Eli Lilly and Amylin Pharmaceuticals have rescinded a request to doctors not to prescribe new prescriptions for their diabetes treatment Byetta after boosting manufacturing capacity for the drug.

In June, the two companies were forced to ask doctors to limit prescriptions for Byetta (exenatide) after manufacturing capacity for the drug failed to meet increasing demand, thought to have resulted from data showing that the drug can help prevent diabetics from gaining weight, which is a major problem with existing drugs to treat the disease.

Supplies were limited by a shortage of cartridges that fit into the injector pen used to administer the drug.

Despite this constraint, Byetta looks set to be a major new product, racking up $99 million in sales for Lilly in the second quarter of 2006, despite only being launch in June 2005.

It also has a clear lead in the marketplace, with a rival drug from Novo Nordisk – liraglutide – not scheduled for launch until 2009, although competition could increase with the launch of new drugs in the dipeptidyl peptidase-IV inhibitor class, namely Merck & Co’s Januvia (sitagliptin) and Novartis’ Galvus (vildagliptin), which are scheduled for approval later in 2006 and in 2007, respectively.

Lilly and Amylin have outsourced some of the manufacturing of Byetta to Baxter International, in addition to capacity farmed out to Wockhardt.