There are five tech companies valued at over $1 trillion. In healthcare, the closest contender is Eli Lilly.

This year it became the first big pharmaceutical to surpass a market capitalization of $500 billion thanks to the popularity of its obesity and diabetes medications and, to a lesser extent, its experimental Alzheimer’s drug. But hanging over Lilly and rival Novo Nordisk is a reality that puts the brakes on big pharma’s ascent: the patent cliff.