The alarming slide in Amylin’s share price has been checked by the presentation of very promising data for a once-weekly version of Byetta at the American Diabetes Association meeting in San Francisco.

Amylin’s stock ended the day up 3.4% at $27.74, reversed in part a 10.3% decline from the previous day. That fall was a result of investors absorbing promising data from Ipsen/Roche’s once-weekly glucagon-like peptide-1 (GLP-1) analogue taspoglutide (in Phase II) and Novo Nordisk’s recently-filed once-daily jab liraglutide.

Fears have been growing that twice-daily Byetta (exenatide), the only GLP-1 analogue on the market at present, could be in for some stiff competition soon. However those concerns seem to have been answered in part by the data presented by Amylin and partners Eli Lilly and Alkermes for the slow-release once-weekly formulation, Byetta LAR.

The data came from the 295-patient DURATION-1 trial, which showed that patients taking Byetta LAR over the course of one year sustained a similar improvement in glucose control, ie A1C down 2%, compared to those receiving treatment for 30 weeks. It also showed that patients who switched from exenatide injection after 30 weeks to Byetta LAR experienced additional improvements in A1C (1.9% vs 1.5%) and fasting plasma glucose.

74% of all patients in the study achieved an endpoint A1C of 7 percent or less at 52 weeks, while people in both treatment groups experienced a statistically significant and sustained average weight loss of 9.5 pounds over the year.

The data led to FBR Capital Markets analyst Jim Reddoch issuing a research note which said "the results were unprecedented”. He added that there are no diabetes medications, either in development or currently on the market, that have shown a 2% blood-sugar reduction combined with nearly 10 pounds in weight loss”.

Mr Reddoch said that Byetta LAR will likely become a first choice for type 2 diabetes patients when it hits the market, possibly near the end of 2009. He is predicting peak annual sales of $2 billion, despite competition (liraglitude could be available early next year) as the diabetes market is big enough to accommodate more than one blockbuster.

However Salveen Kochnover at Jefferies & Co was more cautious and expressed concerns that taspoglutide may have a better profile than Byetta LAR in terms of effectiveness, weight loss and dosing. He did note, nevertheless, that the side effect profile could be a point in favour of Amylin’s new formulation, but given the “lofty expectations for LAR's growth trajectory, we are concerned that taspoglutide could pose a valid concern” to potential future revenues.