The buyout of Amylin Pharmaceuticals by Bristol-Myers Squibb (BMS) completed in August called for BMS to pay $31 per share and gather up ownership of Amylin for about $5.3 billion. But the uniquely structured deal also brought in a third party (London-based AstraZeneca) and added a $1.7-billion payout by BMS to cover both Amylin debt and a contractual obligation to Eli Lilly, putting the total deal value at $7 billion.

New York–based BMS immediately packaged Amylin's products together into a new collaboration with AstraZeneca, in which the latter pays the now wholly-owned subsidiary Amylin $3.4 billion, and any forthcoming profits and losses are split equally between AstraZeneca and BMS. The assets in the collaboration are Amylin's GLP-1 agonists, Byetta (exenatide) and Bydureon (exenatide extended release); metreleptin, being reviewed by the FDA for diabetes and/or hypertriglyceridemia in rare forms of inherited or acquired lipodystrophy; and Symlin (pramlintide acetate), approved for type 1 and 2 diabetes in patients with inadequate glycemic control already taking meal-time insulin. The three approved products combined to sell about $830 million worldwide in 2011.

The side payments to Indianapolis-based Eli Lilly in the buyout stem from Amylin's initial development and commercialization partnership for Byetta with Eli Lilly, signed in 2002, with a total potential value of $300 million. But in May 2011, Amylin sued Lilly for engaging in anticompetitive acts and for breaching that original 2002 agreement, as Lilly earlier in the year had formed a collaboration with Boehringer Ingelheim in Ingelheim, Germany. The two companies were to jointly develop and commercialize two oral diabetes agents, Boehringer Ingelheim's linagliptin and BI10773, and Lilly's two basal insulin analogs, LY2605541 and LY2963016, with an option to co-develop and co-commercialize Lilly's anti-TGF-β monoclonal antibody. Lilly planned to use the same sales force to sell both exenatide and the direct competitor Boehringer Ingelheim's linagliptin, and this is the detail that caused Amylin to file suit. The issue was resolved when Lilly and Amylin ended the alliance and Amylin regained rights to exenatide. Having full rights made Amylin an attractive acquisition target, except that the breakup called for Amylin to, among other things, pay 15% of global sales of exenatide until the sum reached $1.2 billion, plus interest. Any potential suitor needed to take on that long-term financial commitment, and thus, BMS's multiparty buyout deal, with money flowing in three directions.