5 record-breaking biotech deals

Value: $14.9 billion

Announced: April 2007

British-Swedish giant AstraZeneca (the world's fifth-largest pharmaceutical company by sales) is considered to have one of the industry's weaker pipelines, according to S&P analyst Steven Silver. Its top product is ulcer treatment Nexium, which generated $5.5 billion in sales in 2007, second only to Pfizer's Lipitor.

But AstraZeneca needed a stronger biologic pipeline. MedImmune helped develope HPV vaccine Gardasil and currently markets three drugs, including FluMist, a nasal-spray flu vaccine. The pipeline didn't come cheap: Carl Icahn was among MedImmune's top shareholders, and he got a 53% premium to its share price before the firm put itself on the block.

"It set a new benchmark in pricing expectations for biotech companies," says Adam Berger, the head of M&A at Leerink Swann, a healthcare-focused investment bank. "They're betting big on the long-term potential, not just one superdrug."

NEXT: Takeda/Millennium