Worldwide sales of Humira, AbbVie's heavily advertised prescription drug that treats rheumatoid arthritis and other ailments, hit $18.4 billion in 2017 — an increase of more than 14%. Humira represented about two-thirds of AbbVie's total revenue.

The big picture: Humira, which costs $38,000 after rebates, is the top-selling drug on the planet. If Humira were a standalone company, it would be larger than many Fortune 500 conglomerates, such as General Mills, Halliburton or Xerox.