the treatment but the approval comes with a risk evaluation and mitigation strategy "to ensure that the benefits of Bydureon outweigh the risk of acute pancreatitis and the potential risk of medullary thyroid carcinoma".

Amylin also has to "fulfil a number of post-marketing requirements" to further assess the impact of the drug on MTC and cardiovascular disease. Despite this, the company is delighted and chief executive Daniel Bradbury  noted that "as the first and only once-weekly diabetes treatment, Bydureon represents an important milestone [and] builds upon the proven benefits of (twice-daily) Byetta, offering significant improvements in glycaemic control in a single weekly dose".

The approval comes a few months after Amylin and then-partner Eli Lilly dissolved their pact (signed in 2002) for Byetta and Bydureon. The former had questioned Lilly's commitment to the drug after it signed a deal with Boehringer Ingelheim, including a marketing link-up for the German firm's oral dipeptidyl peptidase-4 inhibitor Tradjenta (linagliptin).

However, part of the terminated deal means that Lilly is entitled to $150 million upon FDA approval of a once-monthly suspension version of exenatide that is currently in Phase 2, as well as royalties on sales of exenatide products. It also banked a $250 million one-time, upfront fee. 

The drug will go up against Novo Nordisk's GLP-1 drug Victoza (liraglutide), which requires once-daily injections. Analysts believe the convenience of an injection just once a week should benefit Bydureon and will be watching to see how successful Amylin is at marketing the drug without its former heavyweight partner Lilly.