With its Bloomington facility in Indiana, Baxter this summer became the second supplier of the cartridges, which hold the medication so that it can be injected, after Indian biopharmaceutical firm Wockhardt struggled to keep up with demand at its production site in the UK.
Despite Wockhardt exceeding contractual obligations to supply these cartridges in view of the shortage, the immense popularity of the drug led to a restriction in the number of patients that started using Byetta.
"Although Lilly puts together the pen that is used in the administration of the drug, the cartridges are provided by external suppliers, so there has to be enough supply to support production," Amylin spokeswoman Alice Bahner told In-PharmaTechnologist.com.
"The demand was above and beyond what we expected."
About 1.3m Byetta prescriptions have been written for 250,000 patients since the drug was launched in June 2005, raking in $88m (€68m) in sales since January and predicted by many to be a blockbuster.
Byetta, which is derived from Gila monster saliva, causes weight loss in many patients instead of the weight gain most existing diabetes treatments bring about, making it attractive to patients.
Amylin is determined to exploit the full potential of Byetta to dominate the global diabetes drug market, worth $15bn this year and projected to reach $25bn by 2011, and is in search of new formulations to take on three major competitors - Exubera, Galvus and Januvia.
Exubera, Pfizer's inhalable insulin, is expected to be launched in September, despite a patent dispute with Novo Nordisk, while Novartis's Galvus and Merck's Januvia, both taken as pills, are likely to be approved by the US Food and Drug Administration (FDA) by early next year.
After a two-month sales disruption in the supply of Byetta, Lilly's sales force will now target some 60,000 physicians to promote the drug, as the company is confident they can now cope with demand.
Both Lilly and Amylin have stressed that Wockhardt did everything it could to deal with the shortage and also played an important role in solving the problem.
In fact, during the shortage, Sirjiwan Singh, managing director of Wockhardt UK, told In-PharmaTechnologist.com that his factory was operating seven days a week to supply Byetta.
Wockhardt announced in June it will commission in September a new UK facility to boost its Byetta cartridges manufacturing capacity fourfold.
Meanwhile, Amylin plans to produce in-house a long-acting release (LAR) version of Byetta, currently in development with drug delivery firm Alkermes; last December the company announced it will spend up to $150m on an Ohio facility to make LAR formulation of exenatide, the active ingredient in Byetta, by the end of 2008.