Icahn, Byetta Sales Boost Amylin (Update)

Updated from 3:19 p.m. EST

Amylin Pharmaceuticals' (AMLN Quote) got a strong boost Monday from an uptick in prescription numbers for diabetes drug Byetta and news that Carl Icahn has been increasing his stake in the biotech stock.

Overall prescriptions of Byetta -- although still down 9% year over year -- increased 3.9% during the first week of November, according to new IMS data. Also on Monday, CNBC's Mike Huckman reported that Icahn recently increased his stake in the company.

The billionaire, activist investor disclosed holding about 10.7 million shares of Amylin at the end of the most recent quarter, up from roughly 6.8 million shares at the close of the second quarter, according to a Friday filing with the Securities and Exchange Commission.

Amylin's shares rose 50 cents, or 7.8%, to $6.91 on Monday, bucking the trend of an otherwise down day for Wall Street.

Piper Jaffray analyst Thomas Wei notes that Byetta's week-over-week increases were not as large as other name-brand diabetes drugs like Avandia (up 6.6%), Actos (up 7.8%), Januvia/Janumet (up 5.9%) and Lantus up 6.2%). "However, given two weeks of Byetta prescription growth exceeding 3%," wrote Wei, "we believe it remains unclear if media dissemination of what we regard as misleading headlines on pancreatitis risk will have a long-term negative impact on the company's new sales effort to expand Byetta prescriptions." Wei has a buy rating on Amylin stock.

The biotech company lately has been taking much-needed steps toward profitability, but restoring investor confidence in the struggling diabetes-drug maker is still very much a work in progress.